Tektronix Water Dispenser 494A Users Manual

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2015-02-03

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Service Manual

Tektronix

494A& 494AP
SpectrumAnalyzers
Volume 1

070-ss60-00

Warning
The servicing instructions are for use by qualified
personnelonly. To avoid personal injury, do not
perform any servicing unlessyou are qualified to
do so. Refer to the Safety Summary prior to
performing service.
Pleasecheck for change information at the rear
of this manual.
First Edition: January1987

I

Copyright @ Tekrronix, Inc. 1987. All rights reserved.
Tektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication supercedes
that in all previously published material. Specifications and price change privileges reserved.
Printed in the U.S.A.
Tektronix, Inc., P.O.Box 1000, Wilsonville, OR 97070_1000
TEKTRONIX and TEK are registered trademarks of Tektronix. Inc.

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RELEASEOF COPYRIGHT
Tektronixcannotprovidemanualsfor measurementproductsthat are no
longereligiblefor longterm support.Tektronixherebygrantspermission
and licensefor othersto reproduceand distributecopiesof any Tektronix
productmanual,includingusermanuals,operato/s
measurement
manuals,servicemanuals,and the like,that (a) havea Tektronixpart
Numberand (b) are for a measurementproductthat is no longer
supportedby Tektronix.A Tektronixmanualmay be revisedto reflect
changesmadeto the productduringits manufacturing
life.Thus,
differentversionsof a manualmayexistfor anygivenproduot.Gare
shouldbe takento ensurethatone obtainsthe propermanualversionfor
a specificproductserialnumber.This permissionand licensedoesnot
applyto any manualor otherpublicationthat is still availablefrom
Tektronix,or to any manualor otherpublicationfor a videoproduction
productor a colorprinterproduct.Tektronixdoes not wanantthe
accuracyor completeness
of the information,text,graphics,schematics,
partslists,or othermaterialcontainedwithinany measurementproduct
manualor otherpublicationthat is not suppliedby Tektronixor that is
producedor distributedin accordancewith the permissionand license
set forthabove.TEKTRONIX
SHALLNoT BE LIABLEFoR ANY
DAMAGES
WHATSOEVER
(|NCLUD|NG,
WTTHOUT
LtMtTATtON,
ANy
CONSEQUENTIAL
OR INCIDENTAL
DAMAGES,DAMAGESFOR
LOSSOF PROFITS,
BUSINESS
INTERRUPTION.
OR FOR
pROpERTylAR|S|NGOUTOF
TNFRTNGEMENT
OF TNTELLECTUAL
THEUSEOF ANYMEASUREMENT
PRODUCT
MANUALOR OTHER
PUBLICATION
PRODUCED
OR DISTRIBUTED
IN ACCORDANCE
WITHTHEPERMISSION
ANDLICENSE
SETFORTHABOVE
ThomasF. LenihanChieftntellectual
PropertyCounselTektronix,
tnc(503)627-7266

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WARRANTY
Tektronix warrants that this product will be free from
defects in materials and workmanship fbr a period of one (l)
year from the date of shipment. If any such product
proves defective during this warranty feriod, Tektronix, at its
option, either will repair the defective product without charge for parts
and labor, or will provide a replacementin
exchange for the defective product.
In order to obtain service under this warranty, Customer must
notify Tektronix of the defect before the expiration
of the warranty period and make suitable arrangementsfor
the performance of service. Customer shall be
responsible for packaging and shipping the defective product
to the service center designatedby Tektronix, with
shipping charges prepaid- Tektronix shall pay for the return of
the product to Cusromer if the shipment is to a
location within the country in which the Tektronix service
center is located.customer shall be responsiblefor
paying all shipping charges,duties, taxes, and any
other charges for products returned to any other locations.
This warranty shall not apply to any defect, failure or damage
caused by improper use or improper or inadequate
maintenance and care' Tektronix shall not be obligated to furnish
service under this warranry a) to repair damage
resulting from attempts by personnel other than Tektroriix
representativesto install, repair or service the product;
b) to repair damageresulting from improper use or connection
to incompatibleequipment;or c) to servicea
product that has been modified or integrated with other products
when the effect of such modification or
integration increasesthe time or difficulty of servicing the product.
TIIIS WARRANTY IS GIVEN BY TEKTRONTX WITH RESPECT
TO THIS PRODUCT IN LIEU OF
ANY OTI{ER WARRANTIES, EXPRESSED OR IMPLIED.
TEKTRONIX AND ITS VENDORS
DISCLAIM ANY IMPLIED WARRANTIES OF MERCHANTABILITY
OR FITNESS FOR A
PARTICULAR PURPOSE. TEKTRONIX'RESPONSIBILITY
TO REPAIR OR REPLACE DEFECTIVE
PRODUCTS IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED
TO THE CUSTOMER FOR
BREACH OF THIS WARRANTY. TEKTRONIX AND ITS VENDORS
WILL NOT BE LIABLE FOR ANY
INDIRECT' SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
DAMAGES IRRESPECTIVE OF
WHETHER TEKTRONIX OR THE VENDOR HAS ADVANCE
NOTICE OF TIM POSSIBILITY OF
SUCH DAMAGES.

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494A/494APServiceVot.1

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PREFACE
This manual contains servic€ informationfor the
TEKTRONfX494A1494Ap.The informationis tocatedin
two volumes. Volume1 containsthe text and Volume2
contains the diagrams and parts lists. The Tabte of
Contents in each volume lists the contents of both
volumes.
Manualsthat describeother aspectsof the product
are:
. Operator's
Manual
. Operator'sHandbook
o Programmer's
Manual
o Programmer's
ReferenceGuide
Who Should Use This Manual?
This rnanualis intendedfor electronictechnicians
with experiencein servicingdigital,analog,and rf circuitw. Circuit analysis is mostly functionil and shoutd
help isolate most malfunctioneto a board or block of
circuitry.The technicianshould then be abte, with the
aid of test equipment,to isolate the malfunctionto a
specificcomponentor components.
This instrumentcontains firmwarethat provides a
thoroughinstrumentcheck during power up and during
operation,and if needed,guidesthe usei throughai
abbreviatedfront-panelcalibrationprocedure. lf cali_
brationcannotbe achieved,a diagnostictest detects
and isolatesmost problemsto the system,suchas 1st
LO. The techniciancan then run troubleshooting
diagnostics to further isolate the problemto the board or
blockof components.Referto the Maintenance
section
for diagnosticsinformation.
DocumentationStandards
Most terminologyand graphicsfollow ANSI stan_
qalds. A glossaryof terms is providedas an appendix.
Referto the followingstandards:

. ANSIY1.1- Abbreviations
. ANSIY32.2- GraphicSymbots
o IEEE91 - Logic Symbots
Change/History Inf ormation
Sometimesinstrumentchanges occur or manual
errors are found that make some of the informationin
the manual inaccurate.When that happens,Manual
ChangeInformationnoticesare insertedat the rear of
the manual.This helpsensurethat the manualcontains
the latestand most accurateinformationavailable
when
the productis sold.
History information, with the updated data, is
integratedinto the text or diagrams: Whena text page
is updated,the revisedpages are identifiedby a revision date in the lowerinsidecornerof the page. When
a diagramis updated,the revisiondate is placedat the
lower center of the diagram. History informationis
shown with a gray tint. When a componentvalue is
changed,the designatoron the drawingis boxedwith a
grey outline. Whena circuit is deletedor changed,the
originalconfigurationis shown in grey, drawn eitherat
its originallocationor to the side of the drawing.
lf you havea manualother than the one that came
with your instrumentit may containrevisionsthat do not
applyto your instrument;however all historyinformation that pertainsto the earlierinstrumentsis retained.
When a major modificationhas been made to an
assemblyor circuit board, the data for the replaced
assernblywill follow the new informationand will be
identifiedwith appropriatetitles or headingssuch as
instrurnentserial number range or the assemblyor
boardpart numbers.
Also, if your instrumenthas an assemblyreplaced
with a newer version,documentationfor the newer
assemblymay be supplied. Contactany TektronixServiceCenterfor information.

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494A/494APServiceVot. 1

TABLEOF CONTENTS
The 494A/494APservice Manuatis divided into two volumes.

VOLUME1
Page
PREFACE
........................
i
TABLEOF CONTENTS
..............
..........
iii
LISTOF ILLUSTRATTONS
...........
........x
LISTOF TABLES
.............
xiii
SERVICING
SAFETYSUMMARY
.........xv
Section1 GENERALINFoRMATION
productDescription
...........
1_1
Conformanceto
IndustryStandards
............
1_1
ProductService
.................
1_1
Instrum€ntConstruction
.... 1-z
Installationand
,l_2
Preparation
for Use
...........
powerInputRange....,.....,.....
Changing
1_2
Replacing
Fuses.........
Selected
Components
.......1-2
Assemblyand
CircuitNumbering
..............
1_2
FirmwareVersionand
Error MessageReadout
.... 1-g
Options
..........
1-g
Accessories
..,....................
1-3
Section2 SPEC|F|CAT|ON

'

ELECTRICAL
................
.....2-1
Verificationof ToleranceValues .....,. Z-1
FrequencyRelatedCharacteristics... 2-1
AmplitudeRelatedCharacteristics
.... 2_6
InputSignatCharacteristics
..............
2-11
OutputSignalCharacteristics
...........
2-1g
GeneralCharacteristics
....................
2-1s
PowerRequirements
........,.........,.....
2-15
ENV|RONMENTAL..........
... 2_16
PHYSTCAL
.....2-.t7

Section3 INSTALLATION
UNPACKING
AND
tNtilAL TNSPECTTON
.......,3-1
coNNECTtNGPOWER
.....3_2
PowerSourceand
PowerRequirements
g_2
........................
STORAGE
ANDREPACKAGING
......,....
3.2
Storage
.....g_2
Repackaging
g-3
for Shipment................

Page
Section4 PERFORMANCE
CHECK
Introduction
..,.4-1
Incoming
Inspection
Test ......................
4_1
OptionInstrumentChecks..............,......
4_1
Verification
of ToleranceValues............
4_1
HistoryInformation
............
4-1
Equipment
Required
..........4-1
PRELIMINARY
PREPARATTON
.............
4-4
InitialPower-Up............
.....44
CalibratePosition,
CenterFrequency,
ReferenceLevel,
and DynamicRange
..........4-s
PERFORMANCE
CHECK
pRocEDURE................
.....4_6
1. Check't0MHz Reference
OscillatorAccuracy
...........
4_6
2. CheckCounterAccuracy..................
4-6
3. CheckCounterSensitivity................
4-6
4. CheckCentErFrequency
Accuracy
.,......4-T
5. CheckCenterFrequency
Stability
...........
4-9
6. CheckResidualFM ..........................
4-9
7. CheckFrequency
Span/DivAccuracy
............
4-10
8. CheckMarkerAccuracy...................
4-12
9. CheckSweepTime
Accuracy
........4-19
10. CheckPulseStretcher....................
4-19
11.CheckResolutionBandwidth
and ShapeFactor
..........-...4-14
12.CheckCalibrator
Output..................
4-15
13.CheckNoiseSidebands..................
4-15
14.CheckFrequency
Response
............
4-16
15.CheckDisptayDynamic
RangeandAccuracy.............................
4-1g
16. CheckPreselector
UltimateRejection
.........-...4-20
17. CheckRF AttenuatorAccuracy.......4-20
18. ChecklF GainAccuracy..................
4-25
'l 9. Gheck
GainVariationBetween
Resolution
Bandwidths
......4-26
20. CheckSensitivity
.........4-26
21. CheckResidual
SpuriousResponse
...........4-27
22. Cheeklntermodulation
Distortion
........4-2A
23. CheckHarmonicDistortion........,.....
4-29

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49441494AP
ServtceVot. i

I

TABLEOF CONTENTS
(Gonr.)
page
Section 4 PERFORMANCE
CHECK(Conr.)

24.CheckLO Emission
.....4-29
point.......4-29
25.Check1 dB Compression
26. CheckExternalReference
InputPower
.... 4-31
27. CheckTriggeringOperation
and Sensitivity..............
.....4-31
28. CheckExternal
SweepOperation
...............
4-92
29.CheckVERTOUTPUTSignat..........4-34
30. CheckHORTZOUTPUT
SignafLevel
....4-94
oPTloN TNSTRUMENTS
.......................
4_34
31. CheckOption07
CalibratorOutput
...............
4-94
32. CheckOption07
Frequency
Response
.........4-95
33. CheckOption4i Frequency
Span/DivAccuracy
............
4-gz
34. CheckOption42
110MHz OUTLevel
..........
4-gB
35. GheckOptiopn42110MHz tF
OutputBandwidth,CenterFrequency,
BandpassRipple,and Symmetry
About110MHz
..................4-gg
GPIBVERIFICATTON
PROGRAM..........4-39
Section 5 ADJUSTMENT
Introduction
.... 5-1
Equipment
Required
..........5-1
ADJUSTMENT
PROCEDURE
................
5-2
PREPARAT|ON
.............
.....5-2
1. AdjustLow Voltagepower Suppty ... 5-3
2. AdjustZ-Axis and
HighVoltageCircuits
.........5-5
3. Adjust DeflectionAmptifier
Gainand Frequency
Response.............
5-6
4. Adjust DigitalStorageCalibration.... 5-g
5. AdjustSweepTiming
.... 5-g
6. AdjustFrequencyGontrolSystem
and Dot Marker Position
.... S-g
7. AdjustLog Amplifier.........................
5-11
8. Adjust ResolutionBandwidth
andShapeFactor
..............
5-14
9. Presetthe VariableResolution
Gainand BandLeveling.....,..................
5-19
10.AdjustCalibratorOutputLevet ........5-20
11.AdjustlF Gain
..............
S-20
12.Adjust B-SAVEA
Refergnce
Level .........
.......5-21
13.AdjustPreselector
Driver................
S-21
14.AdjustBandLevelingfor
CoaxialBands
...................
5-24

tv

.|

Page
15. AdjustBandLevelingfor
WaveguideBands
..............
5-25
16. PhasELockCalibration
....................
5-2S
OPTIONINSTRUMENTS
ONLY.............
5-29
17. AdjustOption07 VR Band Leveling 5-29
18. AdjustOption42 Module.................
5-29
Section 6 MAINTENANCE

TNTRODUCTTON
...............................
6-1
Removingthe
lnstrument
from its Cabinet..........6-1
static-sensitivecomponents .......6-1
PREVENTIVE
MAINTENANCE
...............
6.2
ElapsedTimeMeter .....................
6-2
Cleaning
......-............
6-2
Lubrication
...............
6-2
Fixturesand Tools
for Maintenance
.................,.........
6-2
Visuallnspection
..........................
6-2
Transistorand Integrated
CircuitChecks
..........6-2
PerformanceChecks
and Recalibration
.........................
6-3
SavingStoredDatain
Battery-Backup
Memory...............
6-3
TROUBLESHOONNG
........6.3
Troubleshooting
Aids ...................
6-9
Diagrams
.............
6-3
CircuitBoard
lllustrationsand Component
LocatorCharts
..... 6-4
Diagnostics
..........6-4
GeneralTroubleshooting
Techniques
...............
6-4
Semiconductor
Checks............
6-4
DiodeChecks..........................
6-4
Diagnostic
Firmware................,...
6-5
Troubleshooting
Steps .................
6-5
DTAGNOSTTCS
......................................
6-5
TROUBLESHOOTING
USING
THEERRORMESSAGE
DISPLAY....6.5
Introduction
..............6-5
Combinationof Error Messages... 6-6
ProcedureFormat
.... 6-6
............
TRACEMODES
6-14
AlternateFrequency
Display........6-14
AuxiliarySynthesizer
Control.......6-14
........-...
CorrectionDisable/Enable
6-14
coRRECTtVE
MATNTENANCE
..............
6-15
HandlingStaticSensitive
.............6-1
5
Components
Parts.......6-15
ObtainingReplacement
PartsRepairand Return
Program
...................
6-15

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494A/494APService Vot. 1

TABLEOF CONTENTS(Conr.)
page
Section6 MAINTENANCE
(Conr)
FirmwareVersionand
Enor MessageReadout...............
6-15
SelectedComponents..................
6-15
ReplacingEPROM
or ROMDevices
........6-15
Surface-Mounted
Components..... 6_16
ReplacingSurface-Mount€d
Components
..............
6_17
Transistorand Integrated
CircuitConfigurations
................,..
6_1
7
DiodeCotorCode.........................
6_1g
MultipleTerminal
(Harmonica)
Connectors...............
6_1g
Resistor
Values
.........
6-1g
CapacitorMarking
.....6_1g
Soldering
Techniques
...................
6-1g
Replacingthe Squarepin for
the Multi-pinConnectors..............
6_1g
Servicingthe VR Module..............
6-1g
REPLACING
ASSEMELIES
ANDSUBASSEMBLTES
....................
6_19
Removingand Installing
the GPIBBoard
.........6-22
Removingor Replacing
Semi-rigid
CoaxialCables............
6_22
Replacingthe DualDiode
Assembtyin the 1st Mixer ............
6_22
Replaeingthe Crt
......6_23
Repairingthe Crt
Trace RotationCoil
... 6-29
FrontPanelAssemblyRemoval...6-29
Front-Panel
BoardRemoval.........6_24
ReplacingFront panel
Pushbutton
Switches....................
6_24
MainPowerSuppty
ModuleRemoval
........6_24
HighVottagepower Supply..........6_25
Removingand Replacingthe
lst LO
..6_25
Replacingthe l st LO
InterfaceBoard
.........6_25
FanAssembtyRernovaf................
6-25
MAINTENANCE
ADJUSTMENTS
......6.26
110MHz tF Assembty
ReturnLossCalibration
................
6-26
2072MHz2nd Converter.............
6_26
FourCavityFilter..........
...........
6_27
Mixer.........
...........,9-27
110MHz ThreeCavityFitter.........6_29
829 MHz Converter
Maintenance
..............
6_29
Troubleshooting
and Calibrating
the 2ndLO .............
..6-32

Page
Preparingthe 2nd LO
Assemblyfor Adjustment.............
6-35
Reassembling
the
2nd LO Assembty
.....6-9g
Troubleshootingand Calibrating
the 16-20 MHz PhaseLock
Section
.....................
6-40
Troubleshooting
Aids for the
2182MHzPhaseLocked
2nd LO Assembty
.....6-42
100MHz Osciltator
in the
3rd Converter
...............................
649
l st ConverterBias .....................,.
6-44
AuxiliarySynthesizer
VCOAdjustment
...........................
6-44
BaselineLeveling
(VideoProcessor)
..... 6-46
10 MHz Reference
OscillatorAccuracy
.. 6-49
MICROCOMPUTER
SYSTEM
MATNTENANCE
.............
.... 6-50
OptionSwitches
.......6-50
Power-upSelf Test
... 6-50
MicrocomputerSystemTest ........6-51
AddressBus Test
.....6-52
Microcomputer
Bus .................
6-52
MernoryAddressDecoders..... 6-52
ProcessorAddressDecoder.... 6-59
GPIBBoard
AddressDecoders
6-s3
Clocksahd ControlLines.........6-54
Instrument
Bus Test
6-54
TROUBLESHOOTING
ON THE
INSTRUMENT
BUS
6-54
Instrument
Bus DataTransfers.... 6-54
Instrument
Bus Registers,............
6-56
Front-PanelRegisters
6-62
TAPEOATATRANSFERPROGRAM.... 6-63
Section 7 THEORY OF OPERATION
F U N C T T O N AD
L E S C R | p T t O N. . . . . . . . . ...... . 7- 1
W h a t l t D o e s . . . . . . . . . . . . . . . . - . . . . . .7. .-.1. .
How lt Works
.......7-1
First, Second, and
T h i r d G o n v e r t e r s. . . . . . . . ...... . . . . . . .7. - 1
lF Section
..-.........7-2
D i s p l a yS e c t i o n
....7-2
FrequencyControl Section .,.... 7-2
Counter and
P h a s eL o c k S e c t i o n. . . . . . . . . . . . . , .7.-. 2
DigitalControl Section .............7-3
P o w e r S u p p l yS e c t i o n. . . . . . . . . . . . 7
. .- 3
O t h e r S e c t i o n s. . . . . . . . . . . ........ . . . . . 7. - 3

494A1494AP
ServlceVol. 1

TABLEOF CONTENTS(Cont.)
Page
Section7 THEORYOF OPERATTON
(Cont)
DETAILED
DESCR|PT|ON
................
.....7-4
1STCONVERTER
SECTTON
.............
7_4
RF InterfaceQircuits....................
7-4
'l st
Converter.................
..........,,,..
7-4
RF Input
...............
7-4
Preselector
Circuits...........,.....
74
lst Mixer
..............
7_5
1st LocalOscillator..................
7_5
powerDivider
......7-s
Transfer Switch
.... 7-s
Directional
Filter................,......
Z-6
2O72MHztF Fitters....,............
7-6
Diplexerand Filter...,...............
Z-6
2NDCONVERTER
SECTTON
............
7_7
2072MHz 2ND CONVERTER
.......7-8
Four-Cavity
Fi|ter..........
...........
Z-g
MixerCircuit............................
7-g
PrecisionExternalCables........7-9
Filterto Mixer
RF InputGable....................
7-10
2nd LO to Mixer
LO InputCable....................
Z-10
2182MHzPHASELocKED
2NDLO
.....................7-10
2182MHz Microstrip
Oscillator
.............
7-10
2200 MHz Reference
Board
....................7-11
220OMHz Reference
M i x e r. . . . . . . . .
...........7-11
16-20MHz phaselock
Board
....................7-11
829MHz 2NDCONVERTER
.........7-19
lF Section
............
7,13
829 MHz Diplexer
.,..............
7-tg
829 MHz Amplifier
...............
t-13
829 MHz 2nd Converter...,..7-14
1 1 0M H zl F S e | e c t . . . . . . . . . .7. -. .i 5
..
LO Section
...........
7-16
PhaseLockCircuit..............
7-16
2nd Local Oscillator
OuputCircuit
... 7-19
719 MHz OutputCircuit.......7-18
3RDCONVERTER
SECTION......,.....
7-19
1 1 0M H zt F A M p L t F t E R
. . . . . . . . . . .7. .-.1. 9
110MHz FILTERS
3rd CONVERTER
............
..............
7 -2A
100MHz Oscillator..................
7_20
Mixer.........
...........
7_20
Distribution
Amplifier...............
7 -20
Calibrator
.............2-21
REFERENCE
LOCK......,...............
7-21
ExternalReferance
Det€ctor
...,...,,..,...7-21
vl

Page
Frequency
Synchronizer
..........7-21
Phase/Frequency
Detector
...,.,..,.....,7-21
er ...............
TuneAmplifi
...........
7-22
LockDetector..............
.........
"..7 -22
rF sEcTtoN
...................7-22
VAR|ABLERESOLUTION
.............
7-22
VR fnput
...............7-22
1st FilterSelect
.....7-22
100Hz and 10 Hz
BandpassFilter..........
..............
7 -24
1st Mixer
,..,,.....7-25
Filter..........
Bandpass
....,.,..
7 -25
2ndMixer
.........7-25
LocalOscillator.............
......7-26
10 dB GainSteps..........-..........7-26
20 dB GainSteps.....................7-26
BandLevelingCircuit........,......
7-27
VR MotherBoards...................
7-27
2nd FilterSelect
....7-28
PostVR AmplifierCircuit .........7-28
LOG AMP and DETEGTOR..........7-29
Log AmplifierCircuits..............
7-29
DetectorCircuit
.-...7-31
DTSPLAY
........7€3
SECTTON
DESCRIPTION
.......7-33
FUNCTIONAL
.,,.7.33
VIDEOAMPLIFIER
Log ModeCircuits...................
7-33
LinearModeCircuits..............-.
7-34
PulseStretchCircuit................
7-34
.......7-35
ldentifyCircuit
DigitalControlCircuit...............
7-35
vrDEo pRocESSoR....................
7-35
Interfacewith 1405TV
7-35
SidebandAdapter.............-......
7-36
MdeoMarker...........................
VideoLeveling.......,......
7-37
...........
VideoLevelerCircuits..............
7€7
VideoFilterCircuits......,..........
7-37
VideoBlanking.-..............,........
7-39
7-39
DIGITAL STORAGE
VerticafSection
.....740
D i g i t i z i n gC i r c u i t s . . . . . . . . . . . . . .7. .4 3
Address Decoding ...............7-43
I n t e r f a c eL o g i c . . . . . . . . . , . . . . . . .7. 4 3
M a x i m u mH o l d . . . . . . . . . . . . . . . . .7. .4. 3
. .-. 4 3
C o n s t a n tC i r c u i t . . . . . . . . . . . . . . . 7
O u t p u tC i r c u i t s . . . . . . . . . . . . . . . . .7. .-.4 4
Peak/Average Level
.............7-44
Circuits
H o r i z o n t aS
l e c t i o n . . . . . - . . . . . . . . . .7. .-.4 4
. .-.4. .6
M a r k e rl C . . . . . . . . . . . . . . . . . . . . . . . 7
Tracking Digital-to7*46
Analog Converter ................
Update Marker Circuits .......746

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494A1494AP
Service Vot. I

TABLEOF CONTENTS(Conr.)
Page
Section7 THEORYOF OPERATION
(Conr)
FastRetraceBlanking...,.,...742
Memories
........7-47
DEFLECTION
AMPLIFIERS
..........7-47
Horizontal
Section...............,...
747
VerticalSection
....249
Z.AXISANDRF INTERFACE
.......7-48
RF InterfaceCircuits................
7_49
Z-AxisCircuits
.....7_49
power-FailDetector.................
7-50
powerSupplyMonitor.............
7_50
OptionsSwitch
.....7-50
Timer .........
..........
7_50
HIGH.VOLTAGE
SUPPLY.............
7.50
High-Vottage
Osciilator............
7-50
VoltageDoubter
... 7_SO
High-Voltag€
Regulator............
7_S0
Z_AxisGtipper
......7_51
cRT READOUT
............................
7_51
Generating
Readout.................
Z_51
R€adoutOnlOtrTiming.......Z-S1
Character
Scan ...................
7-Sj
CharacterGenerator
Timing
.............
z-54
DotDefay
.....-..2-54
lnstrument
Bus Interface.........7-56
ControlPort.........................
7-56
Address/Data
Port ...,...,......
T-Sz
Frequency
Dot Marker.,...........
7_57
FREQUENCY
CONTROL
sEcTtoN
.. 7_60
Sweep
..................
7-60
SpanAttenuator.......................
Z-60
CenterFrequency
Control........7-60
1st LO Driver...........................
7-60
preselector
Driver....................
Z_60
swEEP
.....................
7-60
DigitalControt
......7_61
SweepGenerator.....................
7_62
TriggerCircuits
....7-62
SweepOutputCircuits.............
7_62
MarkerDAC.............................
7-63
SweepControl
.....Z_69
TriggerControl..................;.....
Z-69
SweepHoldoff
.....7-64
Interface
Circuits.....................
7_64
spAN ATTENUATOR
...................
7-65
DigitalControl
......7-65
lnputSection
........7_65
Digital-to-Analog
Converter..... 7_65
DecadeAttenuator
...................
7_66

Page
lst LO DRIVER
.........7-67
DigitalControf
......7-6g
InputSwitching........................
7-69
OscillatorFilter
SwitchDriver
.......7-69
Summing
Amptifier
...................
7-69
OscillatorDriver
... 7-69
Reference
Suppty....................
Z-69
MixerBiasDriver.....................
7-69
Programmable
Bias .................
7-69
PRESELECTOR
DRTVER
..............
7-69
DigitafControlCircuits.............
7-70
OscillatorVoltageProcessor... 7-lO
lF Offset
...............7-21
Summing
Amplifi
er ...................
7 -71
Trackingand
ShaperCircuits
....7-71
CurrentDriver
......Z-72
Preselector
SwitchDriver.,......7-22
CENTERFREQUENCY
CoNTROL
-................7-72
Operating
Modes.....................
7-72
DigitalControl
......7-73
StorageRegisters..,..,.........
7-74
Digital-to-Analog
Converters
.......7-75
Track-and-Hold
Amplifier.........7-75
Write-Back
Circuit........,...........
7-76
-1 0 V Reference
Buffer.........
..7-76
and PHASELOCK
COUNTER
sEcTroN
...7-77
FUNCTIONAL
DESCRIPTION
.......7-77
PhaseLock Assembly.............
7-77
Frequency
7-78
Gontrol...................
Controllingthe
OscillatorFrequency......,.,.,
7 -78
Counting
7-78
the lF ....................
HARMONIC
MIXER
..7.78
AUXILIARY
..........7-79
SYNTHESIZER
BOARD
COUNTER
.,,7.82
7-82
AddressDecoder.....................
ServiceRequestCircuits.........7-82
DataBuffers
.........7-82
InputAmplifiersand
Multiplexer
...........
7-83
+2n Gounter
.........7.83
21-bitCounter..........................
7-83
PHASELOCKSYNTHESIZER
...,..7.83
Synthesizer
..........7-83
PhaseLock ..............................
7-84
7-84
OffsetMixer ........................
7-85
ErrorAmplifier.....................
ControlledOscillator............
7-86
StrobeDriverCircuit............
7-86

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4944/494APServlce Vot. 1

I

TABLE OF CONTENTS(Cont.)
Page

Page

Section7 THEORYOF OPERATTON
(Conr)
DtctTALCONTROLSECTTON
..........7_88
Microcomputer.............................
7-gg
Processor
.............
7-gg
Microprocessor
...................
7-88
Cfock.........
......7-92
Microcomputer
Bus ........,....
T-92
AddressDecoder................
Z-92
Timer.........
......7-gz
PIA and lnstrumentBus ......7-92
DMAController.............
......7 -gz
InterruptProcessing...........:
7-93
Memory
.................2-94
AddressDecoders..............
7-94
RAM ..........
......7-94
Options
.............
7-95
ROM ..........
......7-96
ROM Banksand GptB .............
7-96
AddressDecoder................
7-96
BankSelector......................
7-96
BankROMs
.....7-96
GPIBSwitches...............,....
7-97
GPfA..........
......7-97
AccessorissInterface.......,.,....
Z-gT
Frontpanel
..........7_97
Pot€ntiometers
....................
7-98
output Mode shift
R€gistersand LEDs ............
7-98
Processor
...,....7-98
Scanningthe Keyboard.......7-98
Scanningthe FREQUENCY
ControlCoder
.. 7-gg
Outputtingthe
CorrectCode .......................
7-99
Software
..........7-gg
MainScanRoutine..............
7-99
KeyboardCheck
Subroutine
.......7-100
FrequencyCoder
Subroutine
Check................
7-100
OutputSubroutine...............
7-100

,

POWERSUPPLY
..........7-103
PrimaryCircuits
........7-103
Line InputCircuits....................
7-103
Invert€rCircuit
..... 7-103
Multivibrator
.... 7-103
RampGenerator..................
7-l 04
PrimaryRegulator...............
7-104
InverterLogic ......................
7-104
InverterDriver.............,.......
7-105
OutputStage.............,.........
7-105
Soft Start and Primary
Over-Current
Circuits ......"...7-105
Secondary&
Fan DriveCircuits
.....7-106
Rectifier-FilterCircuits..................
7-106
*5V Voltage
ReferenceSupply
RegulatorCircuits
.....7-106
+5V Over-Voltage
ProtectionCircuit
......7-106
Fan DriveCircuit
-......7-107
Sectlon8 OPTIONS
OptionsA1-A5 PowerCordOptions .... 8-1
OptionBl ServiceManuals...................
8-1
OptionsMl-MS ExtendedService
and WanantyOptions
........8-1
Option07 75O Input..............................
8-2
Option 08 Delet€ External
MixerInput
....8-2
Options 21 and 22
Waveguide
Mixers
.............
8-g
Option39 AlternateBattery...................
84
Option41 DigitalRadio .........................
8-4
Option42110 MHz lF Output................
8-4
...........
Option45 MATECO
8-4
Option52 North American220V ............8-4
AppendlxA

GLOSSARY
........A.1
GENERALTERMS
FREQUENCYTERMS
... A-2
..... A-2
AMPLITUDETERMS
DIGITAL STORAGETERMS ..-..........A-3
WAVEFORMMARKERTERMS ........A-3

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494A/{94APServiceVot.1

TABLEOF CONTENTS(Cont.)

VOLUME2
Sec|ion9
Section10

REPLACEABLE
ELECTRICAL
PARTS
DTAGRAMS

Section1.I

REPLACEABLE
MECHANICAL
PARTS

I

494A/494APServlce Vol. 1

LIST OF ILLUSTRATIONS
page

Figure

The 494APSpectrumAnalyzer....................
xvi
2-1

Dimensions.

3-1

Locationof input power selectorswitch
and finefuse..._.......
.....,..,.........9-2

4-1
4-2

....,....,..2-12

Crt displayat initialpower-up.......................
4-4
Typicaldisplayof catibrator
signalin Max SpanlDiv................................
4-5
4-3 Test equipmentsetuplor checking
centerfrequencyaccuracy.
.......4-g
44
Centerfrequencydrift with
the 1st LO tocked.
....................4-9
4-5 Typicaldisplayfor measuring
r e s i d u aFl M . . . . . . . . . . . . .
..................4-10
4-6
Typicalmarkerdisplayfor
measuringSpan/Divaccuracy......................
4-11
4-7 Test equipmentsetupfor checking
frequencySpan/Divand sweep
Time/Divaccuracy.
....................
4-13
Typicaldisplayfor measuring
4-8
Time/Divaccuracy.
....................
4-14
4-9
Typicaldisplayfor measuring
bandwidthand shapefactor.
.....4-14
4-10 Typicaldisplayfor measuring
noisesidebands.
...........
............
4-15
4-1'l Test equipments€tuptor
measuring0.01GHzto 21 GHz
frequency
response.
..................
4-17
4-12 Test equipmentsetupfor
measuring
10 kHzto l0 MHz
frequency
response.
..................
4-19
4-13 Test equipmentsetupfor checking
dynamicrangeand accuracy,and
preselector
rejection.
................
4-19
4-14 RF attenuatortest equipm€ntsetup.............4-21
4-15 RF attenuatortest equipmentsetup
lor 50-60 dB step.
.........,.........4-24
4-16 . Test equipmentsetupfor checking
intermodulation
distortion
....,,,....4-28
products
4-17 fntermodulation
............4-29
4-1I Test equipmentsetupfor checking
harmonicdistortion.
..............,...
4-90
4-19 Test equipmentsetupfor checking1 dB
inputcompression
point...........................,...
4-31
4-20 T€st equipmentsetupfor checking
internaltriggercharacteristics.
..............
......-4-92
4-21 Externalvideo selectpins and
MARKERIVIDEOinput...........
.. 4-30
4-22 Test equipmentsetupfor checking
externaltriggeringand horizontal
inputcharacteristics.
.................
4-33
x

Figure

Page

4-23 Test oscilloscopedisplayof VERT
outputwith a full screendisplay
on the SpectrumAnalyzer.
.......4-34
4-24 Equipmentsetupfor checking
Option07 frequencyresponse
from 0.01GHzto 1 GHz.
..........4-35
4-25 Equipmentsetupfor checking
Option 07 frequencyresponse
from5 MHzto 10 MHz.
............
4€6
4-26 Test equipmentsetupfor checking
Option41 Span/Divaccuracy.
.. 4-37
4-27 Test equipmentsetupfor checking
Option42 frequencycharacteristics.
4-38
............
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12
5-13
5-14
5-15
5-16
5-17
5-18
5-19
5-20

Low voltagepower
supplyadiustmentsi
.....................................
5-4
Crt displayadjustmentand
test pointlocations.
..................
5-5
Adjustmentand test point
locationson HighVoltagemodule................
5-6
Test equiprnentsetup for
adjustingthe Deflection
Amplifier.................
5-7
Test pointson the CRT
Readoutboard.
.....5-7
DeflectionAmptifiertest points
andadjustments.
............
..........
5-8
Digitalstorageadjustment
.........,....
5-9
locations.
Test equipmentsetupfor
............
5-9
adjustingsweeptiming.
Sweepboardtimingadjustment
andtestpointlocations.
...............................
5-10
Frequencycontrolsystemtest
pointand adjustmentlocations....................
5-11
P3035on the VideoProcessorboard. .........5-12
Test equipmentsetup for adjusting
.....................
5-12
the LogAmplifier.
Log and VideoAmplifiertest point
...........5-13
and adjustment
locations
Test equipmentsetup for adjusting
5-14
the Variabl€Resolutionmodule...........,.......,
Adjustmentson the rear of the
.....5-15
VariableResolution
module.
5-16
100kHzover10 kHz filterresponse............
Adjustmentson the tront of the
.....5-18
VariableResolution
module.
on the 10 Hzl'|00Hz
Adjustments
5-18
...........................
Bandpass
FilterAssembly.
10 kHz,100kHz,and
5-1I
1 MHzfilterresponse.....,.............................
lF gaintest setup,and adiustment
..........5-21
and connectorlocations.

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o

LIST OF ILLUSTRATIONS
(Conr.)

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Figure

6-1
6--?
9-9
9-1
9-9
6-6
6-7
9-9
6-9
6-10
6-11
_
6-12
6-13
6-14
6-15
6-16
6-17

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6-19

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5-21 PreseleetorDriver
adjustment
setup..........
............5_22
5-22 PreselectorDrivertest point
and adjustment
locations
...........
S_Zg
5-23 Test equipmentsetupfor band
levelingadjustment.
,.................S-24
5-24 Band levelingadjustmentand
gaindiodelocations.
...-.....,,,....5-24
5-25 Test equipments€tupfor adjusting
the phaseLockassembly............................
5_26
5-26 PhaseLock assemblyadjustment
and test pointlocations..............,.................
S_27
5-27 Option42 adjustmenttest
equipment
setup..........
.............
S_g0

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6-21
6-22

construction
details.
..................
6-gg
6-23 2182MHz2nd LO PhaseLock
adjustmentsetup.........
..............
6_39
6-24 Tuneand SweepRange
adjustments
............641
6-25 3rd Convertertest points
and adjustments.
..........
............
6_43
6-26 FirstConvertersetupfor adjustment...........6-45
6-27 1st LO Driverboard adjustment
andtest pointlocations.
...............................
646
6-28 Baselinelevelingtest setup,
.....647
6-29 Typicalbaselinelevelingresponse..............,
649
6-30 Baselinelevelingadjument
andtest pointlocations.
...............................
649
6-31 Typicalbaseline
compensation
response.
...........
6_49
Surface-mounted
components
6€2 A15throughA12 in
leadconfiguration.
....................
6_1
6
microcomputer
test mode.
.......6-52
Diodepotaritymarkings.
..........6-18
6-33 Four main bloackselectoutputs
Multipin(harmonica)
connectors..................
6_1g
of addressdecoderU2045.
......6_59
Servicingthe vR assembty.
......6_19
6-34 RAM selectoutput
Topdeckassembties.
.............................,-...6-20
in relationto O'XXX.
...................
6-53
RF deckassemblies.
................
6_2.1
6-35 RAM setectoutput
Removingthe 1st LO
in relationtoTffi.
...................6-5g
-UOand
Interfaceboard.
..... 6-25
6-36
S1050setecttines
Fanassembtymounting.
..........6-26
in relationto oxxx.
...................
6-53
110 MHz lF returnloss
6-37 ChipselectsY0, Y1, yS,
adiustment
setup..........
............6-2T
and Y7 in retationtoT/O-.
...........6-54
110MHztF test points
6-38 ChipselectsY2, Y4, and y6
and adjustments.
..........
............
6-2g
in retationtd:IIO.
.. 6-54
2072MHz Converterbias
6-39 Instrumentbus check.
..............
6-55
adjustments.
..........6_2g
829 MHz LO test points
andconnectors.
...........
............
6-29
7-1
Crosssectionof
829 MHz amptifiertest
a four-cavity
filter. ..........
..........7-g
iack andjumper.
.... 6_30
7-2 Equivalent
circuitof
829 MHz filtertest
the four-cavity
filter.
..................
7-g
equipment
setup..........
.............
6-gi
7-3 Simplified
diplexerdiagram.
.....7-19
829 MHz Converterfilter
7-4
Equivalentac circuitof
tunetabs.
.............
6-32
an 829MHz amplifier...................................
7-14
Correctresponsefor 929 MHz
7-S Equivalentdc circuitof
first and secondresonators.
.... 6-92
an 829MHz amplifier...........................,.......
7-'t4
Correctresponsefor 829 MHz
7-6
Blockdiagrarnof the phaselock loop
thirdand fourthresonators..........................
6_9g
in the 829 MHz 2ndConverter.....................7-16
2182MHz2nd LO frequency
7-7 Bridged'T"attenuator
accuracytest setup.........
.........6_94
equivalent
circuit.
.....................
7-lg
2182MHz phase Locked2nd LO
7-8 Blockdiagramof a three
adjustment
setup..........
............
6_96
stagelog amplifier.
....................
7-29
16-20 MHz phaseLock circuittest
7-g Log amplifiergaincurve
pointand component
locations.
................,..
6_32
showingbreakpoints
.................
7-90
2182MHz2nd LO adjustment
7-14 Curveshowingend-of-range
for a log amplifier.
....................
7-gO
Coaxialtest probe
7-11 Simplified
detectorcircuit.
........,2-gz
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494A/494APServlce Vot. 1

LIST OF ILLUSTRATIONS
(Cont.)
Figure

Page

7-12 Selectionof disptayposition
on the log scale.
.....7-94
7-13 Functionaldiagramshowingthe
sp€ctrum analyzerand 1405 TV
SidebandAdaptersystem.
........7€6
7-14 Simplifieddiagramof
videofilter.
.............
Z-39
7-15 Verticalcontrol lC
bfockdiagram...............
.............241
7-16 Horizontalcontrollc
bfockdiagram...............
.............145
7-17 Blockdiagramof
crt readout.
.............7-52
7-18 Characteron/offtiming
...............
7-53
7-1I Characterscan..,........
...............
7-54
7-20 Charactergenerator
blockdiagram................
............
7-5S
7-21 Charactertimingdiagram.
.........7-56
7-22 Frequencydot markersimplified
diagramwith timingwaveforms....................
7-Sg

Figure
7-23

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Page

7-35

Simplifieddigital-to-analog
converter.
....-........
7-66
Simplifiedspandecadeattanuator...............
7-67
DACvariancegraph.
................7-73
Simpfffiedtune voltageconverter.................
7-74
Simplifiedschematicof harmonicmixer.......7-79
Block diagramof a basic synthesizer..........7-80
Basic block diagramof a -rN synthesizer
with a variablemodulusprescaler................
7-80
Systemmemorymap. ..........
.... 7-89
l/O addressspac€.
...................7-90
PIA and Timeraddressmap.
.... 7,91
Optionsswitchbank
on the Memoryboard.
..............
7-95
Primary regulator
input/outputwaveforms.
...........7-104
Timingwaveformsfor soft-startcircuit. .......7-105

8-1

Int€rnational
Powercord options.................
8-1

7-24
7-25
7-26
7-27
7-28
7-29
7€0
7-31
7-32
7€3
7-34

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494A1494AP
ServiceVot.1

LIST OF TABLES
Table

page

Table

1-1

TEKTRON'X
WAVEGUIDE
MIXERS..............
1-3

6-6

2-1

FREQUENCY
RELATED
CHARACTERTSTTCS
..................
2-1
AMPLITUDERELATED
CHARACTERTSTTCS
.................
2_6
INPUTSIGNAL
CHARACTERTSTTCS
..................
2_11
OUTPUTSIGNAL
CHARACTERTSTICS
........,.........
2_13
GENERALCHARACTERTSTTCS
...................
2_15
POWERREQUTREMENTS
............................
2_15
ENVIRONMENTAL
CHARACTERTSTTCS
........,.........
2-16
pHySIcALCHARACTERIST|CS
..................2-17

6-7

2-2
2-3
24
2-5
2-6
2.7
2-8
4.1
4.2
4-3
44
4.5
4.6
4-7
4-8

EQUIPMENT
REQUIRED
..........4-2
CENTERFREQUENCY
ACCURACY
CHECKpOtNTS(1stLO UNLOCKED)
.........4-a
SPAN/D|VVERSUSTIME
MARKERSFORSPAN/DIV
ACCURACY
CHECK
.................4-11
FREQUENCY
RESPONSE
CHECK
SETTINGS
FORBANDS3_5 ..........
.,..........
4-17
OTO 30 dB RF ATTENUATOR
TESTSETT|NGS
...........
...........
4-22
30 TO 60 dB RF ATTENUATOR
TESTSETTINGS
..4-2g
CORRECTION
FACTORTO
DETERMINE
TRUESIGNALLEVEL.............
4-25
SENSlTlury
.........4_27

5-1
5-2
5-3
5-4

EQUIPMENT
REQUIRED
..........5-2
powER suppLy ToLERANCES.................
5_3
FTLTER
ADJUSTMENTS
...............................
5-1I
EXTMIXERBANDLEVELING
ADJUSTMENTS
.............
..........
5-25

6-1

RELATIVESUSCEPTIBILITY
TO
STATTC
DTSCHARGE
DAMAGE...................
6_1
SERVICE
KITSANDTOOLS
.... 6-3
POWERSUPPLYRANGES
......6.8
SELECTED
COMPONENTS
..........................
6-16
SERVICING
TOOLSFORBOARDS
WITHSURFACEMOUNTED
C O M P O N E N T. .S. . . . . . . . . . .
...........6_17

6-2
6-3
64
6-5

6-8
6-9
6-10
6-11
6-12
6.13
6.14
6-15
7-1
7-2
7.3
7-4
7.5
7.6
7-7
7-8
7-9
7-1O
7.1'I
7-12
7-13
7.'14
7-15
7-16
7-17
7-18
7-19
7-20
7-21
7-22
7-23
7-24

page
EQUIPMENT
REQUIRED
FORRETURN
LOSSADJUSTMENT
...............6-27
EOUIPMENT
REQUIRED
FOR
2ndLO CALIBRATION
.................................
6-94
EQUIPMENT
REQUIRED
FOR
CALIBRATING
THE16-20 MHz
PHASELOCKCtRCUtr................................
6-39
EQUIPMENT
FORADJUSTING
FIRSTCONVERTER
BIASAND
STARTSPURAMPLITUDE
......645
OPTIONSWTTCH
SETTTNGS
...6-50
RAMTEST
...........6-51
ROMTEST
...........
6-51
INSTRUMENT
BUS REGISTERS
..................
6-57
AUXILIARY
SYNTHESIZER
VALUES
AS A FUNCTTON
OF N ANDA .....................
6-62
FRONT-PANEL
REGrSTERS
........................
6-62
zNDCONVERTER
tF SELECTTON
...............7_7
SWITCHANDAMPLIFIER
SELECTION
..........7-1s
BANDWIDTH
SELECTION
........7.23
GAINSTEPCOMBTNATTONS.......................7-27
PROGRESSION
OF
cAlN REDUCTTON
..........
.........7_30
FILTERCOMPONENT
COMBINATIONS
......7.38
RF TNTERFACE
LTNES
.............7-49
U2039TRUTHTABLE
..............
7-49
CONTROL
PORT
..7-57
ADDRESS/DATA
PORT
...........7-57
SWEEPRATESELECTION
CODES.............7-61
TRtccERSELECTTON
MODES...............,...7-62
SWEEPHOLDOFF
SELECT|ON
....,..............7-62
CALIBRATION
CONTROL
SELECTTON
CODES
.................
7-66
AfiENUATIONSELECTION
CODES...........
7.67
u4017oUTPUTLTNES
.............
7-68
u5031oUTPUTLrNES
.............7-70
PRESELECTOR
FREQUENCY
BANDS..,...,.7-71
ADDRESS
70 FORMATS
..............................
7-75
DACTUNINGCODES
..............7-75
u2025oUTPUTLTNES
.............
7-8s
POLLBITS
...........
7-93
ROMBANKSELECTTON
DATA...................
7-97
FRONTPANELSW'TCHMATRIX
CoDE/FUNCT|ON
TABLE
........7-101

xltl

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{944/494AP Service Vot. 1

LIST OF TABLES(Cont.)

)
Table
8.1
8.2
8.3

page
EXTENDEDSERVICEAND
WARRANWOPT|ONS
.............8_1
OPNON07 ALTERNATE
spEctFtcATloNs
...................
8-2
OPTIONS21 AND 22 WAVEGUIDE
MtxERSCHARACTERTSTTCS
......................
8_3

page

Table
84
8-5

OPTION41 ALTERNATE
SPECTF|CAT|ONS
.........
OPTION42 ELECTRICAL
CHARACTERTSTTCS

............8-4
..................
8-5

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494A|494APServiceVot. 1

I

SERVICINGSAFETYSUMMARY

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FORQUALIFIED
SERVICEPERSONNEL
ONLY
Do Not ServiceAlone
Do not perform internalserviceor adjustmentof this
product unless anoth€r person capable of rendering
first aid and resuscitation
is present.
Do Not Wear Jewelry
Removejewelry prior to servicing. Rings, neck.
laces, and other metallicobjectscould come into con_
tact with dangerousvoltagesand currents.
Use Gare When Servicing With power On
Dangerousvoltages exist at several points in this
product. To avoid personal injury, do not touch
exposed connectionsand componentswhile power is
on.
Djsconnect power before removing protective
panels,soldering,or replacing
components.
Power Source
This product is intendedto operate from a power
source that will not apply more than 250 volts rms
betweenthe supplyconductorand ground. A protective
ground connectionby way of the groundingconductor
in the power cord is essentialfor safe operation.
X-Radiation
X-ray emissiongeneratedwithin this instrumenthas
been sufficientlyshielded. Do not modify or otherwis€
alter the highvoltagecircuitryor the crt enclosure.

TERMS
In This Manual
CAUTION statements identify conditions or prac_
tices that could result in damage to the equipment or
other property.
WARNING statements identify conditions or prac_
tices that could result in personal injury or loss of liie.

As Markedon Equipment
CAUTIONindicatesa personalinjury hazardnot
imm€diately accessible as one reads the marking, or a
hazard to property including the equipm€nt itself.

DANGER indicates a personal injury hazard immediatefy accessible as one reads the marking,

SYMBOLS
In This Manual
This symbol indacateswhere appticablecautionaryor other informationasto be tound.

As Markedon Equipment

t

- Highvortage.
DANGER

e

Protectiveground(earth)terminal-

A

ATTENTION- Referto manual.

o

Referto manual.

Groundingthe Product
This productis groundedthroughthe grounding

conductorof the power cord. To avoidelectricalshock.
plug the power cord into a properly wired receptacle
before connectingto the product input or output terminals. A protectiveground conn€ctionby way of the
groundingconductorin the power cord is essentialfor
safe operation.
Danger Arising From Loss of Ground
Upon loss of the protective ground connection,all
accessibleconductiveparts (includingknobs and controls that may appearto be insulating)
can renderan
electricshock.
Use the Proper Power Cord
Use only the power cord and connectorspecifiedfor
your product.
Useonlya powercord that is in goodcondition.
For detailedinformationon power cords and connectorssee Section1.

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Sedon 1 -

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Product Description

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The 494A and the 494Ap (programmabte)instru_
ments are high performance,compict, portablespectrum analyzers. Microcomputercontrol of most functions simplifiesand enhancesoperation.

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4g4[l494Ap Servlce,Vol. 1

GENERALINFORMATION

The analyzersfeature:
. singleand delta markermodes
o synthesizerfreguencyaccuracy
o precisionsignalcounting
r preciseamplitudemeasurement
o digitatstoragedisptay
o internal memory for front-panel settings
and
displays
o helpand diagnosticcrt messages
. keypadentryand menuselections
r abilityto ptot the disptay.readout,and graticule
o abilityto hold g personalizedmacrosin memory
o 10 Hz to 3 MHz resolution
o multiband
sweepcapability
, The frequencyrange is 10kHz to 21 GHz with the
internalmixer, extendingup to 925 GHz with ext€rnal
waveguidemixers. Resolutionbandwidthis 10 Hz to
3 MHz. Digital storage provides flicker-freedisplays
plus functionsto compare and subtract displays,anO
save maximumvalues. In addition,up to nine separate
displayswith their readouts can be stored in batterypowered non-volatilememory, then later recalled for
additionalanalysisand comparison.Up to ten different
front-panelcontrol setups can also be stored for future
recall. The signalcountingf€atureallows the spectrum
analyzer-toselectivelycount a particularsignal out of
severalthat may be presentat its input.
Select center frequency either by the front-panel
tuning knob or by the Data Entry keypad. When using
the keypad,it is not necessaryto alter the Span/Dii
setting regardless of the frequency selected. oiher
parameters,such as vertical display and reference
level,are also keypadselectable.

Marker functions provide direct readout of frequency and amplitudeat any point along any displayed
trace. Relative(delta)frequencyand amplitudeinformation-betwe€nany two points along any displayedtrace
is also available.The tuning knob moves ihe-markers,
and it can also move the display with a stationaryfrequency marker. lt is possible to fix the marker to a
position on the display and use th€ knob to move both
the spectrumand the marker at the same time. Refer
to using the MarkersFeaturein section 6 of the opera_
tors Manual.
The programmable(p) version of the instrument
adds remote controlcapabilitiesto the manualinstru_
ment features. The front-panel controls (except those
intended exclusivelyfor local use, such ai lrufLruSlW1
can be remotelyoperatedthrough the GplB port. Thia
allows the spectrumanalyzerto b€ used with a variety
of systemsand controllers.Refer to the programmers
Manualfor additionalinformation.
The programmable instrument also adds the
macroinstructions(macros) feature. The,nstrument
memory has 8K bytes set aside for the constructionof
made-to-ordermacros. The macro menu can hold the
titles of eight macrosfor easy access. Specificmacro
informationis locatedin the programmersManuat.
Conformance to fndustry Standards
This spectrumanalyzercomplies with the following
Industry Safety Standards and Regulatory Requirements:
Safety
csA - ElectrlcalBulletin
FM - ElectricatUtitizationStandardCtass3g20
ANSI C39.5- SafetyRequirementsfor Etectrical
and ElectronicMeasuringand ControllingInstrumentation.
IEC 348 (2nd edlton) - Safety Requirements
for
ElectronicMeasuringApparatus,
Regulatory
VDE 0871 Class B
Regutationsfor RFI
Suppressionof High Frequency Apparatusand
Installations.
Product Service
To assure adequateproduct service and maintenance for our instruments,Tektronix has established
Field Offices and Service Centers at strategic points

1-1

Generaf Infornation -

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4g4[l4g4Ap Service, Vol. 1

throughoutthe UnitedStatEsand in countrieswherEour
products are sold. Several types of maintenanceor
repairagreementsare available.
For example,for a fixed fee, a maintenanceagreement program provides maintenanceand recalibration
on a regular basis. Tektronix will remind you when a
product is due for r€calibrationand performthe service
within a specifi€dtime.

Compartmentsare enclosed on both sides by metal
plat€s and interconn€ctions
betweencompartmentsare
made by feedthroughterminalsrather than cables. lf
the compartmentsare opened,be sure that the shields
and coversare properlyreinstalledbeforeoperating.
Installation and Preparation for Use

. Tektronix emergency repair service provides
immediate service when the instrument is urgently
needed.

The Installation section of the manual provides
unpacking information and the procedures to prepare
the instrum€ntfor use. lt also includes repackaging
information.

Contact your local Tektronix SeMce Center,
representativeror sales engineerfor details regarding
productservice.

Changing Power lnput Range

I nstrument Construction

The procedurefor changingthe input voltage range
is describedin the Installationsection. Detailson how
to changethe line fuse are also given.

Modularconstructionprovides ready accessto the
major circuits. Circuit boards containingsensitivecir_
cuits are either mounted on metal castings,each of
which providesshieldingbetweenadjacentmodules,or
they ars mountedwithin honeycomb-likecastings,with
feedthroughconnectorsthrough the compartmentwall.
All boards and assembliesplug onto a commoninterconnect board. Most adjustm€nlsand test points are
aecessiblewhile the anstrumentis operationaland with
the modulesor assembliessecuredin their normalposi_
tion.
Extendersare availablein an optional ServiceKit
(see Maintenancesection under Service Fixtures and
Tools for Maintenance).Any module or board can be
removedwithout disturbingthe structuralor functional
integrity of the other modules. The extendersallow
most circuit board assemblies to function in an
extended position for service or adjustment. The circuit
boards mountedon the metal casting can be removed
by removing the securing screws. All other circuit
boards (which should require minimal service) are
accessibleby removinga cover plateover the assembly
or module.

Disassemblyof some modulesmay require
special tools and procedures. These pro_
cedur€s are located in the Maintenance
section.
Circuits are isolated in shielded compartmentsto
obtain and maintainth€ frequencystability,sensitivity,
and EMI characteristics.While shieldinghetpsensuie
spurious-freeresponse,the closeness of the circuits
minimizeslosses and interactionswith other functions.
1-2

The power cord that is suppliedwith the instrument
and the instrumentpower voltagerequirementsdepend
on the availablepow€r source (see Specificationsection). Powercord optionsare describedin the Options
section.
Replacing Fuses
Referto the Installationsectionfor line fuse replacement and the Maintenancesection for replacing the
power supplyfuses.
Selected Components
Some componentsare selected,matched,or preconditionedto meet Tektronix specifications.These
componentsare shown in the parts list and may carry a
Tektronix Part Number under the Mfr. Part Number
column.
Selectedvalue componentsare identifiedon the circuit diagramand in the parts list as a 'SEL" value. The
componentd€scription lists either the nominal value or
a range of values. Selectioncriteriais includedin the
Maintenance section. Selection procedures are
includedin the AdjustmentProcedureor Maintenance
sectionsof the manualas needed.
Assembly and Circuit Numbering
Each assembly and subassembly are assigned
assembly numbers. Generally,each component is
assigneda circuit number accordingto its geographic
locationwithin an assembly.The ReplaceableElectrical
Parts list prefixes these circuit numbers with the
correspondingassemblyand subassemblynumbers.

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GenerafInformation -

EXAMpLE: R2090 on
becomss420R2090.

assembly A2O

4g4Ll4g4ApService,Vol. 1

I cord clamp
. Crt light filters; 2 - one each arnberand grey

EXAMpLE: U1044 on subassemblvAl of
assembly A36 is found in the ejectrical
parts tist as A3641U.t044.

o Crt meshfilter
. R€arConnectorShield

Firmware Version and Eror Message Readout

o 494A1494AP
Operators Manual

This feature of the spectrum analyzer provides
readoutthat identifiesth€ versionof firmwareinstalled.
The readoutis momentarilydisplayedwhen the power
is turned on. Ail front-panettights ivitt temporarilyflash
on when the power is first turned on. In addition,
programmableinstrumentwill flash that informationthe
and
the GplB address and macro status when RESETTO
LOCALis pressed.

. 494APProgramrnersManual;494ApOnly
Table 1-1 lists the Tektronixwaveguidemixers that
are availableas optionalaccessories.
Tabte 1-l
TEKTRONIX WAVEGUIDE MIXERS

Mlxer

lf the spectrumanalyzerfaits to compteteany routine or function, an error message will flash on th€
screenexplainingthe failure.
4

Accessories
The ReplaceableMechanicalparts list in the Service
Manual,Volume2, containsthe part numbers,descriptions, and ordering informationfor all standard and
optionalaccessoriesoffered for the spectrumanalyzer
at thistime.
The followinglist includesall standardaccessories
currently shipped with each instrurnent.Refer to the
Optionssectionof this rnanualfor alternateinformation.

490U
WM 49OV
wM 490E
490W
490F

wM4

1 8t o
26.5to
33 to 50
40 to

1 1 0G H z
GHz

| 10 to 170GHz
ro 220GHz

WM 490GOption01

. 50 O coaxialcable;N to N connector,72 inch

Options

. 50 O coaxialcable;bnc to bnc connector,1g inch

The Options section of this Manualcontainsinformation on all of the options currentlyavailablefor the
spectrumanalyzer.

. Adapter;N maleto bnc female
o 44 fast-blowfusesl; 2 each
o Powercordt

It the insttument It wired lor 22o'24o v ope.ation (optiona.Al,
*ilh rtandsrd powe. cord), 2A medium_blow turerlr!
used.

A2, 43, 44, A5) or it opfion s2 lr Inrralled (North Arnerlc.n conliguration lot zloy

1-3

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Section2 -

494A1494Ap
Service,Vol. 1

SPECIFICATION
This section includesthe eiectrical,physical,and
environmentalcharacteristicsof this insirument.Any
instrumentspecificationchanges due to options ari
listedin the Optionssectionof this manual.

ELECTRICAL
CHARACTERI
STICS

The instrumentperformsan internalcalibrationcheck
each tirne poweris turnedon. This checkverifiesthat the
instrumentfrequencyand amplitudeperformanceis as
specified.An InstrumentCheck Out procedure,which
requireslittleexternaltest equipmentor technicalexpertise, is providedin Section5 of the OperatorsManual.
This procedurewill satisfy most incominginspections
and will helpfamiliarizeyou with the instrurnent
capabilities.

- The followingtablesof electricalcharacteristics
and
featuresapplyto the spectrumanalyzeraftera 3O_minute
warm up and after doing the front-panelCAL adjust_
Verification of Tolerance Values
ments,exceptas noted.The performanceRequirement
columndefinessomecharacteristics
in quantitativeterms
Performcompliancetests of specifiedlimits,listedin
and in limit form. The Supplemental
lnformationcolumn
the PerformanceRequirernentcolurnn,only after a 30_
explains performancerequirementsor provides performinutewarm-uptime (exceptas noted)and attera doing
mance information.Statementsin this column are
not
the front-panel
CAL procedure.Use measurement
instruconsideredto be guaranteedperformanceand are not
mentsthat do not affectthe valuesmeasured.Measure_
ordinarilysupportedby a performance
checkprocedure.
ment toleranceof test equipmentshould be negligible
P.rocedures
to verify performancerequirementsare pro_
when comparedto the specifiedtolerance.lf the toler_
videdin the Performance
Checkportionof thrsmanual.
ance is not negligible,add the error of the measuring
deviceto the specifiedtolerance.

Table 2-1
FREOUENCYRELATEDCHARACTERISTICS
Characteristic

CenterFrequency
OperatingRange
InternalMixer

PerformanceRequirement

Supplemental Intormation

10 kHz-21 GHz
Tuned by the CENTER/MARKER
FREQUENCY control or the DATA
ENTRY pushbuttons

External Mixers (optional)

Accuracy (after front-panelCAL
has beenperformed)

10 kHz-325GHz
Center Frequency Accuracy
specifiedby two characteristics:

is

. initial accuracy (firmwarecorrected)
o center frequency drift during the sweep
lnitial (start of sweep)
B a n d s 1 & 5 - 1 2 w i t h *{2Oo/oD+ (CF x REF) + 15N kHz)
Refer to lF Frequency, LO Range,
SPANiDIV >200 kHz, and
and Harmonic Number specification
Where:
Bands 2-4 with SPAN/D|V
later in this table for the N value
:
D
S
P
A
N
/
D
|
V
o
r
R
E
S
O
L
U
T
T
O
N
>100 kHz
BANDWIDTH, whichever is Allow a settlingtime of one second
(1st LO unlocked)
greater
for each GHz change in CF within a
band. In bands 4-'12, dividethe CF
CF - Center Frequency
change by N.
REF
Reference Frequency
Error
N : H a r m o n i cN u m b e r

2-1

Specffication -

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494A1494ApService, Vol. 1

Table 2.1 (Continued)
FREQUENCYRELATEDCHARACTERISTICS

Characteristic
InitialAccuracy(continued)
Bands1&
5-12 with
SPAN/DIV(200 kHz, and
Bands2-4 with SpAN/DlV
(100 kHz
(1stLO locked)

PerformanceRequirement
t{20%D + (cF x REF) + (2N +
25)Hz)
Where:
D - SPAN/D|Vor RESOLUTTON
BANDWIDTH, whichever is
greater
CF : CenterFrequency
REF
Reference Frequency
Error
N : HarmonicNumber

Drift

Supplemental Information

Refer to lF Frequency,LO Range,
and HarmonicNumberspecification
laterin this tablefor the N value

With constantambient temperature
and fixed centerfrequency
Correctionwill occur at the end of
the sweepfor sweeptimes >5 s/div
<(25 kHz)Nper minute

After30 minutewarm up
Bands 1 & 5-12 with
SPANiDIV>200 kHz, and
Bands2-4 with SPAN/D|V
> 1 0 0k H z
(1stLO unlocked)
Bands 1 & 5-12 with
SPAN/DIV (200 kHz, and
Bands 2-4 with SPAN/DtV
(100 kHz

<150 Hz per minute

(1st LO locked)

Aftert hourwarmup
Bands 1&
5-12 with
SPAN/DIV>200 kHz, and
Bands2-4 with SpAN/DtV
> 1 0 0k H z
(1stLO unlocked)
Bands1&
5-12 with
SPAN/DIV(200 kHz, and
Bands2-4 with SPANiD|V
(100 kHz

<(5 kHz)Nper minute

(50 Hz per minute

(1stLO locked)
Readout Resolution

SignalCounter
Accuracy(with span to resolution bandwidthratios(10:1)

A t l e a s t1 0 % o f S P A N / D I V
* { ( F x R E F )+ ( 1 0 + 2 N ) H z + l L S D }
Where:
F - Center or Marker Frequency
and LSD
REF
Reference Frequency
Error
N - H a r m o n i cN u m b e r
L S D : L e a s t S i g n i f i c a nD
t igit

Refer to lF Frequency, LO Range,
and Harmonic Number specification
later in this table for the N value
Count at center, marker, or delta
markers

a

a
a
o
o
O
a

o
a

a
O

o

o
o
a
I
o
o
o
o
a
o
o
o
o
I
o
e
o
o
I
o
o
a
a
o
o
o

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Specification-

494Al4g4ApService,Vol. 1

Tabte2-1 (Continued)
FREOUENCY
RELATED
CHARACTERISTICS
Characteristic

SignalCounter(continued)
DeltaFrequency
Accuracy

Sensitivity

tal Inlormation

+tAF. x BEF) + (20 + 4N)Hz+ Refer to lF Frequency,LO Range,
1LSD]
and HarmonicNumber specification

laterin this tablefor the N vatue
Where
AF: DeltaFrequency
REF
Reference Frequency
Error
N : HarmonicNumber
Digit
!9D LeastSignificant
Signal level,at center screenor at
marker, must be 2A dB or rnore
above the average noise level and
within60 dB of the referencelevel.

ReadoutResolution

Selectablefrom Hz to 1 GHz with
 COUNT RESOLUTIONpushbutton.

ReferenceFrequency
Error
AgingRate
ShortTerm

( 1 x 1 9 - s p e rd a y
(7x10-e per week

Firstsix months

(1x10-7 in first six months

After the first six months

(1x.t0-z per year

Accuracy during warmup at
+25oC(30 qlin. after poweron)
Temperature
sensitivity

within 5x10-8 of the frequencyafter
24 hours

R e s i d u aF
l M

Bands1 & 5-12 with SpAN/D|V ((7 kHz)Ntotal excursionin 20
ms
> 200 kHz, and Bands2-4 with
SPAN/DIV
>100 kHz

Within 2x10-8 over the instrument
operatingrange ol -1 SoCto +55"C
(referenced
to +25"C)
Shortterrn,after t hour warm up
Refer to lF Frequency,LO Range,
and HarmonicNumberspecification
laterin this tablefor the N value

B a n d s 1 & 5 - 1 2 w i t h S p A N / D I V {(10+2N)Hz total excursion
in 20 Refer to lF Frequency, LO Range,
(200 kHz, and bands 2-4 with rns
and Harmonic Number specification
S P A N I D | V( 1 0 0 k H z
later in this table for the N value
1st LO lock
Static Resolution Bandwidth (6 dB Within 20/" ot selected
bandwidth
1 0 H z t o 1 M H z i n d e c a d es t e p s ,a n d
down)
MHz
Shape Factor
(150 Hz
Within 20"h, impacted by residual FM
60 dB bandwidth
and drift during sweep time

3 MHz-100Hz

Noise Sidebands

7.5:1or less
At least -70 dBc at an offset of 30 x
the selected bandwidthfor resolution
bandwidthsof 100 Hz and 1O Hz
At least -75 dBc at an offset of 30 x
the selected bandwidth for all other
bandwidths

2-3

Specilication -

494A/494Ap Service, Vot. 1

Table 2-l (Continued)
FREQUENCYRELATEDCHARACTERTSTICS

Characteristic

Performance

uirement

Line-relatedSidebands

SupplementalInf ormation
cally (-55 dBc (47 Hz - 44A Hz)

EffectiveVideo Bandwidth
kHz

3 kHz
300 Hz
30 Hz
3Hz

0.3 Hz
Typically 30 psldivision of pulse
tude

Pulse StretcherFall Time
Marker(s)

When activated, the marker is a
bright dot positioned by the
CENTER/MARKER
FREQUENCY
control or the DATA ENTRY pushbuttons.

Normal
Accuracyand Resolution

ldenticalto centerfrequency

For the active trace

Delta Marker
Accuracy

t1o/o of the tolal span

For the active trace.
5/" at the measurernent on multiband and stored displays
Displays delta time in Zero Span
mooe
AMKR activates a second marker at
the position of the single marker on
the trace. Parenthesisappear on the
marker display line indicatingthat the
delta mode is active. The display
shows the difference in frequency
and amplitude. 1-MKR-2
selects
which marker is tuned.

Resolution
Frequency
Span/Div
OverallRange

MinimumSpan/Div

2-4

At least10/ ot Span/Div
10 Hzldivto 10 GHz/div(in a 1-2-5
sequencewith SPAN/DIVcontrol)or
10 Hzldiv to 15 GHz/div(from the
DATA ENTRY pushbuttons)to two
significant
digits.
10 Hz in all bands

o
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O
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a
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Specification-

Tabte2-1 (Continued)
FREOUENCY
RELATED
CHARACTERISTICS
Characteristic

Frequency
Span/Div(cont)
MultibandMode

o

o
t
o
o
o

o
o
e
o
I
o
I
o
?

Supplemental Intormation

In bands2-5, 
FREQ
STARTSTOPpermitsentryof a start
frequency in one band and a stop
frequencyin anotherband.
Start and stop frequenciesare limited to a singleband in Band 1 and
B a n d s6 - 1 2
Maximumrangeis 1.7-21GHz
The FREQRANGEreadoutdisplays
MULTIBD when in the Muttiband
Mode

MaximumSpan/Div
with SPAN/DtV
Band1 (0-1.8GHz)
Band2 (1.7-5.5GHz)
Band3 (3.0-7.1GHz)
Band4 (5.4-18GHz)
Band5 (15-21GHz)
Band6 (18-27GHz)
Band7 (26-40GHz)
Band8 (33-60GHz)
Band9 (50-90GHz)
Band10 (75-140GHz)
B a n d1 1 ( 1 1 0 * 2 2G
0 Hz)
Band12 (170-325GHz)

O

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o
o
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a
o
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494A1494Ap
Service,Vol. 1

100MHz
200 MHz
200 MHz
'l
GHz
500 MHz
500MHz
1 GHz
2GHz
2 GHz
5 GHz
1 0G H z
1 0G H z

With DATA
ENTRY
1 7 0M H z
370 MHz
400 MHz
1.2GHz
590 MHz
790 MHz
1 . 3G H z
2.6 GHz
3.9 GHz
6.4 GHz
10GHz

ln addition, MAX SPAN sweeps
across an entire band and ZERO
SPAN provides a 0 Hz display. With
ZERO SPAN the horizontal axis is
calibrated in time/div instead of

Accuracy/Linearity

f

Within 5% of the selected span/div, Measured over the center 8 divisions
750 Hzldiv
below 50 Hzldiv, within 10%

Specificationas not applicableto
lF Frequency,
LO Range,
and HarmonicNumber(N)
Bandand Freq Range
1 (0-1.8GHz)
2 (1.7-5.5GHz)
3 (3.0-7.1GHz)
4 (5.4-18GHz)
5 (15-21GHz)
6 (18-27 GHzl
7 (26-40GHz)
I (33-60GHz)
9 (50-90GHz)
10 (75-140GHz)
0 Hz)
1 1( 1 1 0 - 2 2 G
12 (170-325GHz)

iband

LO Range
(MHz)

2072
829
829
829
2072
2072
2072
2072
2072
2072
2072
2072

1t-

1+
33+
6+
10+
10+
15+
23+
37+
56+

2072-3872
2529-6329
2't71-6271
2476-6276
4309-6309
2655-4071
2443-3793
3092-5790
3195-5862
3170-6000
2917-s890
2998-5841

2-5

Specification -

494A,1494ApService, Vol. 1

Table 2-2
AMPLITUDERELATEDCHARACTERISTICS
Characteristic

Performance Requirement

requencyResponse

SupplementalInformation

Measuredwith 10 dB RF attenuation
and peaking optimized for each
centerfrequencysetting(whenapplicable)
Responseis affectedby:
o input VSWR
r harmonicnumber(N)
o gain variation
. mixer

Coaxial (direct)Input

Band and Freq Range
1 (10kHz-l.8 GHz)
2 ( 1 . 7 - 5 . 5G H z )
3 (3.0-7.1 GHz)
4 ( 5 . a - 1 8G H z )
5 (15-21GHz)

Referenced
to 100 MHz

r1.5 dB
*2.5 dB
1 2 . 5d B
a 3 . 5d B
f 5.0dB

i2.5 dB
*3.5 dB
:t3.5 dB
r4.5 dB
:86.5dB

7 (26-a0 GHz)

*2.0 dB
*2.0 dB
+ 2 . 0d B
*2.5 dB

f 6.0 dB
*6.0 dB

8 (33-s0GHz)
(40-60 GHz)
9 (50-90 GHz)
1 0 ( 7 5 - 1 4 0G H z )
1 1 ( 1 1 0 - 2 2 0G H z )
1 2 ( 1 7 0 - 3 2 5G H z )

t

o

o

Refer to the Options section for
alternatespecifications

I

With Tektronix External High
PerformanceWaveguideMixers
Band and Freq Range
6 (18-27GHz)

e
o

Display flatness is typically 1 db
greaterthan frequencyresponse.

Refer to the Options section of this
rnanual for alternate specifications.

About the midpoint between
two extremes

a
o
o
o
a
e
a
o
o

*6.0 dB
*6.0 dB

Typically:h3 dB overany 5 GHz
range
Typically+3 dB overany5 GHz
range
Typically13 dB overany 5 GHz
range
Typically*3 dB overany 5 GHz

o
t

a
o
o
a
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s
a
o
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o
o
o
a
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?

o

o
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a

o

e.
2-6

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Specification_ 494A1494Ap
Service,Vot. 1

AMPLITUDE
RELATED
CHARAiTERISTICS
Characteristic
ReferenceLevel
Range
Log Mode

tal Informalion

Top of the graticule.
From-117 dBmto +50 dBm;
+50 dBm inctudes20 dB of tF gain
reduction(+30 dBm is the maximum
safe input).Alternatereferencelevels
arei
. dBV (-130 dBVto +97 dBV)
o dBrnv (-70 dBmVto +97 dBmV)

Linear Mode

Accuracy

o dBpV (-10 dBpV to +157 dBpV)

39.6 nV/Divto 2.8 v/Div
(Maximumsafeinputlevelis .t W cw
orl0Vpeak)
Dependent on the foltowing charac-

teristics:
. RF AttenuationAccuracy
o lF GainAccuracy
r Resolution
Bandwidth
. DisplayMode
o CalibratorAccuracy
. FrequencyBand

Steps
10 dB/divLog Mode
2 dBldiv Log Mode
L i n e a rM o d e

o Frequency
Response
o CAL routinere_
duceserror,betweenresolution
bandwidths
at -20 dBm REF
LEVEL.Otherreferencelevels
may havelargererrors.
o AmbientTemperature
Change
(+0.15dB/"Cmaximum)
The inputRF attenuatorsteps 10 dB
for reference level changes above
-30 dBm (-20 dBm when MtN
NOISEis active)unlessthe MIN RF
ATTENsettingis greaterthan zero.
The lF gainincreases10 dB for each
10 dB referencelevel changebelow
-30 dBm (20dBm whenMtN NOISE
is active)
'1
0 dB for the Coarse Mode
1 dB for the Fine Mode
1 dB for the Coarse Mode
0.25 dB for the Fine Mode
1-2-5 sequencefor Coarse Mode
1 dB equivalentsteps for Fine Mode

2-7

Specification -

494A!494Ap Service, Vol. 1

Table 2-2 (Continued)
AMPLITUDERELATEDCHARACTERISTICS
Characteristic

SupplementalInformation

ReferenceLevel(continued)
SEt With DATA ENTRY pushbuttons

Steps correspond to the disptay
mode in coarse; except, tor 2 dB
whenthe stepsare 1 dB.
In FineMode:
1 dB whenthe modeis 5 dB/divor
more
0.25 dB for display modes of
4 dB/div or less (referred to as
DeltaA Mode)

VerticalDisplay Modes

10 dB/Div, 2 dB/Div, and Linear any integer between 1-1 5 dBlDiv
can also be selected with the DATA
ENTRYpushbuttons.

DisplayDynamicRange
Accuracy

90 dB maximumfor Log mode

10 dB/div Log Mode

*1.0 dB/l0 dB to a maximumcumulativeerror of *2.0 dB over B0 dB
range

2 dBldiv Log Mode

40,4 dBP.A dB to a maximum
cumulative
erroro,f+1.0 dB over 16
dB range

Linear Mode

t5o/" ot full scale

RF Attenuatol
Range
Accuracy
D c t o 1 . 8G H z

slonsfor Linearmode
+4.0 dB maximumcumulativeerror
over 90 dB range

0-60 dB in 10 dB steps
Within0.5 dB/10 dB to a maximum
of 1 dB over the 60 dB range

1.8GHz to 'l8 GHz

Within 1.5 dB/10 dB to a maximum
of 3 dB over the 60 dB range

18 GHz to 2'l GHz

W i t h i n3 . 0 d B / 1 0 d B t o a m a x i m u m

of 6 dB overthe 60 dB range
Marker(s)

When activated, the marker is a
bright dot positioned by the
CENTER/MARKER
FREQUENCY
control,

Accuracy (Normal or
Mode)

Delta

ldentical to REF LEVEL accuracy
pluscumulative
errorof displayscale
(dependent
on verticalposition)

Gain Variation Between Resolution
Bandwidths

Measurementconditions:
o measured at -20 dBm
o Minimum DistortionMode
o after front-panelCAL adjustments

3 MHz Fi
Two Filters

2-8

< i0.4 dB

o
o
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Specification_ 494A1494Ap
Service,Vot. 1

I

o

o
o
o
o
o
o

c
I
o
o

o
o
o

a
o
I
o

o
)

o

o
o
o
I
o
?
o
a

o
O

o
o
I
o
o
a
o
I
o

Tabte 2-2 (Continued)
AMPLITUDE
RELATEDCHARAiTERISTICS
Characteristic

Performancq
Requirement

lF Gain
Range

lt_ ielst 0.2 dB/dB step to
0.5dB/g dB steps except at the
decadetransitions
0.5dB or less
-29
-39
-49
-59

..-DecadeTransitions

the * 2 d B

3rd OrderIntermodulation
Products
10 kHz-21GHz
(Bands1-5)
Harmonic Distortion
10 kHz-21 GHz
(Band't)
't.7
GHz-21 GHz
(Bands 2-5)
LO Emission
DifferentialAmplitude Measurement

Range

lnfarnari

87 dB of gain increase, 20 dB of gain
decrease (MlN NOISE and reduled
gain mode activated), in 10 dB and j
dB steps

Accuracy
'l
dB Step

Maximum Deviation
107 dB Range
Spurious Responses
Residual

emehlrl

-100 dBmor less

to -30
to -40
to -50
to -60

dBm
dBm
dBm
dBm

Maximum1 dB cumulative
errorover
1 0d B

No input signal,with 0 dB attenua_
tion terminatingin 50 O, and funda_
mental mixing for Bands 1_3. (See
Options 30 anO gl in the Options
sectionfor alternatespecifications.)

-70 dBc or less
from any two on_ In MinimumDistortion
Mode
screen signals within any frequency
span.
-60 dBc or less

Measured at -40 dBm input level in
Minimum DistortionMode.

Not discernible above the average At least-100
dBc
noise floor
Less than -70 dBm to 21 GHz
With 0 dB RF Attenuarion

Delta A Mode provides differential
measurements
in 0.25dB increments
(This is not related to the Delta
MarkerMode)
Maximum range of SZ.7SdB dependent on reference level when the
Deita A Mode was activated
Ditference
Steps
Error
0.25 dB

1

2dB

I

0.4 dB

10dB

40

1 . 0d B

20 to 57.75dB

80 to 231

2.0dB

0 . 1 5d B

2-9

Specification -

4g4[l4g4Ap Service, Vol. 1

Table 2-2 (Continued)
AMPLITUDE
RELATED
CHARACTERISTICS
PerfgrmanceRequirement

Characteristic
Sensitivity
Frequency Range
Band 1
1 0 k H z - ' t . 8G H z

Equivalent Input Noise in dBm vs. Resolution Bandwidth
1 0 H z 1 0 0 H z 1 k H z 1 0 k H z 100 kHza 1 MHz 3 MHz
-134 -125
-115
-10s -v5
-85
-80

Supplemental Intormation

quivalentmaximuminput noise
rr eachresolutionbandwidth.
leasuredat 25" C with:
. 0 dB attenuation
(MinAtten0 dB)
o NarrowVideoFilteron

Bands2 & 3
1.7 GHz-7.1GHz

-125 - ' t 1 9

-1 09

-99

-89

-79

-74

Band4
5 . 4 G H z - 1 2G H z

-111 -105

-YC

-85

- //b

-65

-60

Band 4
1 2 G H z - ' t 8G H z

-107

-100

-90

*80

-74

*60

-55

. VerticalDisplay2dBlDiv
(5 dBidiv in 10 Hz RBW)
o DigitalStorageon

Band 5
1 5 G H z - 2 1G H z

-'a07 -1 00

-90

-80

-70

-60

-55

o Max Holdoff

Band 6
1 8 G H z - 2 7G H z u

- 1 1 6 -108

-100

-90

-80

-70

-oc

Band 7
26 GHZ-40 GHzb

- 1 1 1 -103

-v5

-85

-75

-65

-60

Band8
33 GHz-60GHzb

-111 -103

-85

-{5

-65

-60

-qq

Band 9
50 GHz-90 GHzb

B a n d1 0
75 GHz-l40GHzb
B a n d1 1
1 1 0 G H z - 2 2 0G H z b

B a n d1 2
170GHz-325GHzb
aOption 07 replaces the 100
kHz fitter with a 300 kHz filter.
bspecified using externar rektronix
High-performance waveguide Mixers.

o Peak/Average
in Average
o 1 sec Time/Div
o Zero Span
o lnputterminatedin 50O

pically -95 dBm for 1 kHz
ndwidth at 50 GHz, degrading
-85 dBm at 90 GHz
pically -90 dBm for 1 kHz
ndwidth at 75 GHz, degrading
- 7 5 d B m a t ' 1 4 0G H z
pically -80 dBm for 1 kHz
n d w i d t ha t 1 1 0 G H z , d e g r a d i n g
-65 dBm at220GHz

pically -70 dBm for 1 kHz
ndwidthat 170 GHz,degrading
-55 dBm at 325GHz

e
o
o
I
o
t
a
o
o
o
t
o
I
o
I
o
o
c
o
I
o
o
a
)

t

o
o
O

o

o
e
o
t

2-10

o
c
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o
a
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o
o
o
)

o

I

o

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t
o
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Specification -

Tabte2-3
INPUTSIGNALCHARACTERISTICS
Characteristic

Supplemental
Informaton

RF INPUT

Type N female connector,specifieO
to 21 GHz.

I

o
t

I

o

o
I
a
I
o
o
o
o
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o
O

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3

4g4Al494Ap Service, Vol. 1

(See Option 07 in the Optionssection for supplemental
specifications
concerningan additional
75 O input.)
50()

lmpedance

VSWRwith 10 dB or moreRF
Attenuation
10 kHz-2.5GHz
2.5-6.0GHz
6.0-18GHz
18-21GHz
VSWRwith 0 dB RF
Attenuation

1.3:1(typically
1.2:1)
1 . 7 : 1( t y p i c a l l y1 . 5 : 1 )

2.3:1(typically1.9:'t)
3.5:1(typically
2.7:1)
Measured from '10 kHz to 1.9 GHz
on Band 1, and measured within 3
MHz of the center of the preselected
b a n d o n B a n d s2 , 3 , 4 , a n d 5 .

10 kHz-2.5GHz

T y p i c a l l y1 . 9 : 1

2 . 5 - 6 . 0G H z

T y p i c a l l y1 . 9 ; ' l

6.0-18GHz

Typically2.3:1

18-21 GHz

T y p i c a l l y3 . 0 : 1

MaximumSafeInput
With 0 dB RF attenuation)

+30 dBm (1W) continuous or 75 W
peak, pulse width of 1 ps or less with
a maximum duty factor of 0.001
(attenuatorlimit)
DO NOT APPLY DC VOLTAGE TO
THE RF INPUT

point
1 dB Compression
(Minimum)
Bands1-5
(10kHz-21GHz)

With no RF attenuation
With MIN DISTORTIONon and not in
reduced gain mode
Measured at the 10 MHz lF output
- 1 0 d B m w i t h M t N N O T S Eo n

EXTERNAL
MIXER

EXT REF IN
Frequency

Waveshape
lmpedance

Input for an lF signal from an external waveguide mixer.
Provides dc bias for the external
mixer. See Output Characteristics.
1 MHz, 2 MHz, S MHz, or 10 MHz.
*5 PPM
-15 dBmto +15 dBm
Sinewave, ECL or TTL, with a duty
cycle of 40%-60%
50Oacor500Odc

2-11

t

Specification -

o
o

494A1494ApService, Vol. 1

I

a

Table 2-3 (Continued)
INPUT SIGNAL CHARACTERISTICS
Characteristic

SupplementalInformatlon

HORIZITBIG
(RearPanel)

Dc coupled input for external horizontal drive (selected by the EXT
positionof the front-panelTIME/DIV
control) and ac coupled input for
externaltrigger signals(selectedat
otherpositionsof the TIME/Dlvcontrol).
0 to +10V (dc * peak ac) tor tutl
screendeflection

SweepInputVoltageRange
TriggerInputVoltageRange
Minimum
Maximum
dc + peakac

At least 1.0 V peak from 15 Hz to
1 MHz

50v

Video lnput Level

30 vrms to 10 kHz, then derate
linearlyto 3.5 Vr." at 100 kHz and
above.
0.1 rs minimum
External Video input or External
Video Markerinpul,switchedby pin
1 0f the J104 ACCESSORY
connector.
0to*4V

MarkerInputLevel

0 to -10 V

PulseWidth
MARKERIVIDEO
(RearPanet)

lnterfaces with Tektronix 1405 Sideband Adapter.
J104 ACCESSORY(Rear Panet)

25-pin connector
(Not R5-232 compatible)
Provides bi-directionalaccess to the
instrumentbus. Also provides external Video select and external
preselector drive. Except for the
external preselector drive output, all
lines are TTL compatible.
Maximum voltage on all lines is
+'l5 v.

Pin 1

ExternalVideo Select
Low selects ExternalVideo lnput.
High (default) selects Video Marker
Input.

Pin 2

ExternalPreselector
Drive
Drivesignalfor an externalpreselector. Outputvoltageis proportionalto
frequency change (only in Bands

2-s\.

P i n3

ExternalPreselector
Return
Ground return for the External
Preselector
siqnal.

2-12

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Speclfication-

494Al4g4ApService,Vol. 1

Table2-3 (Continued)
INPUTSIGNALCHARACTERISTICS
Characteristic

SupplementalInformation

J104 ACCESSORy
(Continued)
Pin4

InternalControl.
High(default)selectsinternalcontrol.
lnstrumentbus lines are output at
theJ104ACCESSORy
connector.
Low selects Externalcontrol.lnstrument bus lines at the J104 AccESSORY connector accept input from
an externalcontroller.
ChassisGround

Pin5
P i n s6 - 1 3 a

InstrumentBus Address lines 7-0a

Pin14a

Instrument
Bus DataValidsignala
InstrumentBus ServiceRequestsignal

Pin15
Pin16a

InstrumentBus Poll signala

Pin17

Data Bus Enable input signal for
externalcontroller.
High (unasserted) disables external
data bus.
Low enables externaldata bus.

Pins18-25

Instrument
Bus Datalines0-7
Active when external Data Bus
Enable(pin17)is low.

soutput when internally
controlled {pin 4 high) and input when externally controled (pin
4 low).

Table 2-4
OUTPUTSIGNAL CHARACTERISTICS
Characteristic

ualrbrator(cAL ouT)

Performance Requirement
-20 dBm *0.3 dB at 100 MHz

1st LO and 2nd LO OUTpUTs

1st LO OUTPUTpower
2nd LO OUTPUT power

SupplementalInlormation
100 MHz comb of markers provide
amplitudecalibrationat-100 MHz
Phaselockedto referenceoscillator
Provide access to the output of the
respective local oscillators
THESE PORTS MUST BE TERMINATEDIN 50 O AT ALL TIMES.

+ 7 . 5d B mt o + 1 5 d B m
-12 dBm.*5 dB

aover lhe operating temperature
range this is +15 ppM.

2-13

Specification-

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494At494ApService,Vol. 1

I

Table2-4 (Continued)
OUTPUT
SIGNALCHARACTERISTICS
Characteristic
EXTERNALMIXER

I
Supplemental lnformation

When EXT MIXERis selected,provides bias from a 70f,) sourcefor an
externalmixer. Bias is set by the
MANUALPEAK controlor internally
set if AUTOPEAKis selected.
Also see InputCharacteristics.
Replaced by 75 O RF Input for
ion 07. See Ootions

Bias Range

+1.0 V to -2.0 V (default)
or.
-1.0V to +2.0V(internally
selectable)

VERT (OUTPUT)(Rear Panet)

Provides 0.5V t5% of signal per
division of video that is above and
below
centerline. Source
the
impedanceis approximately1 kO.

HORIZ(OUTPUT)
(Rearpanet)

Provides 0.5 V/Div either side ol
center.Full range -2.5 V to +2.5 V.
Sourceimpedanceis approximately
1 ko.

PEN LIFT (Rear Panel)

TTL compatible, nominal +5 V to lift
plotter pen

10 MHz lF (OUTPUT)(Rear Panet)

Providesaccess to the 10 MHz lF
signal. Output level is approximately
-5 dBm for a full screen signal at
-40 dBm reference level. Nominal
impedanceis approximately50 O.

IEEESTD488PORT(RearPanel)

ln accordance with IEEE 488-78
standard

Manualversion
(plotteroutput)
Programmable
{P)version

lmplemented
as SHl, AHo, T3, L0,
SR0,RL0,PP0,DC0,DT0,and C0.
lmplemented
as sH1, AH1, T5, L3,
S R 1 ,R L 1 .P P 1 ,D C 1 ,D T 1 ,a n dC 0 .
Manual.
See Programmers

PROBEPOWER(RearPanet)
Outputs

voltages for

P i n1

+ 5 V a t ' 10 0 m A m a x i m u m

Pin 2

Ground
-15 V at 100mA maximum
+'15V at 100mA maximum
All inputs and outputs are listed in
Tab|e 2.3 INPUTSIGNALCHARAC.
TERISTICS.

Pin3
P i n4

J104ACCESSORY
(RearPanet)

2-14

Provides operating
active probes.

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Specification -

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494A1494Ap Service, Vol. 1

Tabte 2-5
GENERALCHARACTERISTICS
Characteristic

Performance Requirement

Sweep Modes
Sweep Time

Accuracy
Triggering

20 ps/Div-S s/Div in 'l -2-5 sequence
s/Div avaitable in AUTO)
!],,.9

Information

Triggered, auto, manual, external,
and singlesweep

*57o overcenterI divisions
lNTernal,EXTernal,FREERUN.and
LINE

InternalTrigger Level

2 divisionsor more of signal

ExternalTriggerInputLevel

1.0V peak,minimum

EXTernal is ac-coupled (15 Hz-1
MHz). Maximum external trigger

inputis 50 V (dc+ peakac).
Displaysall parameterslistedon the
crt bezel, plus help and operating
rnessages.
lnstrument settings, macros (programmableinstrumentonly)displays,
calibration offsets, and peaking
codes for each band are stored in
battery-powered,
non-volatile
RAM.
1-2 years

Crt Readout

Battery-Powered
Memory

BatteryLife
At +55"C Ambient Temperature
At +25"C Ambient Temperature

(See Option 39 in the Options section for alternatespecification)

least5

Temperature Range for
Retaining
Data
Operating
Non-Operating
MarkerTimeMeasurement
Accuracy(in zerospan mode)

-1 5"C to +55oC

-30"C to +85"C
*.10"h for single marker and isyo
for delta marker
Marker time available only in zero
span
Table 2-6
P O W E RR E O U I R E M E N T S

Characteristic
Line Voltage Range

Supplemenlal Information
90 V.^ to 132 V

47 lo 440 Hz
11 5 V n o m i n a l

180V,^ to 250V

230 V nominal

Line Fuse
1 1 5V N o m i n a l

230V Nominat
InputPower
LeakageCurrent
47Hz-63Hz
63 Hz - 440 Hz

4A
2 A Medium-Blow

210W maximum(3.2A)

A t 1 1 5V a n d 6 0 H z

3.5 mA maximum
5 mA maximum

2-15

Speclfication-

494A1494AP
Service,Vot. 1

Table 2-7
ENVIRONMENTALCHARACTERISTICS

MeetsMIL T-28800C,type

class 3, style C specifications.

Characteristic

Temperature
Operatingand Humidity
Non-operating

Altitude
Operating
Non-operating

Descr
-15oC to +55oC/95"/"(t 5o/"relative humidity).

-62"C to +85 "C

15,000feet (testedto 25,000fee$
40,000feet (testedto 50,000feet)

Humidity(non-operating)
Five cycles (120 hours)in accordancewith MIL-Std-8l0 Procedure lll {modified)
Vibration(operating)
MIL-Std-810D,Method 514, Procedure| (modlfied).Resonant searchesalong all
(instrumentsecuredto a vibra. t h r e e a x e s f r o m 5 H z t o 1 5 H z a t 0 . 0 6 0 - i n c hd i s p l a c e m e n l t o r T m i n u t e s ,1 5 H z
tion platformduringtest)
to 25 Hz at 0.040-inch displacement for 3 minutes, and 25 Hz to 55 Hz at
0.020-inchdisplacementfor 5 minutes (tested to 0.025 inch). Additionaldwellfor
10 minutes in each axis at the frequency of the major resonance or at 55 Hz if
none was found. Resonance is defined as twice the input displacement. Total
vibrationtime is approximately75 minutes.
Shock (operatingand non-operating) Three guillotine-typeshocks of 309, one-halfsine, 11 ms duration each direction
along each major axis for a total of 18 shocks (tested to 509).
Transit drop (free fall)
One 8-inch drop on each of six faces and eight corners (tested at and meets
d r o p h e i g h to f 1 2 i n c h e s ) .
Electromagneticlnterference(EMl)
Meets requirementsdescribed in MIL-Std-461B, Part 4, except as noted.

Remarks
Conducted Emissions
ConductedSusceptibility

CE01- 60 Hz to 15 kHz

CS06-spike power leads

RadiatedEmissions

1 kHz to 15 kHz only

CE03-15 kHzto 50 MHz powerleads 1 5 k H z t o 5 0 k H z , r e l a x e db y 1 5 d B
CS01-30 Hz to 50 kHz power leads
Fulltimit
power
CS02-50 kHz to 400 MHz
Fulllimit
leads
Fulllimit

R E 0 1 * 3 0 H z t o 5 0 k H z m a g n e t i cf i e l d Relaxed by 10 dB for fundamentalto
(measuredat 30 cm)
1oth harmonic of power line
Exceptioned,30 kHz to 36 kHz
RE02-14 kHzto 10 GHz

RadiatedSusceptibility

aAfter

Fulllimit

RS01-30 Hz to 50 kHz

Fulllimit

RS02- Magnetic lndu6tion

To 5 A only

RS03-14 kHzto 10GHz

up to 1 GHz

storage at temperatures below -1soc, the instrument may not reset when power is first turned on. It this happens, allow the
instrument to warm up {or at least 15 minutes, then turn the power off for 5 seconds and back on.

2-16

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Specificaiion -

Table 2-8
PHYSICALCHARACTERISTTCS

,

t

Characieristic

a

Weight

o

Dimensions
(seeFigure2-1)

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494A1494ApService, Vol. 1

Descriotion

47 pounds, 14 ounces (21.8 kg) maximumlsee the
Optionssectionfor alternatespecifications)
Includingcoverand standardaccessories,
exceptmanuat>

Without Front Cover, Handle,or Feet
With Front Cover, Feet, and Handle

6 . 9 x 1 2 . 8 7x 1 9 . 6 5 i n c h e s( 1 7 5 x 3 2 7 x 4 9 9 6 6 ;

HandleFoldedBackOverthe lnstrument
H a n d l eF u l l yE x t e n d e d

9,15x 15.05x 23.1inches(282x 382 x 567 p1r1
9.15x '15.05x 28.85inches(232x 392 x 732.gmm)

l---t7'6cm(23''-

20.32cm(8.0in.)

23.24cm
(9.15in-)

srDEvtEw

2726-10C

Figure 2-1- Dimensions.

2-17

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Section 3 -

494A1494ApService,Vot. I

INSTALLATION
This section describes unpacking, installation,
pow€r requirements,storage informationand repackaging for the spectrurn analy;er.

UNPACKING
AND
INITIALINSPECT|6N
Bglorg unpackingthe spectrum analyzer, inspect
..
the shippingcontainerfor signs of externatdamage. lf
the containeris damageO,nbtity the carier as well as
Tektronix, Inc. The shipping Lontainer contains the
basic instrumentand its standardacc€ssories. For a
list of the standardaccgssori€s,refer to Section1 of
this manual(or, for ordering information,refer to the list
followingthe ReplaceableMechanicalparts list in the
ServiceManual,Volume2).
lf the contentsof the shippingcontainerare incomplete, if there is mechanicaldamige or defect,or
if the
instrumentdoes not meet operationalcheck requirernents, contact your local Tektronix Field Office or
representative.
Keep the shippingcontainerif the instrumentis to
be -stored^or shipped to T€ktronix tor service or repatr.
Referto Storageand Repackagingfor Shipmentlaterin
this section.
The instrumentwas inspected both mechanically
and electricallybefore shipment,and it should be free
of mechanicaldamageand meet or exceedall electrical
specifications.Th€ Operationsectionof the Operators
Manual contains procedures to check functional or
operationalperformance. perform the functionalcheck
procedure to verify that the instrument is operating
properly. This check is intendedto satisfythe require-,
ments for most receivingor incominginipections.
{A
detailedelectricalperformanceveriticition procedurein
the PerformanceChecksectionof this manualprovides
a check of afl specified pertormancerequirements,as
listedin the Specification
section.)

The instrumentcan be operatedin any positionthat
allows air flow in the bottom and out the rear of the
instrurnent. FEeton the four corners allow ample cfearance sven if the instrumentis stackedwith other instru_
ments. The air is drawn in by a fan through the bottom
and expelled out th€ back Avoid locating the instru_
ment where paper, plastic, or any other materialmight
block the air intake.

The front cover providesa dust-tightseat and a con_
venient place to store accessories and extemal
waveguide mixers. Us€ the cover to protect the front
panel when storingor transportingthe instrument.To
removs the cover, stand the instrumenton the h^/oback
feet so the name on the handle is facing up and
towardsyou, and pull slightlyout and up on the sidesof
the cover. Attachedto the inside of the cover is the
accessoriespouch. To open the accessoriespouch,
pull up evenlyon the flap.

You can position the handle of the spectrum
analyzerat severalanglesto serve as a tilt stand. To
stack instruments,positionthe handleat the top rear of
the instrument.To changethe handleposition,press in
at both pivot points and rotate the handleto the desired
position.

Removingor replacingthe cabinet on the
instrument can be hazardous. Only
qualifiedservice personnelshould attempt
to rernovethe instrumentcabinet.

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Installation- 494A/494ApServlce,Vol. 1

CONNECTING
POWER
PowerSourceand power Requirements

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Changing the
dangerous.

powef

input

can

be

03s3

o Work safely
o Knowthe intendedpowersource

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o Set the instrument for the power
source

I

o Checkthe fuse for properratings

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. Use the power cord and plug intended
for the power source
WATTS ([AXl 210
AMPS 3.2 AT 1'ls Y 60 Hr
FREO a! TO i|'.o X!
FANGE
90-132 V

The spectrum analyzer operates from a single_
phase power sourcethat has one of its curent-carrying
conductors(neutral)at ground (earth)potentiat.Oo-no-t
operate the spectrum analyzer from power sources
where both current-carryingconductorsare isolated or
above ground potential(such as phase-to_phase
on a
multi-phasesystem or across the legs ot a fiA-220 y
single-phase,three-wire system). tn tms method of
operation, only the line conductor has over_current
(fuse) protectionwithin the unit. Refer to the Safety
summaryat the front of this manual.
The ac power connectoris a three_wire,polarized
plug with the ground (earth)lead connecteddirecflyto
the instrumentframe to provideelectricalshockproiection. lf th€ unit is connectedto any otherpowersource,
connectthe unitframeto an earthgroundOperatethe spectrumanalyzerfrom Either11SVac
or 230 Vac nominalline voltage with a range of 90 to
132 or 180 to 250 Vac, at 4g to 440Hz. power and vol_
tage requirementsare printed on a back_panelplate
mountedbelowthe power inputjack.
tnput powerrequirementsare changedwith a switch
on the back panel(see Figure3-1) and by replacingthe
input line fuse. The instrumentuses a 4A fast blow
fuse for 115Vac operation,and a 2A slow blow fuse for
230 Vac operation.
Removethe protectivecover and set the line select
switchfor the appropriatevoltagerange.

g-2

a

o@

CAUTION
r POWER IEFORE NI
FIRE
OilLY WITH

FUItE
250Y aA :AST FUSe.

Figure3-1. Inputpowerselectorswitchandfuse.
Removethe fuse holder and replace the line fuse
with the appropriatefuse for the voltagerange selected.
The internationalpower cord and plug configuration
is shownin the Optionssectionof this manual.

STORAGEAND REPACKAGING
Storage
Short Term (less than 90 days) - For short term
storage, store the instrum€ntin an environmentthat
meetsthe non-operatingenvironmentalspeciticationsin
Section2 of this manual.

)

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Instaltaton-

Long Term - For instrumentstorageof more
than
90 days,retain the shippingcontainerti iepacXage
ttre
instrument. The battery in tt e instrume-rit
does
not
require rernoval. package the instrumentin
a vapor
barrierbag with a dryingagent and store'in a tocation
rnat meets the
non-op€rating environmental
specifications
in Section2 of this manlal.
|f Lgr. l1o: any questions,contact your tocat Tektronix FieldOfficeor representative.
Repackaging for Shipment
_ . Whgnthe spectrum analyzeris to be shippedto a
Tektronix Service Center for serviceo, ,"j"ir, attach
a
tag that shows the owner and address,the name
of the
individualat your firm that can be contacted,
the com_
plete instrumentserial number.and a description
of the
servicerequired.lf the originalpackageis unnt for
use
or not available,use the followingrepickaginginforma_
tion.

494[l4g4Ap Service,Vol. 1

1. To allow for cushioning,use a corrugated
cardboard container with a test strengttr oi gZS
pounds (140 kilograms)and inside dimensions
that
are at least six inches more than the equipment
dimensions(refer to the physical Characteristicsin
Section2).

2. Installthe instrumentfront cover,and surround
the instrument with plastic sheeting to protect the
finish.

. 3. Cus.hionthe equipmenton all sides with packing materialor plasticfoam.

4. Seal the container with shipping tap€ or an
industrial,heavy-dutystapler.

3-3

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Secton 4 -

4g4Al494ApServiceVol. 1

PERFORMANCE
CHECK
Introduction
All performancechecks are carried out without
removingthe instrumentcovers.
The proceduresin this sectionverifythat the instrument performancesatisli€s the performancerequirernents specified under the performanceRequirement
columnin Section2, Specification.
Some parametersand instrumentfunctionsthat
are
not explicitlyspecifiedare also checked.These
checks
verifythat the instrumentperformsas described.
Checksshould be performedin sequencebecause
som€ tests rely on the satisfactoryperformance
of
related circuits. Also, the cneck iteps have
arrangedso that the changingof test equipment been
setups
from one step to the next is minimized.
lf a measurementis marginalor belowspecification,
an adjustmentprocedureto enhanceperformance
will
be found,undera similartreading,in Section5, Adjustment Procedure.After adjustment,recheckthe perfor_
mance. Adjustonly those circuitsthat do not meet performancecriteria.
lf adjustmentfails to return the circuit to specified
performance, refer to the Maintenancesection
for
troubleshooting
and repairprocedures.

Incoming Inspection Test
The Operators manual contains an operationalor
functionalcheckthat checksall functions.This eheck
is
recommendedfor incoming inspectionsbecause
it
requiresno externalequipmentor specialexpertise
and
is a reliableindicationthat the instrumentis perforrning
properly.

Option Instrument Checks
. Wheneverpractical,performancechecks for option
instrumentsare integratedin the performancecheck
steps for the standard instrument,otherwise special
check-steps are provided under OPTION INSTRUMENTStowardsthe backof this section.

Verification of Tolerance Values
Compliancetests, of thoselimitslistedin the p€rformance Requirement column of the instrum€nt
specifications,shall be perform€dafter sufficientwarmup time and comptetionof preliminarypr€parationsteps
(suchas front-paneladjustments).
Measurementtoleranceof test eguipmentshouldbe
negligiblein comparisonto the specifiedtolerance;and,
when not negligibte, the error of the measuring
apparatusshall be addedto the tolerancespecified.

History Information
The instrument and manual are periodically
evaluated and updated. lf modifications require
changes in the procedures,informationapplicableto
earlierinstrumentswil be includedwithina step or as a
sub-partto a step.

Equipment Required
Table 4-1 lists the test equipmentand calibration
fixturesrecommendedfor the performanceCheck, This
equipmentis also applicablefor the adjustmentpro_
cedures in Section 5, Adjustment procedure. The
equipmentcharacteristicsspecified are the minimum
required for the checks. Substituteequipmentmust
meet or exceed these characteristics.These fixtures
are availablefrom Tektronix,Inc., and may be ordered
throughyour local TektronixField Officeor representative.
Some checks may not be practical becausethey
may require sophisticatedtest equipmentand/or procedur€s.In those cases,a compromisemay be made
in the procedures. When that occurs, a statementor
footnote to that fact is added to the step. The more
exact method of measuringthe characteristiccan be
suppliedby your TektronixServiceCenter.

4-1

PerformanceCheck Procedure- 494A/4g4ApServiceVol. 1

Table4-1
EOUIPMENT
REOUIRED
or Test Flxture
Test Oscilloscope

Time Mark Generator

Vertical sensitivity, 50 mV/Div to
V/Div;Bandwidth,DC to 100 MHz

FrequencyCountera

Marker output, 5 s to 20 ns; accuracy
0.001%
0 to 200 MHz, 1 Hz resolution,25 mV

Prescaler

Compatiblewith TEKTRONTX
DC S09

Functionor Sine-WaveGenerator

1 Hz to'l MHz;0 to 20 V p-p

Signal Generator

10 Hz to 't0 MHz,constantoutput

SignalGenerator

Two leveledgenerators,500 kHz to 2.0
GHz. Output,-100 dBm to *10 dBm;
spectral purity 60 dB or more below
the fundamental.

Low Loss RF Cable (WL Gore)

Flat to at least 21 GHz

CrystalDetector
SweepOscillator

0.01 to 21 QHz; frequency response
f 1 . 0d B

Power Meter with Power Sensor

-30 dBm to +20 dBm tuil scale: 100
kHz to 26 GHz

750-to-50(}
Minimum
Loss
Attenuator
lmpedanceMatchingPowerDivider

VSWR1.1to 100MHz
Frequency
Range:DCto 1000MHz

BNC MAIE tO BNC Male Adapter,
75()

Recommendationand Use
Any TEKTRONIX7000-Seriesoscilloscope with plug-in units for realtime display sueh as 7A11/7850A,
and P610810XProbe
TEKTRONIXTG 501 (time/div and
span accuracycheck)
TEKTRONIX DC 509 Option 01
(Calibratorfrequencymeasurement)
TEKTRONIXDP 501 (Center frequencymeasurement)
TEKTRONIXFG 503 FunctionGenerator (externaltrigger and horizontal input requirementscheck)
Hewlett-Packard
Model3336C(gain
accuracy and frequency r€sponse
checks)
TEKTRONIX SG 504, HewlettPackardModel 8ilOA/B and Model
generators (frequency
8614A
response,lM, and displayaccuracy
checks)
Tektronix Part No. 006-7609-00(frequencyresponsecheck)
Hewlett-PackardModel 8473C (treresponsecheck)
Hewlett-PackardModel 8350A with
Model 83595A Option 002 Plug-in
(frequencyresponsecheck)
WeinschelModel 1

Hewlett-PackardModel 435A or
436A with 8/,82Aand 8485A Power
Tektronix Part No. 011-00s7-01
(Option07 only)
Tektronix Part No. 067-1232-00
(Optlon07 only)
Tektronlx Part No. 103-0254-00
(Option07 only)
Texscanor Lark

Low-PassFilter

Must have rolloff of 40 dB or more al

UHFCombGenerator

Providecomblineto 18 MHz;accuracy
0.01%

TEKTRONIX Calibration Fixture
067-088s-00 (frequency readout
accuracy

Power Module (At least 4-wide)

For use with TG 501,DC 509, DP 501,
FG 503,SG 504.and 067-0885-00

TM 500 Power Moduleb

I The frequency counter must
b€ clocked by an external frequency standard such as wwvB.
b Option 07 it checking en Option 42 Spactrum
Analyzer.

4-2

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Performancecheck procedure -

4g4br4g4Apservice vor. 1

Table 4-1 (cont)
EOUIPMENT
REOUIRED
Equipmentor Test Fixture
spectrumAnalyzer
TrackingGenerator
10 dB StepAttenuatora

dB step Attenuatora

lnterconnect
Kita

Characteristics

Recommendation and Use

Frequencyrange,50 kHz to 2_2GHz

TEKTBONIX 492A, 494, or ZLIU;
Option39 (compressionpointcheck)

Frequency
range,100kHzto 1.9 GHz

TEKTRONIX
TR502(Option42 check)

0 dB to 110 dB in 10 dB steps :L3yo Hewlett Packard
84968
from dc to 12.4 GHz, and *4oh trom dc compression point
check)
to 18 GHz

0 dB to 11 dB in.t dB steps;*0.3 de Hewlett Packard 84948
1-2d8, +0.4 dB g-4 dB, :r0.5 dB compression point check)
5-6 dB, *0.6 dB 7-10 dB, and *0.7
dB 11 dB from dc to 12.4GHz; *0.7
dB 1-5 dB, :b0.8 dB 6-9 dB, and
*0.9 dB 10-11 dB fromdc to 1g GHz
For Hewlett packard 94948 and 94968
step Attenuators

50O Terminator

(1

dB

(1

dB

Hewlett Packard 1 12.16A

TektronixPart No. 011-0049-01

StepAttenuator-

Range, 0 dB to 90 dB in 10 dB steps Hewlett Packard g55D
(input
*0.1 dB from dc to 1 GHz
compression,displaydynamicrange,

st"pnttenui-

Ra.nge!0 dB - 12dB, in 1 dB steps; dc Hewlett

and lF gain steps checks)

LrlrGtr,
lodB/sooltt"ffi
20 dB/50O Attenuator

dc to 21 GHz;*1 dB accuracy
dc to 21 GHz; +1 dB accuracy

2NMaretoApc@
APcg.5rt,tur"to@

Arlenuator(sMA connectors)

3 dB, 50o; dc to 20 cHz

Two Attenuators(bncconnectors)

20 dB,50o; dc to 2.0GHz

(5url uoaxtal cable with sma connec- 5 n s
N Mate to sMA Male Adapter
N Mate to BNC Female Adapter
UNU I Adapter

_
Two 50O CoaxialCables

355C

(input

and lF gain stepschecks)

Hewlett Packard 3gg40c Option 10
(RFattenuatoraccuracycheck)
Hewlett Packard ggg4oc Option 20
(RFattenuatoraceuracycheck)
Maury Model 8023D (RF attenuator
accuracycheck)
Maury Model 80218 (RF attenuator
accuracycheck)

APC 3.5 Femaleto ApC 3.S Femate
Adapter

tors)

Packard

accuracy
*0.2s dB io 0.5 compression,displaydynamicrange,

Maury Model 8021A (RF attenuator
accuracycheck)
WeinschelModel 4M. Tektronixpart
No.015-1053-00
TektronixPart No. 011-00S9-O2
TektronixPart No. 015-1006-00
TektronixPart No. 015-0369-00
TektronixPart No. 103-0045-00
TektronixPart No. 103-0030-00
TektronixPart No. 015-1006-00

8 The 10 dB step attenuator'
1 d-Bstep attenuator. and interconnect kit must be
calibrated iogether as a single unit. using p(ecision standard attenuators such as Weinschel Model AS_6 attenuator.

4-3

PerformanceCheck Procedure-

4g4Ll4g4ApServlceVol. 1

PRELIMINARY
PREPARATION
lnitial Power-Up
During initial power-up cycle, the instrumenttype,
instrumentoperating system processor firmware ver_
sion, and the front panel processor firmwareversions
are displayedon the crt for approximatelytwo seconds.
The ReplacementParts List in the Serviie manual,lists
the ROMs used for each version. The servicemanual
also lists the firmware operatingnotes associatedwith
eachfirmwareversion.
lf the microcomputerdetects a hardwarefailure.a
failurereportwill come on screenand remainfor about
2 seconds. A status messagewill then appear and
remain for the duration of the failure. press  MAX HOLD to bring eror messagesto the
screen.
a. Connectthe spectrumanalyzerpower cord to an
appropriatepower source (refer to power Source and
Power Requirementsin Section g, Installation). Set
TIME/DIVto AUTOand switch pOWERon.
b. When POWERis sivitchedoR, the pOWERindicator(a greenLED)shouldcome on.
c. The microprocessorruns a memoryand UO t€st.
lf no processorsystem problemsare found,the powerup programwill completein approximately10 seconds,
and the instrumentwilt be ready to operite. After the
power-uproutine,the crt will initiatizeas shown in Figure 4-'l.

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d. The operating functions and modes should initialize to th€ following state:

Readout
REF LEVEL
CENTERFRECIUENCY
MARKERFREQUENCY
sPAN/DrV
VERTDISPLAY
RF ATTEN
FREORANGE
REFOSC
RESOLUTION
BANDWIDTH
TRIGGERING
AUTO RESOLN
DIGITALSTORAGE
MIN NOISE
All other pushbuttons

On
ODBM
0.90GHZ
0.00GHz
MAX
10DB/
2ODB
0-1.8a
t-ub
3MHZ
FREERUN
On
VIEWA&VIEWBon
On
lnactiveor off

e. Set the MIN RF ATTENdB controtto 0 (NORM)
and th€ PEAK/AVERAGE
controlfully counterclockwise.
set the TlMEiDlv controlto AuTo, REF LEVELto read
-20DBM, and adjust th€ INTENSITYcontrol for the
desired brightness.Note that the RF ATTENreadoutis
now 0DB.
f. Apply the CAL OUT signal to the RF INPUT
througha 50O cableand a N-TO-BNCadapter.
g, A dot markerwill appear in the upper portionof
the screen in the MAX frequencymode. This marker
indicatesthe locationon the displayto whichthe spectrum analyzer frequencyis tuned, With a frequency
readoutof 0.00GH2,the markerwill be in the upperleft
portion of the screen. Rotate the CENTER/MARKER
FREQUENCYcontrol and note that the dot marker
moves across the display. Notice that the oENTER
FREOUENCYreadout (top line) remains at 0.90GH2,
and that the MARKERFREOUENCYreadout (second
line) changes accordingto the positionof the marker
(dot).
h. Harmonicsof the 100 MHz calibratorsignalwill
be displayedas shown in Figure4-2. To select100
MHz centerfrequency,press the pushbuttonsequence
of 
FREO'100
MHz.
i. To changethe SPAN/DIVto 100 MHz, pressthe
pushbuttonsequenceof SPAN/DIV100
MHz. The dot markeris now horizontallycentered,and
the 100 MHz calibratorsignalis at centerscreen.

55€{t24

Figure4-1. Grt disptayat initial power-up.

4-4

aGHz
btntEnNeL UNLOCK:Most lrequency measurementswill not be
accurateunlil after this readouthas changedto lNT.

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PerformanceCheck procedure -

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This calibrationshould be done at regular
intervals so the instrument can meet its
eenterfrequencyand referencelevel accu_
racy performancespecifi,cations.lt should
also be done each time the ambienttemperatureof the instrumentis changed.
To observethe results after the microcomputer has cornpleted a calibrationroutine,
pressthe LIN seguence.A
message will appear on the screen that
shows the correction factor used by the
microcomputer to center the resolution
bandwidth filters to produce a calibrated
centerfrequency. lt also showsthe correction that was requiredto bring the ampli_
tude levelwithin0.4 dB of the 3 MHz filter.

DII

ssqx2
Figure
-4-2.
Span/Div.

4g4Ll4g4ApServiceVol. 1

Typical display of catibrator signat
In Max
i

CalibratePosition,Center Frequency,Reference
Level,and DynamicRange

Whenthe CAL sequenceis
pressed, the microcomputerpe*orms
a
center frequencyand referencelevel calibration. Prompts app€ar on the screen to
guide
.the user step-by_stepthrough the
procedure.

Press the  CAL sequenceto start
the calibration routine. A prompt message on the
screen will guide you through setting the four frontpaneladjustmentsof verticaland horizontalpOSlTlON,
and AMPL and LOG CAL. This sets thE absolut€refer_
ence levelfor the 3 MHz resolutionbandwidthfilter. An
automaticcalibrationis then done,whichmeasuresand
correctsfor absolutefrequencyand amplitudo(r€lative
to 3 MHz)errorsof the filters. tnis takesapproximately
60 seconds. lf a messageappearson the screen,rsfer
to Error MessageReadoutearlierin this section. The
correctionfactors are held in memory. press FINEto
continuecalibrationas instructedor 
to
exit the routine.
lf any amplitude correction factor for a fitter is
greaterthan 1 dB. at roorntemperature,the tilter in the
VR assemblyshouldbe readjusted.Referto SectionS.
AdjustmentProcedure.

4-5

PerformanceCheck Procedure-

4g4Ll4g4ApServlceVot..l

PERFORMANCE
CHECKPROCEDURE
1. Check 10 MHz Reference Oscillator Accuracy
(Agingrate <1 x 10-7)

e. ResetSPAN/DIVto 500 kHz.
f. Press  COUNT RESOLN and
enter 1 kHz for a counterresolutionof 1 kHz.

The 10 MHz ReferenceOscillatoraccuracyis not a
performancerequirement;however,it must be checked
so the centerfrequencyaccuracycan be verified. Since
the calibrator is locked to the 10 MHz oscillator this
procedureverifies accuracyby countingthe frequency
of the calibratorsignal.

g. Press COUNT and note that the error over
severalcountsdoes not exceed1 kHz.

a. Connectthe CAL OUT signal to the frequency
counter. (Counterswith a frequencyrange above 200
MHz may requirea 150 MHz low pass filter to €nsurea
stabletriggeron the 100 MHz CAL OUTsignat).

i. SEt thE CENTERFREOUENCYtO 1.8GHZ Or
1.7 GHz and repeatthe counteraccuracycheckfor this
end of the band.

The TektronixDC 509 must.be modifiedto
accept an external oscillator reference.
Refer to the TMS00ffM5000Series Rear
InterfaceData Book, part No. 070-2099_04
for modification instructions.
b. Connectthe frequencystandardto th€ External
FrequencyStandardInput of th€ frequencycounter.
c. Checkthat the frequencyof the GAL OUT signat
i s 1 0 0M H z* 1 0 H z .
d. Disconnectthe counterfrom the CAL OUT con_
nector.

2. Check Counter Accuracy
Error+ (10+ 2N)Hz+ l LSD
[CFx gslslsnceFrequency
a. SettheSpectrum
Analyzer
controlsas follows:
CENTERFREOUENCY 500MHz
sPAN/DrV
2AkHz
AUTO RESOLN
REF LEVEL
VERTICALDISPLAY

TrME/DrV
TRIGGERING

On
-30 dBm
10 dB/Dlv
AUTO
FREERUN

b. Applythe CAL OUT signatto the RF lNpUT,and
centerthe 500 MHz markercalibratorharmonic.
c. Press  COUNT RESOLN and
enter 1 Hz via the Data Entrykeypad.
d. Press COUNT and note that the error over
several counts does not exceed .lSHz. The factor
(CF x Reference
FrequencyError)is canceledwhenthe
CAL OUTsignalis used.

4-6

g.

h. Resetthe sPAN/Dlv to 200 kHz and repeatpart

3. Check Counter Sensitivity
(At least 20 dB above the average noise level at
center screen and no more than 60 dB down from
the refer€ncelevel)
a. Applythe CAL OUTsignalto the RF INPUTvia a
1 dB and a 10 dB step attenuator.Set both attenuators
for 0 dB attenuation.
b. Set the SpectrumAnalyzercontrolsas follows:
CENTERFREOUENCY
sPAN/DrV
RESOLUTION
BANDWIDTH
REF LEVEL
NARROWVIDEOFILTER
VERTICALDISPLAY
TrME/DtV
TRIGGERING

100MHz
1 MHz
1 MHz
0 dBm
On
10 dB/Drv
AUTO
FREERUN

c, Set the 1 dB and 10 dB attenuators such that the
signal amplitude is approximately 20 dB above the
noise floor.
d. Press  COUNT RESOLN and
enter 1 Hz via the Data Entry keypad.
e. Press COUNT and note that the counter is counting the signal with the accuracy noted in performance
check step 2.
f. Reset SPAN/DIV ancl RESOLUTIONBANDWIDTH
to 100 Hz, REF LEVEL to -30 dBm, and activate WIDE
VIDEO FILTER.
g, Reset the 1 dB and 10 dB attenuatorssuch that
the signal amplitude is approximatety60 dB down from
the referencelevel.
h. Press COUNT and note that the counter is counting the signal with the accuracy noted in performance
check step 2.

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PerformanceCheck procedure -

4. Check Center Frequency Accuracy
This is a two part procedure;part I checks
center
.
frequencyaccuracy with the 1st LO unlocked,part
ll
checksaccuracywith the l st LO phase lockecl.
A
front
panel CAL should be done before performing
this
check.
Part | - lst LO not phase Locked
Accuracywith the .lst LO unlockedis :r
{(20%of the
Span/Div or Resolution Bandwidth, whichever
is
g.relter)+ (CF x ReferenceFrequencyEror) + 15N
kHz).

4g4ful4g4ApServlce Vol. .l

f. Check that the disptayedsignat
is within 0.271
divisions(5T kHz)of center screen.
S. Continuechecking frequenciesas indicatedin
Table4-2 as per the foilowingexample:
CheckCenterFrequencyAccuracyat 19.5GHz
Fundamentalindicated by frequency counter :
499.99831
MHz.
Deternine Center Frequencyto the nearestkHz:
Fundamentalx 37 (from Table 4-2)
0.499998
GHz x 37 - 18.a99926
GHz
Use Data Entry keypad to s€t CENTER FRE_
QUENCYto 18.499926
eHz.
Check that the disptayed signat is within 0.424 divi_
sions (89 kHz) of center screen.

The 1st LO is not phase_lockedin Fre_
quency Span/Div settings >200 kHz. For
Span/Divsettings (200t200kHz for band 1 and bands s
through 12 and SPANIDfV>10OkHzfor bands 2
through4.))
{Within(10 + 2N)Hzover 20 ms with the 1st LO
locked(SPAN/D|V<200kHz for band 1 and bands5
through 12 and SPAN/D|V 10 dB/DlV. A message "FREOUENCY CORRECTIONSDTSABLED: USE HELp,.wiil
be displayed on the CBT.
cl. Reset the SPAN/DIV to 100 kHz, and recenter
the 100 MHz calibrator signal on screen with the
CENTERFREOUENCYcontrot.
E. SEt thE VERTICALDISPLAY tO LIN. POSitiON
thE
signal so the slope (horizontalversus vertical excursion)
of the response can be determined as illustratedin Figure 4-5A. Slope determination may be made easier by
switching VIEW B off, and using SINGLE SWEEp and
SAVE A to freeze the display at a convenient position
on the graticule. The slope should calculate to approximat€ly 1 0 kHzldivision.

4-9

PerformanceCheck procedure-

4g4Al4g4ApServiceVol. 1

SPAN/DIVto 50 Hz and RESOLUTTON
BANDWIDTH
to
10Hz.
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h. Tune the CENTERFREQUENCYcontrotto position the signal so its slope can be determined.Again,
slope determinationrnay be made easier by switching
VIEW B off, and using SINGLESWEEPand SAVEA to
treeze the displayat a convenientpositionon the graticule. The slope should calculate to approximately
2 Hzldivision.
i. DeactivateSAVE A and SINGLE SWEEP and
switch the TIME/DIVto 20 ms. ActivatezERo spAN
and positionthe displaynear centerscreenso the vertical excursionsper horizontal division (20 ms) can be
measured.ResidualFM must not exc€ed12 Hz within
any one horizontal
division.

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Figure 4-5. Typical display for measuriag residual FM.

f. lf SAVEA was used in part e, de-activateSAVEA
and vtEW B. Activate zERo spAN, set TtME/Dlv to
20 ms, and set CENTERFREQUENCY
controtto position the displaynear centerscreenas shown in Figure
4-58. Use SAVE A to freeze the display for easl in
measuring FM. The peak-to-peakamplitude of the
display (numberof vertical divisions)within any given
horizontaldivision, scaled to the vertical deflections
accordingto the slope estimatedin part e, is the FM.
ResidualFM must not exceed7 kHz over 20 ms (1 divi_
sion).
S. Press 10 dB/DlV to re_enable
the phase tock, then set the FREQUENCYto 100 MHz
and switchthe TIME/DIVto AUTO. Reducethe FREQ
4-10

7. Check Frequency Span/Div Accuracy
(Within5% of the selectedspan/div)
(Measuredover the center I divisionsof a 10 divisiondisplay)
Span accuracyis checked by noting the displacement of calibratedmarkersfrom their respectivegraticule lines over the centereight divisionsof the screen.
The frequencyspan/div accuracy is checked, for all
SPAN/DIVsettingson band 1, at 100 kHz/Divon band
2, {2nd LO check)and at 500 MHz/Divon band4. The
accuracyof the 1 GHz, 2 GHz. 5 GHz, and 10 GHz
spanldiv of the upper bands is directly relatedto the
100 MHz/Div and 200 MHz/Div spans. Therefore,the
1 GHzlDiv, 2 GHz/Div, 5 GHz/Div, and 10 GHz/Div
spans are not includedin this procedure.
FREOUENCY
SPAN/DIVrangeis 20 Hz to 100MHz
for the 0 to 7.1 GHz bands,in a in a 1-2-5 s€quence
when selected via the SPAN/DIV control, or up to
400 MHz when selectedvia the DataEntrykeyboard.
a. Set the SpectrumAnalyzercontrolsas follows:
CENTERFREOUENCY
1 GHz
SPAN/DIV
100MHz
RESOLUTIONBANDWIDTHAUTO
-30 dBm
REFLEVEL
T|ME/D|V
AUTO
VERTTCAL
DTSPLAY
10 dB/DtV
b. Applythe CAL OUT signalto the RF INPUTand
set the CENTERFREQUENCYto align the 100 MHz
markersso the 100 MHz/divaccuracycan be measured
over the centereightdivisionsof the display.lt may be
necessaryto changethe REF LEVELto obtainadequate
markeramplitude.Maximumdeviation(seeFigure4-6)
must not exceed5 MHz/Div,

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PerformanceCheck procedure-

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Figure4S. Typicalmarkerdlsplayfor measuring
Span/Div
accutacy.
c. Removethe CAL OUT signatfrom the RF tNpUT
and set up the test equipment;s shown in Figure
4_7.
set the CENTERFREOUENCyto 10 eni, bnlr.rTDtv
to
500 MHz, RESOLUTTON
BANDWIDTHto'100 kHz, and
REF LEVELto -10 dBm. peak the responsewith
the
MANUALpEAK controtand set REF LE'EL for the
best
markerdefinition.lt may also help to resetthe CENTER
FREQUENCY
for b€ttermarkerdefinition.
d. Tune a markerto center screenthen check
the
accuracyover the centereight divisionsof the display,
Deviationmust not exceed*25 MHz/Div.
E. SEt thE CENTER FREOUENCYtO 2.0
GHZ,
SPAN/DIVto 100kHz, RESOLUION BANDWTDTH
to
1 If.,
T|ME/D|V to 50 ms, and REF LEVEL to
-20 dBm.
f. Modulatethe Comb Generatorsignalwith 1Ops
markers,from the Time Mark Generato-r,
by applying
the MarkerOutputto the pulse Inputof tte iomU denl
erator.asshownin Figure4-7. S;t the MANUALpEAK
controltor optirnummarkerdefinition.
g. C[e9k SPAN/D|V accuracy. Error must not
.
exceed*5 kHz/Div.

4g4AJ4g4Ap
ServlceVol. 1

i. Reset the REF LEVEL for tho best marker
definirion,and the CENTERFREouENcy t" ariln ii.,e
ryt9rs so span/div accuracycan be checkedilr the
50 MHz/div.
j. Reset CENTERFREOUENCY
to 100MHz and
SPAN/D|Vto 20 MHz, and apply 50 ns (20 frlHzymaif10dB/DlV.
(4) R_€setthe spAN/Dtv to 100 kHz white keeping
the 600 MHz harmonicof the calibratorsignal neai
center'screen with the CENTER/MARKERFRE_
OUENCYcontrol. The 1st LO is now unlocked.
(5) Enablea single marker, and position it on the
signalbypressingPEAKF|ND.
(6) Checkthat the marker readout is within 35 kHz
of the centerfrequencyreadout.
(7') Press  1OdB/DtV to enabte
phaselock.

The 1st LO is not phas€-lockedin Fre_
quency Span/Div settings >200 kHz. For
Span/Divsettings (200kH2, the lst LO
may be unlocked by first going to an
unlockedSpan/Divsettingand disablingfre_
quency corr€ctions (Btue_SHtFT
1OdB),
then-spanningdown to a Span/Divsettint
(200 kHz.
QuantityN is the lst LO harmonicnumber
used for the first conversion.press HELp
and BANDV for the value
of N.

a. Check slngle markeraccuracy.
(1) Applythe CAL OUTsignattothe RF tNpUT.
(2) Set the SpectrumAnalyzercontrolsas follows:
CENTERFREOUENCY
sPAN/DlV
AUTORESOLN
REF LEVEL
VERTICALDISPLAY
TrME/DtV
TRlGGERING

4-12

600MHz
500 kHz
On
-20 dBm
10 dB/Dtv
AUTO
FREERUN

(8) Use the CENTER/MARKER
FREQUENCYcontrol to reposition the calibrator harmonic near
center-screen.
(9) Press PEAK F|ND to position
the markeron the signal.
(10) Check that the marker frequencyreadout is
within 47 kHz of the center frequencyreadout. The
factor (CF x ReferenceFrequencyError)is canceled
whenihe CAL OUTsignatis used.
b. CheckA marker accuracy.
(1) Set the SpectrumAnalyzercontrolsas follows:
CENTERFREQUENCY
sPAN/DtV
AUTORESOLN
REFLEVEL
VERTICALDISPLAY
TtME/DtV
TRIGGERING

0-60GHz
1 0 0M H z
On
-20 dBm
10 dB/Drv
AUTO
FREERUN

(2) EnableA markersby pressing
A MKR, and tune one marker to a harmonicof the
calibrator signal.
Press

MKR 1*MKR 2, and tune the second marker to
anotherharmonicof the catibratorsignal.
(3) Check that the A marker frequencyreadout is
within17oof the measuredspan.

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PerformaneeCheck procedure _ 4g4Al4g4Ap
Servlce Vol. 1

SPECTRIfr AI{I.AYZERUI{OERTEST

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OENERATOR
MOOULE

Figure 4-7' Test equipment setup
for checklng frequency span/Dlv and
sweep Time/Div accuracy.

9. ^C.*:*_qyegpTimeAccuracy
(Within
S%of therateserecitJi'
a. Connectthe outputof the Time
Mark Generator
to the rear-panetMARKERI/|DEO
input.--6'onnect
pin 1
of J104 ACCESSORYconnector
ti-groiio
(connect
pin 1 to pin S).
- .b. _Setthe SpectrumAnalyzerTIME/D|Vto 20 ps,
and
activatezERo SpAN ano tNT rireb-lnjr.rc.

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e. check the accuracyof the 20 ps to 5 s TIME/D|V
::l!'!.S_r by apptying appropriate markers ,or each
TIME/DlV setting and noting the displac€ment
as
describedin part d of this step.
f. Disconnectthe-test_equipment,
and the shorting
strap from pin 1 of Jl04 ACCESSORyconnector.

10. Check Pulse Stretcher
Disabledigitalstoragefor sweeptimes
fast€r than 2 ms.
c. Set the Time Mark Generatorcontrols
for 20 ps
time marks.
d. use the horizontalposlTloN controt
to align a
marker..onrhe 1st graticutetine (see
Fd;; 4-B),then
check the displacement
of markerstrori-ineir respective positionsover the c€ntereight
divisions.Marker
dispfacement
mustnot exceedS/o overthe display.

a. Apply .1 ms time marks, from the Time Mark
Generator, to the RF lNpUT. Set the spectrum
Analyzercontrolsas follows:
CENTERFBEOUENCY
ZEROSPAN
RESOLUTTON
BANDWIDTH
REF LEVEL
VERTICAL
DISPLAY
TtME/DtV
VIEWA and VIEWB
TRIGGERING

2.0MHz
On
100kHz
0 dBm
10 dB/Dtv
.1ms
off
INT

4-13

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PerformanceCheck procedure- 4g4A/4g4ApServiceVol. 1

b. ActivatePULSESTRETCHERand nore that this
modeextendsthe talt time of the markers.
c. Removethe test equipment.
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Figure 4€. Typlcal display for measuring Time/Div
accuracy.

11. Check ResolutionBandwidth
and shape Factor

(6 dB bandwidth within 2ov" of the s€lected
bandwidth; shape factor is 7.S:l or less lor all
bandwidths
otherthanthe 1OHz bandwidthwhichis
12:1or less)

a. Applythe CAL OUT signatto the RF lNpUT. Set
the SpectrumAnalyzercontrolsas follows:
CENTERFREQUENCY
sPAN/DrV
RESOLUTION
BANDWIDTH
REFLEVEL
VERTICAL
DISPLAY
MINNO]SE
PEAK/AVERAGE
TrME/DrV
TRIGGERING

100MHz
1 MHz
3 MHz
-20 dBm
2 dBlDtv
Activated
FullyClockwise
AUTO
FREERUN

b, Measurethe 6 dB down bandwidth(see Figure
4-9A). Bandwidthshoutdequal3 MHz *600 kHz.
c. Resetthe vERTtcALDtspLAy to 10 dB/Dtv and
measurethe 60 dB down bandwidth(seeFigure4_gB),

4-14

BAIIDWIDTH
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S}IAPEFACTOR
*r--zffrr*
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a. llolrtqlnq COdAdorn DenrMrt0r end computhg
d'|Pc tactot
556{r..6
Figure 4-9. Typical display for measuring bandwldthand
shapefactor.

d. Check that the shape factor is 7.5:1 or less. The
shape factor is the ratio of -60 dB/-6 dB bandwidths
{see Figure 4-9).
e. Reset the RESOLUTIONBANDWIDTHto 1 MHz,
SPAN/DIV to 500 kHz, and VERTICAL DISPLAY to
2 dB/DrV.
f. Check the resolution bandwidth and shape factor
of the 't MHz filter by repeating parts b through d.

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PerlormanceCheck procedure_ 4g4Ll4g4ApServlce
Vot. 1
g. Checkthe resolutionbandwidths
and shapefac_
tors for the 100 kHz (300ftHa for Option
bA,
1 kHz,and 100Hz fitters. Shapefactlistroufd 10 kHz,
be 7.5:1
or less.
h. RESET
thE RESOLUTION
BANDWIDTH 'IO

tO HZ,
qlglptv to 50Hz, and VERlCnl.'drdpr-ry
ro 2

dB/Dlv.

i. Checkthe resolutionbandwidthand
shapefactor
of the 10 Hz fitter. Shapefactor should
i" iZrt or tess.

12. Check Catibrator Output
(-20 dBm *0.3 dB)
Apply a 100MHz signal to the power
meter
through a 3 dB attenuatoranO a SOO
Set the
generatoroutput levelfor a reading _20
of "d;t".
dBm on the
powermeter.
b. Disconnectthe power meterfrom the signal
gen_
erator,and connectthe referencesignat
established
in
part a to the RF tNpUT,through
thd same 50O cable
and 3 dB attenuator.
c. Set the SpectrumAnalyzercontrolsas follows:
CENTERFREQUENCY
SPAN/DIV
RESOLUTION
BANDWIDTH
REFLEVEL
VERTICALDISPLAY
TfME/Dlv
PEAK/AVERAGE

100MHz
100kHz
1 MHz
-18 dBm
2 dBlDtv
AUTO
FullyClockwise

; .d. .Sel the spectrumanalyzerVERTICALDlSpLAy
factor
to th€ AA mode by pressingfiruE.-'Set the
REF
LEVELsuchthat the top'oi the siinat is'on graticute
a
line near the top of the crt. nesJt ttre neF
LEVELto
0.99 gP by pressingF|NE twice. Store ttre
displayby
activatingSAVEA.

CENTERFREOUENCY
sPAN/DtV
RESOLUTION
BANDWTDTH
REFLEVEL
VERTICALDISPLAY
TrME/DtV
WIDEVIDEOFTLTER

100MHz
1 kHz
100Hz
-40 dBm
10 dB/Dtv
AUTO
On

b. Checkthat the amplitudeof th€ noisesidebands
is at least 50 dB down from the referencelev€l at g0
times the resolutionbandwidth(3 divisionsaway from
the centerfrequencyposition).See Figure4-10.
c. Reset the spAN/Dlv to 1oo Hz and set the
RESOLUTTON
BANDWTDTH
to 10 Hz.
d. check that the amplitudeof the noise sidebands
is at least 50 dB down from the referencelevel at
30
timesthe resolution
bandwidth.
€. Reset the spAN/Dtv to 10 kHz and set the
RESOLUTION
BANDWIDTH
to 1 kHz.
f. Checkthat the amplitudeof the noisesidebands
is at least 55 dB down from the referencelevel at O0
timesthe resolution
bandwidth.

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_e. Removethe referencesignaffrorn the nF tNpUT
and connectthe CAL OU.Tsignll in its place
using the
samecablethat was usedin part b of this step.
f. ActivateVIEWB and VIEWA.
g. Checkthat the amplitudedifference
betweenthe
VIEWB and SAVEA disptays(CALOUi iignar
anOthe
reference)
doesnot exceedb.S'Og.

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13. Check Noise Sidebands
(At least-70 dBc at 30Xthe selectedbandwidth
for
bandwidthsof 100Hz and 10 Hz)
, resolution
(At least-75 dBc at gOXthe selectedbandwidth
for
all otherresolulionbandwidths)
1. Apptythe CALOUTsignatto the RF tNpUT.Set
the SpectrumAnalyzercontrolsas follows:

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556034

Figure 4-10. Typical disptay for measuring noas€sidebands.

4-15

Performance
Checkprocedure_ 4g4Al4g4Ap
ServiceVol. 1

14.Check FrequencyResponse
(Response,about the midpoint between two
€xtremes,measuredwith 10dB of RF attenuation
and peaking optimized in the applicabl€bands for
eachcenterfrequencysetting,is as follows:

Band1: +1.5 dB from 10 kHzto 1.gGHz
Band2: *2.5 dB from 1.7 to S.5GHz
Band3: r2.S dB from 3 to 7.1 GHz
Band4: i3.S dB from 5.4 to 1g GHz
Band5: iS.O dB from t5 to 21 GHz)
(Response
with respectto 100MHz is as,ollows:
Band1: *2.5 dB from t0 kHzto 1.gGHz
Band2: *3.5 dB from t.Z to 5.5GHz
Band3: *3.5 dB from 3 to 7.1 GHz
Band4: *4.5 dB from 5.4 to 1g GHz
Band5: *6.5 dB from t5 to 21 GHz)
. The responseat each check point, above band l,
shouldbe peakedwith the MANUALPEAKcontrot.
^, ?: Check frequency response from 0.01GHz to
21 GHz (Bands1 through5).
(1) Connectthe CAL OUT signatto the RF tNpUT,
and perforrnthe  CAL routine.
(2) Set the SpectrumAnalyzercontrolsas follows:
CENTERFREQUENCY 1OOMHz
SPAN/D|V
500 kHz
RESOLUTION
3 MHz
REF LEVEL
-20 dBm
VERTICALDTSPLAY
2 dB/Dtv
MIN RF ATTENdB
O
TIME/DIV
AUTO
PEAK/AVERAGE
Fully Counterclockwise
(3) Set the CAL AMPL adjustmentfor 5 divisionson
the SpectrumAnalyzerdiiptay. This is the 1OOMHz
reference. Activate SAVE A to save the reference.
(4) Connectth€ test equipmentas shownin Figure
4-11.
(5) Set the sweeposcillatorcontrolsfor a cw output
that rnatchesthe SAVEA display(outputfrequency
of 100 MHz and an output amptituOiof approximately-20 dBm).
(6) DeactivateSAVEA. Reset the CENTERFREQUENCYto 500 MHz, and SpANiDtv to 100 MHz,
and activateMAX HOLD.
(/) R:seJ the sweep oscillatorcontrolsfor a sweep
output from 0.01GHz-1 GHz. Enable singlb
sweepon the sweep oscillator.
(8) Check that amplitude deviation from the
100 MHz referencedoes not exceed*2.S dB.
(9) Make a note of the highestand lowestpeaksfor
later comparison.

4-16

00) D€activateMAX HOLD, and repeat parts 6
through10 for a CENTERFREQUENCy
of 1.5GHz
(1 GHzto 1.8 GHz).
(11) Calculate the hatfway point between the
highest and the lowest peak from the peak data
notedin parts g and 10.
(12) Checkthat swept frequencyflatnessis within
1 1 . 5 d B i n B a n d1 .
(13) Switch the Spectrum Analyzer to Band 2
(BANDA),CENTERFREeUENCyto
2.7 GHz,and SPAN/DIVto 200 MHz.
(14) Reset the sweep oscillator controls for a
sweep output trom 1.7 GHz-3.7 GHz. Enablesingle sweepon the sweeposcillator.

Before sweeping any range in Bands 2
through5, set th€ CENTERFREQUENCyto
the centerof the range;applya cw signalat
this center frequency; and peak the
responsewith the MANUALPEAKcontrol.
(15) Check that amptitude deviation from thE
'100 MHz
referencedoes not exceedf3.5 dB.
(16) Again, make a note of the highestand lowest
peaksfor latercomparison.
(17)- Check frequency response in the range
3.7 GHz-5.5 GHz (CENTER FREQUENCY Lt
4.6 GHz and SPAN/D|V at 200 MHz). Continue
making notes of the highest and lowest peaks for
comparisonlateron.
(18) Check Bands 3 through 5 accordingto Tabte
44. 8e sure to make a note of the highest and
lowest peaks after each check.
(19) Calculate the halfway point between the
highest and the lowest peak from the peak data
notedin parts 16 and17.
(20) Check that swept frequencyflatness is within
*2.5 dB in Band2 and Band3, within *3.5 dB in
Band4, and within*5.0 clBin Band5.

lf any segmentor portion of the span fails
to meet the specification,set the FREQUENCYto the centerof this portion;apply
a cw marker at this center frequencyand
re-peakwith the MANUALor AUTO PEAKlNG. Decreasethe FREQUENCY
SPAN/D|V
to displaythat portionand then recheckthe
frequencyresponsefor this portion.

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Perforrnance Check procedure _

70 EXT. ALC III'PUT CO{IINECTOB-

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RF
OUT

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swEEpoSctLLATOR

€XT
ALC

TORFOtrTCoxnecG

SPECTRUII AilALYZER UNDERTEST
Undor Test

I
Nro sMAooaeten
f

) 3 dB ATTENUATOR

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4g4Ll4g4Ap Servlce Vol. 1

CRYSTAL
DETECTOR

Low LosscoAxcABLEwrrx sul courEEroid

Figurc4-11' Testequipmentsetupfor
measuring0.01GHzto 2r GHzfrequency,esponse.
Table 4-4
Oscillator Sweep Range

3-5.0 GHz
5-7.1 GHz

5.4-7.4 GHz
7.4-9,4 c
1 0 . 4G H z
12.4 GHz

4-17

PerformanceCheck procedure-

4g4A/494ApServiceVol. 1

from 10 kHz to
^ b: Check frequency response
10 MHz (lowerend of Band1).
(1) Reconnectthe_testeguipmentas shownin Figure4.12. ResetCENTERFREQUENCY
Io 10 MHz.
(2) Set the generator output for _20 dBm at
10 MHz,and set the SpectrumAnalyzercontrolsas
follows:
CENTERFREQUENCY 10 MHz
SPAN/DIV
500 kHz
RESOLUTION
1 MHz
-20 dBm
REFLEVEL
VERT|CALDTSPLAY
2 dBlDlV
MIN RF AfiEN dB
O
TIME/DIV
AUTO
PEAK/AVERAGE
FullyCounterclockwise
(3) Manually tune the Signal Generatortowards
10kHz while simultaneousty
tuning the CENTER
FREQUENCYcontrol to hold the signal at center
screen. Note amplitudedeviation,and the highest
and lowest peaks.

SlOllAL SOTRC€ (10 kltr -.t0 lrtltr)

As the Signal Generatoris tuned towards
10 kHz, the RESOLUTTON
on the Spectrum
Analyzer must be reset to 100 kHz when
the generator output frequency reaches
2 MHa Also, at approximatety
200 kHz, the
Spectrum Analyzer SPAN/DIVand RESOLUTION BANDWIDTHmust be reset to
50 kHz and 10 kHz respectivelyto prevent
the 0 Hz spur from interferingwith the signal.

Continue resetting the SpAN/DlV and
RESOLUTION
as the generatorfrequencyis
luneddowntowards10 kHz.

SPECTRT'TAIIALYZER UIIDERTEST

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Figure4-12. Test equipmentsetup for measuring10 kHz to 10 MHz frequencyresponse,

4-18

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PerformanceCheck procedure_ 4g4Ll4g4Ap
ServlceVol. 1
(4)

Check that

amplitude deviation from

100MHz reference_does
not,*.""J-*i.s
checkthatflatn€ssis within*1.5 dB.

the

dB. Atso

c. Connectthe CAL.OUTsignatto
the RF tNpUT,
and performthe CAfiouiin".
15.,Chec_k
Display DVnamic Range and Accuracy
(99 jB._il
dB/DtV moOe,-wirrin-accuracy or
:!1.0 dB/l0_10
dB to^-amaximumcumulativeerror of
*2.0 dB over the g0 dB window;rO
Oe-in
rnodewfth an accuracyof *0.4 ABpia 2 dBlDtV
to a max_
imum cumulative
enor of *1.0 Oe'ovei the 16 dB
window;Lin modeis 15% ot fuffica[l-'
a. Connectthe test equipmentas shown
in Figure
4-13-,usingthe lOdB and 1'dB siep"ti"nrutorr.
S"t
the SpectrumAnalyzercontrolsas foilows:

Signaf Source
*30 dBm to -80 dBm
100 kHz to 10 GHz

CENTER FREQUENCY

sPAN/DtV
AUTO RESOLN
REF LEVEL
MIN RF ATTENdB
VERTICALDTSPLAY
NARROWVIDEOFILTER
PEAK/AVERAGE
TrME/DtV

100MHz
20 kHz
On
*10 dBm
0
10 dB/DtV
On
FullyClockwise
AUTO

b. Set the attenuatorsfor OdB attenuation.Set
the
generatorcontrolsfor a.100 MHz outputfrequency,
and
carefullyset the outputlevelsuchttrai tne signatpeak
is
at the top graticuletine.
c. Add 80 dB of externalattenuationin 10 dB
steps
and note that th€ signalst€psdown in 10 dB steps.

Specfrum Analyzer Under Ted

Calibraled Altenuators
10dB&20d8

Calfbrated 1O dB and 1 dB step ailenuators
or separate 10 dB and i dB attenualors.

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Figure 4-13' Test eguipment s€tup for
checking dynamic range and accuracy, and preserecror
image fejection.

4,19

PerformanceCheck procedure-

494A/4g4ApServiceVol. 1

d. Check that the signal steps down in 10 dB
(r1.0 dB) steps as attenuationis added. Maximum
cumulativeerror should not exceed 2.0 dB over the
80 dB range.
e. Deactivatethe NARROWVTDEOF|LTER,return
the externalattenuationto 0 dB, and changethe VERTICAL OISPLAYto 2 dB/DlV. Set the signatpeakat the
reference(top) graticuleline, with the generatoroutput
control.
f. Add 16 dB of externalattenuationin 2 dB steps,
and note that the displaysteps down in 2 dB steps.
g, Check the display accuracy as attenuationis
added. Error should not exceed +6.+ aep dB step, or
exce€da cumulativeerror of +1.0 dB over the i6 dB
window.

d. Checkthat spurioussignalsare at least too dB
down from the levelestablishedin part b. Spurioussignals above100dB down from the referenceestabtished
in part b indicatethat the ylG-tuned preselectorfilter
could be defective.

17. Check RF Attenuator Accuracy
(Within0.5 dB/10 dB to a maximumof 1 dB over the
60 dB rangefrom dc to 1.8 GHz; within1.5 dB/tO
dB to a maximumof 3 dB over the 60 dB range
from 1.8GHzto 18 GHz;and withing dB/10dB to a
maximumof 6 dB over the 60 dB range from 1g
GHzto 21 GHz)

h. Returnthe externalattenuationto 0 dB. change
the VERTTCAL
DlSpLAy to LtN. Set the signalgenerator outputfor a full screendisplay.
i. Check that the signal amplitude decreasesro
within *0.4 divisionsof half screenas 6 dB of external
attenuationis added.
j. Check that the signal amplitudedecreases
ro
within i0.4 divisionsot 114screenor hatf the previous
amplitudeas an additional6dB of att€nuation
is added.
k. Check that the signal amplitude decreasesto
within *0.4 divisionsot 1lg screen or half the last
amplitudeas an additional6 dB of attenuationis added
(for a total of 18 dB).
t. Returnths vERTtcALDtspLAy to 1o dB/Dtvand
disconnectths generatorfrom the RF lNpUT.

This is a three part procedure. part I
checks the first 30 dB (0-30 dB) range of
the rf attenuator,Part ll checksthe remaining 30 dB (30dB-60 dB) range for frequenciesup to 18 GHz,and part lll checks
the 50 dB to 60 dB step of the RF Attenuator lor frequencies
above18 GHz.

PART I

a. Connectthe test equipm€ntas shown in Figure
4-14. Set the SpectrumAnalyzercontrolsas follows:
16. Check Preseleclor Ultimate Rejection
This is a check of preselectoropeiation,not a per_
formancerequirementspecification.
a. Connectthe test equipmentas shown in Figure
4-13, omittingthe step attenuators. Set the Spect-rum
Analyzercontrolsas follows:
CENTERFREOUENCY
SPAN/D|V
AUTO RESOLN
REFLEVEL
VERT|CALDTSPLAY
MIN RF ATTENdB
WIDEVIDEOFTLTER
T|MEIDIV

3.SGHz (Band2)
10 kHz
On
0 dBm
10 dB/Dtv
O
On
AUTO

b. Set the generatorcontrols for a full screen
displayoutputat 3.S GHz. peak the responsewith the
MANUALPEAKcontrotor pEAK MENUmode.
_ c. Changethe FREQ RANGEto band 3 (3.0_7.1
GHz).

4-20

CENTER FREOUENCY
SPAN/DIV
RESOLUNONBANDWIDTH
REF LEVEL
MIN RF ATTEN dB
MINNOISE

VERTfCALDISPLAY
NARROWVIDEOFILTER
T|ME/D|V
PEAK/AVERAGE
VIEW A and VIEW B

Test Freguency
200 kHz
100 kHz
-30 dBm

o

On
2 dBlDtV
On
AUTO
FullyClockwise
On

b. Set the power meter controls as follows:
Mode
Range Hold
Power Reference

Watts
Out
Out

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PerformanceCheck procedure-

POWERMETER

RF
OUT

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POTYER
SENSOR

AOAPTER

Flgure4-14. RF attenuatortest equipmentselup.

c. Disconnectthe power sensor from the power
divider, and connect it to th€ the I ,WISO MHz
reference output port through an appropriateadapter.
Be
sure that the 50 MHz referenceis'tumedoff.
- d. On the power meter,press SensorZeroand wait
for the-zero light to turn off. Repeatuntil a
zero is
attained.

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ATTET'IUATOf,

LOW LOSSCOAXCABLEIYITHSMA COI{NECTORS

f. Turn off the 50 MHz reference on the power
meter, and reconnectth€ power sensor to th€ power
divider.

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ADAPTER

FOWERDIVTDER

e. .On the power meter, set the 50 MHz reference
on and set the Cal Factor switch to the 50 MHz
reference.. Set the power meter Cal Adj for a 1.000
mW
reading.

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ExT
ALc

ADAPTER

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SPECTRUIIANALYZERUI{DERTEST

SIGI{ALSOURCE

ADAPTER

4g4Al4g4ApServlceVol. 1

g. Resetthe powermetercontrolsas follows:
Cal Factor
Mode
RangeHotd

Test frequency
dBm
Out

con.h. setthe signatgen€rator(Hp g3508/s3595A)
trols as follows:

Frequency
Mode
Frequency
OutputLevel

CW
Test Frequency
--5 dBm

i. Set the generatorcontrolsfor a -15 dBm power
-5 dBm generatoroutput
meter reading(approximately
Ievel).
j. Tune the CENTERFREQUENCY
controt to brino
the signalto centerscreen.
k. The SpectrumAnalyzershould be displayinga
signalof approximately-35 dBm.
l. Use the SpectrumAnalyze/sAMPL CAL control
to positionthe signalpeak at a convenientgraticuleline,
then activateSAVEA.
m. Establisha referencesettingfor the first 10 dB
incrernentby pressingdB[Ref on the power meter.
n. Resetthe MIN RF ATTENdB controlto 10 and
the REFERENCE
LEVELto -20 dBm. Reset the generatoroutputlevel for a power meterreadingof +10 dB
(10 dB increasein outputlevel).

4-21

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PerformanceCheck procedure_ 4g4Ll4g4ApServlce
Vol. 1

Tabte4-5
OTO 30 dB RF ATTENUATOR
TESTSETTINGS
SpectrumAnalyzer
ReferenceLevel
-30 dBm

MIN RF ATTEN dB
Setting

ExternalAttenuator

0dB

-20 ctBm
-20 dBm

20 dB

10dB

20 dB

1 0d B

-10 dB,"
-10 clBm

10dB

20 dB

1 0d B

20 dB

-0 dBm

0dB

30 dB

0dB

o. Check that the differencebetweenthe SAVEA
and V|EWB_disptays
is tessthan O.SdB up to 1.g GHz,
lessthan1.5dB from .t.gGHzto 1g GHz,and tess
than
3.0 dB from 18 GHZ to 21 GHz. Make a note of the
level difference between the SAVEA and VIEW
B
displays.
p. To check the next 10 dB step, reset the genera_
!o^rlor a 0 dB power meter reading,and replace the
20 dB attenuatorwith a 10 dB attenuitor.
_- _e.I"peat parts m through o, except that the next
MfN RF AfiEN dB setting witt Ue 20 and rhe reference
levelwillbe -10 dB flabte 4-5).
. r. lepeat,the procedurefor the third 10 dB step
as a guide for setupinformationfor th€
lfing__T19le-4-5
third MIN RF ATTENdB setting.

PART II
a. The 30-60 dB range is checked in the same
fashion as the 0-30 dB range using differentpower
levelsbecauseof the outputlevellimitition of the signal
generator.
b. Connectthe test equiprnentas shownin Figure
4-14. Setth€ SpectrumAnalyzercontrolsas follows:
CENTER FREQUENCY
sPAN/DtV
RESOLUTION BANDWIDTH
REF LEVEL
MIN RF ATTEN dB
MIN NOISE
VERTICALDISPLAY
NARROWVIDEO FILTER

TrME/DtV
PEAK/AVERAGE
VIEWA andVIEWB

4-22

Test Frequency
200 kHz
100kHz
-25 dBm
30
On
2 dB/Dtv
On
AUTO
FullyClockwise
On

Power Meter
dB(Rel)
0 dB:Ref
+10 dB

0 dB-Ref
+10 dB
0 dB-Ref
+10dB

Power Meter
dBm
--15 dBm
:-5 dBm
--lA;

=-5 dBm

:-15 dBm
:-5 dBm

c. Set the power metercontrolsas follows:
Mode
Watts
RangeHold
Out
PowerReference Out
d. Disconnectthe power s€nsor from th€ power
divider, and connect it to the 1 mW/S0MHz reference
output port through an appropriateadapter. Be sure
that the 50 MHz referenceis turnedoff.
e. On the power meter,press SensorZeroand wait
for the zero light to turn off. Repeat until a zero is
attained.
f. On the powermeter,set the S0 MHz referenceon
and set the Cal Factorswitch to the S0 MHz reference.
Set the power meterCat Adj for a 1.000mW reading.
g. Turn off the 50 MHz referenceon the power
meter, and reconnectthe power sensor to the power
divider.
h. Resetthe power meter controlsas follows:
Cal Factor
Mode
RangeHold

Test frequency
dBm
Out

i. Set the generatorcontrols for a maximumpower
meter reading,then reduce the generatoroutput tevel
untilthe meterreads't1 dB lessthanthe maximum.
j. Tune the CENTERFREQUENCyconrrotto bring
the signalto centerscreen. The REF LEVELmay have
to be varied slightlyto obtain a convenienton-screen
display.
k. Use the SpectrumAnalyzer'sAMPLCAL control
to positionthe signalpeak at a convenientgraticuleline,
then activatesAvE A.

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o
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PerformanceCheck procedure-

4g4Al4g4Ap
ServlceVol. 1

)

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l. Establisha referencesetting for
the first 10 dB
incrementby pressingdB[Ref on tie po*"i
meter.
m. Increasethe tr4tNRF ATTEN dB setting
by 10
and reset the REFERENCE
LEVEL10 dB higherthan
the levetset in part j. Resettn"
!"n"i"i* output level
for a power meter readingof +16
Oe. Eeter to Tabte
4-6 for setupinformationai each rf attenuaior
setting.
n. check that the differencebetweenthe
SAVEA
and VIEW.B_displays
i9 t^e1than0.5 dB up to .t.AGHz,
less than 1.5dB from 1.9GHzto f g Gftz, lnd
'note
tessthan
3.0 dB from 1g GHz to 21 GHz. frrt"f."'"
level differencebetween the SAVEA and of the
VIEWB
displays.

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CENTERFREQUENCY
SPAN/DlV
RESOLUTIONBANDWIDTH
REF LEVEL
MIN RF ATTEN dB
MIN NOISE

VERTICALDISPLAY
NARROWVTDEO
FILTER
TIME/DIV
PEAK/AVERAGE
VIEWA and V|EWB

o. Continueto cheekthe secondand third
attenuator steps usingTable 4;6 as a guide for setup
information. Make a note of the levelliference at each
settingbetweenthe SAVEA and VIEWB ctisptays.step
p. Using the data noted in step o of part
steps n and o of part lt, check that deviation I and
over the
entire60 dB rangeis lessthanI dB up to 1.g
GHz,teis
than 3dB from 1.gGHz to lgGH;, and tess
than
6.0 dB from 1BGHzto 21 GHz.

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b. Connectthe test eguipmentas shown in Figure
4-15. Set the SpectrumAnatyzercontrolsas followj:
Test Frequency
200 kHz
1 MHz
-25 dBm
50
On
21BIDIV
On
AUTO
FullyClockwise
On

c.
^
!o1n_ectthe power sensorto the 1 mW/50MHz
Power Ref Output port_onthe power meterthroughan
appropriateadapter. Be sure that the 50 MHz ieference is turnedoff.
d. On the power meter,pressSensorZeroand wait
for the zero light to turn off. Repeatuntit a zero is
attained.
e. On the power rneter,set the 50 MHz reference
on and set the Cal Factor switch to the S0 MHz reference. Set the power meter Cal Adj for a 1.000mW
reading.

PARTIII
Dueto-outputpowerlimitationsof the signalgen.a.
erator,
a different test setup is required to test
the
50-60 dB step of the RF Att€nuatorfoi frequencies
above18 GHz.

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Table 4-6

SpectrumAnalyzer
ReferenceLevel
-25 dBm
-

30 TO 60 dB RF ATTENUATOR
TESTSETTINGS
MIN RF ATTEN dB
Setting

ExternalAttenuator

30 dB

-15 dBm
-15 dBm

20 dB

40 dB

20 dB

40 dB

-5 dBm

1 0d B

50 d8

-5 dBm

1 0d B

50 dB

0dB

+5 dBm

60 dB

0dB

Power Meter
dB(Rel)
0 dB-Ref
+10 dB
0 dB-Ref

+10 dB
0 dB:Ref

+ 1 0d B

Max Power Meter
Reading In dBm

(Maximum- 11 dBm)
(Maximum- 1 dBm)

- 11 dBm)
(Maximum
(Maximum- 1 dBm)
- 11 dBm
(Maximum
(Maximum- 1 dBm)

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4-23

PerformanceCheck procedure-

4g4Al4g4ApServiceVot. 1

f. Turn off the 50 MHz reference on the power
rneter, and disconnect th€ power sensor from the
PowerRef Outputport.

k. Use the Spectrum Anatyzer's REFERENCE
LEVELand AMPL CAL controls to position tho signal
peak at a convenientgraticuleline,then press SAVEA.

g. Collect the generator output to the Spectrum
AnalyzerRF lN through the precisioncabte and 10 dB
attenuator.

l. Disconnect the Spectrum Analyzer from the
10 dB attenuator,and connectthe power sensorto the
attenuator.

h. Set the generatorcontrolsfor a maximumoutput
power.

m. Establisha referenceby pressingdB[Ref on the
powerrnet€r.

i. Tune the CENTERFREQUENCycontrotto bring
the signalto center screen. The REF LEVELmay hav6
to be varied slightly to obtain a convenienton-screen
display.
j. Reduce the generator output power by 1 dB.
_This allowsenoughof an adjustmentrangeto piovide a
10 dB incrementin power levellater.

n. Without disturbing any settings, remove th€
10 dB attenuatorand reconnectthe cable directlyto the
power sensor.
o. Reset the generatorcontrolsfor a +10 dB power
meterreading.
p. Disconnectthe cablefrom the power sensor,and
connectit to the SpectrumAnalyzerRF lN.

SPECTRUMANALYZER
UNDER TEST

POWER
METER

SIGNAL GENERATOR

--J
PRECISIONLOW
LOSS CABLE

10 dB
ATTENUATOR

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POWER
SENSOR

Figure 4-15. RF attenuato. test equipment setup for 50-60

4-24

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dB step.

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PerformanceCheck procedura q:
..
19.gt the SpectrumAnalyzerRF attenuatorsetting to 60 dB, and increasethe reference
level setting
by t0 dB.

I

c. ActivateMIN NOISEand note signallevel
Level shift must not exceed *0.g dB, o-,+ minorshift.
Oiui_
sions(attenuatorplus gain accuracies).

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dB Ratio
of Signal
Plus Noise

Correction
Factor

change the REF LEVEL from _20 dBm to
-30-9.
dBm, in 1 dB increments,with the 1 dB stef
attenuator,and note incrementaland 10 dB step accuracies.
h. Return the 1 dB step attenuator to 0 clB.
Decrease the signal level by 10 dB with external
attenuation,or with the signat generator output fevel
control, then re-estabtishthe signal referenceampli_
tude.
i. Check the -30 dBm to -40 dBm gain accuracies
as in part e.
j. Repeat the procedurecheckinggain accuracies
to -60 dBm.
k. Establish a signal reference amplitude of
-60 dBm, activate NARROW
VTOEOFILTER, then
checkgain accuracyto -70 dBm.
I. Decreasethe RESOLUTION
BANDWIDTHand
SPAN/DIVto 1 kHz. Re-establisha signal reference
levelof -70 dBm as describedpreviously.
m. Check the -70 dBm to -90 dBm gain accuracies by repeatingthe processpreviouslydeicribed.
n. Decrease the RESOLUTTONBANDWTDTH
100 Hz and SpAN/DIVto 50 Hz, reestabtishthe signal
referencelevel and check the -g0 dBm to _gOdBm
and -90dBm to -1 00dBm gain accuracies.These
rangesare directlyrelatedto the -60 dBm to _70 dBm
check(parts d throughm).

100MHz
10 kHz
10 kHz
-10 dBm
0
1 dB/Dlv
On
AUTO
off

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e. switch ihe REF LEVELfrom _10dBm to _20
dBm in I dB steps, adding.l dB of externatatt€nuation
at each step. Note incrementalaccuracyand the 10
dB
91n.jr9g!racy. Incrementataccuracy must be within
0.2 dB/dB. Maximumcumulativeerroi rnustnot exceed
0.5 dB except when steppingfrorn the g dB to 10 dB
increment, where the error could be an addational
0.5 dB. This exception_does
not apply when stepping
from -69 dBm to _70 dBm,_79 dBm to _go oem, itc.f. DeactivateMtN NolsE. Return the 1 dB step
attenuatorto 0 dB, decreasethe output of the sign;l
generatorby 10 dB or add l0 dB of external
attenuation. Reset the generatoroutput so the signal tevetis
againat the 6th graticuleline.

18. Check lF Gain Accuracy
(+0.2.dB/dBStep to a miximum of *0.S
dB/g dB
exceptat the decadetransitionsof _19 Oem _eO
to
-29
dBm,
dBm to __30dBm, _3s oam to _40 dBm,
-49 dBm ro -S0 dBm,
and _59 dBm io _60 oBm
wherean additionalO.SdB can occurfoi a
totat of
dB/decade.Maximumdeviationover the full g7 t
dB
rangeis within+2 dB)
T.hf".checkrequirescalibratedattenuators
..
to check
the 10dB and 1 dB steps. When mafing
measurements within 10 dB of the noise floor, a correction
tor shouldbe used to correct for the logarithmic facaddition of noisein the system,as shownin fi6te
+-2.
a. Connectth€ test equipmentas shown in
Figure
4-13, usingthe calibrated'1ddB ano t ae
attenuators
!"j ::g^::l the output-of the g"n"r"to, oirecily to the
RF TNPUTif individuatfixed atGnu"tor"
be used
as
"r"1o controls
lhe standard).Set th€ SpectrumAnalyzer
as follows:

- b. Set the generatorcontrolsfor a 100 MHz output
frequency,and a signalamplitudeot six Oivisions.

a

d. Set the output of the signal generatorto repositionthe signallevelat the 6th graticuleline.

between the SAVEA
.r, lheck that t,€
and.VIEWg.gi.prqfr {itEreqce
t\"n
s.ri o-e. Make a note
is \ss
of th€ levetdiffere(rce
OetNqer/ttreSnVe n'anO V|EWB
displays.
\
s. Usingthe data noted in step o of part l,
and o of part ll, and step r of part ttt, ctreck steps n
that deviatlon overthe entire60 dB rangeis lessit
Og.
"n'O

CENTEBFREOUENCY
SPANIDtV
RESOLUTION
BANDWIDTH
REFLEVEL
MIN RF ATTENdB
VERTICALDISPLAY
WIDEVIDEOFILTER
TrME/DtV
SAVEA

4g4Al4g4ApServlce Vol. 1

Table 4-7
CORRECTIONFACTORTO DETERMINETRUE STGNAL
LEVEL

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

't2.0

14.0

3.0

2.20

1.65

1.26

0.97

0.75

0.s8

0.46

4.28

0.18

4-25

PerformanceCheck procedure-

4g4Al4g4ApServiceVol. 1

19. Check Gain Variation Between Resolution
Bandwidths
(Less than *0.4 dB with respect to the 3 MHz fitter
and less than 0.8 dB betweenany two filters)
Before performingthis check, do a front panelCAL
procedure by pressing  CAL and per_
forming the steps promptedby the spectrum analyzer.
a. Apply the CAL OUT signatto the RF tNpUT,and
set th€ SpectrumAnalyzercontrolsas follows:
CENTERFREQUENCY
100MHz
SPAN/DIV
100 kHz
RESOLUTION
BANDWTDTH 3 MHz
-18 dBm
REFLEVEL
MlN RF ATTENdB
0
VERTICALDISPLAY
1 dB/Dtv
MIN NOISE
On
TrME/D|V
AUTO

FREQ RANGE

sPAN/DrV
RESOLUTION
BANDWIDTH
REFLEVEL
MIN RF ATTENdB
VERTICALDISPLAY
NARROWVIDEOFILTER
VIEWA&VIEWB
PEAK/AVERAGE
TrME/DrV

0-1.8 GHz
MAX
10 kHz
-100 dBm
0
2 dBlDlV
On
On
FullyClockwise
1s

b. Enable a marker by pressing TUNE CFIMKR.
Tune the markerto the highestpoint on the noisefloor.
Activate zERo SPAN, and change the RESoLUTIoN
BANDWIDTHto 3 MHz and the REFERENCE
LEVELas
ncessaryto view the baseline.
c. Checkthat the noise floor (level)is down as per
Table 4-8 (at least -80 dBm down if checkinga standard instrument,or -31 dBmV if checking the 7SO
input in an Option07 instrument).

d. Change the RESOLUTTONBANDWTDTHto
1 MHz.
e. check that amplitudedeviationfrom the 3 MHz
referenc€is no morethan *0.4 dB.
f. Change the RESOLUTTONBANDWTDTHto
100 kHz and the FREQSpAN/Dtvto .t0 kHz.
g. Check that amplitudedeviationfrom the 3 MHz
referencelevelis no morethan f 0.4 dB.
h. R€p9at the procedureto check the remaining
filters(10kHz, 1 kHz, 100H2, and 10 Hz) to verifythat
the signal amplitude does not change more than
+0.4 dB from the 3 MHz referencelevel.
i. Check variation between any two filters (0.g dB)
by finding the filter that has the lowest amplitude,sav_
ing it on the A-trace,then comparingthe other filtersto
the saved trace.

a. conn€ct the cAL ouT signat to the RF tNpuT,
and perform th€  CAL routine. Remove
the CAL OUT signalfrom the RF lNpUT, and terminate
the FF INPUTin its characteristicimpedance. Set the
SpectrumAnalyzercontrolsas follows:

4-26

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m. Gheck that the noise floor (level) is down as per
Table 4-8.

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N. RESETthE RESOLUTION BANOWIDTH tO 1O HZ.
and VERTICAL DISPLAY to 5 dB/DlV.

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The REF LEVEL will have to be reset each
tiME thE RESOLUTION BANDWIDTH iS
changed.
d. RESET
thE RESOLUTION BANDWIDTH tO 1 MHZ.
e, Check that the noise floor (level) is down as per
TablE 4-8.
Reset
f.
100 kHz.

the

RESOLUTION BANDWTDTH to

g. Check that the noise floor (level) is down as per
Table 4-8.
h. RESET
thE RESOLUTIONBANDWIDTHtO 1O KHZ.
i. Check that the noise floor (level) is down as per
Table 4-8.
j. Reset the RESoLUTION BANDWTDTHto 1 kHz.
k. Check that the noise floor (level) is down as per
Table 4-8.
I. RESET
thE RESOLUTIONBANDWIDTHtO 1OOHZ.

20. Gheck Sensitivity
(Referto Table4-8)

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b. Activatethe AA mode by pressingFINE.
c. Resetthe REFERENCE
LEVELcontrotto position
the calibrator signal at the 7th graticule line (1 major
division from the top), then activate SAVEA to store the
3 MHz amplitude.

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o. Check that the noise floor {level) is down as per
Table 4-8.
p. Repeat this procedure for the remaining coaxial
input frequency range (1.7 to 21 GHz). lf desired, the
sensitivity for the waveguide bands can be checked as
per the listings in Table 4-8. The values for the 50 GHz
to 140 GHz range are typical and not intended as a performance requirement.

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PerformanceCheck procedurc -

Band/Frequency
eanQ

I MHz

Table 4-8
SENSITIVITY.
tN dBm (dBmVfor 75o tNpUT)
1 MHz
300 kHzb
100kHz
10 kHz

4g4Ll4g4ApService Vol. l

1 kHz

100 Hz

10 Hz

| (cut,

-80

-85

-90

-95

-105

-115

-12s

-134

-31

-36

-41

NA

-56

-66

-76

-85

-74

-79

-u

-89

-99

-109

-119

-125

-60

-65

-70

-75

-85

-95

-105

-111

Band4 (50o Input)
12-18 GHz

-55

-60

-65

-70

-80

-90

-l 00

-107

uano ] (5utr tnput)
15-21 GHz

-55

-60

-oc

-70

-80

-90

-100

-'t07

bano bs (5o{} Input)
78-27 GHz

-65

-70

-75

-80

-90

-100

-108

-116

-60 |

-65

-74

-75

-85

-9s

Input)
10 kHz-l.8 GHz
\rPuonu/ (/5{r Input)
5 MHz-l GHz
E anss z 6( U (5U{1,

Input)
1.7 GHz-7.1 GHz
Eano 4 (curl tnput)
5.4-12 GHz

Eanos / arue(5uo
Input)
26-60 GHz
Band9c (50O Input)
50-90 GHz
Band 10c(50o Input)
7$-140 GHz
Band11c(50O Input)
110-220 GHz
Bandl2c (50O fnput)
170-325 GHz

ypically-95
iHz
ypically-90
40 GHz
ypically-80
20 GHz
ypically-70
25 GHz

MIN RF ATTEN dB
VERTICAL DISPLAY
TrME/DtV

-103

|

-trr

dBm for 1 kHz resolutionbandwidthat 50 GHz,degradingto -g5 oam at g0
dBm for 1 kHz resolutionbandwidthat zs aHz, oegradingto -7s oam ai
dBm for 1 kHz resolutionbandwidthat 110 enr, o"graoingto -65 dBm at
dBm for 1 kHz resolutionbandwidthat 170 GHz, degradingto -55 dBm at

21. Gheck Residual Spurious Response
With no inputsignat,-100 dBm oi tessl
_a. Removeany signal connectedto the RF lNpUT,
and terminatethe RF tNpUT in 50O. Set the Spectrum
Analyzercontrolsas follows:
CENTERFREQUENCY
SPAN/DIV
RESOLUTION
BANDWIDTH
REFLEVEL

|

50 MHz
10 MHz
10 kHz
-50 dBm
0
10 dB/Dtv
AUTO

b. Press STEPSIZE to estabtish
a center frequencystep size. This will allow changing
center frequencyin 50 MHz incrementsby use of the
+STEPand -STEP pushbuttons.
c. Scan the frequencyrange of bands "1, Z, o( S in
100 MHz increments. Note the amplitudeof any spurious response. Spuriousresponseamplitudesmust not
exceecl-1 00 dBm. (ActivatingA F after each increment, makes it easier to determine100 MHz increments.)

a Equivalent maximum inPut
noise (average nois€ {or €sch resolution bandwidth with int€rnal mixer and rEKTRoNtx waveguide
Mixers),
b Option 07 reptaces the 100
kHz filter with a 300 kHz filter.
c TEKTRONIXWaveguide Mixers.

4-27

PerformanceCheck procedure- 4g4A/4g4ApServiceVol. 1

Spactum Analtrar Un(br Totl

al|C T{oilt

clot

Figure 4'16. Test equlpment setup for checking intermoduration distortion.

b. Set the generatoroutputs approximately2 MHz
apart within the frequencyrange of band 1, and set the
outputlevelsfor full screensignals.
c. Decreasethe separation of the generatorfrequenciesto 1 MHz. Reset the spAN/Dlv to 500 kHz
AndRESOLUTION
BANDWIDTH
to 1OKHz.

f1
t2
freq.-..t,
Third (3rd) Order Intermodulationproducts

d. Check that the third order lM productsare at
least 70 dB down trom the input signallevel. See Figure 4-17.
2127_.ts

Figure4-17. Intermodulatlon
products.

22. Check Intermodutation Distortion
fl-hirdorder productsat least 70 dB down from anv
two on-screensignals)
a. connectthe test equipmentas shown in Figure
4-16, and set the SpectrumAnalyzercontrolsas follows:
FREORANGE
CENTERFREQUENCY

0 - 1 . 8 ( B a n d1 )
Within 2 MHz of
Test Generators
sPAN/DrV
5 MHz
RESOLUTION
BANDWIDTH 1 0 0 k H z
-30 dBm
REFLEVEL
n
MIN RF ATTENdB
VERTICAL
DISPLAY
10 dBiDrv
TrME/DrV
AUTO

4-28

Use the Video Filter and very slow sweep
ratesto help resolvethesesidebands.
e. Decr€asethe signal separationand SPAN/DIV
settingsand re-checkfor sidebands. Checkfor lM products at olher spans of the frequencyrange. lM products shouldbe -70 dBc or more.
f. Change the FREQUENCYRANGE to Band 2
(1.7-5.5 GHz),FREQSPAN/DIVto 5 MHz, and RESOLUTIONBANDWIDTH
to 100 kHz.
g. Reset the generator outputs approximately
2 MHz apart within the frequencyrange of band 2, and
set the outputlevelsfor full screensignals.Reducethe
SPAN/DIVand RESOLUTION
BANDWIDTH
so the noise
floor is at least 70 dB down from the referencelevel.
h. Checkthat lM productsare at least70 dB down
from the inputsignallevelor top of the screen.

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PerformanceCheck procedure-

23. Check Harmonic Distortion
{-60 dBc or tessfrorn10 kHz to 1.gGHz)
{Not discernibleabove tt
no]r" ftoor (at
teast100dBc)from 1.7GHz
" "u"r"g"
to 21-cHti
Testedat -90 dBm in MIN DTSTORTTON
mode
a. Gonnectthe test equipmentas shown in Figure
4-18, and set the Spectrum-Analyzer
as fol_
lows:
"onirolu
CENTERFREOUENCY Same as Generator
sPAN/DtV
5 MHz
AUTORESOLN
On
REF LEVEL
-30 dBm
MIN RF ATTENdB
0
VERTICALOTSPLAY 10 dB/Dlv
WIDEVIDEOFILTER
On
MIN DISTORTION
On
VIEWA and V|EWB
On
TrME/DtV
AUTO
Note the SpectrumAnalyzerdisplayas the gen.b.
erator frequencycontroris variid auoui ilie center
frequencyof the bandpassfilter if a bandpass
filter is used
in the test, or as the frequencyis varied below
the
cutofffrequencyif a low pass filter is used.
Set the generatorfrequencyat that frequency
that yieldedthe maximumamplitudein part b, then
set
the outputtevetfor a fuil screen(_30 Oelnyiign"t.

In Figure4-18,the filtershownmusthavea
minimumof 40 dB rolloffto attenuatemulti_
ples of the generator frequency,and the
frequencyot the signal generatordepends
on the frequencycharacteristics
of the fitter.
d.
SEt thE CENTER FREQUENCY tO
!2jlLq$lequency), FREQSPAN/D|Vto 500 kHz, and
RESOLUTTON
BANDWTDTH
to 10 kHz.
e. Checkthat the secondharmonicof the input sig_
nal is at least60 dB belowthe -90 dBm carrier.
f. SEt thE CENTERFREQUENCYtO thE 3rd hAr.
monic.
g, Checkthat the third harmonicof the input signal
is at least60 dB down from the -30 dBm carrier.

24. CheckLO Emission
(-70 dBmor tess)

CenterFrequency
Span/Div
Min RF AttendB
VerticatDisplay
Time/Div
Triggering
BaselineClip
ReferenceLevel
Auto Resolution
View A and View B
Mdeo Filter
Peak/Average

4g4Al4g4ApServiceVd. l

2O72MHz
2MHz
0
t0dB/DtV
Auto
Free Run
Otr
-70 dBm
On
On
Wide
FullyClockwise

.

b. Set the SpectrumAnalyzerundertest as foltows:
CENTERFREQUENCY 0Hz
-30 dBm
REFLEVEL
SPAN/DIV
100kHz
MIN RF ATTENdB
0
PEAK/AVERAGE
FullyClockwise

c. Checkfor any indicationof LO emission.LO
ernission
mustbe fessthan-70 dBm.

25. Check 1 dB Compressionpoint
(-20 dBmBandsI through
5)

Calibrate the power meter befora making
this measurement.
a. Use the power meterto set the outputlevel of a
signalgeneratorto 0 dBm at 1.7 GHz.
b. Connectthe test equipmentas shown in Figure
4-19, using th€ generator with the calibrated output
level. Set the SpectrumAnalyzercontrolsas followsi
CENTERFREOUENCY
sPAN/D1V
AUTORESOLN
REF LEVEL
MIN RF ATTENdB
VERTICALDISPLAY
VIEWA and VIEWB
TIME/DrV

1 . 7G H z
100kHz
On
-30 dBm
0
10 dB/Dtv
On
AUTO

c. Set the attenuatorsfor 25 dB of attenuation.

a. Monitor the RF INPUT with a hioh frequency
spectrum analyzer such as a 4g2A. Set tie test spectrum analyzer controls as follows.

4-29

PerformanceCheck procedure-

4g4Al4g4ApServiceVol. 1

Spectrum AnalyeerUnderTest

Figure4-18. Test equipmentsetuplor checklngharmonicdistortion.

d. Monitorthe 10 MHz lF outputon the rear panel
with a test sp€ctrum analyzer through a 1 dB step
attenuator.Set this step attenuatorfor 0 clB of attenuation.
e. Set the test spectrum analyzercontrols as tollows:
CenterFrequency
FrequencySpan/Div
Resolution
Ref Levet
VerticalDisptay
Time/Div

10 MHz
i MHz
Auto
_20 dBm
2 dB/Div
Auto

f. Use the test spectrumanalyzerCenterFrequency
controlto cent€rthe 10 MHz signalon the test spectrum analyzer.

4-30

g. ActivatezERo spAN and set the CENTERFREOUENCYcontrolto maximizethe 10 MHz signalon the
test spectrumanalyzerdisplay.
h. Resetthe test spectrumanalyzerreferEncelevel
for a four divisionexcursionof the signal.
i. Increasethe input signal level to the Spectrum
Analyzerby switchingout 1 dB of attenuationbetween
the signalgeneratorand the RF INPUT. Add 1 dB of
attenuationbetweenthe 10 MHz lF outputand the test
spectrumanalyzer.
j. Checkthat the 10 MHz lF outputlevelon the test
spectrumanalyzerdisplayremainsconstantas 1 dB of
attenuationis removedfrom the generatoroutput path
and insertedin the 10 MHzlF outputpath.
k. Continueto increasethe input signallevelto the
RF INPUT by 1 dB incrementswhile increasingthe
attenuationbetweenthe 10 MHz lF output and the test
spectrumanalyzeruntil the signalamplitudeon the test
analyzerdecreases1 dB (0.5division).This is the 1 dB
point.
compression

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PerformanceCheckprocedure-

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4g4Al4g4ApServiceVol. 1

TEST SPECTRUMANALYZER

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TO 10 tlHz tF OUTPUT
(REARPANEL)

STEP ATTEI{UATOR

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SIGNAL GENERATOR

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RF INPUT

POWERMETER

@o@o@g@@
SPECTRUTTI
ANALYZER
UNOERTEST

RF INPUT

OUTPUT

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STEP ATTENUATORS

Flgure4'19. Test equrpmentsetuptor checkrng
1 dB inputcompressionpoinl

l. Checkthat the 1 dB compressionpoint occurs
at
-20 dBm or less (20 dB
or less attenuationOetweenthe
generatorand the RF INPUT).

26. Check External Reference Input power
(+15dBm to -15 dBm)
(1 MHz,2 MHz,5 MHz,or 10 MHz.)
a. Connectthe outputof a signalgeneratorto a frequency counter and set the generator frequency
to
10 MHz *50 Hz.
b. Disconnect the generator output from the
counter,and connectit to the EXTERNALREFERENCE
Input connector on the rear panel of the Spectrum
Analyzer.
c. Set the generatoroutputlevelto *1 5 dBm.
...d..Monitorthe SpectrumAnalyzerCAL OUTsignal
with the frequencycounter.

e. Check that the crt readout for REF OSC reads
EXT.
f. Checkthatthe frequencycounterreads100 MHz.
g. Reset the output of the signal generator to
-15 dBm.
h. Checkthat crt readoutstill readsEXTand the fre_
quencycounterstill reads 10x the referencesourcefre_
quency. lf the crt readout changes to E_U (External
Unlock), recheck the external reference source frequencytor 10 MHz *S0 Hz at -15 dBm.

27. Check Triggering Operation and Sensitivity
trigger:2 divisionsor more)
.(lnternal
trigger:1.0V peakfrom .t5 Hz to 1 MHz)
{External
a. Connectthe test equlpmentas shownin Figure
4-20.

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4-31

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PerformanceCheck procedure- 4g4A/4g4ApServiceVol. l

Speclnm Andyrcr Undcr Tcst

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Iodrl.l.d

RF

Figure4'20. Test equlpmentselup for checkingIntemaltrlgger characteri3tica.

b. Set the SpectrumAnalyzercontrolsas follows:
CENTERFREQUENCY
SPAN/DIV
RESOLUTTON
BANDWTDTH
REF LEVEL
VERTICALDISPLAY
TRIGGERING
TIME/OIV
VIEWA and V|EW B

100MHz
10 kHz
1 MHz
-30 dBm
LIN
INT
S ms
Off

_ c. Set the signal source output amplitude for
-30
dBm, and an output frequencyof 100 MHz. Note
that the signalsourcewill be modulatedby the function
9enerator.
d. Decreasethe output of the signalsourceso the
display is half screentthen rnodulatethe signalsource
with a 1 kHz sinewave.
e. ActivateZEROSPANand, if necessary,resetthe
CENTERFREQUENCY
controlfor maximumresponse.
f. Set the function generatoroutput for a modula_
tion amplitudeof two divisions.
g. Checkth€ internaltriggeroperationin the 15 Hz
through1 MHz frequencyrange.

Because of deflection amplifier response,
the displayamplitudewill decreaseat the
high frequencyend. The triggeringsignal

4-32

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can also be appliedto the MARKER/VIDEO
connectoron the rear panel if a jumper is
connected between pins 1 and 5 (Video
Select) of the r€ar-panel ACCESSORIES
connector(Figure4-21).
h. Connectthe test equipmentas shown in Figure
4-22.
i. Set the function generatoroutput frequencyat
1 kHz, and output level at 2 V peak-to-peak,as indicatedon th€ test Oscilloscope.
j. ActivateEXTTRIGGER|NG.
k. Check that the sweep is triggeredover the frequencyrangeot 15 Hz to 1 MHz.
I. REIUTNthE TRIGGERINGtO FREE RUN ANd
disconnect
the test equipment.

28. Check External Sweep Operation
{O to t0 V (dc + peak ac) *1 V for a lull screen
deftection)
This is an operationalcheck, not a performance
requirement.

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PerfonnanceCheck procedure -

a. Connectthe test eguiprn€ntas shown in Figure
4-22. Set the Spectrumenityzer
fouows:
"ontroi, "i
VERT|CALDTSPLAY 2 dB/DtV
T|ME/D|V
EXT
VIEWA and V|EWB Otr
b. Set the functiongeneratorcontrolsfor no output

4g4ful4g4ApServiceVol. l

Pioa€
POWEF

\s7/^t

(0v).

c. Use thE POSITION
to position the crt
"ontroi
beam
-on the left graticuleedge. This'est;btishesthe
0 V reference.
d. Resetthe functiongeneratoroutputfrequency
to
1 kHz, and increaseits outputlevelfor trti t O-Oiri"ion
sweepon the SpectrumAnalyzer.
"
e. Checkthat the functiongeneratoroutput level
is
20 V peak-to-peak*2 V.

t15VMAX

CAUTION
JIdACC-ESSORIT

pin t, Video Setecr -

ooooooo?toooo
oooo ococoooo

NOT RS232 COMPATIBLE

A variablevoltage source can be used in
plac€ of the function generator to check
external sweep operation, lf used. the
rangewould be 0V to +10 V.

Place jumper between pin I antl pin 5 lo selecl
EXTERNALVIDEO.

f, Disconnect and remove the test equipment.
ReturnTIME/DIVto AUTO.

Figure4-21. Extemalvldeo select plns and MARKER
IVIDEO
Input

Test Oscltloscope

Funclion
Generato.

@
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@
@".
ooooooo

Spectrum Analyzer Under Test
(Rear Panel)

Figure 4'22' Test equipment setup for checking
external triggering and horizontal input characteristics.

4-33

Performance
- 4g4Al4g4Ap
checkProcedure
servrceVor.I

29. Check VERTOUTPUTSignal
(0.5V *5% per divisionof disptayfromthe center
line)
a. Monitor the VERT OUTPUT with a dc_coupted
test oscilloscope.
b. S€t the test oscilloscopecontrolsfor a sensitivity
of 1 V/div and a sweeprate of 10 ms.
c. Set the SpectrumAnalyzercontrolsas follows:
CENTERFREQUENCY
SPAN/D|V
RESOLUTTON
BANDWTDTH
REFLEVEL
VERTICALOISPLAY
VIEWA and V|EWB
TRIGGERING
TrME/DlV

100 MHz
100 kHz
100 kHz
-20dBm
2 dB/DIV
Off
FREERUN
AUTO

d. Apply the cAL oUT signatto the RF tNpUT and
verify that the signal amplitude is full screen. lf not,
performthe CAL routine.
e. check that the amplitudeof the VERTouTpuT
signal is 4 V peak-to-peak +0.2 V centered around
0 Vdc as disptayedon the test oscilloscope.See Figure
4-23.

b. Set TIME/D|V to MNL, and vary the MANUAL
SCANcontrolfor a five divisionbeamdeflectionleft and
right of center screen. Note the voltageswe€p on the
test Oscilloscopeas the MANUAL SCAN control is
varied.
c. check that the output voltagevaries 5 v *.10"/o
peak-to-peak,
centeredaround0 Vdc,
d. Reset the TtMEiDtv to AUTo. Disconnectand
removethe test equipment.

OPTIONINSTRUMENTS

31. Check Option 07 Calibrator Output
(+20dBmVr0.5 dB)
a. Connect the 50O port of the 75o to 50o
MinimumLossAttenuatorto a 100MHz 50O source.
b. Monitor the 75o port of the 75o to 50o
MinimumLoss Attenuatorwith the powermgter.
c. Set the generator output level for a readingof
-28.95 dBm on the power meter.

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d. Disconnectthe power meter from the 7SO port
and connectthe 75O port to the 75O INPUT of the
SpectrumAnalyzervia a 75O cable.
e. Set the SpectrumAnalyzercontrolsas follows:

I

r'/DIYISP}I
rttl

OF DISPLAY
FORFIL|.SCREEX) {.

[-i3fil l t r l

OY

Flgure 4-23. Test oscllloscope dlsplay of VERT output wlth a
full screen dlsplay on the Spectrum Analyrer.

30. Check HORIZOUTPUTSignatLevel

(0.5V/division*syo either sid-eof center)
a. Monitorthe HORIZOUTPUTwith a dc_coupted
test oscilloscope.

4-34

CENTERFREOUENCY
sPAN/DrV
RESOLUTION
BANDWIDTH
REFLEVEL
MIN RF ATTENdB
VERTICALDISPLAY
TrME/DlV
PEAK/AVERAGE

100MHz
500 kHz
1 MHz
+18 dBmV
0
1 dB/DrV
AUTO
FullyClockwise

f. Set the AMPL CAL control on the SpectrumAnalyzer
for a O-division
excursionof the signal.
g. Removethe 75O cable frorn the 75O port ot the
75O to 50O MinimumLoss Attenuatorand connectit to
the CAL OUTconnectoron the SpectrumAnalyzer(CAL
OUTto 75o INPUT).
g. Checkthat the displayis 6 divisions*0.5 dB.
i. Set the Spectrum Analyzer REF LEVEL to
+20 dBmV and reset the the AMPL CAL control for an
excursionof the signal.
8-division

PerformanceCheck procedure _ 4g4Ll4g4Ap
Service Vol. 1

32.Gheck Option 07 FrequencyResponse
(Response,about tt"' rniJioini'.0!i*""n
.
two
€xtremes,measured
with 10dg oi nF-ettenuation,
is *2 dBfromS MHzto 1000MH;i

response
farts.lt-trryughf checkfrequency
g il;;;;
fro.mt0 MHzto 1 GHz,anO'partJ

i;ff;:.t*ouency

response
from6 Mllii"

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CENTERFREOUENCY 500 MHz
SPANIDIV
100MHz
RESOLUTION
3 MHz
REFLEVEL
+23 dBmV
VERTICALDTSPLAY 1 dBiDtv
MAX HOLD
On
MIN RF ATTENdB
0
TrMElDlv
AUTO
PEAK/AVERAGE
FullyCounterclockwise

o

RF
OUT

ot a
SWEEPOSCILLATOR

b. Set the SpectrumAnalyzercontrolsas follows:

SPECTRUIIAiIALYZER UilOEF TEST

TO EXT.ALC tilpUTCo0$ttECTOn

I

a. Connectthe test equipmentas shown in
Figure
4-24.

ExT
ALc

o

TO RF OUTCOI{}{ECTOR

r{TOSIIAADAPTER {

POWER
SPLITTER

5G)
REF
LOW LOSSCOAXCABTEWITHSUA CONilECTORS

5560.15

Flgure 4-24' Equlpment retup for
checklng option 0z trequency ?esponse from
0.ol GHr to 1 GHz.

4-35

PerformanceCheck Procedure-

4g4A/4g4ApServlceVol. 1

- c. Set tle_:rlveeposcillatorcontrolsfor a cw output
frequencyof 500 MHz and an amptitudeof +20 Oe;1V
at the 75O INPUT.
d. lf necessary,set th€ cAL AMPL adjustmentfor 5
divisionson the SpectrumAnalyzerdisplay.
e. Reset the sweep oscillatorcontrolslor a sweep
outputfrom 0.01GHz-l GHz. Enablesinglesweepon
the sweeposcillator,and activateMAX HOLD.
f. Make a note of the highestand lowestpeaksfor
latercomparison,then deactivateMAX HOLD.
S, Reconnectthe test equipmentas shownin Figure4-25. ResetCENTERFREQUENCy
to 10 MHz.
h. Set the SpectrumAnalyzercontrols as follows,
then set the generatorcontrolsfor a +20 dBmV of the
signalat 10 MHz.

Srcl|AL SOTRCE (5 ltHz-io

CENTERFREOUENCY 10 MHz
SPAN/DfV
500 kHz
RESOLUTION
1 MHz
REFLEVEL
+23 dBmV
VERTTCAL
DTSPLAY 1 dBlDlV
MIN RF ATTENdB
O
T|MEIDIV
AUTO
PEAK/AVERAGE
FullyCounterclockwise
i. Manually tune the Signal Generator towards
5 MHz while simultaneously
tuning the CENTERFREQUENCYcontrol to hold the signat at center screen.
Makea note of the highestand lowestpeaks.
j. calculate the halfway point between the highest
and the lowest peak from the peak data noted in parts f
and i.
k. Checkthat flatnessis within !2 dB from 5 MHz
to 1000MHz.

SPECTRUTANALYZERUNOERTEST
tdHz]

E!- F

Figure 4-25. Equipment setup for checklng option 07 frequency response from 5 MHz to 10 MHz-

4-36

PerforrnanceCheck procedure-

33. Check Option 4t
Frequency Span/Div Accuracv
!1t73 o.t5 MHz/Divover the cdnter6 divisionsof
the display)
Sp:laccuracy is c_hecked
at centerfrequencyset.,
tingsof 6 GHzand 11 GHz.
a. 'Connectthe test equipmentas shown
in Figure
4-26. set the sp€ctrumAnalyzer
follows:
"ontroir ",
FREQRANGE
5.4-18GHz
CENTERFREQUENCY
6 GHz
sPAN/DtV
5 MHz
RESOLUTION
BANDWIDTH 100kHz
REFLEVEL
As Needed
TrMElDtv
AUTO
VERTICALDISPLAY
10 dB/Dtv

4g4ful4g4Ap
ServiceVol. 1

b. Modulatethe Comb Generatorsignal with .2ps
time markers.
c. peak the responsewith the MANUALpEAK control and set REF LEVELfor the best markerdefinition.
d. use the HorizontalposlTloN control on the
Spectrum Anafyzer to position a marker to center
screenthen checkthe accuracyover the centersix divisionsof the disptay.
e. Check that.the^tim€marks align with the maior
graticulelineswithinS0 kHz.
f. RESET
th€ CENTERFREQUENCY
tO 11 GHZ.
S. Check SPAN/D|V accuracy. Error must not
exceed*50 kHz/Div.

SPECTRUTANLAYZERUIiIDERTEST

COMB
GENERATOR
MOOULE

Figure4-26. Test equipmenisetupfor checkingoption
4i span/Divaccuracy.

4-37

PerformanceCheck procedure-

4g4Al4g4ApServiceVol. 1

34. Check Option 42110 MHz OUT Level
((0 dBm for Band 1)
(>.-40 dBm for Band 5)
. a. Tune the Spectrum Analyzer CENTER FRE_
QUENCY
to 100 MHz.

j. Switch thE FREOUENCYSPAN/D|V control
towards zero span while keeping the signal centered
with the CENTER FREQUENCYcontrol. The crr
SPANIDIVreadoutwill indicate10 ms when zero span
is reached.

b. Connect a signal generatorto the RF lNpUT.
Set the signal generatoroutput frequencyto i00 MHz,
and outputlevelto -30 dBm.
c. Set th€ REF LEVEL to -gO dBm. and RF
ATTENUATION
to O dB.

k. set the CENTERFREQUENCYcontrotto peak
the signaldisplayedon the t€st spectrumanalyzer.
l. check that the 110 MHz tF ouT levet is
)-40 dBm.

d. Switch the FREQUENCYSPAN/D|V control
towards zero span while keeping the signal centered
with the CENTER FREQUENCYcontrot. The crt
SPANiDIVreadoutwill indicate10 ms when zero span
is reached.

35. Check Optiopn 4211O MHz lF Output
Bandwidth, Center Frequency, Bandpass
Ripple, and Symmetry About 110 MHz
(Bandwidth:
>5 MHz)
(CenterFrequency:
108.5MHz-l11 .5 MHz)
(Bandpass
Ripple;<0.5 dB)
(Symmetry:
*1.0 MHz)

e. Monitorthe 110 MHz OUTwith a test spectrum
analyzer.
f. set the CENTERFREOUENCYcontrot to peak
the signaldisplayedon the test spectrumanalyzer.

a. Connectthe test equipmentas shown in Figure
4-27.

g. check that the 110 MHz tF ouT outputtevetis
(0 dBmtypically-8 dBm for Band1.

b. Set the test equipmentcontrolsas follows:

- h. Connecta signalgenerator,capableof delivering
18 GHz,to the RF lNpUT. Set the signalgeneratoroutput frequ€ncyto 18 GHz and outputlevelto -30 dBm.
i. Reset the Spectrum Anatyzer CENTER FREOUENCYto 18 GHz on Band5, REFERENCE
LEVELto
-30 dBm, and RF ATTENUATTON
to 0 ctB.

TR5O2
OutputLevel-dBm
Var dB
Dot Intensity

H:H
ull
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R F In

Spectrsm Analyzer Under Test
(Option 42)

1 1 OM H z
IF

7L14

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15o'it
RF

Input

30
0
Off

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Figure 4-27. Test equlpment setup lor checking option 42 frequency characterlstics.

4-38

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PerformanceCheck procedure-

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7L14
CenterFrequency
Freq Span/Div
Hz Resolution
ReferenceLevel
DisplayMode
DigitafStorage
TimelDiv
Triggering
Source
Mode
VideoFilter

1 1 0M H z
1 MHz
3 MHZ
0 dBm
2 dBlDiv
off
Manuaf
FreeRun
Norm
On

4g4Al4g4Ap
ServiceVol. 1

j. check that the waveformsymmetryis *1.0
MHz
(*1.O division)by checkingthat the 3 dBpoints as
wetl
as the 6 dB points on the waveformare equidistant
from centerscreen. fl-he peakof the signalmiy not
Oe
at centerscreen).
k. Reset the 7L14 Resolution Bandwidth to
0.3 MHz,
l. Set the ZL14 CenterFrequencycontrolsuch that
the intensified
dot is at th€ p€akof th; 7L14disptsr.-'-m. Check that the frequencycounter indicatesa
frequeancy
between1t g.5MHz anOt t t.S MHz.

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DC 509
Function
chA
Source
Atten
Coupl

FrequencyA
Ext
X1
Dc

Opton 42
CENTER
FREQUENCY
FREQUENCY
SPAN/D|V
REFLEVEL
RESOLUTTON
BANDW|DTH
VERTICAL
DISPLAY
MIN RF ATTENdB

t10MHz
1 MHz
_30 dBm
1 MHz
2 dB/DIV
O

c. set the 7L14 dot to center screen with
the
ManualScancontrol.
d, Set the 7L14 Center Frequencycontrotfor
an
indicationof 1j 0.0 on the f requeniyCo'unter.
e. swirch the FREQUENcy spAN/DlV
control
tgward-szero span while keeping the signaf centered
with the oENTER FREOUENCYcontr'ot. The
crt
SPANiDIVreadoutwill indicate10 ms *t"n ."ro
is reached.
"p"n
f. set the 7L14 Time/Divfor a catibrateddisptay,
and set the ReferenceLevel and TR502Var dB
for full
screensignal.
g. Switch the TRS02Dot Intensity,,on",and
reset
the 7L'l4 CenterFrequency
for an indiiationo, 110.0on
the FrequencyCounter.
h. Check that the 3dB bandwidth(1.5 divisions
from the peakof the signal)is )5 MHz.
_^i: th-"-"!_thatany ripple presenton the displayis
<0.5 dB (0.25divisionsor tess).

GPIBVERIFICATION
PROGRAM
This verificationprogram can be used with a TEKTRONIX4050-SeriesComputerTErminalto check the
operationof the GplB in the SpectrumAnalyzer. All
interfacelines and interfacemessages,excludingthose
for parallelpoll, are verified.
In addition,the instrumentinterfaceis checkEdfor
operationon other primary addresses,as well as the
talk-onlyand listen-onlymodes.
The programis written in TEKTRONTX
4OSOBASIC,
and is dividedinto individualtests, each for a sp€cific
interfaceline, message,or function. The tests start on
even 1000 line numbersto allow easy modificationof
the program.
The followingdescribesthe functionof each test in
the program.
Lines 1-5000:lnterfac€sto user definablekeys for
recoveryfrom a failedtest.
Lines 5000-6000:Inputsthe primaryaddressof the
SpectrumAnalyzerundertest (1 shouldbeused).
Lines 6000-7000: tD query response test. The
instrumentmust be able to talk and listen,to send out
its lD? responseand manipulateall eight of the DIO
linesfor the test to be successful,
Llnes7000-8000:Local lock-outtest. Tests correct
operationof the interfacemessagethat shoulddisable
all programmable
front-panelcontrols.
Lines 8000-9000:Go to LOCALtest. Tests correct
operationof the interfacemessagethat shouldenable
all front-panel
controls.

4-39

o

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PerformanceCheck procedure- 4g4A/4g4ApServiceVol. I

Lines 9000-10000: Group Execute Trigger test.
Checksthat a GET messagedoes causethe Spectrum
Analyzerto abort the present sweep and re-arm the
trigger,causinga sweep to start and end, sendingout
an End-of-SweepSRe. Thus, the SRe line and GET
m€ssageare verified.
Lines 10000-11000:Selected Device Clear Test.
This test verifiesthat an SDC messageresetsthe Spectrum Analyzer'sGplB output bufferclearingout it's lD?
response.
Lines 11000-12000:
Devicecteartest. This test is
identicalto the selected device clear test, except the
universalcommandDCL is used instead.
Lines 12000-13000:Addressed as tistener, tatker
test. This t€st checksthat the microprocessor
correcily
recognizEsthat the GPIA chip has been addressedto
listen or talk, and sends the appropriatecharacterto
the ert readout (L or T).
Lines 13000-14000:Seriat poil test. This checks
correct operation of the serial poll enable (spE) and
serial poll disable (SPD) interface messages. The
status byte is read, and if anythingother than ordinary
operationis indicated,the instrumenttailsthe test.
Lines14000-15000:
GptB rear panetswitch test. Atl
five primaryaddress switch€s are checkedfor corr€ct
operation. Three subroutinesare called in the process
of testingone addressswitch. The first two send a formattedrnessageto the 4050 display,and the third performsthe addressswitchtest.
Lines 1500G16000:Line feed or EOt switch test.
Checksfor correct selectlonof line feed as a termina_
tion when selectedby this switch by sendingan lD? ter_
minaledonly by a line feed.

Lines 16000-17000:Talk-only mode t€st. When
selected, this mode should cause the instrumentto
send a SET? response and (optionally)a CURVE?
response whenever the RESET-TO-LOCALbutton is
pressed. The string received from the instrumentis
thus examinedfor existenceof a portion of the correct'
SET? response after the RESET-TO-LOCAL
button is
pressed.
Lines 17000-18000:
Listen-onlymod€ test. When
selected, this mode will cause ths instrum€nt to
respondto any messageon the bus, since it is always
addressedto listen. The commandREF 0 is sentto the
bus without addressingthe instrument,then the listenonly mode is deselectedand the instrumentinterrogated to see if it did respond to the REF command
whilein the listen-only
mode.
Lines 18000-'19000:
Interface clean (and Remote
Enable)test. This IFC line on the GPIB will unaddress
the instrument'sinterface.This is verifiedby notingthat
the L is not present in the crt readout,indicatingthat
the IFC line worked; also the REN line will be
unassertedwhen the end statementis executed(except
for some early 4052and 4054's). Thus, a front panelin
the local mode indicatesthat the RENline was successfully unasserted. (Evidenceit was assertedis that the
instrumentwas able to execut€commandssentto it by
previoustests.)
Lines 19000-end:Utility routines. Rear panel interface switch test text routineputs headerson the interface switch test display. The rear panel test text routine tells the operator what to do after changingthe
addressswitches. Test addressswitch acquiresan lD?
responsefrom the instrum€nton its new addressduring
the addressswitchtest. The SRQ handlerwill handle
SRQ's that occur, althoughnone would be expected,
except the power-up SRO. (fhe end of sweep SRQ
during the GET test is handled by anoth€r SRQ
handler.) Delay Generatorgeneratesdelays lor other
tests. The FailureDecisionHandlerallows the program
to be restartedwith the user-definablekeys if any test
fails.

1 GOTO s000
4 B2-1
5 RETURN
20 B2-5
21 RETURN
REM"'49XP GPIBVERIFICATION
5OOO
PROGRAM'-'
5030tNlT
5O4O
ON SRQTHEN19280
5050DrM V$(400),w$(400)
506017-0
5O7O
PAGE
5080pRtNT'J.JJENTER
49Xp'SpRlMARyADDRESS(DEFAULT:1) ";
5O9OINPUTT$
5 1 0 0t F T S < > " T H E N5 1 3 0
5 1 1 0A 1 - 1
s120GO TO 5180
4-40

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Performancecheck procedure- 4g4A/4g4Apservice vor. 1
5130A1-vALrr$)
5140tF A1>0 ANDA1<31 THEN5180
"{JJGERROR!!';A1;,tS Nor A vALtD
:1i9lllltl
ADDRESS,,;
5160PRINT" ONLYO THRUgOINE VALIDADDRESSESKK'
s170co To 5080
5180PAGE
5190REM
52OOREM
5210REM
5220REM
5230REM
6000REMrrr'IDrQUERYRESPONSE'-'
601O PRINT'r.i '(IDOI'
..".
OUERYRESPONSE
6020PRTNT
:"tNlT;lD?;SlG,,
@A1
6030INPUT@A1:T$
6040v$-sEGCr$,1,9)
6050!FV$:"lD TEK/49'THEN60g0
.r. FA|L-rcil
QUERYRESPONSE
9999lltryI'J,Jf.""tD,,
6070GOTO 19s30
6080WBYTE@32+A1:64,128,-1ZZ
6090PRINT@A1:,WFMENC:B|N;CUR?.
6100 PRINT@37,0:07,255,255
o/"A1:Tg
6110INPUT
6120WBYTE@6a+A1:
6130RBYTER,R,R,T6
6140WBYTE@95:
6150lF R->128 ANDT6<128THEN7O0O
6160 PRINT'JJJ... Dlog TEST..' FAIL,*G"
6170co To 19530
6180REM
6190REM
6200REM
6210REM
6220 REM
7000REM.'r LOCALLOCK-OUT..............LLO
".
7010PRINT""' LOCALLOCK-OUT..........LLo
.,."
7020WBYTE@32+A1,17:
7030PRINT@A1:,.SET?"
7040INPUT
@At:V$

(LLo)"
19!gl!!NI "Ll4exptNLocALLocK-ourMoDE
lggglllNr tLArrEMprro usE4expcoNrRoLs"
RETURN
WHEN
DONE,';
1g1g
ryNr.'!_!_PRESS
7O8OINPUT

T$
7090PRINT@A1:"SET?,'
7100INPUT
@At:W$
7 1 1 0t F W $ < > v $ T H E N7 1 3 0
7120cO TO 8000
7130pntNT'!". LOCALLOCK_OUT.............LLO
'., FAtL..G,'
7140cO TO 19530
7150REM
7160REM
7170REM
7180REM
7190REM
8000REM*.'GO TO LOCAL.............GTL'..
8010 PRINT@Al :"lNtT;TtM?"
8 0 2 0 I N P U@
T A1:R
8030PRINT@A1:"TtMtNC.,
.'."
8040pRtNT*.r co To LocAL.............GTL
8050WBYTE@32+41,1:

4-4'l

PerformanceCheck procedure-

4g4Ll4g4ApServiceVol. 1

8060PRINT@A1:'TlM?,
8070INPUT@41:T6
8080tF R<>T6 THEN8100
8090 GO TO 9000
'* FAIL*rG,
8100PRINT"J".. GOTO LOCAL...........GTL
8 1 1 0c O T O 1 9 5 3 0
8120REM
8130REM
8140REM
8150REM
8160REM
9OOO
REM "' GROUPEXECUTE
TRIGGER........GET'*'
9O1OPRINT"''' GROUPEXECUTE
TRIGGER...GET
"TS
9O2O
ON SRQTHEN9120
9030 r7-0
9040PRTNT@A1:"]NlT;TtM
10OM;S|G;EOS
ON"
9050WBYTE@32+41,8:
9060 T6-3
9070cosuB 19390
9080PRINT@A1:"EOS
OFF',
9090rF 17<>'t THEN9150
91OO
ON SRQTHEN19280
9110GO TO 10000
9120WBYTE@20:
9130l7*1
9140RETURN
9150PRINT"GROUPEXECUTE
TRIGGER...G
9160cO TO 19530
9170REM
9't80 REM
9190 REM
92OOREM
9210REM
..'
lOOOO
REM'" SELECTED
DEVICECLEAR...SDC
-""
1OO1O
PRINT""' SELECTED
DEVICECLEAR...SDC
10020PRINT@A1:'tD?"
10030WBYTE@32+A1,4:
10040WBYTE@64+A1:
lOO5ORBYTER
10060tF ABS (R)<>2s5 THEN10080
10070coTo 11000
*r FAtL.'.G'
10090pRtNT"... SELECTED
DEVICECLEAR........SDC
10090Go To 19530
1 0 1 0 0R E M
1 0 ' t 1 0R E M
10120 REM
1 0 1 3 0R E M
10140REM
11000REM.'. DEVICE
CLEAR...........DCL.'.
..'"
11010pRtNT"... DEVTCE
CLEAR,...........DCL
11020PRINT@A1:"lD?'
11030WBYTE@20:
11040WBYTE@621+A1:
11O5ORBYTER
11060rF ABS(R)<>255THEN11080
11070GO TO 12000
11080pRINT.'." DEVICE
CLEAR...........DCL
11090GO TO 19530
1 1 1 0 0R E M
1 1 1 1 0R E M

4-42

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perrormancecheck procedure4g4A/4g4Apservrcevor. 1

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1 1 1 2 0R E M
11130
REM
1I 1 4 0R E M
12OOO
REM" ADDRESSED
AS LISTENER,
TALKER"'
12010 pRtNT,... 49xp ADDRESSEbndlisreneR...*tr

:76.zg,se,6s,id,-eJ
@32+Al
I ?9?9
I/-BvTE

12030T6-1
12040cosuB 19390
12050INPUT
@A1:vg

r_$*gEG
(v$,1
6,1)
1
?ggg
12070tF T$:"L,'

THENi21 0o
12080PR]NT"J'"'49XP ADDRESSED
Jr' FAIL
AS LISTENER
"iGS
12090cO TO 19530
12100pRtNT"'.* 4gxp ADDRESSED
AS TALKER......_,

:',tNtr;TMsoM;stc;sf
d,wel,r_onooz"
] ?1I n|!] @A1
r$-sEG(v$,16,1)
1?139
1 2 1 2 0 I N P U@
TA1:V$

12140 tFT$-"T"THENi3ooo

12150PRINTO"'49XPADDRESSED
AS TALKERrA.FAIL.irtr
12160cO TO 19530
12170REM
12180REM
1 2 1 9 0R E M
12200REM
't2210
FEM
13OOO
REM*" SERIALPOLL*..
pRtNT'.".
13010
sERtALpoLL.........spD/spE
*rr
13020WBYTEG)95,63,
24,64+4l:
13030RBYTER
13040WBYTE@95.25:
13050lFR-0 OR R-l6 THEN.t3080

POLL...FAIL*..cn
lgggqtltryT'J." SERTAL

13070GO TO 19530
13080T6:3
13090cosuB 19390
13100REM
13110
REM
13120REM
13130REM
13140REM
14OOO
REM"'GPIB TNTERFACE
REARPANELSWITCHTEST"'
14010PAGE
14011WBYTE@32+A1,20. 63:
14020A1*2
14030GOSUB19000
1 4 0 4 0 P R | N T0' ! _ 0 L 0 ! _ 0 0 0 1 0 "
14050cosuB 19070
14060GOSUB19190
14070PAGE
't4080A1-a
14090cosuB 19000
1 4 1 0 0 P R | N T0" ! _ 0 ! _ o L 0 0 1 0 0 ,
14110 GOSUB.t9070
1 4 1 2 0G O S U B1 9 1 9 0
14130PAGE
1 4 1 4 0A 1 : 8
141s0cosuB 19000
1 4 1 6 0 P R I N T0" ! _ 0 ! _ o ! _ 0 1 0 0 0 ,
14170GOSUB19070
1 4 1 8 0G O S U B1 9 1 9 0

4-43

PerformanceCheck procedure_ 4g4Ll4g4ApServiceVol.
1

14190PAGE
14200A1-16
14210GOSUB19000
1 4 2 2 0 P R | N T0" L 0 l 0 l _ 1 o 0 o o .
14230GOSUB19070
14240GOSUB19190
14250REM
14260REM
14270REM
14280REM
14290REM
15000REM., nLFroR ,EOl. swlTcH .,"
15010PAGE
1502041:1
15030cosuB 19000
1 5 0 4 0 P R | N T0. t o L 1 ! _ 0 O O O 1 "
1s050GosuB 19070
15060PRINT"JJTESTTNG
"EOt''SwtTcH"
15070cosuB 19190
15080WBYTE@32+A1:73,68,63,1
0
15090INPUT
@A1:T$
15100 r$-sEG cr$,1,9)
15110lFT$-"lD TEK/49,THEN15140
15120 PRINTU*LF" .OR' uEOl"'swlTcH
15130GOTO 19530
15140 T6-2
15150GOSUB19390
15160REM
15170REM
1 5 1 8 0R E M
1 5 1 9 0R E M
15200REM
16000REM'" TALK ONLYMODE""
16010PAGE
16020cosuB 19000
1 6 0 3 0 P R | N T0" ! _1 ! _ 0 ! _ o o o o 1 '
16040cosuB 19070
16050PRTNT
!{JTEST|NG TALKONLY"
16060INPUT
@A1:V$
16070I7-POS(V$,"rrNeoFF",l)
160801F
t7<>0 THEN17000
16090PRINT''JJJTALKONLYMODEO" FAILrr'GT
16100co To 19530
16110
REM
16120REM
16130REM
1 6 1 4 0R E M
1 6 1 5 0R E M
17OOO
REM'" LISTENONLYMODE"'
17010PAGE
17020GOSUB19000
1 7 0 3 0 P R | N T1' ! _ 0 ! _ 0 ! _ 0 0 0 0 1 "
17040cosuB 19070
17050pRtNT"JJJTESTTNG
LISTENONLY"
17060PRINT@A1:"tNt',
17070T6-0.5
17080GOSUB19390
17090WBYTE92,69,70,32,_48
17100PAGE
17110GOSUB19000

4-44

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performancecheck procedure-

4g4Ar4g4Ap
servrcevor. 1

17120
P R | N T ' 0 L o l _ 0 L O O O OI ,
17130cosuB 19d70
17140PRTNT
@A1:'REF?,,
1 7 1 5 0 I N P U@
TAt:V$
17160tF v$<>"REFLVL+0.0.THEN17180
17170co To 18000
IJ{L|SrEN ONLYMODE'r. FA|L*.Gn
11199lltu
17190co To 19530
17200REM
17210REM
17220REM
17230REM
17240REM
'8OOO
REM"'INTERFACECLEARANDREMOTE
ENABLETEST......IFC
& REN','
18010PAGE

rFc(TNTERFACE
CLEAR),
AND
REN
(REMorE
ENABLE)"
13333
fiBlI.6gilT:-"

18040T6-3
180s0GosuB19390
l!999llfNr lJcHEgK-rHE 4expcRr, FOR
BETWEEN
rHE vERflCAL"
18070
PRTNT
"OISPLAY
ANDTHEr"IirrN'EATTENREADOUTS."
pRtNT
18080
"JPRESS
RETURN
rO Corvrir.ruE.,;
18090INPUT
P$
1 8 1 0t0N t T
18110PRINT UF AN" "L" "IS STILL PRESENT,
THE IFC

pRtNT'lFTHE""L""VAN|SHID,'tr-crEsreo LINE IS FAULW,,
18120
ox."
18130PRINTlJcHEc^KALSOTHE4bip raor'rr pANaL
FoR pRopERLocAL coNTRoL'
'lF
18140PRI THEFRONTPANELrS iOcxeo
--' ouT, THanir.t r_rivE
ts FAUL,", tF,
18150PRINT"NOT,RENTESTED
OK;-

cotapr-erEo"
]9199
nryr !J{GPIBvERlFlcArtoH
18170END

1 8 1 8 0R E M
18190REM
18200REM
19OOO
REM*'REAR P4NELINTERFACE
SWITCH
"'
19010PRINT"SETGPIBADDRES' SWIiCTTES TESTTEXTROUTTNE
rO,.

"JJLrsrEN!_TALKTLF

oCrnoiness"
199?9
fllNr
19030pRtNT. ONLy!_ONLy!_Eor!_ro
s q 2 l"
19040pRtNT*---t ---l ----t ___-------19050RETURN
19060REM
19070REM ''' REARPANELTESTTEXTROUTINE
"'

rHEswrrcHEs,,;
1?gg?
llfNr IJAFTERCHANGING

19090PRINT"PRESSTHE REMOTCIUObIiBUTTON
ONCEJJ.

"r-(NorE:
rFyou eer i eiia rNieRiobE
lglgg
lllNr
L"#o=n
MESSAGE,"
,'!_ trI4EANS
19110
PRINT
*rer rr_re
swrrcH6SlWERE
Nbi "

19120PR]NT-!READCORRECTLY.IORE-TEST,TYPE"
19130PRINT1
rouowEo ei rHe LINENUMBERIN THE"
19140PRTNT'!_ ERRORMESSAGE)'

 WHEN
19119
IINI lJ!_pREssRETURN
DoNE";
19160INPUT

T$
19170RETURN
1 9 1 8 0R E M
19190REM"'- TESTADDRESSSWITCH"'
19200PRINT@At:,,1D?"
1 9 2 1 0 I N P U@
T A1:T$
19220T$:SEG Cr$,1,9)
19230tF T$-,lD TEK/49"THEN19260
19240PRINT'ADDRESS
SWITCHTESTFAIL"
19250cO TO 19530

4-45

PerformanceCheck procedure _ 4g4Ll4g4ApServlce Vot.
1

19260RETURN
19270REM
19280REM ". SRQ HANDLER".
19290T6-3

19300
cosuB 19390

19310POLL21,21;A1
19320PRINT@A1:"ERR?"
19330INPUT
@A1:S$

TNTERRUPT
occuRRED
oN rHEBUs,rHE4expRETURNS
19919
!l!NT "GGAN
";s$
19350pRtNT

"JPRESS
RETURN TO CONTTNUE';
19360INPUT
T$
19370RETURN
19380REM
-'
19390REM "'DELAY GENERATOR
19410REM... T6 GTVEN
tN SEC(GLOBAL)**. tg scRATcH ...
19420tF T6<0 THEN19510
19430tF RND(0)>0.5THEN19490
19440REM ... 4051*r
19450T6-T6'220
19460FORt9-1 TO T6
19470NEXTt9
19480GO TO 19510
19490REM'..4052
19500CALL "WA!T..T6
19510T6-0
19520RETURN
19530REM"'' FAILUREDECISION
HANDLER.',19540PRINT!{SELECT A UDK:'
19550PRTNT"!_ (1)RE-START'
19560PRTNT"L (5) END"
19570SET KEY
19580B2-0
19590tF B2<>1 ANDB2<>5 THEN19590
19600lF B2-5 THEN19630
19610PAGE
19620 cO TO 6000
19630END

4-46

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Secdon 5 -

4g4Al494ApService Vot. 1

ADJUSTMENT
fntroduction
l{ the lnstrumentperformanceis not withinspecified
requarementsfor a particular characteristic,determine
the cause,repair if necessary,then use the appropriate
adiustmentprocedureto retuln the instrumentoperation
to
.performancespecification. After any adjustment,
verify performanceby repeatingthat part;f the perfor_
manceCheck.
Allow the instrum€ntto warm up for at least one
hour, in an ambienttemperatureof *20" C to
+30oC
FI:* m.akingany adjustments.Waveformiilustrations
tn tne adrustmentprocedureare typical and may
differ
from one instrument to another: These waveforms
should not b€ construed as being repres€ntative
of
speciftcationtolerances.

1. Handle static-sensitivecomponentsor
circuitassembliesat or on a static-freesur_
face. Work station areas should contain a
static-free bench cover or work plane such
as conductivepolyethylenesheetingand a
grounding wrist strap. The work plane
shouldbe connectedto earthground.
2. All test equipment, accessories, and
soldering tools should be connected to
earthground.
3. Minimizehandlingby keepingthe com_
ponents in their original containers until
ready for use. Minimize the removal and
installationof semiconductors
from their cir_
cuit boards.
4. Hold the lC devicesby their body rather
than the terminals.

STANC DISCHARGE
CAN DAMAGEMANY
SEMICONDUCTOR
COMPONENTSUSED
IN THISINSTRUMENT.
Many semiconductorcomponents, esDecially MOS types,can be damagedOystitic
discharge. Damage may not be catastrophic and, therefore, not immediately
appare-nt.lt usuallyappearsas a degradailon or the semiconductorcharacteristics.
Devices-lhat are particularly susceptible
are: MOS, CMOS, JFETa, and high
impedanceoperationalamplifiers(FET inp-ut
stag€s.) The damagedparts may operate
wttntn acceptedlimits over a short period,
but their reliabilitywiil have been severely
impaired.- Damage can be significanily
reducedby observingthe followingp.ecautions.

5. Use containers made of conductive
material or filled with conductivemateriat
for storageand transportation.Avoid using
ordinaryplasticcontainers.Any static sen_
sitive part or assembly(circultboard)that is
to be returnedto Tektronix,lnc., should be
packaged in its original container or one
with anti-staticpackagingmaterial.

Equipment Required
Table 5-1 lists additionaltest equipm€ntand test
fixtures recommendedfor the adjustmentprocedure.
Test equipmentlist€d in Table 5-1 together with those
listed in Table4-1 in Section4, performanceCheckare
requiredfor the adjustmentprocedure.The characteris_
tics specifiedare the minimumrequiredfor the checks.
Substitute equipment must meet or exceed these
charact€ristics.

5-1

Adluctment Procedure-

4g4A/4g4ApServtce Vot. 1

Table 5-l
EOUIPMENTREOUIRED

Equlpmentor Test Flxture

Recommendatlonand Use

lsolationTransformer

1:1 turns ratio AND AT LEAST500 VA

StancorG|S21000

Att€nuator(3 dB miniature)

Frequency,to 5 GHz;connectors5 mm

WeinchelModel 4M, TektronixPart
No. 015-1053-00

Autotransformer

Capable of varying line vottage from 90
Vac to 130 Vac
100 pV to 350 Vdc

GeneralRadioVariacTypeWl0MT3

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Dc Block

TektronixPart No. 015-022140

Adapt€r (Sealectromale to male)
Adapter (bnc female to Sealectro
male)

TektronixPart 10i!-0098-00
TektronixPart No. 103-0180-00

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Three Extension Cables (Sealectro
femaleto Seal€ctromale)
Adapter (bnc to Sealectro)

TektronixPart No. 17$2902-00

;

Adapter(bncfemaleto sma male)
Cable(20"),Tip Ptugsto bnc

TektronixPart No. 015-1018-00

CoaxialCable(8)

TektronixPart No. 012-020&00

50 O Terminator

TektronixPart No. 011-0049-01

Screwdriver,Tuning
AlignmentTool

Tektronix Part No. 003-0675-00

Multimeter

TEKTRONIXDM 5O1Aor DM 5O2A

TektronixPart No. 175-241240
TektronixPart No. 175-1178-00

Tektronix Part No. 003-0968-00

Screwdriver,Flat,6" with 1/8, Tip
Screwdriver,PhillipsNo. 1
Allen Wrenches (3), 3lgl,

7lu

5/il"

ServiceKit (ExtenderBoardsla

TektronixPart No. 672-0865-01

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ADJUSTMENTPROCEDURE
PREPARATION
Removethe cabinetas follows:
1. Set the instrumenton its face or front panel.
2. Loosenthe lour screws throughthe back rubber
feet.

4. Place the instrumenton the bench and reconnect
the power cord.
Some circuit boards or assemblies must be
removed and placed on extendersto gain access to
some test points or adjustments. When this is done,
turn the power off beforeremovingthe assembly.

3. Pull the cover up and off.

e This kit is pari of the service Kit 006-3286-01.
listed in the Maintenance section,

5-2

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,

Adjustment Procedure- 494A/4g4ApService Vol. 1

1. !{iust Low Vottagepower Suppty
(R6028andR6061on the powerSu'pljlyboard)
This high-efficiencypower supply uses an internal
oscillatorwith a frequencyof 66 i PULSE STRETCHER,and
selectingitem 2 (DIGITALSTORAGECAL.) Foilowthe
instructionsthat ar€ displayedon the crt.
Referto Figure 5-7 for adjustmentlocations.
5. Adiust Sweep Timing
(Rl062 on the Sweepboard)
a. Connectthe test equipmentas shown in Figure
5-8. Set the followingSpectrumAnalyzercontrols:
FREQSPAN/D|V 10 MHz or tess
TIME/D|V
10 ms
TRIGGERING
EXT

5-8

b. Connecta jumper between pins 1 and 5 (Ext
Video Selectand Ground respectivety)on the ACCESSORIESconnector.
c. Set the Tim€ Mark Generatorcontrolsfor 10 ms
timE marks.
d. AdjustSweepTiming,Rl062 (see Figure5-9)for
1 marker per division. (Use HorizontalPositionadjustment to alignmarkerswith graticulelines.)
e. Check the accuracyof the remainingTIME/DIV
selections. Error over the center eight divisionsmust
not exceed !.5 o/o.

f. R€set the TIME/D!v to AUTo, FREQ SPAN/D|V
tO MAX, TRIGGERINGtO FREE RUN, ANd ACtiVAtE
AUTO RESOLN.
g. Removethe jumper betweenpins 1 and 5 of the
ACCESSORIESconnector. Reposition the trace if
movedin part d.
6. Adjust Frequency Control System
and Dot Marker position
(R1028,R1032,R3040,and R4040on the CF Control board;R1031,R1032,and R1034on the 1st LO
board; R1063,R1065,R1067,and R1071 on the
Span Attenuatorboard; C1013 and C2011 on the
Controlled Oscillator board: and R1052 on the
Sweepboard)

R1028, R1032, R3040, and R4040 on the
CF Control board: Rl031, R1032, and
R1034 on the 1st LO board: and C'!013 and
C2011 on the Controlled Oscillator board
are adjusted in part d.

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AdJustmentProcedure-

lnput Gain,RlO3a

ouFur GarnR1033

|

494A1494ApService Vot. 1

O.rtput Of*t

nrors

RIINC
iITAL STORAGE
HORIZONTAL

G.io R1OOo

Figure 5-7. Digltal storage adiustment locations.

TO: TTARKEBiVID8O

TITE TIARK
GEI{ERATOR

ffi
Itull

\=z

BETWEEI{PINSl&5.
PARTIAL BACK PANEL SHOWINGJl(X ACCESSORY COilNECTOR.

Figure 5{.

Test equlpment setup lor adiusting sweep timing.

Adjustnent Procedure-

4g4A/4g4ApServtceVot. 1

Figure 5-9. Sweep board tlming adiustment and test point locations.

The SpectrumAnalyzerhas a procedurein firmware
for calibratingthe frequencycontrol system. However,
it is possible that some adjustmentsmay be misad_
justedenoughto causethe microcomputer
io displayan
€rror message. lf this occurs, bypass the step then
returnto the calibratlonroutine.
Test equipment required for this step are a
Voltmeter, Time Mark Generator, and Fiequency
Counter.Set the followingSpectrumAnalyzercontrols:
FREQUENCY
0.0 MHz
FREQSPAN/D|V 5 MHz
TRIGGERING
FREERUN
b. Connect a shorting strap from Tplogs. on the
SpanAttenuatorboard,to chassisground(Figure5-10).
MonitorTP1073on the Span Attenuatorboard with the
voltmeter.
- --c: Adjust Sweep Offset R1063 (Figure S-10) for
0.00v.
d. Removethe shortingstrap from Tp1035. press
PULSESTRETGHER
and selectitem 1
(FREOUENCYLOOPS CAL), then item 0 (OVERALL
SYSTEM)from the menus. perform the calibration
steps as directed ('CONNECTA DVM TO Tp105g ON
THE1STLO DRTVER
BOARDANDGROUND,),etc.
(1) lf a "CAL|BRATION
STEPCANNOTBE COMPLETED"message is displayed,bypass the step,
perform the other adjustmentsthen return to the
adjustmentand try to bring the adjustmentin range.
lf the problempersists,refer to Troubleshooting
the
FrequencyControlSystem,in the Maintenancesec_
tion.

5-10

e. Adjust 1st LO Sweepas follows:
(1) Applythe CAL OUT signalto the RF tNpUT,set
the FREQUENCYto 600 MHz, FREQ SPAN/DIVto
100 MHz, and set the REF LEVEL to display the
mark€rs,
(2) Adjust'Tune Coil Swp R1065, on the Span
Attenuatorboard (Figure 5-10) for one marker per
divisionover the center eight divisionsof the graticule. Reset the CENTERFREQUENCYas necessary to align the markers.
(3) Removethe Calibrator signal and apply 0.2 ps
time marks from the Time Mark Generatorto th€ RF
INPUT.
(4) Set the FREQSpAN/Dtv to 5 MHz, REF LEVEL
to +10 dBm,and FREQUENCY
to about10 MHz.
(5) Adjustthe lst LO FM Coil Swp R1071(Figure
5-10)for 1 marker/divisionover the centereightdivisionsof the display.
(6) Set th€ FREQ SPAN/DIVto 20 KHz and appty
50 ps markersfrom the Time Mark Generator.
Adjust the 2nd LO Sweep, R1067, for one
n
marker/division
over the centereight divisions.

f. AdjustDot Markerpositionas follows:
(1) Press RESET.
(2) AdjustDot PositionR1052on the Sweepboard
to positionthe dot markerover the start spur.

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AdjustmentProcedure-

TuneCoil

R1065:ttl

494Ll4g4ApServlceVol. 1

FM Coil Swcco RtOZl

=?l
rPlo3s-.8

I

Span Attcnualor
boild

\circgir
Ccnter Frcqucncy

control boord

II

Ilst LO Orivct
lcircuit board

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R1031Rro32 R10:t4

556G17

Figure5'10. Frequencycontrorsystemtest potntand
adiustmentrocations.

7. Adjust Log Amptitier
(R1012,R102S,R1030,R1037,and R.t060on the
LogAmptifier
board)

Use only an insulatedscrewdriveror tuning
tool to make these adjustments.
. a. Set the Log Amplifiercorrectionfactors to zero
b_y pressing (Bfue-SHtFT> PULSE STRETCHER
(DIAGNOSTICFUNCTTONS;and setecting item
5
(DISABLE/ENABLE
USE OF CAL FACTORS),tnen item
2 (SET RESULTSTO "UNCALED). Remove Leveler
Disableplug P3035on the Videoprocessorboard (Fig_
ure 5-11).
b. Connectthe t€st equipmentas shown in Figure
5-12. (P621must be removedin order to accessJ621
on the Log Amplifierboard. See FigureS_1g.)Set the
SpectrumAnalyzercontrolsas follovis:
FREQUENCY
FREOSPAN/D|V
AUTO RESOLN
REF LEVEL
MIN RF AfiEN
VERT|CALDTSPLAY
TtMEiDtV

2MHz
2MHz
On
-60 ctam
OdB
1OdB/DtV
10 ms

c. Centerthe two front panel LOG and AMPL CAL
adjustments. Set the signat generatorcontrols for a
10MHzl+6 dBm output. Set the step attenuatorsfor
50 dB of attenuation.
d. Positionthe displayat a graticulereferenceline
with the verticalPOSITIONcontrol,then switchthe REF
LEVELfrom -60 dBm to -110 dBm in decadesteps.
e. S€t the front-panelLOG CAL such that each
10 dB step equalsone division.
f. Reset the REF LEVELto -20 dBm and tha step
attenuatorsfor 0 dB attenuation.Resetverticalposition
to a graticulelineif necessary.
g. Increase the attenuation through the step
attenuatorsin 10 dB incrementsto 50 dB.
_ h- Adjustthe Log Gain,R1037(FigureS-13)so each
10 dB incrementof attenuationresultsin one majordivision of changeon thE display.
. i. Reset vertical position by temporarilyremoving
the signal and settingthe verticatPOSITIONcontrolto
position the baseline at the bottom graticule line.
Returnthe step attenuatorto 0 dB. Displayshouldbe
full screen (+6 dBm); if not, readjustJtrg*iglfial-gene@@

lzJ,r rli,1 [v i:"lllCrerh

j. AdjustInputReferenceLevel,R1012(Figure5-13)
for minimumamplitudechangebetweenthe 10 dB/DlV
and 2 dB/DlV displays while alternatelyswitchingthe
VERTICALDISPLAYbetween10 dB/DtVand 2 dB/DlV.

5-11

Adrustment Procedure-

4g4Ll4g4ApServtce Vot. 1

Figure 5-'11. P3035 on the Video processor board.
BilC fo Sorlos:tro Ad.gtCr

To &21
on Log Ampl Bd
m LHr Lcvclod Signrl
Gcocr.to?,0-lO dBm

@"o.@"@"G)Pt
Spectrum Analyzer Under Tesl

I
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'lO dB Stcp Attcnu.tor

1

1 dB Stcp An nu.to.

5565-19

Figure 5-12. Test equlpment setup for adjusting the Log Amplifier.

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Adjustment Procedure- 4g4A/4g4ApServiceVol. 1

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ffwu"nffEneilercYEl

R10f2
LOGFIOELTTYR1O6O
REFERENCELEVEL RIOIIO

@ftftfl

ll

n

Lqrc^$t*FroilT

fill
oll
l--E
L-.,E

Pl075
(J620)
Pm70
(J621)

L-HHF

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Figure 5'13. Log and video Ampri{iertest pornt and
adiustmentrocations.

.- .k. lctlvate 2 dB/Dtv and add 10 dB of artenuation.
lf..the1098 step (S division)is short,adjustthe gain
slightlywith R'|037 in the same direction;'thenrem-ove
the 10 dB of externalattenuationand adjust R1012for
a full.screendisplay. Repeatthis checkuntitthe
10 dB
step is within0.2 dB of 1OdB. Activate10 dB/OtVand
recheck10 dB logging.
. l: Activate 2 dB/Dlv and momentarilyremove the
input signalto the Log Amplifier. positionthe baseline
on the bottomgraticuleline then returnthe signal
to the
Log Amplifier.
_ 11 Adjust Output-ReferenceLevel, R1030 (Figure
5-13)for a full screen(eightdivisions)
display.
n. Switchto the l0 dB/DtV mode and set the step
attenuatorsfor 40 dB of attenuation.AdjustLog Lineai_
ity, R1060(Figure5-10)so the disptayis mid_screen.
o lf a large change in the setting of R1060 was
f-q-Tregin part t, repeatthe adjustmenlsof R1012and
R1030 becauseof interaction.
p. Checkthe accuracyof 10 ctB/DtVand 2 dB/DtV
gfqPy-T9des by addingattenuationin 10 dB steps for
10 dB/DlVmodeand 1 dB stepsfor the 2 dBlDtV'rnode
an! -gbsqrvingthat the disptay steps 1 major division,
*0.25 minordivision,for eictrl0 A'estep,jnd 0.5
divi_

sion, r0.5 minor division,for the 2 dB mode. (Readjust
the signalgeneratoroutputto establisha new reference
level after each step.) After the accuracyof the indivi_
dual steps has been verified,reset the signal level for
full screen.
q. Add appropriatestep attenuationto step the
displaydown screenand measurethe worst caseerror
over the dynamic range. Error must not exceed
11.5 dB over the first 80 dB of range,or11.0 dB over
the 16 dB range.
r. lf the 10 dB log step in the 2 dB/DtVmode is
long,adjustgainwith R1097for less gainand rebalance
R1012.
s. Set the step attenuatorsto 10 dB and activate
2 dBlDtv.
t. set the Ref Levetto -15 dBm and adjustthe signal generator output for a full screen display in the
2 dB/DlVmode.
u. Press LIN and adjustLin MocJeBalance,R102S
(Figure5-13)for a full screendisptay.Amplitude
of LtN,
zdBlDlV, and 10dB/DtVdisptayshouldnow be the
sarne.

5-13

,

Adjustment Procedure-

494[l4g4Ap Service Vot. 1

5[ton'"*'

I

Filrc.sotocr

I

ffi

6097-18

Figurc 5-14. Test equipment3etup tor adiusting tlre VarlableRe3olutionrnoOut".

v. Check LIN disptay linearity by adding 6 dB,
12 dB. and 18 dB of attenuationand note the display
step down from full screento, 4 +0.4, 6 *0.4, and 7
*0.4 divisions.
w. Remove the signal generator from the Log
Amplifierinput jack and reptacep621. Reptacep3035
on the Video Processorboard.

8. Adjust ResolutionBandwidth
and Shape Factor
(c304r, c5048, C505s, R106s, R3015,R3029,
R3033,and R4025on the VR 2nd Filter Setect
board)

The filters in each section are aligned
separately,then a signal is appliedthrough
both the first and second sections. The
final adjustments trim filter shape and
bandwidth. Because of interaction,it is
easy to offset one filter to compensatefor
another misadjustedfilter; therefore, only
adjusteachfilter in small increments.
Before calibrating the Variable Resolution
Bandwidth and Gain, disable use of cal factors by
pressing  PULSE STRETCHER and
selectingitem 5, then item 0.

(c1034, C1044, C1046, C2030, C3O3O, C3039,
C3045, and R1027 on the VR 1st Fitter Setect board)

a. Equipmentsetup is shownin Figure5-14.

(c1032, C4015, G4028, C4036, C4045, C4051,
C4060, R3010, and R3025 in the 10 Hz Fitter
Assembly)

(1) Remove and install the Variable Resolution
moduleon an extender.

(R2025 on the 10 dB Gain Steps board)

(2) Use a Sealectromale-to-maleadapteranclcoaxial cable to connect the 10 MHz lF output signal,
from the 3rd Converter,to the input of the second
s€ction (make connectionfrom plug removedfrom
J693 to J683).

The 3 dB down bandwidth of each filter section
should be as wide or slighfly wider than the 6 dB down
point of the combined two filter sections.

5-14

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AdJustmentProcedure -

4g4[l4g4Ap Service Vot. 1

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Flgure 5'15. Adiu3tmontson the rear of tre VariabreResorudonmodure.

(3) Connectthe output of the VariableResolution
moduleto the input.of
Log Amplifierassembly
by connectinga cable lhe
from J6g2 on the Variable
ResolutionModule to J621 on th€ Log & Video
-S-t+;.
Amplifierassembly{see FiguresS-10and
(a) Applythe CAL OUT signatto th€ RF tNpUT,and
set the SpectrumAnalyzercontrolsas follows:
FREQUENCY
100MHz
FREOSPAN/D|V
S0kHz
RESOLUTTON
BANDWTDTH 10 kHz
-20dBm
REFLEVEL
MtN RF ATTEN
0 ctB
VERTICALDTSPLAY
2 dBl}tv
b. Resetthe REF LEVELfor a sevendivisionexcur_
sion Tune the display to center screen and activate
SAVEA.
- c. Change the RESOLUTTONBANDWIDTHto
3 MHz and FREQ SPAN/D|Vto 1 MHz. Reset REF
LEVELto bring the signal amplitudeto aboutthe same
levelas th€ 10 kHz response.
-d. Adjustthe four tuning screws(capacitors)on the
110MHz Bandpass Fitter (FL361foi tire best 3 MHz
fi-lter. response (3 MHz bandwidth *600 kHz, 6 dB
down) that is centered about the 10 kHz reference.
Referto Figure5-16.
e. Change the RESOLUTTONBANDWIDTHro
1 MHz and FREQ SPAN/D|Vto 500 kHz. Reset REF
LEVELto bring the signal amplitudeto aboutthe same

levelas th€ 10 kHz response.
f. AdjustC1034,C1044,and C1046,and R1027on
the VR 2nd FilterSelectboard (Figure5,15)for the best
1 MHz filter response (1 MHz bandwidth,3 dB down.
that is centeredabout the 10 kHz reference). Referto
Figure5-16.
g. Change the RESOLUTTONBANDWTDTHro
100 kHz and reset REF LEVELto bring the signatamptitude to aboutthe same levelas the l0 kHz response.
h. AdjustC5055,C5048,and C3041on the VR 2nd
Filter Select board (Figure 5-17) for the best .lOOkHz
filter response(100 kHz bandwidth,3 dB down, that is
centeredabout the 10 kHz reference).Refer to Figure
5-16.
i. RESET
th€ RESOLUTION
BANDWIDTHtO 1OKHZ,
deactivateand reactivateSAVE A to re-establishthe
10 kHz reference.n ', -'
-5
r(
J. Adlust 10 Hz BandpassFllter

lNorE-l
All adjustablecapacitorson the Bandpass
Fifter board in the 10 Hzfi00 Hz Bandpass
Filterassemblyshouldbe set to midrangeif
the filter is badly misadjusted.This minimizes the numberof times interactingadjustrnents must be repeated to eliminate
interaction.

5-15

Adlustnent Procedure-

494ful4g4ApServtce Vot. 1

(9) Adjust C1032 in the loHz/lfi)Hz Bandpass
Filterassemblyfor maximumslgnalamplitude.
(10) Set the SpectrumAnalyzercontrols as follows:
FREQSPAN/DIV
RESOLUTION
BANDWIDTH
VERTTCAL
DTSPLAY
T|ME/D|V

'10Hz
10 Hz
5 dB/DlV
AUTO

(11) Press (Blue-SHIFT> WIDE and select item
#3 CTOGGLE
EOSCORRECTTON
MODE).
(12) Resetthe CENTERFREQUENCY
as necessary
to centerthe 100 MHz calibratorsignal,then set the
REFERENCELEVELfor a seven-divisionexcursion
of the display.
(13) Activate SAVEA. Store s€ttings in register 1
by pressing STORE1.
(14) Set the SpectrumAnalyzercontrolsas follows:
Flgure5-16.100kHzoverl0 kHzlitter respona€.

(1) Set the, foltowing adjustmentsto midrange:
R4025on the VR 2nd FitterSelectboard,and R3OIO
'and
R3025 in the 10Hz/100H2 BandpassFitter
assembly.
(2) Install jumpers on J30i5, JgogS,and J3052 in
the 10 Hzll00 Hz Fitterassembty(Figure5-ig).
(3) Apply the CAL OUT signatto th€ RF tNpUT,and
set the SpectrumAnalyzercontrolsas follows:
FREQUENCY
100 MHz
FREQSPAN/D|V
100Hz
AUTORESOLN
Off
RESOLUTTON
BANDWTDTH 100 Hz
VERT|CALDTSPLAY
2 dB/DtV
-20 dBm
REFERENCE
LEVEL

FREQSPAN/DIV
RESOLUTION
BANDWIDTH
VERTICALDTSPLAY
VIEWA

100 Hz
100 Hz
10 dB/DlV
Otr

(15) Store settingsin register2 by pressing STORE2.
(16) Adjust C4015 in the 10Hz/100H2 Bandpass
Filterassemblyfor b€st symmetry.
(17) Press RECALLSETTINGS1.
(18) Adjust C4028 In the 10Hz/100H2 Bandpass
Filtsr assembly to match th€ trequency of th€ B
display to that of the sAVE A display.
(19) Repeat adiustment of C4015 and C4028 to
eliminateinteraction.
(20) Remove the jumper from J3038 (2nd stage of
the bandpassfilter) and install it on J3015 in the
10 Hzl100Hz BandpassFilter assembly.
(21) Press RECALLSETTINGS1.

Throughoutthe 10 Hz ftlter adiustment,set
the REFERENCE
LEVELas neededto maintain a 7-divisionexcursionof the display.
(4) Adjust R4025on the VR 2nd Filter Set€ctboard
(Figure5-17)for maximumsignalamplitude.
(5) Set TIME/D|Vto 50 ms. (6) AdjustRg0i0 in the
10 Hzl100Hz BandpassFitter assembty(Figure518)for maximumsignalamplitude.
0 Adjust R3025 in the 10Hz/100H2 Bandpass
Filterassemblyfor maximumsignalamplitude.
(8) Removethe jumperfrom JO01S(1st stageof the
bandpassfilter)in the 10 Hzl100Hz BandpassFilter
assembly.

s-l6

(22) Adjust C4036 in the 10Hz/10OHzBandpass
Filter assembly to matoh th€ frequencyof the B
displayto that of the sAvE A display.
(23) PressRECALLSETTINGS2.
(24) Adjust C4045 in the 10 Hzl100Hz Bandpass
Filterassemblyfor best symmetry.
(25) Repeat parts 22 through 25 to eliminate
interaction.
(26) Remove the jumper from J3052 (3rd stage of
the bandpassfilter) and install it on J3038 in the
10 Hzll00 Hz BandpassFilterassembly.
(27) Press RECALLSETTINGS1.
(28) Adjust C4051 in the 10Hz/100H2 Bandpass
Filter assembly to match the frequ€ncy of the B
displayto that of th€ SAVEA display.

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Figure 5-17. Adiu3tments on the front of the Variabte
Resolution module.

(29) PressRECALLSETTTNGS
2.
!30) Adjust C4060.in the 10 Hzl100Hz Bandpass
Filterassemblyfor best symmetry.
lgtt Repeat parts 2g through 31 to etiminate
interaction.
(32) Remove ail jumpers from the 10 Hzl100
Hz
BandpassFilterassembly.
(33) press CAL to start the internat
calibrationroutine. press FINEto continu€calibra_
tion as prompted.
K. RCSCT
thE RESOLUTION
BANDWIDTHtO 1OOHZ
and FREQ SpAN/Dtv to 50 Hz. set the REF LEVEL
su-chthat the responseis near the amplitudeof the
reference.
L Disconnectthe 10 MHz third converterlF signal
from J683 and reconnectit to J690. Reconnectp6g3
to
J683.
m. set the FREQ spAN/DlV to 1 kHz, RESOLUTION BANDWIDTHto 1 kHz and reset the REF LEVEL
tor a 7 divisiondisptay. ActivateSAVEA.
n. set th€ FREQ spAN/DtVto 10 kHz, RESOLUTIONBANDWTDTH
to 10 kHz and adjustREFLEVELfor
a 7 divisiondisplay.
o. Adjust C2030(Figure5-1S)for the best 1OkHz
responsecenteredaboutthe 1 kHz reference.

p. Deactivate SAVE A and then reactivate to save
the 10 kHz display.
q. Set FREQ SPAN/D|V to 50 kHz and RESOLU_
TION BANDWIDTHto 100 kHz.
, r. Adjust C3045, C3039, and C3030 (Figure 5_15)
for the best 100 kHz response centered about the
10 kHz filter reference.
s. Check the waveshape, bandwidth, and centering
of all filters. lf necessary, make only fine or minor
adjustments. Figure 5-1g shows typical response
shapes.
t. Level th€ gain of the filters as follows:
(1) SCt thE FREQ SPAN/DIV tO 5OOKHZ, RESOLUTION BANDWIDTH to 1OOKHz, and REF LEVEL to
-20 dBm.
(2) Adjust all filters to the 1OOkHz tevet as p€r the
follovying Table 5-3. Change FREQ SPANIDIV as
necessary to maintain a
"suitabledisplay.
u. Press  PULSE STRETCHER
(DIAGNOSTIC FUNCTTONS) and setect item #s
(DISABLE/ENABLEUSE OF CAL FACTORS),then item
#1 (USE RESULTS), to re-enable use of cal factors.

5-17

Adiustment Procedure -

494A1494ApService Vol. 1

9. Preset the Variable Resolution Gain

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and Band Leveling
(R1030on the Post VR Amplifierboard)
(R2031on the Va #2 Motherboard).
(R3035on the 10 dB GainStepsboard)
(R2023and R2060on the 20 dB Gain Stepsboard)

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The Log Amplifiermust be calibratedbefore
adjustingany VariableResolutiongain settings. Log Amplifier calibration can be
verifiedby applyinga +6 dBm, 10 MHz signal to the input (J621),of the Log Amplifier,
and checkinglor full screendisplaywith the
REF LEVELat -20 dBM.

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b. Test equipmentsetup is shown in Figure 5-14.
Set the SpectrumAnalyzercontrolsas follows:

go0F

FREQSPAN/D|V
RESOLUTION
BANDWIDTH
REF LEVEL
MIN RF ATTEN
VERTICALDISPLAY

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Figure5-18. Adiustmentson the 10 Hzl100Hz Bandpass
Filter assembly.

Table 5-3
FILTER
Filter
1 MHz
10 kHz
1 kHz
100Hz
10 Hz

5-18

1 MHz
100 kHz
-20 dBm
0dB
2 dB/DrV

c. The gain of the Post VR Amplifier should be
ratio throughthe Variable
20 dB for best signal-to-noise
Resolutionstages. lf any maintenancehas been performed on this stage,performthe followingsteps.

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a. Before adjusting the Variable Resolutiongain
and band leveling,set the correctionfactors to zero by
pressing  PULSE STRETCHER,and
selectingmenuitem 5, then item 2.

Locatlon

Figure5-17
Figure5-17
Figure5-17
Figure5-17
Figure5-15

(1) Removethe cover for the VR 2nd Filter Select
board. Disconnectthe jumper connector to the
input of the Post VR Amplifier(pin JJ).
(2) Apply a '10MHz, -14 dBm signal,from a 50o
signalsource,to pin JJ of the amplifier.
(3) Adjust Post VR Gain R1030 on the Post VR
Amplifierboard for a full screendisplay.
(4) Removethe signaltrom the inputto the Post VR
Amplifier and replace the iumper connector to pins
JJ at the input to the Post VR Amplifier. Replace
the coverfor the VR 2nd FilterSelectboard'
d. Set the front panelAMPL CAL fullycounterclockwise and set the Band 1 Galn R20310n VR Mother
baard #2 (Figure5-15)fully counterclockwise.

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Adjurtment Procedure-

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f. lf the signalamplitudeis over 5 divisions,adjust
the Post VR Gain R1030(Figure5-15)for a 5 diviiion
signalamplitude.
g. Resetthe front panelAMPL CAL for a 7 division
signal.
h. Switch MIN NOISEoff, decreasethe g€nerator
outputto -35 dBm, leavethe REF LEVELat -20 dBm,
and adjustthe 10dB Gain R303S,on the 10dB Gain
board (Figure 5-17) so the signal amptitudeis 7 divisions.
i. Change the generator output to -4S dBm, the
REF LEVELto -40 dBm, and adjust the 20 dB Gain
R2023on the 20 dB Gain Step board (Figure5-17) for a
7 divisionsignalamplitude.

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e. Disconnectp693 (Figure5-17)and activateMtN
NOISE. Apply a 10 MH4 -25 dBm signat,from the signal generator, through a bnc-to-sealsctro adapter to
J693: Set the genorator frequency to peak the signal
amplitude. (Signal amplitude should be between 3.5
and 6.5 divisions. tf signalamptitudeis not withinthese
limits it indicatesa gain problemin the VariableResolution module.)

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FILTER

-4.

j. change the generator output to -65 dBm, the
REF LEVELto -60dBm, and adjustthe t0dB Gain
R2060 on the 20 dB Gain Step board (Figure 5-1Tl tor a
7 divisionsignalamplitude.
k. set the REFLEVELto -30 dBm and the generator output to -35 dBm. Check lor a 7 division signal
amplitude. Repeat this check for -45, -55, and
-65 dBm input levels. Note that each maintainsthe Z
division signal to verify that the gain of the Variable
Resolutiongain stages are correct. Readjust gain il
necessary.

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l. Removethe 10 MHz signalto J680 and reconnect
P680. The final band level adjustmentsar€ described
after calibrating the PreselectorTracking and checking
flatness. The mean level for each band is set to th€
levelof Band1.

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m, Removethe extenderboards and re-installthe
VariableResolutionmodulein the SpectrumAnalyzer.

C. Rcrpoor ot tn|z fihcr.
55@-29

n. Press CAL to reruna calibration
routineand re-establishprocessorcorrectionfactors.

Flgurc 5-19. 10 kHz, 100 kH:" and 1 MHz lilter response.

5-19

AdiustmentProcedure- 494A/4g4Ap
ServiceVot.1

10. Adjusf CalibratorOutput Level
(R1041on the 100 MHz Osc and 3rd Converter
board)

The calibratoroutput level is matchedto a
knownreference. A power meteris usedto
verify the output level of the referencesig_
nal generator.Harmonicsof th€ signalgen_
erator must be greater than 40 dB down
from the fundamental.
a. Apply a 100 MHz signal from the signalg€nera_
tor to the power meter through a 3 dB attenuator.Set
the generatoroutputlevel for a readingof -20 dBm on
the power meter. This sets up a referencesignal for
adiustingthe calibratoroutput level.
b. Disconnectthe power meterfrom the signalgenerator,and connectth€ refencesignal(fromthe generator) to the test spectrumanalyzerRF INPUTusing the
samecablethat was used to set the referencesignal.
c. Set the test spectrum analyzer controis as fol_
lows:
FREQUENCY
FREQSPAN/D|V
RESOLUTION
BANDWIDTH
REFLEVEL
MIN RF ATTEN
VIEWA and VIEWB
PEAK/AVERAGE
TrME/DtV
TRIGGERING

100MHz
100kHz
1 MHz
-18 dBm
0dB
On
FullyCounterclockwise
AUTO
AUTO

d. Set the test spectrum analyzerVerticatDisplay
factor to the A A mode by pressingFINE. Set the REF
LEVELsuch that the top of the signalis on a graticule
line near the top of the crt. Reset the REF LEVELto
0.00dB by pressingFINE twice. Store the display by
activatingSAVEA.
e. Removethe r€ferencesignalfrom the RF INPUT
and connectthe cAL oUT signalin its place, Tune the
CENTERFREQUENCYcontrot to atign the CAL OUT
signalwith the SAVEA disptay.
f. Adjust Cal LevetR1041,in the 3rd converter(#2
in Figure 5-20) for no displacementbetweenthe CAL
OUT signal and the reference(VIEWB and SAVE A
displays).

5-20

11. Adjust lF Gain
(Rl015on the 110 MHz Amptifierboard)
a. Test equipmentsetup is shown in Figure 5-20.
SEt thE RESOLUTIONBANDWIDTHtO 1 MHZ, REF
LEVELto -20 dBm, and VERT DISPLAYto 2 dB/DtV.
Apply a -25 dBm, 110 MHz signat, through step
attenuators,to the input(J365)of the 110 MHz fitter.
b. set the step attenuatorsfor 0 dB. set the signal
generator frequency {or maximurn amplitude display.
With -25 dBm input the signal level shoutd be 7 divisions or more.) Set the generatoroutput for a 7 division signalreferencelevel.
c. Removethe 110 MHz signalfrom the 110MHz
filter and reconnectP365.
d. Set the step attenuatorsfor 21 dB attenuation
and applythe 110 MHz signalto the input(J321)of the
'110MHz lF amplifier(Figure5-20).
e. Adjust R1015,110MHz lF Gain, for a disptay
amplitudethat equalsthe sevendivisionreferenceset in
part b.
f. Removethe 110 MHz signaland reconnectP321.
Apply the cAL ouT signal to the RF |NPUT. set the
SpectrumAnalyzercontrolsas follows:
FREQUENCY
FREQ SPAN/DIV
RESOLUTION BANDWIDTH
REF LEVEL
VERT]CAL DISPLAY

100 MHz
100 kHz
100 kHz
-20 dBm
2 dB/DIV

g. Set the front panel AMPL CAL fully counterclockwise and readjust Rl015 (110 MHz lF Gain) for 5 divisions of signal. (lf this cannot be achieved, it indicates
excessive loss through the front end.)
h. Adjust the AMPL CAL for a full screen signal.
AMPL CAL adjustment should now have 6 dB down
range and 6 dB or more up range.

Two variablecapacitors,C1054 and C2047
on the 110 MHz lF board, do not require
adjustment during calibration. These
adjustments require return loss measurement which is a maintenanceand repair
function.

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Adjustment procedure -

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4g4Al4g4ApseMce vot. 1

Calibrato. Level
R1045 in 3rd Converter
lF Gain R1015
10 ltlHz lF Ampl

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10 dB and 1 dB Step Attenuators

Figure 5-20- lF gain test setup,and adjustnent and conn€ctor rocason3-

12. Adjust B-SAVE A Reference Level
(S1015on the VerticatDigitatStorageboard)
when B-sAVE A is selected,the expressionimplementedis (B-sAVE A) + kl, where k is'a constantset
by the input data for an g-to-4 line encoder, u1015.
Each bit will move the referencelevel about 0.2 minor
division. Normally,the referencelevel is set at the
centergraticuleline; however,it can be set anywhere
within the graticuteare3 the setting of an g_biibinary
!y
switch,S1015(Figure5-7).
The MSB (switch#8) shifti
the display about five divisions,swiich #7 h;lf this
amount,etc. The following proceduresets the referencelevel.

Estimate the amount and direction the reference
level is to be shifted,then close or open the switches
on 31015 to obtain the desired B-SAVEA reference
level.

13. Adjust Preselector Driver
(Rl031, Rl045, Rl049, Rl052, R10s4, Rl056,
R1061,R1063,R1064, R1065,and R2066on the
Preselectordriverboard)
a. Connectthe test equipmentas shown in Figure
5-21.

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5-21

Adlustment Procedure-

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494A/494ApServlce Vot. 1

PRESEIECTONOR]YEREOARD

TtrsooMAN FRATE

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DIGITA
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VOLTreTER GEilERATOR
SOURCE

SPECTRTI AilALYZERlrl'DER TEST
OMGEilERATOR
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Figure5-21. Preselector Driveradiustmentlietup.

b. Set th€ test equipmentas follows:
Time Mark Generator .l0 ns
CombGenerator
On
c. Connect the DVM betweenthe center tap of the
MANUALPEAK potentiometerand ground. Adjust the
control for 0 V indication. lf index on the knob is not
alignedwith the mark on the front panel, loosen knob
and positionthe mark so it is aligned.
d. Set the SpectrumAnalyzercontrols as follows:
FREQUENCY
RANGE
FREQSPAN/D|V
AUTORESOLN
REF LEVEL

1.7-5.5 GHz
20 MHz
On
_30 dBm

E. SEt thE CENTER FREQUENCYtO CENIET
thE
2.1 GHz markEr. Center the Input Ofiset adjustment
R1031 (Figure 5-221,then center the 2.1 GHz marker
with the CENTER FREQUENCY control. Ground
TP1069with a jumperstrap.

5-22

f. Adjustthe PreselectorOffsetRl064 for maximum
responseof the 2.1 GHz signal. Removethe grounding
strap.
s. Peak the 2.1 GHz signal with the -829 MHz lF
OfisetR1049(Figure5-22).
h, Remove the Time Mark Generatorfrom the
comb Generator. change the REF LEVELto 0 dBm.
set FREQUENCYto 5.5 GHz, and center the 5.5 GHz
comb markeron screen.
i. Peak the 5.5 GHz signal with the Preselector
Sense,R1065 adjustment.
j. Due to interactionbetween R1049 and R1065,
repeatparts g throughi.
k. change the FREQRANGEto 5.4-18.0 (Band4).
S€t REF LEVEL and RESOLUTIONBANDWIDTHto
obsgrve the 6 GHz marker. Set the MANUAL PEAK
controlto peakthe 6 GHz signal.
l. Set FREOUENCYto 9 GHz and observe th€
9 GHz marker on screen. Peak this responsewith the
X3 GainRl052 adjustment.

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A Adrustment Procedure- 4g4A/494ApService Vol. l
$tsr.

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Figurc 5-22. PreselectorDrivertest point and adiustmentlocations.

. m. Repeatparts k and I to compensatefor int€rac_
tion.

u. Adjust -829 MHz tF Offset Ri049 (Figure5-22)
to peak the 3.5 GHz response.

n. lncrease FREQUENCYto the 12GHz marker,
then peak the 12 GHz point with Shaper #1 R1OS4
adjustment(Figure5-22).
o. Set FREeUENCYto center the 17 GHz marker,
then peak the signat with Shaper #2, R1056 adjust_
ment.

v. ChangeFREQRANGEto 3.0-7.1 GHz, set the
FREQUENCYto 5.0 GHz to observethe marker,then
peak the 5.0 GHz signatwith the +829 MHz tF Offset
R1045adjustment.

p. Recheckthe 6,9, 12, and 17 GHz pointsto verify
that th€y all peak at the same positionor tne rront_panet
MANUALPEAKINGcontrol. lf they do not, repeatparts
g througho.
_ q. Change the FREQ RANGE to 1.7_5.5 GHz
(Band 2). Center the 5.5 GHz marker, then peak the
signatwith the MANUALPEAKcontrol.
r. change FREQ RANGEto 5.4_19.0 GHz (Band
4). Centerthe 5.5 GHz with the CENTERFREQUiNCY
control. AdjustInput OffsetR10gl, to peak the signat.
:. Repeat parts q and r untit the signat amptitude
peaks, on both bands, occur at the same position of the
MANUALPEAKcontrot.
t. Set MANUAL pEAK control so the index mark
alignswith the front panelmark. ChangeFREQRANGE
tO 1.7_5.5 GHZ, ANdSEtthE CENTERFREQUENCY
tO
centerthe 3.5 GHz comb marker.

w. ChangeFREQRANGEto 15-21 GHz. Set th€
FREQUENCY
to 15GHz, then peak the t5GHz signal
with Rl064.
x. Tune the 19 GHz marker to c€nter screenthen
peak the 19 GHz signalwith Shaper#3 R1061adjustment (Figure5-22).
y. Tune to the 21 GHz markerthen peak the signal
with shaper #4 n1063adjustment.
z. Recheckthe 15, 19, and 21 GHz pointsto verify
that they all peak at the same positionof the MANUAL
PEAKcontrol.
aa. ChangeFREQRANGEto 3.0-7.1 GHz, center
a 5.0 GHz signal on screen;then peak the signalwith
the +829 MHz lF, Rl045 adjustment.
ab. Change to the 1.7-5.5 GHz band, center a
3.5 GHz markeron screen,then peak the 9.5 GHz signal with the -829 MHz tF, Rl049 adjustment.

5-23

Adfustrnent Procedure-

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4g4A/4g4ApServtceVol. 1

TO EXT. ALC IXP|JT@}|IGCTOR-

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SPECTRUT AIIALY:ZER ITIOER TEST

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LOW LOSSCOAXCABI."EWttH SflA OO|,{€CTORS

Figure 5-23. Test equipmentsetup for band leveling adiustmenl

1tt. Adjust Band Levetinglor Coaxial Bands
(Bands 1-5)
(R2031,R3034,R3090,R9019andR3022on theVR
#2 Motherboard)

Inpul trom VR #1

The mean value of the frequencyresponse
for each band is set to a -20 dBm referenceat 100 MHz.
a. Perform FrequencyResponseCheckof bands 1
through 5 as describedin the performanceChecksection and note th€ frequencyat the mean level (average
level betweentwo extremes)for each band.
b. Perform adiustmentstep 11 (presettingthe Variable ResolutionGain and Baseline Leveling)prior to
proceedingwith this step.
c. Remove and install the Variable Resolution
moduleon an extender.
d. Connecttest equipmentas shownin Figure5-23.
Set the SpectrumAnalyzercontrolsas follows:
FREQUENCY
RANGE
FREQSPAN/D|V
AUTTORESOLN
REF LEVEL
MIN RF ATTEN
VERT|CALDTSPLAY
VIEWA and VIEWB

5-24

1.7-5.5 GHz
10 MHz
on
-20 dBm
O dB
2 dB/Drv
on

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Figure5-24. Bandlevelingadiustmentand gain diodelocation3.

e. Apply a calibrated -20 dBm signal, whose frequencyis the same as that noted for the mean level in
part 'a", to the RF INPUT. Set the FREQUENCY
to the
input signal and reduc€ the FREQ SPANIDIV to
500 kHz.

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Adru3tmentProcedure-

. f. Adjust Band 2 Gain RgOg4on th€ vR Mother
b.oard #2 (Figure 5-241 tor a fult screEn (_20 OBml
display.
_ g. Chang€ th€ FREQUENCYRANGE to 3.0_
7.1 GH.z(Band3) and appty a catibrated_20 dBm
signal with the same frequencyas noted for the meanlevel
in Band 3 for part a of this step.
h. set the FREQUENCyto the incomingsignatand
FFEOSPAN/DIVto 500 kHz/Div
i. AdjustBand 3 Gain R3030(Figure5-24)for a futl
screendisplay.
j. Repeat the above procedure for €ach coaxial
band (1-5) and set the gain of each with the appropriate adjustment. lf the range of any adjustmEnt is
insufficlent,
add or r€movea diodebetrr,leen'pin
DD and
th€ -appfopriateadjustmentpotentiometeron th€ vR
Mother board #2. to obtain the reguiredrange. Refer
19 .th: schematicdiagram and componenttocator for
Variable Besolution Mother goarOs, in Volume 2.
Addingthe diodeincreasesgain.

15. Adiust Band Leveling for Waveguide Bands
(Bands 6-11)
(R3024, R3026, Rg02g, R9029, anct R3032 on the
VR Mother board #Z)
?. I:g! equipmentsetup is shown in Figure5-23.
Apply 2072MHz at -€O dBm, through a dt_btocking
capacitor to the EXT MIXER input. Monitor the inpui
with a pow€r meter to set the pow€r tevel then add a
known 30 dB attenuator so th€ input
'Set level to the
EXTERNALMIXERport is -60 dBm.
ttre Spectrum
Analyzercontrolsas follows:
FREQUENCY
RANGE 1g_26 GHz(Banct6)
FREOSPAN/D|V
200 MHz
AUTORESOLN
On
-3OdBm
REFLEVEL

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The baselineof the display will rise when
the 2072MHz signat is apptied to the
EXTERNAL
MTXERinput port connector.
-60
b. With
dBm input level apptied,adjustBancl6
Gain Leveting R3024 (Figure 5-24) lor iuil screen
display.
c. change the FREQUENCY
RANGEand input signalfrequencyand levelas listedin Table54, and adjuit
the appropriateBand Gain adjustmentsfor a fult screen
display. Gainadjustmentfor the waveguidebandsneed
to be adjustedonly if these bandswill be used.
d. Switch POWERoff; replaceVariableResolution
module,then switchPOWERback on.

4g4rl4g4Ap ServiceVot. I

Tabte 5-4
EXT MIXERBAND
LEVELINGADJUSTi,IENTS
Band

6 (18-27 GHz)
7 (26-40 GHz)
8 (33-60 GHz)
9 (50-90 GHz)
10 (75-140 GHz)
11 (110-220 GHz)
12 (r7O-325 GHz)

Gain
AdJustment

R3024
R3026
R3032
R3029
R3028
R3028
R3028

16. Phase Lock Calibration
(C1016,C1018,C1032,and C1034on the Strobe
Driver board; C10i3 and C2011 on th€ Controlled
Oscillator board; and Rl06l and R3Og2on the Error
Amplifier board)

The PhaseLock assemblynormallyrequirescalibration only after some part of the assembly has been
repaired or replaced. phase noise, produced by the
phase lock loop, is specified tor -7AdBc or better,
3 kHz out from the response. This should be checked
beforecalibratingth€ assembly.
a. Test equipmentsetup is shown in Figure5-25.
Remove the Phas€ Lock module and the two cover
plates so all circuit test points and adjustm€ntsare
accessible. Plug the assemblyon extenderboardsand
into the instrument. Use Extendercables and adapters
to reconnect signal cables to their respectiveconnector
(cable with yellow band to J501, and the cable with
blackband to J502).
lf d€sired, the direct reading counter may be connectedto the VerticalOutputof the t€st oscilloscopeto
get a count of a display at each test point, when
appropriate,throughout this procedure. The ground
side of the test oscilloscopeprobe will serv€ as the
commongroundreturnfor both instruments.
b. Press  CAL and do the directed
calibration routine through adjusting the LOG CAL.
Press  to return the instrumentto normal operationand set REF LEVELto -30 dBm. Check
that the AUTo RESoLN is active (button tit).
c. Check O{fset Mixer - This part of the procedure is only requiredafter repair or replacementof
the Mixer board.
(1) Connect the Direct Input of the frequency
counter to pin N (Figure 5-26) and set the counter
controlsfor a count. Notethe frequency.
(2) Connectthe counterto pin K and note the frequency.

5-25

AdJustnent Procedure -

494A/4g4ApServtce Vot. I

To: Vsrt liignel Out
(back penell

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Spectnrm Analyrer Under Tegt

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Flgure 5-25. Test equlpm€ntretup for adjusting llre phase Lock assembly.

(3) Connect the counter to the coll€ctor of e1040
and not6 the frequency. Frequencyshould equalthe
difference between pins N and K (e.g.,
25.080MHz - 25.000MHz - 80 kHz). Disconnect
the counterprobe from the collectorof e1040.
(4) Connecta test oscilloscopeprobe to the collector of Q1040and checkfor a signalwith a frequency
of approximately B0 kHz, 507" duty cycle, and an
amplitudeof approximatety5 V peak-to-peak.

d. Check Synthesizer
(1) Set the SPAN/D|V to 200 kHz. phase tock
should occur.
{2) ChangeSPAN/DIVto 500 kHz and connectthe
counter to J500 on the Synthesizer board. Check
for a readingof 50.00MHz.
(3) Connect the counter to Tp2O40 (Figure 5_26a)
and checkfor a readingthat is near 25.0 MHz.
(4) Connectthe test oscilloscopeto Tpl040 (Figure
5-26a) and check for positive pulses with an amplitude of approximately4 V peak-to-peak.
(5) Changethe SPAN/DIVto 200 kHz and observe
that the signalon Tpl040, in part d(4)is stiil th€re.

5-26

G. Contolled Osc{llator - This part of the checkis
only requirgd after repair or replac€mentof the ControlledOscillatorboard.

Bandpass filter adjustments c1041 and
C1042 are set at the factory becausethey
requirea specialtest fixture. Theseadjustmentsdo not need furtheradjustm€nt.
lf adjustmentof C1013 and C2011 is not
sufncientto achieve phase-lock,the board
shouldbe replaced.
(1) Press  PULSESTRETCHER
and
select item #1 (FREQUENCYLOOPS CAL), then
item #5 (PHASE LOCK SYNTHESIZER)
from the
displayedmenu.
(2) Followthe instructionsuntil the message,'VERIFY LAST STEP'. Due to the interactionof adjustment capacitorsC1013 and C2011, the two steps
will have to be repeated until the voltages are
correct. Alternately press AUTO RESOLN and
IDENTand adjust until the two voltagereadingsare
correct.

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AdrustmentProcedure -

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OSCIIIATOR

4g4A/4g4ApServlceVol. 1

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LOOPOA0T
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STROBEDRIVER

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B. Stiobc Orlyrr rnd Eror Ampllllcr.
Flgure 5-26. Phage Lock ariembly

adjustment and test point locations.

Adiustment Procedure-

494A/tg4Ap Service Vol. 1

(3) Connect the counter to Tp2o11 on th€ controlled Oscillator board (Figure 5-26a) and atternatelypress AUTO RESOLNand IDENTand check
for a count reading of either 25.0g4gMHz or
25.0328MHz.
f. Chec-kOpera0onof Strobe Drlver
The *PhaseLock Synthesiz€r"test is still used for
this test. lf aborted, press  PULSE
STRETCHERto return to the Synthesizerroutine. Any
step in the routinewillwork.
(1) Connectthe test osciltoscopeto Tp2015on the
Strobe Driver board (Figure 5..26b)and eheck for a
square wave response with a Time/Div setting of
.05 ps. Amplitudeshould be ==5V peak-to-peak.
(21 Connect the test osciiloscope to Tp2Og7 and
check for a sinusoidal waveform of approximatety
5vpp.

(5) RemoveP3057 (Figure5-26b). This turns on the
strobe to the Phase Gate. Set Loop Gain R3082
fully counterclockwise.MoveP2035to pins 2 and 3.
(6) Monitor TP3081 with the test oscllloscope.
Triggerthe test oscilloscopeexternallywith the signal at TP2037 (U204&6) shown Figure 5F26b. Set
the test oscilloscopeTime/Divto 5 ms and Volts/Div
to 0.5 v. Note the beat notes. Beat notes are produced by the difference betw€en strobes from the
phaselock (one every5 MHz) and th€ particularfrequencythe lst LO is tunedto.
O) Vary R3082 clockwise slowly and make a note
of th€ amplitude of the beat notes prior to lock The
when lock is achieved.
beatnot€swill dasappsar
(8) Set R3082 fully clockwise. Reset SPAN/DIVto
BANDWIDTHto 100 Hz, and
MAX, RESOLUTTON
TIME/olv to AUTO. D€activatevlEW A and VIEW
B.

(3) lf the amplitude of the strob€ signat is low and
noisy,chang€the values of selectcapacitorsCl01 6,
C1018,C1032,and C1034 for maximumamptitude
and minimumnoise at TP2087. The rangeof values
for thesecapacitorsis 3.3 pF-27 pF.

(9) As the sweep scans across the span, note the
position of the smallest beat note. Tune the
CENTERFREQUENCYto positionthe fr€quencydot
at this location, then reduce the sPAN/Dlv to
100 MHz. Set TIME/DIVto 1 s and activateVIEWA.

(4) Connectth€ counter to TP2087 and check for a
count of either 5.018868or 5.00642 MHz.

(10) Adjust R3082to set the amplitudeof the beat
note to 1.5x the amplitudenoted in sub-part7 of
part g.

(5) Gonnectthe test oscilloscopeto JS04and check
for5Vlogiclevels.
(6) Press  to abort the test.
g. Error Ampllfier- This proceduresets loop gain
whichis requiredwhen either the PhaseLock assembly,
1st LO, PhaseDetector,or Error Amplifieris replaced.
(1) Set SPAN/DIVto 200 kHz then press  PULSE STRETCHER. The DTAGNOSTTC
FUNCTIONSmenu will now be disptayed. Setect
menuitem 3 (DIAGNOST|C
A|DS)and setectt st LO
PHASE LOCK (sub-menu item 0). phase tock
shouldbs disabled.
(2) Connectthe test osciiloscopeto Tp203B(Figure
5-26b) and set the test osciltoscopeTime/Div to
20 ms. Check for a waveform with an amplitude
that is approximately6 V peak-to-peak.
(3) Press lOdBiDlV to enable phase lock and note
that the messageindicates LOCK ENABLED. Connect the test oscilloscopeto Tp 3081 (Figure5-26b)
and vary R3082from stop to stop and note that the
beat note signalvaries in amplitude. Press  to returnto normalop€ration.
(4) Set th6 TIME/DIV to AUTO, FREOUENCY
RANGE to 1.7-5.5 (Band 2), and SpAN/D|V to
50 kHz.

5-28

(11) Reset the TIME/DIVto MNL, and deactivate
VIEWA. Set SPAN/DIVto 50 kHz, then increaseit
to 100 kHz. Center th€ crt beam with MANUAL
scAN control. set the oENTER/MARKERFREOUENCYcontrol lor a null of the displayon the test
oscilloscope.
(12) Positionthe crt beam with the MANUALSCAN
control4 divisionsfrom centerscreen(400kHz from
c€nterscreen).
(13) Monitor TP1031on the Error Amplifierboard
with the test oscilloscope.Externallytriggerthe test
oscilloscopewith the signal at TP1031. Set R1061
to midrange.
(14) Vary Rl061 clockwise until the oscilloscope
displayjust startsto breakup.
(15) Use the MANUALSCANcontrol to position the
beam 4 divisions on the opposite side of center
screen. As the beam crosses center screen, the
displayon the test oscilloscopeshouldgo througha
null. lf no nufl occurs as the beam reachescenter
FREQUENCY
scre€n, reset the CENTER/MARKER
control for a null of the displayon the test oscilloscope.
(16) Adjust R1061 such that break points are
400 kHz on either side of centerscreen.

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Adjustment Procedure-

07) Move p2035 back to pins 1 and 2, reptace
P3057, and disconnectthe iest oscilloscopefrom
the ErrorAmplifierboard.
(18) ReduceSPAN/D|Vto 200 kHz and ensure
that
phaselock occurs, by the absenceof error rnessage
and a sweep. Replacethe covers on the assemdly
and reinstallthe modulein the lnstrument.perform
the phaselock noise check as describedin the performanceGhecksection.
h. Check Strobe Drlver - Excessivenoise on the
display and intermittentlock are indicationsthat the
strobe pulse from the Strobe Driver is noisy or tow in
amplitude.This can be causedby a mismaichin input
g o$qut impedanceto th€ band-passfitter FL20Li4.
The folfowing procedur€ is required if the filter or any
component that affects the input or output impedanc6
matchis replaced.
(1) With the instrument in phase lock rnode
(SPAN/D|V200 kHz or tess),monitorTp1Og2with a
test,oscilloscope.Note the amplitudeof the 5 MHz
strobe signal. Amplitudeof the sinusodialstrobe
signal is normaily5 V to 6 V peak-to_peak.
(2) lf the strobe signal amplitudeis low and noisy,
changethe valueof selectcapacitorsC1016,C.t016;
C1032 and C1034 to obtain the maximum strobe
pulse amplitudeat Tpl0g2. Thesecapacitorsrange
from 3.3 pF to 27 pF.
(3) lf the signatamplitudeis still tow, checkthe fre_
quency at TP1012 with a frequencycounter.
Frequency must fie between 5.0067MHz and
5.0188MHz. The frequency is a function of the
ControlledOscillatorassembiyand counterU1OZ2.

OPTIONINSTRUMENTS
ONLY
17.Adjust Option0Z VR BandLevetino
(R3024on the VR Motherboard#2)

a. Set the front-panelcontrolsas follows:
FREQUENCY
FREQSPAN/D|V
REF LEVEL
MIN RF ATTEN
AUTO RESOLN
TIME/DIV
VERT|CALDISPLAY
vtEW A/V|EWB

.t00MHz
200 kHz
_20 dBm
O dB
on
AUTO
10 dB/Dtv
On

b. Place the VR module on an extender,and con_
nect the cAL ouT signat to the 50o RF tNpUT via a
50O cable.

4g4[l4g4fup ServlceVol. 1

c. lt may be necessaryto set th€ FREQUENCy
control to ke€p the 100 MHz signalat centerscreen.
d. RESETthE RESOLUTION BANDWIDTH tO
300 kHz, and the VERTTCAL
DtSpLAyto 2 dB/DtV.
e. Set the front-panelAMPL CAL for a 7-division
excursionof the 100MHz signat.
f. Flemovethe 50O cable from the instrumentand
reconnectthe cAL ouT signalto the 75o RF INpUTvia
a 75O cabl€. Pushthe 75O RF tNpUTbutton.
g. Resetthe REFERENCE
LEVELto +20 dBmV
h. Adjust R3024 on the VR Mother board #Z tor a
7-divisionexcursionof the 100 MHz signal.
i. Disconnectthe 75O cable,disablethe 7SO input,
and re-fnstallthe VR modulein the spectrum analyzer.

18. Adjust Option 42 Modute
(Cl016, Cl020 and Cl024 in the Option42 Moctute)
This adjustmentn€ed only be done after the circuit
board in the modulehas been replaced.
a. Connectthe test equipmentas shown in Figure
5-27.
b. Set the front-panelcontrolsof the test instrument
as follows:

TR5O2
Output Level -dBm
Var dB

25
0

7L14
CenterFrequency 0110
Freq Span/Oiv
2 MHz
Resolution
3 MHz
VerticalDisplay
2 dB
ReferenceLevel
DisplayAandB Off

DC503A
chA
Term
Slope
Atten
Coupl
FreguencyA
Autotrig

50O
+
dc

5-29

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Adrustment Procedure- 4g4A/4g4ApServlce Vot, I

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DC503A

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[[
ORF
Input

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lc

ba1* RFOurO
LO
lst LO
P1024

(rFouT)

P1012

P1010

(OUr)

(tN)

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Figure 5-27. Opton 42 adiustmenttest equipmentsetup.

c. set the 7L14Time/Divto Manual,and adjustthe
crt beam (dot)to center screen.

(1) Set the 7L14 Spectrum Analyzer Reference
Levelto 0 dBm.

d. The DC503Areadout shoutd indicate approximately 110.000MH2. Set Level as nec€ssary,and set
the 7L14 Center Frequency for an indication of
110.0MHz.

(2) Checkthat the displayon the 7L14 is between4
and 7 divisionsin amplitude(-5 dBm, i3 dBm).

e. set the 7L14Time/Divto catibrateddisplay.
f. Adjust C1016,C1020 and C1024for maximum
amplitude, symmetry and bandpass (3 dB and 6 dB
points).

(1) Increasethe TR502 Output Level and REFERENCE LEVEL setting in 1 dB incrementsuntil the
amplitudedisplayedby the 7L14 decreasesby 0.5
division(1 dB compression).

(1) Adjust the bandwidthsymmetry +0.5 divisions
(r1 MHz)at th€ 3 dB and 6 dB points.
(2} Check that bandwidth at the 3 dB point is
7.5 MHz,*1.5 MHz.
(3) Checkthat 3 dB and 6 dB points are equidistant
from centerscreenwithin0.5 division.
(4) Checkthat any ripple presenton the waveform
is (0.2 div (0.4dB).

A slightchangein display may be observed
whenthe coveris reinstalledon the module.
S. Check the CoupledFonuard Gain (tF OUT port
P1O24l.

5-30

h. Checkthe Input Compression.

(2) Checkthat the signaldisplayedon the 7L14 indicates)0 dBm.
i. CheckForwardGain
(1) Return the TR502 Output Level to -25 and
removethe connectionto the modulo]F OUT.
(2) Connecta 50o terminationto the lF OUT connector,P1024.
(3) Connectthe OUT (P1012)connectorto the 7L14
RF Inputwith a 50o cable.
(4) Adjust the 7L14 Reference Level until the
displayedsignalis nearfull screen(8 divisions).
(5) Checkthat the signaldisplayedon the 7L14 indi-23 dBm (-21.5 dBm
cates -20 dBm to
*1.5 dBrn).

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Sectfon 6 -

494A/494Ap Servicc Vot. 1

MAINTENANCE
INTRODUCTION
This section describes proceduresfol reducingand
pr€venting instrum€nt. malfunction, tioubleshootint
methods, correctavemalntenance,and procedures
for
recalibratingthose assembtiesthat normally do
not
requireroutinecalibration.
Removing the Instrument trom its Cabinet
T-opreparethe standard instrumentfor maintenance
or adiustment,perform the following steps1. S€t the instrumenton lts facs or front panel.
2. Loosenthe four screws in th€ feet.
3. Pull the cover up and off.
4. Place the instrument on the work bench and
reconnectthe power cord.

4. Nothingcapabl€of generatingor hotdinga static
charge should be allowed on the work station surface.
5.. Keep the cornponent leads shortEd together
wheneverpossible.
9 Pick up components by the body, never by the
leads.
7. Do not slide the componentsover any surface.
8. Avoid handlingcomponentsin areas that hav€a
floor or work-surfacecovering capabfeof generating
a static charge.
9. UsE a solderingiron that ls connectedto €arth
ground.
10. Use only specialanti-staticsuctiontype or wick
type desolderingtools.
Tabte 6-1
RELATIVESUSCEPTIBILITY
TO
STATICDISCHARGE
DAMAGE

Static-Sensitive Componentg
This instrumentcontainselectricalcomponentsthat
9an be damagedby static discharge. See iabte 6_1for
the relativesusceptibitityof varioui classesof semiconductors. Static voltages of 1 kV to 30 kV can occur in
unprotectedenvironments.

MOS or CMOS microcircuits or
discretes,or linearmicrocircuitswith

Static dischargecan damageany semicon_
ductorcomponentin this instrumint.
Observethe following precautionsto avoid damage:
1. Minimize handling of static-sensitivecomponents.
2. Transportand store static-sensitive
components
or assembli€sin their originalcontainers,on metalized or conductivefoam, Labelpackagesthat contains static-sensitiveassEmblies or com,-ponents.
3. Discharge body static voltage by wearing a
grounded wrist strap while handling these com_
ponents. Statie-sensitive assemblies or components should be handted and serviced only at
staticfree work stationsby qualifiedserviceperson_
nel.

TTL (L€astSensitive)

VoltageEqulvalentfor Levels:
1-100to500V

a-500V

fa400to
1000V (estl

2 - 200to 500 v

5 - 400 to 600 v

8-900V

3-250V

6-600to800V

9-1200V

a Voltage discharged from a 100 pF
capacitor through a resistance
of 100{).

6-1

Maintenance-

4g4Al4g4ApServlce Vot. 1

PREVENTIVEMAINTENANCE
Preventivemaintenanceconsists of cleaning,visual
inspection,performancecheck, and if needed a recalibration. The preventive maintenanceschedule that is
establishedfor the instrumentshould be based on the
environmentin which the instrumentis operatedand the
amount of use. Under av€rage conditions (laboratory
situation)a preventivemaintenancecheck should be
performedevery 1000 hours of instrumentoperation.
Elapsed Time Meter
A 5000 hour elapsed time indicator, graduated in
500 hourincrements.is installedon thE Z-AxislRFInterface circuit board. This provides a convenientway to
check operating time. The meter on new instruments
may indicate from 200 to 300 hours elapsed time
becausemost instrumentsgo through a factory burn-in
tim€ to improvereliabitity.This is simitarto usingaged
componentsto improve reliabilityand operatingstability.
Cleaning
Cleanthe instrumentoften enough to preventdust
or dirt from accumulatingin or on it. Accumulationof
dirt and grease acts as a thermal insulatingblanket and
preventsefficientheat dissipation.lt also provideshigh
resistanceelectrical leakagg paths between conductors
or componentsin a humidenvironment.
Exterlor. Clean the dust from the outside of the
Instrumentby wiping or brushingthe surfacewith a soft
cloth or small brush. The brush will removedust from
around the front-panel selector buttons. Hardeneddirt
may be rernovedwith a cloth dampened in water that
contains a mild d€tergent. Abrasive cleaners should
not be used.

Do not allow water to get inside any
enclosedassemblyor compon€ntssuch as
thE hybrid assemblies, RF Attenuator
assembly,pot€ntiometers,etc. Instructions
for removingthese assembliesare provided
in the CorrectiveMaintenancepart of this
section. Do not clean any plasticmaterials
with organiccleaningsolventssuchas benzene, toluene, xylene, ac€tone or similar
compoundsbecausethey may damagethe
plastic.

Lubrication
Componentsin this instrumentdo not requirelubrication.

Fixtures and Tools for Maintenance
Table 6-2 lists kits and fixtures that are availableto
aid in servicingthe spectrumanalyzer.

Visual Inspection
After cleaning,carefully check the instrumentfor
such defects as defective connectionsand damaged
parts. The remedyfor most visibledefectsis obvious.
lf heat-damagedparts are discovered,try to determine
the cause of overheatingbefore the damagedpart is
replaced;othenwise,
the damagemay be rep€ated.

Interlon Clean the interior by looseningaccumulated dust with a clry soft brush, then remove the
looseneddirt with low pressureair to blow the dust
cl€ar. (High velocity air can damage som€ components.) Hardeneddirt or grease may be removed
with a cotton tipped applicatordampenedwith a solution of mild detergentin wat€r. Do not leavedetergent
on critical memory components. Abrasive cleaners
should not b€ used. lf the circuit board assemblies
need cleaning,removethe circuit board by referringto
the instructionsunder CorrectiveMaintenancEin this
section.

Transistor and Integrated Circuit Checks

After cleaning,allow the interior to thoroughlydry
beforeapplyingpow€rto the instrument.

observethe necesWhenhandlinga static-sensitive,
sary handlingproceduresto preventdamage.

6-2

All transistorsand integratedcircuits are soldered
on the boards to prevent pin contact problems,
Periodic checks of the transistorsand integratedcircuits is not recommended.The best measureof performance is the actual operationof the componentin the
circuit. In most cases any degradationin performance
will be detectedby the microcomputerwhen it runs its
power up routine. Performanceof thesecomponentsis
also checkedduring the performancecheck or recalibration; any sub-standardtransistorsor integratedcircuits will usuallybe detectedat that time.

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Maintenance-

Table 6-2
SERVICE KITS AND TOOLS

Nomenclature

006-3286-01
067-0973-00
067-0971-00

I AccessoriesInterface extender
1 Ribboncabte

067-0972-00

3 Coaxialcables, Sealectromale-to-S€atectro
temate

17$2902-00

1 VR modulehandle

o

1 Circuitboard extenderassemblykit consiiiing of:

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Tekfonix Part No.

ServiceKit consistingof:
'l Front panel
extender
1 Power moduleextender

)

t

494A1494Ap
ServiceVol. 1

175-2901-00

367-028s,00
672-0865-01

I Left €xtender board

670-5562-00

2 Right exlender boards

670-5s63-00

1 Right GPIB extender board

670-8493-00

1 Frameeldrusionfor circuitboardextender

426-1527-A0

6 Screws,panheadwith flat and tockwasheii

211-0116-00

screwdriver,flat, with 1/4 to 3lg-inchbit
Screwdriver, posidrive@ 440-2

Wrench,5/16-inch open-end
Hex drive wrenches,glg2, SI€/',ZlGzt-inch
TorqueWrench Kit

003-1324-00

Performance Checks and Recalibration
The instrument performance should be checked
after each 2000 hours of operationor every 12 months
if the instrumentis used intermittentlyto insure max_
imum performanceand assist in lociting defects that
may not be apparent during regular operation. Instruc_
tions for conductinga performancecheck are provided
by the Performance Check section of the service
instructions.

Saving Stored Data in Battery-Backup Memory
lf backup-battery power to the memory is interrupted,such as when changingthe battery,data stored
in battery-backedup memorywill be lost. This data can
be down-loadedonto tape using the programprovided
at the end of this section.
Macros cannot be down-loadedonto tape. However, these macros can be readilyreconstructedif they
had beensavedon a tape or disc.

TROUBLESHOOTING
The spectrum analyzyer contains firmware that will
troubleshoot the frequency control system and the
power supply. Troublsshootingprocedurefor this sys_
t€m and the power supptyis providedln the Diagnostics
part of this section. Also includedwith this part is a
descriptionof the trace modesand their actions. After
th€ def€ctiveassemblyor componenthas be€n tocated,
refer to the ReplacingAssembliesand Sub_assemblies
pert of this section tor removaland repfacementinstruc_
tions.

TroubleshootingAids
Diagrams - Functional block and circuit diagrams.
on foldout pages in the Diagrams section, eontain
significant waveforms, voltages, and togic data information. Conditions for getting the data are provided on
the diagram or adjacent to it. Refer to the Replaceable
Electrical Parts list section for a description of all
assemblies and components. Diagrams are arranged in
signal flow sequence and by sections, such as RF section, lF section, frequency control section, etc., with an
accompanying functional block diagram.

6-3

Malntenance-

tl94A/494ApSeMce Vot. 1

Schematic diagrams list the Tektronix part No.
(670-xxxx-) for the assembty or board atong with the
assemblynumber (e.9. AS0) and name. The tast two
digits or sufftx of the part number are not indicatedon
the diagram, however, they are list€d in the El€ctrical
Parts section. These two digits rsflect changes or
modifications to the assembly or board. When a
change is made to the assemblythe suffx rolls one
digit. The diagramindicatesthesechangeswith a grey
tint drawing of the original circuit or if a component
changes value the symbol is enclosed with a grey tint
box. When a major modificationis made to an assembly or board and it is no longercompatiblewith eadier
instrumentsa nsw part number ls asslgned and a
separate schematic with associated illustrations are
added. all diagrams indicate the new part number and
the instrumentserlal numberbreak. lf the assemblyis
compatiblewith earlier lnstrumentsand the change is
significantenoughto requirea separateschematic,this
will also be identified.

Correctionsto the manualand instrument
modificationsare documentedby ad MAX HOLD. Combinations
of error m€ssagesmay help determineand expedite the
proc€ss of findingthe problem.

has been isolatedto the assemblyor circuitlevel,refer
to the diagrams and circuit descr{ption, as suggested
under General TroubleshootingTechnigues,for further
isolation.
The proceduresare structuredas follows:

Error Message
Troubleshooting Procedure
1.
a.

b.

. . Some of the proceduresuse firmware diagnostics
aid routineswhich can only be accessedby pressing
>Blue-SHIFT> PULSE STRETCHERanO- ietecting
menuitem #3 (DIAGNOST|C
A|DS).
Combination of Error Messages
The followingis a list of error m€ssagecombinations and suggestionsas to their cause. lf the problem
is not resolvedwith the followingsuggestions.or if the
combination of effor messages displayed is not
covered,proceedto the listing of each error message
and how to troubleshootthe problem.
POWERSUPPLYOUT OF REGULATION
(in comblnatlonwlth any otfrer meseage/s)
A missingor inaccuratesupplyvoltage is probably
causingthe other errors. proceedto the POWERSUpPLY OUTOF REGULATTON
procedure.
TUNINGFAILURE- lST LO
and
TUNINGFAILURE- 2ND LO
The CF Controlboard is probablythe cause,particularly if signalsdo not tune or do not tune smoothly.
The problemis probablythe voltagereterenceor in the
digitalcontrolsection.
Procedure Format
The format for thes€ proceduresis such that the
problemis diagnosedin a dEscendingorder. The aim,
to isolate a problem down to one part of the system,
usuailyan assembly(such as a module or boardl or a
functionalsection of the assembly. After the pr6btem
6-5

(1)

(2)
2.

Steps at the same level are either sequentialor
alternativesteps, based on measurementor observation. Proceedto the lower-levelsteps only if the conditions of the higher-levelsteps are met. lf the conditions
are not met, proceed to the next step at the same level.
An "(E)' at the end of a step, signifiesthis is as far as
this procedur€can tak€ you to locate the problem.
Several of the troubleshootingproceduresrequire
that frequenciesbe countedand comparedto eitheran
expectedvalue,or the numbercountedby the spectrum
analyzer'sinternalcounter. The frequenciescan differ
by up to [(1x107)+ (counteraccuracy).
Theseprocedures,unlessspecifted,assumethe frequencyrangeis either0 - 1.8GHz or 1.7- 5.5 GHz.
Some failures,in the frequencycontrol system,may
appear only at sp€cific oscillator frequencies.lf this
occurs, in a higher frequencyrange, the fundamental
frequencyof the appropriateoscillatorshouldbe determined so it can be set to the same frequencyin the
lower bands. This can be done by:

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Malntenance_ 4g4Ll4g4ApServlceVol. 1
(1) Press  PULSE STRETCHEB
and
#0, then setect either the lst to reaoout
lmenu
item #1) or the
lnd fg.readout (menu iteni *e1.
I!9 _LO frequency wiil be displayect on the crt
CENTERFREQUENCY
readoutpbsition.
(2[fter n-otingthe.freque^ncy
of the oscillator,press
 PULSE STRETCHERand #0, and
select center frequencyreadout to return to the
normal center frequencyreadout mode.
Sincethe instrument'spower is usuallyswitchedon
and off during troubleshooting,the ponJer-do*n
settings, that are automatically Ltored in register
0 of
Paltery-backed-upmemory, lhout6 be recalted so the
instrumentsettlngs and operatingmode dupticatethose
that existedwhen th€ error messagewas ginerat"d.
. The following, describeseach error messageand
the proceduresrecommendedto locate the problem.
POWERSUPPLYOUTOF REGULATION
Any out-of-tolerancevoltage will cause this eror
m.?.":"g.e
to be displayed.A pow€r supptystatuscircuit
withinthe power supply will change tne itatus LED on
the Z-Axis board to red,whenany
supptyexcept_17 v
-error'message
changesby more than 25%. An
will be
also-be displayed. An apparent power suppty failure
can be producedwhen eitherthe supplyfails or a circuit
demandsexcessivecurrent and Ofowi L protectivefuse
or produces a current limit condition. The following
procedureshould determinethose voltages that are
out
of range and whether the failure is in th6 supply or in a
circuitoutsidethe supply.
Troubleshooting procedure

The spectrum analyzer uses a high
eficiency pow€r supply, with the primJry
ground potential difierent from chassis or
€arth ground. An isolation transformer,
with a turns ratio of 1:1 And a 5OOVA
minimum rating, should be used between
the power source and the spectrum
analyzer power input receptacle, The
transformer must have three-wire input and
output connectors with a through
- ground
99!*99n input and output. S-tancor
GlS1000 is an €xample of a suitable
transformer. A iump€r should also be conn€ctedbetweenth€ primarygroundside to
chassis ground (emitterof e2061 and the
groundt€rminatof the input fitterFL301).

lf the power supply is separat€d from the
instrument and operated on the bench,
hazardouspotentialsexist withinthe supply
for several seconds after power is discon_
nected. This is due to the slow discharge
of capacitorsC6101 and C61fi. DS5112
(next to 96111) tights when the potential
exceeds80 V.
_ - 1. Verify that the power supply status LED, on the
Z-Axis board, is red. lf the LED is green,there is probably a failure in the microprocessorlnterface.(E)
.2, Measurethe power supply voltagesat the test
points on the Z-Axis board. To accessine test points,
remov€ the hold down cover over the Sweep and
Z-Axis boards.

Hazardous voltages (900 V and 100 V) are
presenton the Z-axis board.
The rangesfor each supply are listed in Table 6€.
ThEseare tolerancelimits which are much tighterthan
the limits used by the power supply sensingcircuit. A
supply that exceedsthese limits may not trigger the
error messageor cause the instrumentto malfunction.
The +15 V supply is adjustableand affects the other
supplies. Referto the Adjustmentproceduresectionof
the manualfor adjustmentinformationif a supplyis iust
out of tolerance.
. a. lf all suppliesare within limitsand the powersup_
ply status LED is r€d, the probtemis probablyin the
power supply status circuit on the Z-Axis board.
R1065may be misadjusted;adjust Rl065 to see it the
LED changesto green. lf it changes,set R1065at the
centerof the 'green'range.(E)
b. lf the +17 V or -17 V supptyand any other supply or supplies are inaccurate,or, if both the +9 V and
+5 V suppliesare inaccurate,the troubleis likelyin the
PowerSupply.(E)
c. lf the voltage is high (in absolutevalue),the
troubleis probablyin the Power Supply.(E)
d. lf the voltagefrom a fused supplyis inaccurate,
the trouble is probabtyin the power Suppty.{E)
e. lf the voltagefrom a fused supply is absent,it
indicatesthe fuse could be blown. To accessthe fuses.
remove the cover at the top left hand corner of the
Power Supply module (as viewed from the front of the
instrument),A blown fuse generallyindicatesthat one
of the circuits that this supply furnishesis defective;
however,a fuse may open without an overcurrentcondition. Replace the fuse and try again. lf the fuse
opens,the troubleis definitelyin one of th€ circuitsthe
supplyfurnishes.

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Table 6-3
POWER SUPPLYRANGES

Supply
+300 v

Range

Test Polnt

280V to 310 V

TPl052

Fuse(F1033)

+100v

Circult Protecton

95Vto105V

TPl048

Fuse (F1035)

10.8V to 18.6V

TPl047

Fuse (F2013)

15V

14.85V to 15.15V

TPr046

Currentlimit

+9V

8.5 V to 10.5V

TPl011

+5V
-5V

4.8 V to 5.2 V
-4.8 V to -5.2 V

TPl044

Fuse{F1014
Curent limit

TPl036

Gurr€ntlimit

TPl037

Fuse(Fl013)

TPt035

Currentlimit

+ 1 7V

-7V
-15 V

-7 V to -8.5 V
-14.85V to -15.15V

-17V8

Fuse (F3038)

Gnd

TPl034

f. lf the fuse does not open and the vottageis still
absent,it indicatesthe troubleis the power Supply.(E)
g. lf the voltage from a current limited supply is
absent or low, the problemcould be the supply,or circuits the supply furnishesmay be drawing excessive
curr€nt. Turn the POWER ofr, then disconnect the
suspect assembliesor modules from the supply and
re-measurethe voltage; or, remove the power Suppty
from the instrumentand measurEthe unloadedvoltagei
on the PowerSupplyconnector.
(1) lf the supplyvoltageis correctwith assembtyor
module removed, or when the voltage with th€
power supply removed is normal, the circuits this
supplyfurnishesare causingthe problem.(E)
(2) lf the voltage for the unloadedsupply voltage
is still inaccurate,the power supplyis defective.(g
TUNINGFAILURE-

1ST LO

The 1st LO is set by a combination
hardware/software loop. There are two distinct
hardwareblocks to the loop: the block that measures
the oscillator frequency and the block that sets the
oscillator to frequency. The microprocessorsystem
closes the loop by det€rmininghow muchthe oscillator
rnust b€ tuned to set the desired frequency. The
microprocessorindirectlycountsthe 1st LO, tunes it as
needed,and countsagain.

GroundRefer€nce

The l st LO Tuning Failure error message is
displayedwh€n the lst LO has not been set correcuy
after a numberof iterations. The number of times the
1st LO is countedand tuned varieswith instrumentsettings.

The l st LO Control DiagnosticAid displays data on
the crt screen which can be used to determinewhich
part of the loop has failed. To displaythis data, press
 PULSE STRETCHERand #3. th6n
select#1.

The first two lines list the voltage to b€ exp€ctedat
the output of the lst LO s€ction of the Center Frequency Control and the voltag€ across the sense resistor of the l st LO Driver. The nominalvaluesare based
on the Desiredlst LO Freq and the nominaltuningsensitivityof the oscillator.

The DAG Set valuesare basedon the settingof the
lst LO tuning DACs. The DAC Set values can differ
from the Nominalvaluesbecausethe systemcannotbe
exactlycalibrated,tbe tuningsensitivityof the oscillator
is possiblynot its nominalvalue,and the DACSwill be
movedin an attemptto set the oscillator.

a The -17 V..:upPty is nol
monitored. by trre Power supply status cirouit nor does it have a iest point on the z-axis board, It this suppty rails, the
cooling fan wilt not tun. The fsn will atso not run it tre im5ient tempe.ature is tow. The -17 v suipty witt probably affect other suppliei ai weil.

6-8

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4g4ful4g4ApServtceVot. 1

1STLO CONTROLDIAGNOSTIC
AID
TUNEVOLTS
SENSEVOLTS

NOMINAL
-6.79 V
3.43V

DAC
-6.80 V
3.43 V

DESIRED
lST LO FREQ
MIXERFREO

2.720 504 c|-1.z
45.896MHZ

1ST LO SETNNGACCURACY
AUXILIARYSYNTHESIZER

2.719735 cHZ
46.665MHZ
4.981MHZ
212.800 MHZ

PRESS'SH|FT"TO EXIT

The Desiredl st LO Freq is th€ frequ€ncyto which
llre qroge.ssor,is trying to move the oscillator. The
uounted l st Lo Freq is the frequencythe microcomputer has calculatedfrom, the internaltycounted
harmonic mixer outputfrequency,the Auxiliiry Synthesizer
frequ€ncy, and the assumed harmonic numOerof
the
AuxiliarySynthesizer.BEcauseof this lasi assumption,
if the lst LO is not near the Desired Frequency,
the
counted Frequencywiil not be the actuarosciilatorfrequency,eventhoughthe counteris functioning.
The Desired Mixer Freq is the difierencebetween
the the Desired1st LO Fr€q and the nearestharmonic
of the Auxiti.arySynthesizer.(fhe AuxitiarySynthesizer
wiil atways be higher in frequencythan rhe
laryolig
desiredlst LO frequency.)
The 1st LO Setting Accuracyis the maximumper_
mitted difference.betweenthe actual and desired LO
frequencies. The setting process will end when the
differencebecomes less than, or equal to, this value.
The tolerancedependson frequencyspan and band.
Auxiliary Synthe.sizerFreq is the frequency
.. -T"
that is programrnedinto the +N synthesizer.
This troubleshootingprocedure should localize a
problemto the oscillator,the oscillatorsettingblock,
or
the.oscillatorcountingblock. lf the failur€ is not in the
oscillator, it is further localized within one of the
hardwareblocks.

Troubleshooting procedure

1. Press PULSESTRETCHER
and
#3 to displaythe DiagnosticAids menu,then sefect#1
to display the 1st LO Control DiagnosticAid information.
2. lf the counted lst Lo Freq is within the 1st Lo
Setting-Acgyracy of ths Desired Freq readout, press
 to retum to normal operation. Now
detennine if the error occurs, for the same center frequency,at frequencyspans/divisionabove S MHz only,
or at spans less than 5 MHz/div. (Frequencyrange
mustbe 0 - 1.8GHzor i.fl(em 5.5 GHz.)

a. lf the frequencycontrol error occurs only at fre_
quency spans of 5 MHz/div or more, the capacitor
switchingrelay,on the 1st LO assembly,is probably
shorted.(E)
b. lf the error occurs with a frequencyspan/divof
5 MHz or less,the 1st LO is probablydefective.(E)
3, Measurethe voltage across th€ sense resistor
(R1040)on the lst LO Driver board. tf this vottageis
within 50 mV of the DAC Set value, measurethe frequency on the l ST LO Output connector. This measured frequencyshould be within S0 MHz of the frequencycalculatedby multiptying800 MHz/V by the vottage that was measured across the sense resistor
R1040.

6-9

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Mafntenance-

494A1494ApServtceVot. 1

a. lf the calculated and measured frequenciesare
within 50 MHz of each other and the mbasuredfre_
quency agrees with the internallycount€d 1st LO
Freg readoutor differs from it by a multipleof the
AuxiliarySynthesizerFreq, r€turnto normal opera_
tion-(by pressing). Now attemptto
calibratethe CF Controlboardand the 1st LO Driver
board by pressing  PULSE
STRETCHERand select #1 from the menu for the
FREQUENCY
LOOPSCAL, and #1 againfor the CF
Control board. or #2 for the lst LO Driver board.
Exit from the CF Control board calibrationroutine by
pressingwhenthe step for Ra040ii
displayed. lf you are able to completethe calibration routin€, check to gee if the error message is
still present. lf it is, or if the calibrationroutines
cannot be completed,continuetroubleshootingwith
step 4. (E)

(a) lf the tune voltage is within th€ center of
its normal range and the output frequencyat
P1060 is stable (varies no more than l2Hzl, the programmable divider in the
phase-lockedloop is probablydefective.(E)
(b) lf the tune voltageis in th€ centerportion
of its normal range and the output frequency
at P1061 is unstable,the loop amplifierii
probablydefective.(E)

b. lf the calculat€dand measuredfrequenciesare
within 50 MHz, but do not m€Etthe abovecondition
in step 3a, measurethe AuxiliarySynthesizeroutput
frequency at P1060 on the Auxiliary Synthesizer
board.

(d) lf th€ tuning voltage and the Auxitiary
Synthesizerfrequencyare in oppositedirections from the c€nter of their respective
ranges(8.5Vand 210 MHz),the VCO is probably defective.(E)

0) lf the AuxitiarySynthesizeroutputfrequency
is coffect, measurethe input frequencylrom the
HarmonicMixerwith a spectrumanalyier,at the
cabte connectionto p261 on ttre euiitiary Syn_
thesizer board. (A counter woutd probaOiygive
an eroneous reading becauseof the harmonic
mixing process). The frequencymeasuredwith
the speetrumanalyzershould equal the sum of
the Desired Mixer Freq and the measured1st
LO frequency,less the Desired lst LO Freq, if
the catculatedfrequencyis between10 MHz and
90 MHz. lf the calculat€dfrequencyis outside
th€ 10 MHz to g0 MHz range, the lst Lo fre_
quencyis far from the d€siredvalue. Repeatthe
previousstepsin this procedure.
(a) lf the HarmonicMixer outputfrequencyis
correct. measurethe frequencyat edge con_
nector 'l5, on the Auxillary synthesizer
board, with a countgr. This should be
1i100th of the Harmonic Mixer output fre_
quency.
(b) A correct frequencymeasurementindi_
cates the Counterboard is defective.(E)
(c) An incorrect frequency measurement
indicatesthe AuxiliarySynthesizeris defective. (E)
(d) The HarmonicMixer is probablydefec_
tive if no signal is present at the output or
the signalfrequencyis incorrect.{E)
(2) tf the output frequency, at p1060 is
incorrect, measurefie 200_220 MHz VCo tune
voltage between Tp1066 and Tp1074 on the
Auxiliary Synthesizerboard. The range of the
tuningvoltageis normally+S V to +12 V.
6-10

(c) lf the tune voltage and oscillator freguencyare at the end or outsidetheir range,
in the same dir€ction(highor low), C1070tn
the VCO may be misadjusted.lf adjustment
of the capacitor do'es not conect the problem it is not in the VCO but somewhereelse
in the loop. (E)

{e) lf the calculatedand measuredfrequencies difier by more than 50 MHz, removethe
jumper plug P3043 on the 1st LO Driver
board and measurethe oscillatorcurrent.

The oscillator coil has significant
inductance. Interruptingthe oscillator current will gen€rate hlgh voltage. Remove/replace P3043 or
connect/disconnecta current meter
after the power is off. fiypical voltages at P3043can rangeas high as
35 V.)

The coil current should be: 40 mA/y, where
the voltag€ is the sense-resistorvoltageas
previously measured across Rl040. The
measuredcurrentshouldbe within1oloof this
value.
(3) lf the measuredand calculatedcurrentsare
within 17o.return to normal op€ration (by pressing ) and determineif the frequency control error occurs with frequency
span/divof 5 MHz or less, or above 5 MHz/div,
with the sam€ center fr€qu€ncy.The frequency
rangeshouldbe in eitherband1 or band 2.
(a) lf the frequencycontrolerror occursonly
with frequencyspans of 5 MHz/div or less,
one of the noise filter capacitors on the
1st LO Assemblyis probablydefective.(E)

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Malntenance_ 4g4A/494ApServlceVol. 1
(b) lf the
-e1o-r-9cnr: with frequencyspans
greater than
5 MHz/div, ttre t si t-O is
iroOabtydefective.(E)
(4) lf the measuredand calculatedcurrents
are
not equal,th€ problemis likelyin the final stage
of the LO Driver.(E)
4. Measurethe lst LO tuningvoltageat edge
connector 47, of the Center Frequeniy Conirot
boarO. Ttris
voltageshoutdbe within 200 mV 6t tne tisteo
DAC Set
value.
?. lffl".vottage is within this timit, faitureof the
l st LO Driver board is indicated.(E)
b. tf th€ vottageis not withinthe limit, failureof
the
CenterFrequencyControt board is inOicateO.
6y
TUNINGFATLURE
- zND LO
The 2nd LO is set by a combination
hardware/software loop. There are two
distinct
hardwareblocks in the loop; the block which measurEs
the..oscillatorfrequencyanO tne Uoct wfrictr sets
oscillatorto frequency.The micropro""".o, closesthe
the
roop by d€termininghow far the oscillator
must be
moved to bring it to the desiredfrequency.
setting is
an iterativeprocesswhereinthe microprocesso,
counts
the oscillator frequency, moves it as needed,
and
counts again. The error messagels displayed
if the
2nd LO is not set to the Oesiid trequlncy
after a
numberof iterations,dependingon instrumentlettings.
The 2nd LO Controt DiagnosticAid displays
data
which can be used to deternrinewhich part ot
t'tretoop
has. fait€d._11typicat disptay is snown below. press
 PULSE STRETCHERand setect
#3
from the menufor the DIAGNOSTIC
AIDS, then select
#2tor the 2nd LO Control.
2NDLO CONTROLDIAGNOSTTC
A'-

TUNE VOLTS

O.O1V

2ND LO FREQ 2.182OOO
GHZ
OFFSETFREQ 18.OOO
OOO
MHZ
OFFSET SET.
TING ACCU.
RACY
PRESS
"SHIFT'
EXIT

TO

0 . 1 9V

2.182140c4z
17.860
MHZ
540.672
KHZ

The Tune Volts is the voltage that would be
expected at the output of the 2nd Lo section of
the
Cent€r FrequencyControl. The Nominalvoltageis the
value neededfor the Desiredfrequency
-me of the 6scillator
in a perfecflycatibrat€dsystem.
beC Set vonale
should be producedby the present seuing of the 2;d
LO tuning DACs. The DAC Set vottage may ditrer trom
the Nominal value because_the system may not fully
calibratedand the DACswitf be movedto tryto set
th;
oscillator.
The Desired2nd LO Freq is the frequencyto which
the microcomputeris trying to move the osciitator. The
Counted 2nd LO Freq is that frequency the microcom_
puter has calculatedfrom the CountedOfset freq.
The Offset Freq is the frequency of the towofrset VGO in the 2nd LO Asiembly. ln the
lr9^e-u9ncy
2182 MHz LO, this frequ€ncyis the differencebetween
22OAMHz and the LO frequency.
-aniFtre 719 MHz LO is
derived from the Z1g2MHZ LO,
the frequencyretationshipsare more complex.) Again,the DesiredFreq
is--thefrequ€ncythe microcomputlr is trying to set the
offset, and the CountedFreq is the value iead by the
internalcounter.
.If-|j, Offset€etting Accuracy is the maximumpermat_
ted differencebetweenthe actual and desiredotriet frequencies. The setting process ends when the
difference beeomesless than or equal to this value.
The tolerancedependson frequencyspanand band.
The following procedureshould localizethe failure
to the 2nd LO assembly,the hardwaresettingblock,or
the hardwarecountingblock.
Troubleshooting Procedure
1. Displaythe diagnosticinformationfor the 2nd LO
control loop as outlinedabove.
2. lf the CountedOffsetFreq and the DesiredOffset
Freq are within the OffsetSettingAccuracy,the 2nd LO
probablyhas failed.
3. lf the CountedOffset Freq is within 100kHz of
the DesiredOffsetFreq,make sure that p1049is prop_
erly seatedon J1048. lf the fine tune groundlead is not
making .good contact, the tuning voltage can shift
sufflcientlyto causesettingfailures.(E)
4. lf the Counted Offset Freq readout is within
100 kHz of the DesiredOffset Freq, the oscillatormay
be out of calibration. Return to normal operation by
pressing . Try to calibratethe 2nd LO
by pressing  PULSE STRETCHERand
selecting #1 from the menu for the FREQUENCY
LOOPS GAL, then setecting#4 {2nd LO). Now, foilow
the instructionsof the displayedmessages. lf you are
able to completethe calibrationroutine,checkto see if
the error condition sfllt exists. lf the error is stiil there
or you where unableto completethe calibrationroutine.
proceedto the next step.(E)

6-11

Malntenance-

494A1494ApServtce Vol. 1

5. Measure the 2nd LO Tune Volts at Tp1044 on
the Center FrequencyControl board.
a. lf the 2nd LO tuning vottage is within 200 mV of
the DAC SEt value, measurethe 2nd LO frequency
at the front-panet2ND LO Output connector.
(1) lf the measuredfrequencydoes not agree
with the internallycounted roadout.the couhter
board is probabtyat fautt. (E)
(2) lf the frequency agrees with the Counted
value, measur€the mixed down frequencyat the
cable going to p513 on the Count€rboard. This
frequencyshould equal the sum of th€ Desir€d
Offset Freq and the Desired 2nd LO Freq, less
the measured2nd LO frequency.
(a) lf this freguency 19present, measurethe
2182MHz oscillator tuning voltag€ on the
feedthrough capacitor CZaO} between the
16-20 MHz phase Lock circuitand the 2tg2
MHz Microstrip Osciltator in the 21g2 MHz
Phase Locked 2nd LO Assemblv. The normal range of this voltageis 0V to -12.5V.
With the phase locked loop unlocked,this
vottage wiil probably be stighuy outside one
end of the range.
(0 tf the absolute value (magnitude)of
the tuning voltage and the oscillatorfre_
quency are ofi in the same direction from
the centers of their respective ranges [6
{-6) V and 2182 MHz , the Microstrip
Osciltatorhas probablyfaited.(E
(ii) tf th€ absotutevalue (magnitude)of
the tuning voltage and the oscillator frequency are off in the opposite direction
from the centeror their respectiveranges
16(-6) V and 2i 82 MHz , someother part
of the lock loop, besides the Microstrip
Oscillator,has probablyfailed.(E)
(b) lf the mixed-downfrequencyis absent,
either the 22OOMHz Reference, the
2182MHz Microstrip Oscillator or the
22AAMHz Reference Mixer probabty has
faited. (E)
b. lf the tuning vottageis not within 200 mV of the
DAC Set value,the Center FrequencyControlboard
probablyhas faited.(E)
PHASELOCKFAILURE-

1ST LO
The followingprocedureassumesthat the oscillator
is at the conect frequency,so the probtemmust be in
the phase lock system.
The following crt display of th€ lst LO phase lock
DiagnosticAid displaysdata for troubteshooting
th€ 1st
LO phaselock loop.

6-12

lST LO PHASELOCKDIAGNOSTIC
AID
lst LO FREQ
2.A72000000 cHZ
STROBEFREQ
5.016949 MHZ
LOCKDISABLED
PRESS

TO
ENABLE
PRESS'SHIFT'TO
EXIT

While the troubleshootinginformationis displayed,
the lst Lo is repetitivelybeing stepped *750KH2. lf
LOCK DISABLEDis display€d,the lock loop is open
betweenthe outputof the phase gat€ and the input to
the FM coil. lf lock is enabled,the loop is closed,and
the fourth line of thE display changes to LocK
ENABLEDPRESS"HELP"TO DISABLE.
The lst LO Freq readoutis the frequencythe oscillator should be at when locked. The frequencythat is
measuredat the front-panel1ST LO Out connectorwill
not check exactlywith this value becausethe oscillator
is unlockedand steppingin frequency.
The StrobeFreq is the frequencyat P502and P504
of the PhaseLock module.
This procedureshouldhelp localizethe failureto the
PhaseGateor to a sectionof the phaselock circuitry.

Troubleshooting procedure
Beforetroubleshootingdata on the phaselock loop
is displayed,the Freq Span/Divmust be in those spans
that enablethe phase lock mode (200 kHz or l€ss for
band1).
1. Press PULSESTRETCHER
and
select #3 from the menu to bring up the DlAGNosTlc
AIDS menu, then select #0 to display the 1st LO
PHASELOCKdiagnosticaid information.
2. With an oscilloscope,examinethe signal atP242
on the PhaseGate. Beat notes (burstsof signal at up
to 500 kHz) at a 10 Hz rate should'be present as th€
oscillatoris stepped. Beat note amplitudeshould be
about6 V peak-peak.The amplitudeof the positiveand
negativepeaksshouldnot differ by more than2Oh.

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Malntenance-

a. lf.b€at notes are present,press HELP
to enable
the lock. Check the- Error' Amplifiei output
at
T?2O3T,on th€ Error AmplifierOolrJln
the prrase
Lock module. gutput signat amptituOe'sfroufO
Oe
approximately 6 V peak-peak aho its
frequency
should be 10 Hz. fhe up anO Oown-oui.t_r"ng"
:igngj:, on edge connectors g and 10 oi tn" error.
Amplifierboard, shoutdbe toggling Oetween
0 V and
+5 V.
(1)..1fthere is a signatat Tp2O37but
one or both
or tne out-of-rangelines is not toggling,
the outof-range comparator on the frior- Amptifier
board, or the sensing circuit on the phase Lock
Controt board, has probabty failed. firis coutO
cause problems in maintaininglock but not
in
acquiring lock. lf the instrument does
not
acquire lock. note the out-of_rangeproblem
and
continuetroubteshootingwith steF gj.
(2) lf there is no signal at Tp20g7,
the Error
Amplifierhas probabtyfailed.(E)
(3) ff there is a signal atTp2A}Z, th€ switching
circuit that connects the output of the
Error
Amplifierto th€ FM coil of tne i st LO has prob_
ably failed. (E)
lf b€at notes arg present,but their amplitude
P
is
v (peak-peak),or the amptitude
::::_^T"l
!:9
qrnerenceof the positiveand
negativesxcursionsis
more than 2AVo,the phase GatJ is probably
defective. (E)
c. lf there are no beat notes, mEasurethe strobe
frequency,at p504 on the phase l_ocf moOuie.
(1) lf the strobe frequencyis the same as
the
readouton the diagnosticaiOdisplay,it is possi_
ble, but not probable,that the r it [o systemis
miscalibratedand that th€ lst LO is near tne
wrong harmonic of the Auxiliary Synthesizer.
Press to returnto'normatoperation and look at the calibratorline that is ctosest
in. frequency to the frequency (in Band 1) at
which the error occurs. lf the irequency indi_
cated for the calibratorline is correci (a multiple
phase cate has proOa-Uty
9t..tlO MHz), the
failed.
lf the frequencyindicatedis incorrect, attemptto
calibratethe 1st LO system by pressing PULSESTRETCHERand sete-cting#1
(FREQUENCYLOOPS CAL), and tben #O
(OVERALLSYSTEM)from the rnenu. Exit from
the calibration routine when the display for
R4040, on the CF.
_C*ontrolboard appears by
pressing .
lf the calibrationcan
not b€ completed,or it does not rEsult in the
correct frequency indication for the calibrator
rine, troubleshootthe lst LO system using
the
procedure under TUNTNGFAIiURE _rst
LO
error messagestep 3b. (E)

4g4Ll4g4ApServiceVol. 1

(2) lf there is no strobe signal,checkfor a signal on feedthrough M, on the Strobe Driver
boardin the PhaseLock module.

(a) lf there is a signat,the StrobeDriverhas
probablyfaited.(E)
(b) lf there is no signat,the ControiledOscitlator has probablyfaited.(E)

(3) lf the frequency of the strobe signal is
effoneous.but is stable (within1_2 Hz), in the
normal strobe range of 5.006477MHz to
5.018868MHz, the programmabtedividerin the
Synthesizerhas probabtyfaited.(E)
(4) lf the listed Strobe Freq is betow5.OOZ10O
MHz and the actual strobe frequencyis slightly
aboveth€ desiredfrequency;orabove 5.01g240
MHz and the actual strobe frequencyis slightly
below the desired frequency,attempt to cali_
brate the Phase Lock Synthesizer. press
PULSESTRETCHER
and select
#1, then #5. lf you are able to completethe
calibration,check to see if the error messageis
still present. lf it is stilt displayed,or the calibra_
tion routinecould not be completed,proceedto
th€ next step as if th€ strobe frequencywas not
withinthe aboverange.(E)
(5) lf the listedStrobe Freq is outsidethe range
pr_ejgdingstep, measurethe tune voltage
in th.e
for the VCO, at feedthroughH on the Controll€d
Oscillatorboard in the phase Lock module. The
normalrange is from 5.9 V to 11.3V. With the
loop unlocked,the voltage wiil probablybe near
or beyondone end of the range.
(a) lf the voltageis aroundthe centerof the
range, the loop filter and amplifier,on the
Error Amplifierboard, are probablyat fault.
(E)
(b) lf the tuning vottageand the strobefrequencyare displacedfrom the centerof their
range (8.6V and 5.013MHz) in the same
direction,the VCO is good and something
else withinthe loop has faited.(E)
(c) lf the tuning voltageand the strobefr€quencyare displacedin oppositedirections
from the center of their range,th€ VCO has
probablyfaited.(E)

6-13

Malntenance-

4S4Al4g4ApServtceVol. 1

TRACE MODES
Trace Mode provides information on how the frequency control system is working. lt is acc€ssed by
pressing  PULSE STRETCHER.menu
item #7, then selectinglst LO (menuitem #1),2nd LO
(menuitem #2} MARKER(menuitem #3), or CORREG_
TION TIMER (menu item #4), gRD tF dOUrur (menu
item #5), or DISPLAYRESULTS(menuitem #6).
Trace Mode 1, starts tracing the l st LO control
actions. Trace Mode 2, starts tracing the 2nd LO con_
trol actions. Trace Mode g, starts tracing signal counts.
Trace Mode 4 starts tracing marker conection cycles.
Informationfrom these four trace modesis stored in
RAM and can be disptayed by setecting DtSpLAy
RESULTS(menuitem 6) from the TRACEMbDE menu.
This mode disptaysup to 16 lines of data gatheredby
the trace modes.

data applies to the primary marker and S if the data
applies to the secondary marker. The second letter is
c if th€ oscillators are being counted at the marker
positionto determinethe markerfrequency,or S if the
markerpositionis being synthesizedto maintaina constant markerfrequency. The numberin this columnis 1
if the 1st LO is being countedat the marker and 2 if the
secondLO is being counted. The fourth column is the
hexadecimal setting of the marker DAC. The fifth
column is the decimal digital storage location of the
mark€r. The sixth columnis the oscillatorsettlingtime
in ms before the count. The last column is the harmonic mixer output frequency in KHz for a 1st LO
count,or the 16-20 MHz VCO fr€quencyfor a 2nd LO
count at the rnarkerposition.
The sequencEPULSESTRETCHER,
#7, #0, terminatestrace actionsand erases the RAM
of alldata.
Alternate Frequency Display

Informationused is obtainedonly wh€n the
internalfrequencycorrectionoccurs.
Thihs correction is related to the drift rate
of the spectrum analyzer. The time
between corrections can be as long as
30 s.
To assure informationis available,change
th€ FREO SpAN/Dtv one position then
retum. This forces the correction cycle to
occur.
For modes1 and 2, the flrst field of the displayindicates which mode was active at the time the information was gathered. The secondfield of th€ displayindicates which attempt at tuning or correctingthe oscilla_
tor the data is for. The next lield containsthe tuning
DAG settings before a tune or conection took ptace.
The first three digits are the upper DAG settings, the
next three dagitsthe lowEr DAC s€ttings. The next field
containsthe DAc settingsafter the tuningor correction
was attempt€d. Again, the first three digits are the
upper DAC, and the next three digits the lower DAC
settings. The next field indicates the time delay
betweensettingthe DACSto the new valuesand reading the resultingfrequency,in units of millisecond.The
final field contains the frequency of th€ oscillator in
question,after the tune or correctionattempt. Actually,
the displayedfrequencyis the beat notefrequencyfrom
the auxiliary mixer for the l st LO (in KHz), and the
16-20 MHz oscillatorfrequencyfor the 2nd LO.
For mode 3, the resultingtrace displayconsists of
sevencolumns. The first columnis alwaysg. indicating
that the marker is being traced. The second column
gives the iterationnumberof the correctioncycle which
the displayedline describes. The third columnconsists
of two lefters and a number. The first letter is p if the
6-14

The Alternate FrequencyDisplay mode selects an
alternatefrequencydisplayinstEadof the normalGenter
Frequencydisplay. These alternate frequencies are
selected by pressing  PULSE
STRETCHER,selecling menu item #0, and selecting
#0, #1, or #2 as indicat€dby the menu.
The normalCenterFrequencyis displayedwhen #0
is selected.
The frequencyof the 1st LO is displayedwhen #1 is
selected. This displayis updat€deach time ths 1st LO
frequencyis counted.
The frequencyof the 2nd LO is displayedwhen #2
is selected. This displayis updatedeach time the trequencyof the 2nd Lo is counted.
Auxiliary Synthesizer Control
The AuxiliarySynthesizerControl can be turned on
continuously,or turned on only duringcorrectionfor the
1st LO tunes. This mode is toggled (turnedon continuously or during 1st LO corrections)by pressing  PULSESTRETCHER,
#4, A messagewill come on screen indicatingwhich
modethe AuxiliarySynthesizeris in.
Correction Disable/Enable
Correctionof the 1st and 2nd LO frequenciescan
be disabledor enabledby pressing 
and
10 dB/DlVor PULSESTRETCHER,
selecting menu item #6. When corrections are disabled. the oscillator frequenciesare counted but no
furtheractionis taken. This mode can be used to monitor the drift of the oscillatorsby activatingthe respective trace mode. When correctionsare disabled.the
1st LO cannotbe phaselocked!

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Maintenance-

494Al4g4fupService Vof. 1

CORRECTIVE
MAINTENANCE
Corrective maintenance consists of component
replacementand instrumentrepair. Speciat
tecnhiques
and procedures that may be iequirJj to-remove
and
replace assombliesand/br
in tnis instrumsnt are describedhere. "ompon"nis

Tel(ronix iepair centers provide ,replacementor
repair serviceon maior assembliesas well as the unit.
Returnthe instrumentor assemblyto your local Field
Office for this seMce, or contact your l6cat Field Oftce
for repair and exchangerates.

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Handling Static Sensitive Components
Most semiconductor..types,
both separatetyand in
assembliEs,are susceptibleto damageto statii
charge,
see Table 6-1 for voltagelevels. WJrecommend
static
sensitive procedures be implementedfor att operations
involvingsemiconductorhandling.
Obtalning Replacement parts
All electrical and mechanicalparts are available
throughyour locat TektronixFielddffic; oi'r"pr"r"nt"tive. The Replaceabteparts rist section contains
informationon how to order these replacementparts.

Some componentsthat are heat sinked to
the circuit board extrusionor module wall,
are soldered to the board after the board is
mounted in place. This is necessary to
avoid crackingthe case when the mounting
lgrew ls tightened. These componentsare
identifiedby a note on the schematicdrawilg.
.Their part number appears with
chassis mounted componenis in the
ReplaceableElectricalparts list.
Parts orientationand lead dress should be dupli_
cated because some components are oriented
to
reduce interaction between circuits or control circuit
characteristics.
Where applicable,an improvedpart will b€ substi_
tuted.whena replacementis ordered. tf the changeis
complex, your local Field Office or representativewill
contact you concerningthe change. After repair,
the
circuitsmay need recalibration.
Parts Repair and Return program
Assembliescontaininghybrid circuits or substrates
in a semi-sealedmodule,and complexassembliessuch
as ths 1st LO, 829 MHz conv€rter,or phasegate ctetector, can be returnedto Tektronixfor repair under
the
repairand returnprogram.

Firmware Version and Error Message Readout
This feature provides readout of the firmware ver_
sion when the power on/off is cycled. Duringthe initial
power-upcycle, the instrumentfirmware and iront panel
firmwar€ versions are displayed on the crt for approxi_
mately two seconds. The ReplaceabteElectricalparts
list section,under Memory board (A54),lists the ROM
devices and their Tektronix part' numbers for each
firmwareversion.
Wheneveran error occurs in an operationalroutine,
an eror message on screen describes the nature of
the error. Status messagesor prompts(see Diagnositics part of this section), are also displayedwhen running a diagnostictest or calibrationproceiure.
Selected Components
A few componentsthat are selectedto meetcertain
parameterssuch as temperaturecompensation,or to
center the range of some adjustable component. The
selected componentsare identifiedas selectableon
the circuit diagram and in the ReplaceableElectrical
Parts list. The Replaceableparts list descriptionfor the
componentgiveseithera nominalvatue. The procedure
for selection is explained in the adjustmentpart of
recalibrationprocedure. Table 6-4 lists these components,their nominalvalues,and the criteriafor selec_
tion.
Replacing EPROM or ROM Devtces
Firmware for the microcomputeris contained in
ROM packs on the Memoryand GplB boards. Referto
the ReplaceableElectricalparts list (vot.2) underthese
assemblies(A54 Memory and A56 GplB) for the versions and integrated circuit part numbers. All
integrat€d circuits are soldered into sockets on the
board to reduce problemsthat occur due to poor contact becaus€ of corrosion or loose pins. Refer to
replacing Transistor and Integrated Circuit for procedure.

6-1s

Malntenance-

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494A1494ApService Vot. 1

Table 6-4
SELECTEDCOMPONENTS
t Number
422A1Rl070
422A1R2049
422A1R2070
422A1R2072
A46A1R1011
1Rl012
446A1Rl013

Selection Crlteria
Sets ReferenceMixer outputat 18 MHz
linearityof the 2nd LO sweep
Adjusts2nd LO tune range
Sets 2nd LO sweep
Matchedfor temperaturecoefficientto 5PPM/oC

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Matchedfor temperaturecoefficientto SPPM/"C

446A1Rl014

A46A1Rl015
446A1Rl010

I

Match€d for t€mperature coefficient to SPPM/oC

1R1020
446A1Rl048
Rl049
446A1R1050
1Rl
A46A1Rl052
A46A1Rl053
A46A1Rl055
45045C1038
450A5C1048
450A2C1016
A50A2C1018
A50A2C1032
450A2C1024

Matched for temperature coefiicient to SPPMI"C

Matchedfor temperaturecoefiicientto SPPM/"C
Matchedfor temperaturecoefficientto SPPM/oC

3.3 pF-27 pF
3.3 pF-27 pF
3.3 pF-27 pF

MoveC1041frequencyadjustmentrange
MoveCl042 frequencyadjustmentrange
FL1024 inputloutput i mpedancematch

Surface-Mounted Components
Surface-mountedcomponents are used in this
instrument. These componentsare mountedon pads
on the circuit board, rather than through holes in the
board. (ln some rare instances,componentsmay be
mount€d on pads around through holes.) Lead
configurations
of these componentsare shownin Figure
6-1.

.#
#.
E

CATE

)

TRATT|3IION

The positive end of electrolytic capacitors is
identifiedwith a band. Other capacitorsand resistors
have no visibleidentification.However,like their axialleadedcounterparts,their valuescan be measuredwith
a meter.
Surface-mounted
semiconductordevicesare sensitive to static €lectricity discharges, and should be
treatedas outlinedin the beginningof this section.

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2

c
c

5

OIO€

Figure 6-1. Surface-mountedcomponentslead conliguration.

6-16

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Mafntenance-

494[l4g4Ap ServtceVot. 1

SERvIcING
TooLsFoRBoARD'Tffi3.i*,o"= MouNTED
coMPoNENTs
Model Type

Hor Alr HepairTerminal

Nu-ConceptsSystemsHART2OOA

Tempilaq
TempilaqThinner
Flux Dispenser
Solderinglron
uordertngtron SMDTips

Nu-ConceptsSystems
Nu-ConceptsSystemsTLTH
Nu-ConceptssystemsFD2
HexaconModel SMD1O

Semi-Chisel,
1/16'
Conical,1132'
SharpContcat"
Bevel,1/32"
Chisel,1/16'
Bevel,l/16'
0.062"Stot"
0.195"Slot
0.195"Slot
0.195'Slot

HexaconModet ZTAOX
HexaconModet ZTB}X
Hsxacon Modet ZI&4X
Hexacon Model ZZ$6X
H€xaconModel ZZ|TX
HexaconModetZT$BX
HexaconModel 5303
HexaconModelS30g
HexaconModel S314
HexaconModel 3316

0.195"Stot
HexaconModified3302
titainbss Steel, Non-Magnetic
Tweezers
StraightTip
CurvedTip

Replacing Surface-Mounted Components
A Hot Air Machine, such as Hart Model 200A
manufacturedby Nu-ConceptComputerSystems lncor_
porated of Colmar, pennsylvania,is recommendedfor
unsoldering and soldering surface-mounted components.
Table 6-5 lists tools that are suitablefor servicing
circuitboardswith surfac€-mouni€d
components.
. Do not apply too much heat, as th€ pad/s on which
the device is soldered may be lifted fiom the circuit
board.
1. Unsolderthe component.
2. Cleanthe boardwith isopropylalcohot.
3. Solder in the replacement. Surface-mountecl
componentsare pretinned,and shoutdbe solderedonto
the boardwith solderpasteratherthan solder.

Tektronix Part No.
N/A
N/A
N/A
N/A
003-1401-00

003-1402{0
003-1403-00
@3-1404-00
003-1405-00
003-140&00
003-1407-00
003-1408-00
003-1409-00
003-1410-00
003-141
1-00
003-1412-00

Tektronix Part No. 003464-00
Tektronix Part No. 003-046$.00
Tektronix Part No.251-0514-00

lf you use a solderingiron, use one with a
small tip. After applying th€ sotderpaste,
touch the corner of the pad with the iron to
fasten the component. Avoid touchingthe
component with the hot soldering iron.
Thermal shock causes hairlinecracks that
are not visibleto the eye.
Transistor and Integrated Circuit Configurations
Lead identificationfor transistorsand integratedcircuits, is readily available from manufacture'sdata
books. Integrat€dcircuit pin-outs for Vcc and ground
are shown with a box on the schematicdiagram. Refer
to SolderingTechniquein CorrectiveMaintenancepart
for unsolderingand solderinginstructions.

6-17

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Maintenance
ServtceVot.1

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Diode Color Code
The cathode of each glass encaseddiode is indigated by a stripe, a series of stripes, or a dot. Some
diodeshavea diodesymbolprintedon one side. Figure
6-2 illustratesdiode types Lnd potarity markings'that
are used in this instrument.

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(x)95-11

Flgure 6-3. Multpln (harmonlca)conneciors.

Resistor Values
Many types of resistors (such as composition,metal
film, tapped,thick film resistornetworkpackage,plate,
etc.) are used. The value is either color coded in accordance with the EIA color code, or printedon the body of
the component.
Capacitor Marking
The capacitancevalue of ceramic disc, plate, and
slug, or small electrolytic capacitors, is marked in
microfarads on the side of the component body. The
ceramictubularcapacitorsand feed-throughcapacitors
are color coded in picofarads.

)

ct66.t-14

Soldering Techniques
Figure 6-2. Diode polartty marklngs.

Multiple Terminal (Harmonica) Connectors
Som€ int€rcircuitconnectionsare madethroughpin
connectors that are mounted in a harmonica-type
holder. The terminalsin the holder, are identifiedty
numbers that appear on the holder and the circuit
diagrams. Connectorsare identifiedon the schematic
and board with eitherthe prefix letter p or J followedby
a circuit number. Connectororientationto the circuit
board ls keyed by a triangle on the holder and the cir_
cuit board (seeFigure6-3).

6-18

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Disconnectthe instrumentfrom its power
source before replacingor solderingcomponents.
Extreme caution must be used when removingor
replacingcomponentsbecausethe instrumentcontains
severalmultilayercircuit boards. Excessheat from the
solderingiron and bent componentleads may pull the
plating out of the hole. We suggest clipping the old
componentfree. Leaveenoughlead length so the new
componentleadscan be solderedin place.

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Maintenance-

494AJ494ApService Vot. 1

lf you desire to remove the componentl€ads,
use a
ol tess pencil type iron. Straigtrten-the
teads on
J.5Y
me oacKside of the board;then whenthe sotder
melts,
gently puil the sotdered tead through
the hote. A
-remove
desolderingtool should be used to
the old
solder. Use a desolderingtoot that has a low
build-up
of static charge,such as SiMerstatSoldapullt
desoldering tool, when unsolderingintegratedcircuiisor
transis_
tors.

Replacing the Square pin tor the
Multi-pin Connsctors
It is importantnot to damageor disturbthe ferrule
when removing the old stub of a broken pin. Tne
ter_
rule is pressed into the circuit board and provides
a
basefor solderingthe pin connector.
lf the broken stub is long enough,grasp it with
a
pair of needlenose pliers,apptytreatlwiih
a smallsoldering iron, to the pin base of ine ferrute and pull
pin.out. (Ihe pin is pressed into th€ terruie the old
so a firm
pull is r€quiredto pult it out.)
lf the broken stub.is-too short to grasp with pliers,
use a small dowel (0.029inch in diameter;clamped
in a
vise to.push the pin out of the ferruleafter the solder
has melted.

A. Locetionrnd positionof mountingplate.

VR mountingptate

The old ferrule can be cleaned by reheatingsocket
and placinga sharp object such as a toothpicklr small
dowel lnto the hote. A O.Oglinch driil mountedin a pin
vise may also be used to ream the solderout ol the
old
ferrule.
pair of diagonal cutters to removethe ferrule
- Ur." a
from the new pin; then insertthe pin into the otd ferrule
and solderthe pin to both sidesoi the ferrute.
lf it-is,-necessary.to
bend the new pin, grasp the
.
base of the pin with needle_nosepliirs and bend
againstthe pressureof ths pliErsto avoid breakingthe
boardaroundthe ferrule,

Servicing the VR Module
The VR modulerequiresmechanicatsupportwhen it
is installedon board extenders. Mechanicalsupport is
provided by moving the mountingplate at
the upper
.
:'.qe of the modut€ (Figure 6_Anfti the bottom sicte.
This allows installationof a mountingscrew through a
supportbracket into the mountingplate screw hole as
shown in Figure6-48. For bettei iupport, we recommend using a second bracket on the other end.
Removethe bracket, turn it over and install it so the
threadedstuds are below the module.

B, VR module on €rtender boards and secrred for rervicing.
5565-41

Figure6.4. Serviclngthe VR ass€mbly_

REPLACING
ASSEMBLIES
AND
SUBASSEMBLIES
Most assembliesor sub-assembliesin this instrument are easily removedand replaced. The following
describesproceduresfor replacing those assemblies
that require special attention. Top and bottom views
are shown in Figures6-5 and 6-6, respectively.These
illustrationsshow the locationand identifymost assemblies by their nameand assemblynumber.

6-19

A30-POWER
St,PPLY
A30A57-GPIB
INTERFACE

A62-LOG &
VIOEO ATPL
A61_DIGITAL
STORAGE YERT
A6O-DIGITAL
STORAGE }IORIZ
As8-PROCESSOR
456_GPIB
A5'-MEMORY
A26_AUXILARY
SYNTHESIZER
A51_COUNTER

PHASE LOCK
SYNTI{ESIZER

A/f0-SPAN
ATTENUATOR
A/16-CENTER
FREOCOilTROL

A{2PRESELECTOR
ORIVER

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Maintenance-

494Al4g4ApServiceVot. 1

FL36
FL15

A32-110 ilHr
IF AMPL

413_POWER
OIVIDER

A23-E29 trtHz
2NDCO}IVERTER

434-3RD
CONVERTER

AlE- 2072MH:
2NDCONVERTOR
A2{-PHASE
GATE

s11
sl2
FL'1

FL12_
PRESELECTOR

A1'-DIPLEXER

FL'O&
A1OLIMITER

All-B|AS

RETURN

sr3-

TRANSFER SIV

il
II

lt

412-1ST

llrxER

ATI{'_STEP
ATTENUATOR

FL16_DIRECTIOI{AL FILTER

Figure 6-6. RF deck assemblies.

6-21

Mafntenance-

494A1494ApService Vot. 1

Somecircuit boardsand assembliesmust be placed
on extenders to access test points or adjustments.
Before removingthese boards and assembli6s,the air
bafie attached to the left siderail must also be
r€moved.
Turn the power off before removingan assembly.
Removing and Installing the GplB Board
The GPIB board connectsto the GplB port on the
back panel,througha GptB Extend€rboard (A56A1),a
ribbon cable (W560), and a GplB Interface board
(A30A54 in the Power Suppty modute. The GptB
Extender board edge connector is clamp€d to th€ con_
nector on the GPIB board by means of a locking key
that extendsthrough the connector. When the fly ii
turned, so it faces inward, the connector is clamped.
To releasethe connector,so the GplB board can be
removed,proceedas follows:
1. Unscrew the mounting screws that hold the
metal shield over the GPIB, processor. and Digital
Storageboardsand removethe shield.
2. Lift th€ key to the GptB Extenderboard connector up so it iust clearsthe board and turn it gOdegrees,
so it faces the rear of the instrument.This will spread
the connectorso the GPIB board can now be pull from
the connectoron the Motherboard.
3. Use a board puller to pull the GplB board free
from the Mother board.

lnstallthe board as tollows:
1. With the key tor the GplB Extenderboard connectorturnedso the connectoris spread(top of the key
facing to the rear of the instrument),slide the GplB
board through the guides and onto the Mother board
connector.Ensurethat the board is well seated.
2. Turn the key 90 degreesto lock the connectors
of the GPIB Extender board and the GplB board
together. Pushthe key down to its rest position.
3. Re-installthe shield over the GplB, processor,
and DigitalStorageboards.
Removing or Replacing Semi-rigid
Coaxial Cables
Performanceof the instrumentis easily degradedif
theseconnectorsare loose,dirty, or damaged. The followingprocedurewill help ensurethat the connectionis
good enoughto maintainproperperformance.
1. Use a 5/16 inch open-endwrenchto loosenor
tighten the connectors. lt is good practice to use a
secondwrench to hold the rigid (receptacle)portion of
the connectorto preventbendingor twistingthe cable.

6-22

2. Ensure that the plug and receptacleare clean
and free of any foreign matter.
3. Insertthe plug connectorfully into the receptacte
before screwingth€ nut on. Tightenth€ connectionto g
in-lbs to ensure that the connectionis tight. Do not
overtighten('l5 to 20 in-lbs)becausethis can damage
the connector.
Replacing lhe Dual Diode Assembly
in the 1st Mixer
The diode subassemblythat houses the Schottky
mixer diodes permits easy field replacementof the
diodes. The subassemblyis securedin place with four
0-80 screws. An 8-32threadedhole is providedto facilitate insertionand removalof the subassembly.There
are threecontactpointslocatedon the substrateside of
the subassembly.Use care to ensure proper fit when
mounting and orienting these contacts in the mixer
assembly. Insertionand removalof the subassembly
more than twice is not recommendeddue to th€ goldribbonattachingtechniqueused in fabrication.
' A
tuning screw is adjustedto null a start spur on
Band 1. This tuningscrewis mountedthroughthe top
of the diode asssembly,adjacentto the 8-32 hole. lf
adjustmentof this screw is warranted.care shouldbe
taken to not force the tuning screw after it bottoms out
on the surfaceof the quartz-suspended
substrate.
The diode assemblyis packaged in a static-free
package. Keep the diode subassemblyin this package
until ready to install. The following should be used
when replacingthis assembly.

The diodes are beam-lead devices,
mountedon a quartz-suspended
substrate.
These diodes are extremely sensitive to
static electricity discharge. Refer to the
caution note on static discharge at the
beginningof this section. Do not expose
the diodeassemblyto RF fields.
1. Loosen and disconnectthe three coaxial cable
connectionsat the 1st converterassembly.
2. Removethe two mountingscrews, and remove
the assemblyfrom the instrument.
3. Removethe four 0-80 screwsthat hold the diode
subassemblyin the 1st Converter,and insert a 8-32
screws into the threadedhole providedin the centerof
the diodeassembly.
4. Lift the diode assemblyout of the mixer assembly by m€ansof the 8-32screw,then removethe screw.

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Maintenance-

5. Openthe diode package. Use a pair of tweezers
to grasp th€ diode assemblyby its side,and place
it on
a static-freesurface. Grasp t-heside of the'"rr"rOty
with^thefingers. Avoid coniact with the diodes.
Insert
the 8-32 screw.
6, Orient the diode assemblyso the three contact
tips are arignedwith their respictive contacts
in the
mixer; then, using the index fingers of both
hands so
equal pressureis applieO,presJ the subassembty
into
place.
7, Insert the four mounting screws, then
replace
and tighten the three coaxial ionnectois to g
in-lbs.
Remountthe lst Conv€rterassemblyOy instatting
itre
two mountingscrews that hold ttre aisembtyto
th; RF
deck.
-. . 8. The Spectrum Analyzer may not meet the
flatness specificationafter the Duat CIodeassembly
is
replaced. Refer to MATNTENANCE
ADJUSTMENTS
in
this_seetionfor a procedurefor adjustingconverter
bias
and flatness.
Replacing the Crt
1. Removethe snap_inprinted bezel and crt tight
filter.
2: Use an g/64 inch AllEn wrench to remove
.
the
four bezelscrews,unplugand removethe innerbezel.
3. Unsolderthe ground wire from the front panel
casting and unplug the crt cables at their respective
?oarg_connections(High Voltage module, Deflection
Amplifierboard,and Z-Axis UoarO;.
4. Slidethe crt, with its shletd,out throughthe front
panel.
5. Removethe crt shieldas follows:
a. Remove the tube base cap and unplug the
socket.
b. Removethe two side screws that hold th€ upper
shieldin place,then removethe shield.
c. Loosenthe screwsthat clampthe plasticbracket
around the crt, then remove the bracket.
. 6. Jnstallthe plastic bracket so the back on the
ctamp is 5.07inches from the back of the cn socket
guide.
- 7. ReplacEthe crt shield plus the socketand base
shieldby reversingthe removalprocedure.The finished
crt
^assembly length. with cap installed, must equal
11.05inches. lf it is longer,the assemblymayshortcir_
cuit the DeflectionAmplifier circuit boird when it is
installed.
Place the spectrum analyzeron its rear panel
. 8..
_
then loosenthe four crt blue ptasticmountingblockson
the front castingso they can be readilypositionedwhen
the crt is installed.

4g4Ll4g4ApService Vol. 1

9. lnstall the crt with shield assemblythrough the
front panel;seat the wedgeson the siOeof the crt, into
the blue plasticrnountingblocks.
10. Positionthe cast bezel and implosionshieldin
place to €nsurethat there is clearancebetweenthe crt
face and the bezel, fl'he bezel must bottom on the
front casting.)

It. is very importantthat the four mounting
blocks are loose enough so the bezel
retainingscrews can be tightenedwithout
the bezel touchingthe crt face. lf not the
crt or the bezelmay crack when the screws
are tightened.
11. Removethe bezel and tighten the mounting
block screwsevenlyin a cross pattemto approximatel!
8 in-lbs. Make sure the crt stays centereOin tf,e Utui
plasticmountingblocksas the screwsare tightened.
12. Replacethe bezel and implosionshield,reconnect cablesto their respectiveboard connectors,and
resolderthe groundlead to its terminal.
13. Replacecrt light filter and snap-inprintedbezel.

Repairing the Crt Trace Rotation Coil
The trace rotationcoil is part of the crt assembly.tf
the coil is damagedbeyondrepair,the crt with the coil
must be replaced.
'finish"(red)lead
is broken,removethe tape
.lf the
and unwindone or two tums so it can be resplicedand
solder€dto the leadwire. Rewindand retape.
.lf the "start"(black)lead is broken and the lead is
too shortto re-splice,atempt to fish out the brokenend
so one or two turns can be unwound,re-splice and
solderto the lead;then rewindand retape.

Front Panel Assembly Removat
It is not necessaryto removethe front panelassembly to replace any of the push buttons. (Refer to
ReplacingFront Panel pushbuttons,that follows this
procedure.) The crt is removed with the front-panel
assembly,
1. Set the instrumentupright on its rear panel,then
unscrew and removethg mounting nuts and washers
for the RF INPUT,EXT MIXER,lst Lo oUTPUT.and
2nd LO OUTPUTconnectors.
2. Removethe two screws that holdthe front panel
to the RF deck(centerand left side).

6-23

Maintenance-

4g4A/4g4ApSeruiceVot. 1

- 3. Unplugthe CAL OUT coaxialcabtefrom the grd
Converter;then disconnectthe five crt cables from the
Z-Axis/RF Interface, High Voltage module, and
DeflectionAmplifier.
4. Lookingat the top of the instrument,removethe
one screw that holds th€ front panelto the side extru_
sion betweenthe crt and the right side of the instru_
ment. Removethe four screwsthat holdthe tront panel
to the side rails.
5. Pullthe front panelup and off the Motherboard.
Replacethe front panel by reversingth€ removal
procedure.
Front-Panel Board Removal

A replacementFront panel board comes
with switches and controls for programmablo diffErent versions of the spectrum
analyzer. Before replacing an existing
board, removethe switchesand controlson
the new board that are not used on the par_
ticularversionof the instrument.
1. Removethe front panel assemblyas previously
described,then removeall the knobs.
2. Placethe front panelon its face and removethe
eleven circuit board screws plus the screw that heat_
sinks and holds U6090 on the board. Note that the
screw next to the connectorplug has a fiberwasher.
3. To preventtosing the groundingrings or bush_
ings, betweenthe front panel controls and the front
panel casting,hold th€ circuit board againstthe front
panelcastingwhile turningthe completeassemblyso it
r€sts on the base of the crt assembly.
4. Gently lift the casting from the circuit board.
Ensurethat the groundingrings remainon the shaft of
all controlsas the castingis removed.
Reversethe r€moval procedure,ensuringthat the
fiber washeris on the board screw next to the connec_
tor plug. This waEherpreventsthe screwfrom shorting
a circuitboardrun to the front panelcasting.
Replacing Front Panel pushbutton Switches
Removalof the front panelassembtyis not required
to replace any pushbuttonswitch. The procedurefol_
lows:
1. Remove the front panel knobs. Loosen and
remove nuts and washers for the RF lNpUT, EXTER_
NAL MIXER,and the 1st and 2nd LO connectors.

6-24

2. Remove the screw under the CENTER FRE_
QUENCYtuning knob that holds the panelto the front
panelcasting.
3. Loosen the black screws through the crt bezel
so the panelcan be movedenoughto lift it off the casting.
4. Unplugand replacethe desiredswitches.

Main PowerSupply Module Removal

[eAUloNl
To avoid damageto the Mother board connector J5041 and lnterface connector
J1034, during removalor installationof the
Power Supply module, use the following
procedure.
1. Disconnect the power cord and remove the
instrumentcover.
2. On the circuit board side of the instrument.
unplug the coaxial cable connectorP620 from the Log
and Video Amplifier assembly. On the RF deck side
disconnectth€ plug for the cable to the ReferenceLock
assembly,at the lower right comer of the PowerSupply
module.
3. For programmableinstruments,removethe cable
clamp for the GPIB interconnectcable and unplugP560
to the GPIB Extenderboard.
4. Remove the three screws that hold the power
moduleto the RF deck flange(bottom right side),then
remove the four screws that hold the power supply
moduleto the side rails.
5. With the instrumentRF deck on the near side,
pull the left side of the power moduletrom its side-rail
(no more than 1.5 inch). Now grasp both sides of the
moduleand lift to separatethe modulefrom the Mother
board.

Because C6111 and C6101 dischargevery
slowly.hazardouspotentialsexist withinthe
pow€r supply for several minutesafter the
power switch is turned off. A relaxation
oscillator,formed by C5113, R5111,and
DS5112, indicatethe presenceof voltages
in the circuit until the potentialacross th€
filter capacitorsis belowB0 V.
6. Loosenand removethe two screwsthat holdthe
mounting bracket for P361. Lift the cover off the
module and unptugP3045to the Fan Driveboard. The
power supplyshouldnow be accessible.

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Malnfenance-

4g4Ll4g4ApServiceVot. 1

7. Reinstallp361.mountingbracketthen ptugpg045
ontoth€ power supplyboardanOrepacJ
the cover.
8. Set the instrumentwith the RF deck on
the near
side.then hold the power supply module at
the rear of
the instrumentso the right side is touctring
the side_rait
and the teft side is aboui 1.5inchaboveiti
side-rait.
9. Align connectorsp5041 and p1034 with
their
respectiveMother board and Interface
board connectors' then press the modureinto pracebeh^/een
the side
rails.
10. Replace the four module holding screws
and
the thre€flangescrews.
11. Reconnectthe.coaxialcablesand GplB
cable,if
appropriate,then installthecableclamp.
12. Replacethe instrumentcover.
High Vottage power Suppty
A screw must be removedbeforethe High Voltage
Power
luqpty circuit board can Oe unplugged
removed. The screw goes througt tt" iib"-rail and
into a
nylon standoff bushing at the bottom corner
of the
board.
Removing and Replacing the lst LO
. 1. Unplug and removethe multipinconnectorsto
the assembty. Cut the tie_downthai hoids the
black
encasedRF coil to the semi-rigidcable.
.. 2. Using a S/16 inch open-endwrench,toosenand
disconnectthe semi-rigidcoaxialcable.
3. Loosen and removethe four mountingscrews
that holethe assemblyto the RF deck. Remove
the 1st
LO assembly.
4. To replace the assembly,reverse the removal
procedure.Use a tie_downto ri-tie the RF
coil to the
semi-rigidcable to preventvibrationfrom breaking
the
coif leads.
Replacing the 1st LO Interface Board
The 1st LO assemblyincludesan interfacecircuit
boardthat
^c1nbe reptaced.To replacethe boardrefer
to Figure6-7 and the following procedure.
Use a
desolderingtool to removetne sotOlr as the teads
are
unsoldered.
1. Unsolderand tiftone_end
of C1014(g20uF capa_
citor)at the top of the board
2. Unsolderand tift oneendof VRl010.
3. Unsolderand lift the + leadof C1016.
4. Unsolderthe eight leadsto the oscillatorand
lift
the boardoff the assembly.

A. Oscillator assembly.

Unsolder circled connections.

@@
tr\
@o
o\
DOU

pJ
trD

ff
B. Interface board showing terminals to unsolder for
removal.

Figure6-7. Removingthe lst LO Intertaceboard.

Fan Assembly Removal
1. Removepower supplyas describedin this sec_
tion.
2. Removesix screws that hold the power supply
cover in place. Take the coaxialcableout of the plastic
retainerclip and lift the power supplycoverwith fan up,
so harmonicaconnector pgO4Scan be disconnected
and the coverremoved.
3. Removethe nuts and lockwashersthat hold the
fan brackets from the back side of the power supply
housing. The fan will fall free from the brackets.

6-25

Maintenance-

494A1494Ap
ServlceVol. I

4. The resilient mounts at the corners of the fan
frame shouldbe replacedif a new fan is to be installed
or fan vibrationis generatingspurs on the display.
5. Insert four resilient mounts into the corners of
th€ fan, flushwith the fan frame.
6. Installone ol the fan bracketsto the power supply housing by attachingits lock washers and nuts to
th€ back of the housing.

MAINTENANCE
ADJUSTMENTS
The following procedures are not part of the regular
calibration. They are only performed when certain
assemblies are replaced or after major repair.

110 MHz lF Assembly Return Loss Calibration
Table6-6 lists test equipmentrequiredfor
adjustingthis assembly.

Fan bracketsshould be installedas in Figure 6-8.
7. Insert the posts of the brackets into the holes
providedin the resilientmount and installthe remaining
bracket,with lockwashersand nuts, to the back side of
the power supplyhousing.
8. Reconnectthe fan to the Fan Drive board then
replacethe cover, with the fan, onto the power supply
module.
9. After installingthe six screwsthat hotd the cover
in place, ensure that the fan assemblymoves freely.
Replacethe coaxialcable in the plasticretainingclip.
10. Reinstall the Power Supply assembly as
directed under Power Supply Replacement. Apply
power and checkfor normalfan operation.

1. Test equipmentsetup is shown in Flgure 6-9.
The lF assemblymust be removsdto gain accessto the
adiustments.
2. Apply 110 MHz at 2V peak-to-peak
(+10 dBm)
through 35 dB of attenuationto the RF Input of the
vswR bridge. connect the RF out of the vswR bridge
to the RF Input of the spectrumanalyzer.(Do not connectthe 110MHz lF to the vswR bridge.)
3. Set the test spectrumanalyzerCenterFrequency
to 110MHz, FrequencySpan/Divto 5 MHz, REsolution
Bandwidthto 3 MHz, VerticalDisplayto 10 dB/Div, and
Ref Levelto-20 dBm.
4, Set the step attenuator for a full screen
(-20 dBm)display.
5. Connect the 110MHz lF input to the vswR
bridge and connecta 50O terminationto the output of
the lF amplifier. Now plug the power cable P3045into
the + and -15 V source and ground the case of the
assembly.
6. Adjust C2047and Cl054 (Figure6-10)simultaneously for minimuh signal amplitudeon the spectrum
analyzerdisplay. Minimumamplitudemust be at least
-55 dBm.
7. Disconnectte6t equipmentsetupand replacethe
110MHzlF assembly.
2072MHz 2nd Converter
The 2nd Converterassemblyconsistsof a four cavity 2072MHz band-passfilter, mixer, and a 110 MHz
low-passfilter. The assemblyis precalibratedprior to
installation,and requires no calibration after it is
installed. We recommendreplacingthe assemblyif it
shouldmalfunction.The followingproceduresdescribe
adjustmentsthat can be madeif the biasingshouldmalfunctionor the seal on any of the filter tuning slugs is
broken. The mixer diodes are not to be replacedin the
field. Returnthe assemblyto Tektronix,lnc., for repair.

Flgure5{. Fan assembtymounting.

6-26

Do not open the assembly. Adjust the tuning slug only after checking the filter
characteristics.

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Malntenance- 494A/494ApServiceVol. 1
Four Cavlty Fllter-The characteristicsof the
filter
are checkedwith a network analyzer. Freguency
of the
filter is 2A72MHz, bandpass,t-SUl-lz down, is
1 dB,
return loss is 20 dB or greater, and insertionloss
is
1 clB. lf the seal is brokenon anytuningslug,adjust
for
maximumreturnloss.

Mlxer*To gain access to the Bias adjustments,
rernove the assembly from its mounting; then remove
the mounting ptate on the bottom of the assembly.
Reconnectthe Mixerto the input/outputlines,usingthe
same cables (cablelengthof semi rigid cablesis iriti_
cal). Appty the CAL OUT signatto the RF INpUT and
tune a rnarkerto centerscr€en, Simultaneously
adjust
99th bjas porentiometers,R1021 and R1022, liee
Figure6-11)for maximumsignalamplitude.

Table6-6
EOUIPMENT
REQUIRED
FORRETURNLOSSADJUSTMENT
Test Equlpment
SpectrumAnalyzer
SignalGenerator
VSWRBridge
10 dB & 1 dB Step Attenuators

Frequency
range)110 MHz
+ 1 0 d B ma t 1 1 0M H z
50O, 0 dB to 40 dB

Termination
Adapter

RecommendedType
TEKTRONIX
49X-Seriesor 7L14
TEKTRONIX
SG 503 for the TM S0O-Series
Wiltron628F50
HewlettPackard355C& g55D
TektronixPart No. 011-0049-01
TektronixPart No. 175-0419-00

Tll 50O M.ine F.rme

Test fg0-S€ries Spoctrum Anatyz€r

a{te76

Figure 6-9. 110 MHz lF return loss adjustment setup,

6-27

Mafntenance-

494A1494Ap
ServtceVot. 1

110 MHz Three Cavity Filter
Alignmentof this filter is not required unless the
spectrum analyzer fails to
meet bandwidth
specifications.The filters are adiust€dfor center frequency and response shape so the resolution
bandwidthis within specifications.The adjustmentprocedureis as follows:

Input

c1045
c2047

1. With the cAL ouT signat apptied to the RF
INPUT,tune the signalto center screenand reducethe
RESOLUTION
BANDWIDfi to 1 kHz.
2. Tune the signal to center screen to establish
centerfrequencyreference;then increasethe RESOLUTION BANDWIDTHto 1 MHz.
3. Adjustthe tuning slugs for best responseshape,
centeredaroundthe reference. Ensurebandwidth(6 dB
down)is 1 MHz.

Flgure6-10. 110 MHz lF test poinb and adiuetmenb.

4. Check resolution bandwidthaccuracy over the
range of the RESoLUTIoNBANDWIDTHcontrotas per
instructionsin the PerformanceChecksectionto ensure
that bandwidthis within specifieation

Figure 6-11. 2O72 MHz Converter blas adiustments.

6-28

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Maintenance-

829 MHz Converler Maintenance
Some circuit boards in this assembly contain
critical-lengthprinted elements. Whendamaged,
elementsare usuallynot repairable;therefore, these
the cir_
cuit board must be replaced. even itroujfr repfacement
bgards .are precalibrated and ,"p"i,
be accom_
plish.ed.byreplacingthe board, we recommend
"-"n
sending
the instrumentor assemblyto your Tekironix
Service
Centerfor repairand calibrition.
The 829 MHz band-passfilter in the lF section,
and
the 7'l9 MHz LO in the
section, requireadjustment
-Lo
only if the board has been damaged'J,
ponents (transistor or varactor) hive
""tiu"
"o*been
reptaced.
The following describes prepaiation foi service
and
replacementprocedures. The first two steps
describe
how to gain access to either the LO or the lF
section;
the.remainingst€ps describeadjustmentprocedure
for
each section.

4g4N494ApServtceVol. 1

for th€ DVM,a 50O coaxialcabtewith bnc connec_
tors ffektronix part number 012-04g2_00)and a
sma male-to-bnc f_emaleadapter Cfektronix part
number015-1018-O0).
b. The 2nd LO range is 714.5 MHz to 223.5 MHz
(withthe coveroff). 71g MHz is the optimumcenterfre_
guen!{. . Frequencyof the osciltator is controlledby the
TuneVoltsfrom the 25 MHz phase Lock circuit
at TPl011)whichvariesfrom +5 V (lowend)to ltoiateO
+11.gV
(high end) with +6.75 V to +2.5 V as the timits for
op€rationat 719 MHz. set the digitalvoltmeterto meas_
ure 12 V then connectat betweenTplolt (Figure6-12)
and ground.
c. Disconnectthe 100 MHz referencefrom the grd
Converterby unpluggingp235 (Figure6-12). The oscit_
lator shouldgo to its upperlimit and the voltmeterindicate about11.9 V.

1. To gain access to the LO section:
a. Switch POWERofi; use a 5/64 Ailen wrench
to
loosenand removethe cover screws.
b. Removethe cover.
c. Referto step 3 (withinthis procedure)for adjustment procedure.
2. To gain access to the lF section
a. Switch POWERoff; use a 5/16 inch wrench
to
disconnect and remove all coaxial connectors
to the
829 MHz converter.
b. Removethe six mounting screws, unplugthe
input power connector P4OSO,ihen remove the g2g
MHz converterassembly.
c. Turn the assemblyover and removethe cover
for
the lF section.
d. To troubteshootor calibratethe circuits,set the
assemblyat a locationso the input power plug p4050
can be reconnectedto the Mother boarO. Be sure
to
observeplug orientation(pin 1 to pin 1).
e. Referto step 4 (withinthis procedure)for adjustment procedure.
Figure6-12. 829MHzLOtest pointsandconnectors.
3. 719 MHz Osciilator Range Adjustment
a. Adjustment requires the foilowing test equipment:
| ^frequency counter with a frequency range to
1 GHz (nine digit readout),sensitivityof 20 mV rms
for prescaledinput or 15 mVrms tor a direct input
(suchas TEKTRONIX
Dc 510 counterwitha Dp 501
pres.calee;a digital voltmeter with a g.5
digit
readout(such as TEKTRONIXDM 502A);test teads

d. Connectthe 75 MHz-1 000 MHz input of the frequencycounterthrougha 50O coaxialcableto the front
panel2nd LO OUTPUTconnector.
e. Minoradjustmentsto the oscillatorfrequencyare
made by shorteningthe U-shapedtransmissionline
stub, off the main line. Graduation marks (see
Figure6-12)along the side of the stub providea guide
to calculatefrequency correction. Each minor mark
from the end or cut across the stub, representsan
approximatechangeot 2 MHz.

6-29

Maintenance-

494A1494ApService Vot. 1

_ Check the freguency by noting the readingon the
frequency counter. lf above 729.900MHz, the stub
must be lengthened. Solder a bridge across the cut
r.e"!99\ frequency. Nominalfrequencyfor an uncut
"q
stubis 710 MHz.
f. Shorten the line so the frequency is near
723.500MHz. For example: The frequencydifference
betweenthe desired and thE actuatdivideciOy Z Unz,
equalsthe numberof minor divisionsfrom thE line end
for the new cut. Make a cut across the line and check
that the new frequency is between 723.100MHz and
723.900MHz.Repeatas necessary.
g. Coverthe 719 MHz osciltatorcavitywith the g29
MHz Converter cover, press down to ensure good
shielding, and note the frequency readout of the
counter. Frequencyshouldfall within 723.600MHz and
724.400MHz.

\
\

h. Reconnectp2S4(100 MHz) andp237(2i82 MHz)
and confirmthat phase lock is operatingby notingthai
the voltageon Tp1011 is betweenO.7SVand 7.5V.
This completesthe adjustmentof the 71gMHz Lo.
Replacethe cover and reinstallthe g2g MHz converter
assembly.

4. 829 lr/lHzCoaxial Band-pass FitterAdjustment
Figure6-13. 829MHzampllfier
testiack andiumper.

This procedureis necessaryif the position
of one of the variablecapacitorloops (tabs)
has been altered, changingthe bandpass
characteristica
of the filter.
a. Test equipmentrequired:
Spectrum analyzer with tracking generator(such as
a TEKTRONIX49X-Series SpectrumAnalyzerwith
TR 503 TrackingGenerator,or 7L,t4 with i TR 502
TrackingGenerator);FrequencyCounter(suchas a
TEKTRONIXDC 510 Counter with a Dp 501 pres_
caler);and a Beturn Loss Bridge (suchas a Wiltron
Model62BF50.)
b. Unsolderand reconnectthe jumper,on the g2g
MHz Amplifierboard, to the test peltolajack J1029(see
Figure6-13).
c. Connectthe spectrumanalyzer,trackinggenerator, and frequencycounter together as a system,with
the frequencycounter connected to the Auxiliary
- RF
Outputof the trackinggenerator(seeFigure6-14).

6-30

d. Connect the spectrum analyzerltrackinggenerator system throughthe returnloss bridgeto the Peltola
jack (J1029) on the 829MHz amplifier board {see
Figure6-14). ReconnectP235(100MHz referencesignaf)and P2g7(2182MHz input)to the LO sectionof the
converter.
Terminatethe 110 MHz Output (J2 21 connector
with 50o, using a bnc-to Sealectroadapterand 20 dB
bnc attenuator. Pull the lF SELEGTline high by switching to band 2 (1.7-5.5GHz).
e. Set the test spectrum analyzerReferenceLevel
to -20 dBm, VerticalDisplaymode to 2 dBldiv,Resolution Bandwidth to 300 kHz, and Freq Span/Div to
20 MHz. Tune the Center Frequencyfor a readoutof
829.00MHz on the frequencycounter.
f. Adjust the 114 wavelengthlines in the filter in
sequence,startingwith the resonatorat the 829 1 MHz
input (see Figure6-15), Adjustmentis madeby shorting
the adjacentresonatorto groundwith a low inductance
conductor, such as a broad blade screwdriver,then
bend the loop or tab of the respectivestub with a nonmetallictuning tool to changethe series capacitanceof
the resonator.

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Maintenance-

494[l4g4Ap ServlceVot. I

Test Osciltoscope

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J231
I
Tracking Generator

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lo

IRF
Out

829 MHz Converter
lF Section

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Aur.

Return Loss Bridge

(Device Under Test)

2727-157

Flgure 6-14. 829 MH: filter test equlpment setup.

g.
.With the adjacent resonator (second) shorted to
ground, adjust the series capacitance by
benOing tne
tab so the response on the_spectrumanalyzer display
is
centered at 829 MHz (see Figure 6_16A).
h. Now move the shorting strap (screwdriver) to the
next resonator and adjust the tab of the second
resona_
tor for a response as indicatedin Figure OiOe.
i. Remove the short from the third resonator
and
short the fourth resonator. Adjust the third
resonator
for a response similar to that snown in Figure
6-17A.

j. Repeatthe procedurefor the final(fourth)resonator for a responsesimilarto that shownin Figure6-178.
k. Checkthat the return loss is equalto or greater
than12 dB.
l. Disconnectthe return loss Device Under Test
leadto the pettotajack J1029on the g29MHzAmptifier
board, then unsolderand r€connectthe jumperto the
amplifieroutput.
m. Replacethe 829 MHz Convertercoverand reinstall the assemblyin the SpectrumAnlyzer.

6-31

Malntenance-

o
o

494A/4g4ApService Vol. 1

A. lsl ResonalorResponse

Fe5

Flgure 6-'15. 829 MH: Converbr lilte. hlne tabs.

B. 2nd Regonator Response
2727-159

Figure 6-16. Correct responeefor 829 MHz first and second
resonators.

Troubleshooting and Calibrating the 2nd LO
The 2182MHz Oscillatorand 2200 MHz Reference
Mixer containcritical printed elementsthat are difficult
to repair. Therefore the board should be replaced if
damaged. lf the oscillator frequency is beyond adjust_
ment with the frequ€ncyadjusttab after replacingeither
the varactor or the oscillator transistor for the
2182MHz Oscillator, the circuit board must be
replaced.
Eventhough repair can be accomplishedby replacing the board, it is recommendthat the instrumentor
assemblybe returnEdto your TektronixServiceCenter
for repairto ensurebest performance.

6-42

The 2182MHz 2nd LO requires calibration only
when a component within the assembly has been
replaced.
Table6-7 lists test equipmentrequiredto calibrate
the LO section, and Table6-8 lists equipmentfor the
PhaseLock section.

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Malntenance-

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Frequency
FrequencySpan/Div
ReferenceLevel
Auto Resolution
VerticalDisplay
DigitalStorage
TimelDiv
Triggering

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4g4A/4g4Apservice vot. 1

2GHz
10 MHz
+20 dBm
On
10 dB/Div
ViewA&ViewB
Auto
FreeRun

d. Set the Time Mark generatorfor 0.1 Fs markers.
Markers should appear on the test sp€ctrumanalyzer
display,approximately
one marker/division.

A 3rd Resonator

e. Press degauss,and peak the 2.0 GHz signalfor
maximum amplitudewith the peaking control, if available.
f. Usingthe 2 GHz signalas a startingpoint,begln
countingmarkersuntil the 18th markeris located. The
2 GHz signal should be greater in amptitudethan the
time markers. The frequencymust be tuned towards
2.18 GHz to locatethe 18th marker. Increasethe reference levelas necessaryto view the markers.
S. Center the 18th marker on the test spectrum
analyzer (center frequency should be approximately
2.18GHz).

Retu?nLo-ss>12 dA

h. Reset the test spectrum analyzer frequency
span/divisionto 1 MHz.

B. 4th Resonator and Fllter

i. Positionthe 18th marker 2 major divisionsto the
left of the center graticule line on the test spectrum
analyzer (center frequency should be approximately
2.182GHz),then activateSAVEA.

Figure 6-17. Corect re3ponse tor g29 MHr tlrlrd and fourth
resonators.

J. Disconnectthe output of the comb generator
from the rf inputof the test spectrumanalyzer.

1. Check 2nd LO Frequency
(2182 MHz *i MHz)

k. Resetthe ReferenceLevel of the test spectrum
analyzer to +10 dBm. Connect the 2ND LO output,
from the spectrumanalyzerundertest, to the rf inputof
the test spectrumanalyzer.

The referencefrequencypositionset up in this step
...
will also be used in the adiustrnentprocedure.
a. Connect the test equipment as shown in
Figure6-18.
b. Set the Spectrum Analyzer to Band 1 and Max
Span.
c, Set the test spectrum analyzer front-panel as follows:

l. Checkthat the 2nd LO output signalis withinone
majordivisionof the centergraticuleline(2.181GHz to
2.183GHz).
m. lf the frequencyof the znd Lo is greaterthan
2.1813 MHz or less than 2.181 MHz, adjustmentis
required. The SAVEA display referenceused in part I
will be used in the adjustmentprocedure.

6-33

Maintenance -

o
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494A/494Ap Servlce Vol. 1

Table 6-7
EQUIPMENTREOUIREDFOR 2nd LO CALTBRATTON

Test Equipment

Characteristics

RecommendedType
TEKTRONIX 49X-Series or 7L'14
Option39

SpectrumAnalyzer

Frequencyrangeto 2.2 GHz

UHF GombGenerator

500 MHzPulseInput

Tektronix 067-0885-00 Calibration
Fixture with TM 500 Series Power
Module

Time Mark Generator

0.1 ,rs markers;accuracy0.001o/o

TEKTRONIXTG 501 with TM 500
SeriesPower Module

Signal Generator

Calibrated100 MHz.with +20 kHz accuracy

Hewlett-Packard Model 8640 A/B

Voltmeter

Measuresto within 0.01 V, impedance TEKTRONIXDM 502A with TM 500
>1 MO
SeriesPower Module
0 to 12.5V, accurateto 0.1 V
TEKTRONIXPS 501 with TM 500
SeriesPower Module
50O, 3 mm connectors
T€ktronixPart No. 011-0049-01

VariablePowerSupply
Terminations(2)

Tt 5@ X.an Fr.m.
Tcrt Spcclnrm An.lyrct
Timc trrt
Gcnetrlor

Comb Gcnc
Sourcc

Coorb Goneclor

lodrlc

5560-{X

Figure 6-18. 2182 MHz 2nd LO frequency accuracy test setup.

6-34

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Maintenance_ 4g4[l494Ap ServtceVot. 1
Preparing the 2nd LO Assembly lor
Adjustment
T_":!
setup
is
shownin Figure6-19.
..
_"guipment
the POWERoff. Rernovethe cabinet and placeTurn
the
Spectrum Analyzer_upsideOownio-ine
nf Oect1Mo

o

Frequency
Counter

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Time-Mark
Generator

I

Tabte 6-g
EOUIPMET.IT
REOUTRED
FORCALTBRATING
THE
16-20]VtHz pHASELOCKC|RCU|T
Characteristlcs
Recommended Type
Measuresto within 0.Ol V, impedance TEKTRONTX
Frequencyto g0 MHz

TM S00-seriesDM
501A,DM502A,or DM SO10

TEKTRONIX TM SO0-Series DC
503A, DC 508A,DC 509
y1ll9l output, 1 s to 1 ps; accuracy TEKTRONIXTG 501

0.001o/"
servtce Kit Extend€r Board

Tektronix Part No. 622-0g65-00

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DIGITAL
TITE
VOLT
OIGITAL TARX
METER COI'NTER GENERATOR

CENTERFREOUENCY
CONTROLSOARD
Oil EXTENDER

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SPECTRUil ANALYZER

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Flgure 6-23. 2182 MHr 2nd LO phase Lock adiu3tment setup.

6-39

Maintenance-

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494A/{g4Ap Servtce Vol. I

Troubleshooting and Galibrating the 16-20
Phase Lock Section

MHz

Replacingoscillatorcomponentsin this sectionmay
alter sweep linearity and the oscillator frequency. Thi
following checks and calibrationaid in repairingand
retuningthe assembly.
1. Preliminary
_ a. Test equipmentsetup is shown in Figure6-23.
Removeand install the Center FrequencyControl board
on an extenderboard.
b. SwitchPOWERon and set the FREOSPAN/D|V
to 1 MHz.
2. Check Voltages
- a. Checkall inputvoltagesat the feedthroughcapa_
cJtorsin the housingwall. RefErto FigureOZb or ine
data printed on the tid. The vottage LEVEL at the
sweep and tuns input lines shouldbe 0 V +O.OSV with
the FREQSPAN/D|V)500 kHz.
b. Switchthe POWERoff. Removethe tid frorn the
mu-metal housingassemblyto gain access to internal
circuitry.
c. SwitchPOWERon, then check the internalregulated voltages;+12 V *0.4 V at C2201,-12V *O.i V
at C2202, and +S.2V *0.2S V at TplO109 (see
Figure6-16). Checkthe outputof the shaperat Tpl0gg
for a levelbetween+0.9 V and -0.3 V (0 V i0.g V).
3. Setting Center Frequency
a. Connecta frequencycounterto Tp2O35and note
the frequency. tf the frequency is within S0 kHz of
18 MHz no correctionis necessary;proceedto part 4
(Setting Tune Sensitivityand nangay. tf outside the
rangeproceedas follows:
(1) Turn POWERoff. Unsotderand removeone end
of ShaperOffset resistor R1070. Unsolderthe wire
strap betweenT2092 and T1091,at the T1091end.
and lift it free.
(2) Soldera flexiblewire jumper to the T2092end;
then, by meansof a a plastictuningtool, attachthe
free end to one of the three pads for T1091 and
notethe frequencyreadoutof the counter.

ll this flexible wire touches ground whil€ the
circuit is operating, the supply regulators
can be damaged. The regulators are not
protected against a short circuit.

6-40

(3) lf one of the pads provides a frequencythat is
within the rangeof 17.5MHz *0.2S MHz, solderthe
wire strap to this pad. lf the frequ€ncyis still outside the range, movEthe jumper to the other pad for
T2092 and repeat the procedure. Frequencymust
equal17.5MHz +0.25 MHz.
b. Turn POWEROFF. Replace R1070 with a 10
turn 25 kO potentiometerin serieswith a S ko resistor.
c. Turn POWERon and with the counter connected
to TP2035, adjust th€ potentiometer for a frequency
readoutof 18 MHz *50 kHz.
d. Turn POWER off, measure the total resistance
valu6 and teplace R1070 with a lyo resistor of thls
measuredvalue. Switch POWERon and recheckthe
frequency to ensure that it is 18 MHz *50 kHz.
Disconnectthe counterfrom TP2035.

4. Setting Tune Sensitivity and Range
a. Centerthe Fine Tune adjustmentR4040,on the
CenterFrequencyControlboard and the 2nd LO Sweep
adjustment Rl067, on the Span Attenuator board
(Figure6-24).
b. Decreasethe FREQ SPAN/D|Vto 200 kHz or
less. The 2nd LO is now in the centerof its tune range.
c. Press 10 dB/DlV to disabtefrsquency corrections. Press  PULSE
STRETCHERand select item #0 (ALTERNATEFREQUENCY DfSPLAY), then item #2 (znd LO FREOUENCYDISPLAY).Beadoutwill now indicatethe 2nd
LO frequency.
d. Tune the 2nd LO to one end of its rangewhere
the frequencyreadout no longer changes. Note the frEquency and measurethe voltage on the Tune Line at
the input feed-throughcapacitor(Figure6-20).
e. Tune the 2nd LO to the other end of its range
and again note the frequencyand the new voltagereading.
f. Calculate the frequency change per vott (frequencyrangeversusvoltagerange). Frequencychange
per volt should equal 128.0kHz *10o/o or range
between115.2kHz and 140.8kHz.
g. lf the frequency/voltchangeis low, decreaseihe
vafueof R2072(Figure6-20).
h. Press PULSESTRETCHER
and
menu item #1. then select the 2nd LO for calibration.
Perform the procedurethat is called out for adjusting
the Fine Tune Range R4040and Fine Tune Sensitivity
R3040to calibratethe 2nd LO tuningrange.

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Maintenanco-

R404OFine TuneRanee-+!

CENTER F REOUE'{CYCOI{TROL
A. Location of R4040, Fine tune Renge.

)

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4g4A/4g4ApServlceVol. 1

B. Location ot R|O6Z.2nd LO Sweep.

Figure 6-24, Tune and Sweep Range adjustnents.

- 494A/4g4Ap
Maintenance
ServlceVot.1

5. Setting Sweep Range
a. Apply 5 ps time markersfrom the Time Mark
Generator
to the RF tNpUT. Setthe FREOSPAN/D|V

to 500 kHz then back to 200 kHz to center the 2nd LO
frequency.

b. Adjust the REF LEVEL to disptay the 200 kHz
markers then center one of the markers with the
CENTERFREOUENCY
controt.
c. Adjust the 2nd LO Sweep R1O6Z,on the Span
Attenuatorboard (Figure6241, so the comb lines on
oppositesides of the screen,are exactlyg major divi_
sionsapart.
6. Check and Adjust Tune Linearity
a. With Frequency Corrections disabled (see part
2), apply 5 ps markers from a Time Mark Generatorto
thE RF INPUT. SEt thE FREQUENCY
tO 20 MHZ.FREQ
SPAN/DIVto 200 kHz and activate AUTO RESOLN.
Adjust th€ REF LEVELso a comb of 200 kHz markers is
displayed.
b. Turn the CENTERFREQUENCY
controtcount€rclockwise until the c€nter frequency stops tuning,
decrease FREQ SPAN/D|V to 50 kHz then tune tfre
CENTERFREQUENCYup untit a marker signal is one
major division from the left edge of the graticule. A
comb line (or marker signal)should appearon or near
the first major division in from the right sid€ of th€
scr€en.
c. lt the right marker is not exacily g divisionsfrom
the left marker,note the €rror to th€ nearest0.5 minor
division.
d. Tum the CENTER FREQUENCYcontrol ctockwise, to increase center frequency, until the next
marker signal is one divislonin from the lett edge and
again note thE spacing between this marker and the
markernearthe right edge.
e. Continuethis process of tuning up in frequency
until the centerfrequencystops tuning,notingthe slgnil
spacingat eachcheck point.
f. lf the peak-to-peakenor is 2.5 minor divisions
(25 kHz) or l€ss, the lin€arityover the center2 MHz of
swEepis satisfactory;if more, the shaperneedsadjustment or repair.
g. Switch the FREQ SPAN/D|Vto 200 kHz, tune to
the low end of the sweep range and note the linearity
over the centereight divisionsof span,then tune to the
high end of the 2nd LO rangeand againnote the linearity. Peak-to-peakdeviation should not exceed 0.5
minordivision.
h. lf the shaperneeds adjustm€ntor repairproceed
as follows:

6-42

(1) A shaper diode or resistor may be defectiveif
the comb line spacingis consistentfor part of the
tuning range and 30 kHz or tnore off for the other
parts of the sweep. To test the diodes for forward
conduction, tune to the low end of the range and
short R2049 (Figure6-20). The output of U1073A
(pin 1) should equal about *3V. Ut0S9 diodes B
throughG and U2059diodesA throughF shouldail
have a 0.48 V forward drop. Use a floating or digital
voltmeterto check the drop.
(21 Tum POWER off then temporarily replace
Shaperresistor R2049with a 20 kO potentiometer.
Switch POWERon, and adjust the potentiometerto
obtain the best overall linearity; decreasing reslstance will decreasethe spacingbetweencomb lines
in the upper portion of the tune range and spread
the spacing for the lower portion. Increasingthe
resistanceof R2049 will reversethe effect. When
the correct setting is found, turn POWERoff, measure the resistance,and replacewith a fixed resistor
of the sameor nearthe samevalue.
i. Checkthe tun€ sensitivityand sweep rangeof the
2nd LO. Repeatsteps4, 5, and 6 if necessary.
7. Conclusion
a. Replacethe housinglid with its 14 screws.
b. Tightenthe screwssequentially,
startingfrom the
centerof the lid and progressingtoward the cornersto
prevent gaps between the lid and the housing. Use
care to not strip the screws as you tighten them.
c. This completesthe 2182MHz PhaseLocked2nd
LO calibration.Referto "Adjustcontrol system"in Section 5 for readjustingthe system.
Troubleshooting Aids for the 2182 MHz Phase
Locked 2nd LO Assembly

lf the Phase Locked assembly is in the
instrurnent,set the FREQsPAN/Dlv to 500
kHz or more so the 2nd LO is not sweot.
The differencefrequencysignal (18 MHz) from the
2200MHz Reference Mixer is amplified and fed to
P224. Nominally,its amplitudeis -5 dBm into 50O.
P224 is convenient for monitoring the 16-20 MHz
VCO. When phase lock is operating,the differencefrequency exactly equals the frequencyof the vco. lf
phase lock is not functioningproperly, the difference
frequency signal will either disappear completelyor
tune to its rangelimit of -6 MHz or 30 MHz.

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Maintenance_ 4g4N4g4Apservice vot. I
wIT the foop is unlocked,RF teakagefrom
_^
the
16-20 MHz osciilatorbuffer is present.ip224
with a
level of --35 dBm. The-amplifiedOmeience
frequency
can be monitoredat Tp20gS.
Another check of phase lock operation can be
done
by measuring the dc voltage on the 21g2 MHz
Tune
Line at.feedthrough capaciior C22Og.-ttominally
voltage is approximately-5 V when phase lock€d. itris
Use
a FREQ SPAN/D|V of S00kHz or greater
before
measuring. lf there is no differencefreq-uency,
the voltage wilt be about 0 V.- vottageof _13 V may indicate
l
loss of signalfrom the VCO.
Narrow-bandnoise on the 2nd LO signal
may be
due to noisemodulationof ths 16_20 MiivCO.
trton_
itor the stgnatat the tg MHz port to
ii ttre oscittator
signal is noisy. Noise on this line is
"""often caused by
noise on the *12V lines. Use a differentiat
oscillo_
scope with 1 Hz to 300 Hz bandwidthlimits
to check
supply noise. Measurethe ac Oifferentiat
Letweenthe
supplyand the 2nd LO housing. Less than 5 pV peakto-peak of noise will cause noticeable performance
jeOradatign. Output noise from the shapel is typicaily
less than 5 pV peak-to-peak.

. When making power m€asurem€ntsof microwave
circuitry, at circuit board interfaces, use a coaxial probe
with v9ry litfle stray. inductance (see figure'O-ee1
Ground the outer conductor of the pioUe tolhe circuit
housingas close as possibleto the measurementport.
Disconnectotherloadsfrom ths meaEurement
point.
100 MHz Oscillator in the 3rd Converter
A variable capacitor, C10gg, inside the cover
(Figure6-25),should only need actjustingafter reptacing
a. componentor componentsin the 100MHz oscillatoi
circuit.

1. Wth the cover removed, monitorthe CAL OUT
connector with a frequency counter and adiust Cgoiil
,
with a non-metallictunning tool, for a reading of 100
MHz rlkHz.

2. The Cat Amplitude adjustment, Rl041, is
describedin the Adjustmentproceduresection.

1?8
TPttt4!

Flgure 6-25- 3rd Converter test poinb and adjustments.

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6-43

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- 4g4A/4g4Ap
Malntenance
ServlceVol.i

1st ConverterBias
This procedurepresetsflatnessfor Band4, Band5,

and Bands '1, 2, and 3,: then adjusts the Start (OHzi
Responseamplitudeand overallflatness.
These adjustmentsshould only be performed after
replacem€ntof the Dual Diode Assem'blyin the First
Converter. Test equipmentneeded to adjust the 1st
Converterare listedin Table6-9.
a. Removethe lst Converterassemblyfrom the
SpeetrumAnalyzer. Connectthe assemblyt6 the Spectrum Analyzeras shownin FigureG26.
b. MonitorTp1011on the lst LO Driverboard with
a_voltmeter(meter ground at crt shield). See Figure 6_
27 tor the locationof Tpl01 1.
c. Set the SpectrumAnalyzercontrolsas follows:
TIME/DtV
REFERENCE
LEVEL
FREQUENCY
RANGE
FREOSPAN/D|V
VIEWA and VIEWB
MIN RF ATTEN
PEAK/AVERAGE

AUTO
-30 dBM
5.4-18 GHz(Band4)
MAX
ofi
0dB
FullyGlockwise

d. Preset Bias 2 R1022 (Figure 6-271tor a meter
readingof -0.25 V.
e. Change the FREQUENCYRANGE to Band s
(15-21 GHz.)
f. Preset Blas 3 R1026 (Figure 6_27)for a meter
readingof -0.25 V.
g. Resetthe SpectrumAnalyzercontrolsas follows:
FREQUENCY

2MHz
FREOUENCY
RANGE 0-1.9 GHz(Bandt)
FREOSPAN/D|V
200 kHz
VIEWA and MEW B
On
WIDEVIDEOFILTEH on

Calibratethe power meter before making
measurements.
h. Connect a 50O cable from the output of the
SG503to the PowerMeter(Sensor.)

6-44

i. Set the SG503 output frequencyat 2 MHz, and
outputlevelat 0 dBm as indicatedon the power Meter.
j. Disconnectth€ 50O cable from the power Meter
and connect the cable to the SpectrumAnalyzer RF
INPUTthrough the 10dB and gdB attenuators.The
CENTERmay have to be reset to bring the 2 MHz signal to centerscreen.
k Activate SAVEA to save the bandwidth of the
2 MHz for reference.
l. Monitor TP1011on the lst LO Driver board with
the voltmeter.
m. Preset R1013 on the 1st LO DrivEr board for
-1.0 V at TP1011.
n. Reset FREQUENCY
to 0 (0.00MHz) to bringthe
0 Hz spur to centerscreen.

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DO NOT ALLOW THE VOLTAGE AT
TPlOll TO EXCEED+0.1 V WHILE THE
FOLLOWINGADJUSTMENTSARE BEING
MADE.

o. Adjust the tuning screw on the 1st Mixer assembfy and R1013,R1022,and Rl026 on the 1st LO Driver
board to match the response of the 0 Hz spur to the
bandwidthof the 2 MHz reterence(SAVEA disptay).

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Auxiliary Synthesizer VCO Adjustment
a. Monitor TP1066 on the Auxitiary Synthesizer
board with a voltmeter.
b. DisconnectP261, P1039,and p1060 from the
AuxiliarySynthesizermodule.
c. Disable frequency corrections by pressing
 10 dB/DlV.
d. Enable the Auxiliary Synthesizerby pressing
 pulse STRETCHER
and selectingmenu
item #4.
e. Adjust Cl070 on the AuxiliarySynthesizerboard
for +5 V at TPl066.

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Malntenance-

494A1494Ap
Servtce Vol. 1

Table 6-9
EQUIPMENT FOR ADJUSTING FIRST
CONVERTER BIAS

AND START SPUR AMPLTTUDE

Test Equipment
vottm€ter

Characteristics
(10 pV to )350 Vdc

SinewaveGengrator
PowerMeter
...PolrrerSensor

2.0 MHz,o dBm,+10 dBm to _100 dBm
Capableof measuring0 Ogm it 2 t\,tt-tz
Capableof measuring0 dBm at Z Unz
*0.3 dB at 2 MHz
*0.6 dB at 2 MHz

Attenuator(3 dB)
Attenuator(10dB)
50O CoaxiatCabte
5U{} CoaxiatCable
50O CoaxiatCabte

Recommended Tvoe

TEKTRONTXDM502A and TM SO0_series
Power Module
TEKTRONIXSG5O3
Hewlett€ackard 4358
Hewlett-Packard8482A
Hewlett-Packard8491AOption 003
H€wl€tt-Packard
8491AOption010
Tektronix Part No. 175-276$00
Tektronix Part No. 175-2ggT-W
TektronixPart No. 17S€g1O-00

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CONNECTTO A13
tvtTH 175-2765-d'
CABLE
CONNECTTO AT1O
wtTH 175-3310-d)
CAELE
CONNECTTO FL16
wfTH 17s-2337-fi'
CAELE

Nole:
Adiu3tnent is
facing the back
ot the instrumeni.

Figure 6-26. First Converter setup for adjustment

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6-45

Maintenance -

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4g4A/4g4Ap Servlce Vol. I

Coarse Tune Range R1032

3_Z.B EtiasI

5.4-18.Bias2

15-21 Bias 3 R1026

Mirer BiasTptoll

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Flgure 5-27. 1st LO Ddyer board adjustment and test point locatlons.

Baseline Leveling (Video processor)
a. Connectthe test equipmentas shown in Figure
6-28. Set the ALC switch on the RF ptug-into the MTR
position. Set the power Levef to approximately
-10 dBm thsn set the Gain on the
Sweepbscittatorfoi
stableoperation(outputstops oscillating).
b. S€t the SpectrumAnalyzercontrolsas follows:
FREOUENCY
FREQSPAN/D|V
AUTORESOLN
REFLEVEL
MIN RF ATTEN
VERT|CALDTSPLAY
PEAK/AVERAGE

0.00 GHz
MAX
on
-20 dBm
O dB
2 dB/Dtv
FuilyCounterctokwise

c. Set the Sweep Oscillatorto the AutomaticInternal Sweep (Marker Sweep),sweep time to 100 s, and
se! lhg SweepOscillatorso it sweepsfrom 10 MHz to
1.8GHz.
d. Activate MAX HoLD, VIEW A, and VIEW B.
Selecta TIME/DIVso there ar€ no breaks in the stored
display(Figure6-29a).
e. ReactivateMAX HoLD and SAVEA. Trace and
record the response of Band 1. Note the number of
divisionsfrom the baselineto the lowest point in the
first 5 divisionsof the disptay.
f. set the CENTERFREQUENCYto ptace the dot
marker directly over the towest point within the last o
divisionsof the display.
-9. Set the Sweep OscillatorCW Marker controlOn,
ancladjustit so a signalis at the cent€rof the crt.
h. AdjustR1O12(Band1 Stope)on the Video processorboard(Figure6€0) to set the top of the signalto
the levelnotedin part e.

6-46

i. Repeat until the frequency response is within
1.5 dB of the mid-pointbetweenth€ h^/oextremes.
j. Resetthe SpectrumAnalyeercontrolsas follows:
FREQUENCY
RANGE
FREQUENCY
FREQSPAN/DIV
AUTORESOLN
REF LEVEL
VERTTCAL
DTSPLAY
TIME/DIV

5.4-18.0 GHz
10 GHz
MAX
ON
-10 dBm
10 dB/DlV
10 ms

The UNCALindicatorwill light.
k. Adjustmentresistor R3030 is set at the factory
and usually does not require adjustment. Remove
P3035and replaceit. lf the baselineremainsstraightor
breaks up after the plug is replaced.compensationis
required. Adjustmentprocedureis as follows:
(1) Activate wlDE vtDEo FTLTERand change
TIME/DIVto 50 ms.
(2) Set the REF LEVELso the basetineis near the
top of the graticule.Reset the VERTICALDtspLAy
to 2 clB/Dlv,and set the REF LEVELsuch that the
displayis at mid-screen.
(3) Vary R3030 counterclockwiseuntil the display
breaks up towardsthe right side of the display(Figure 6-31a).
(4) Vary R3030clockwise1/8th tum past the point
where the display broke up. Store the display in
RegisterA.
(5) Alternately
set Rl013 throughRl061 fullyclockwise and fully counterclockwise,
so that everyother
potentiometeris fully clockwise and the adiacent
potentiometeris fully counterclockwise.The display
shouldnow look like a triangularwaveform.

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Maintenance-

4g4Al4S4ApServtceVot. 1

TO EXT.ALC lltPUT COt{ftECTCn-

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RF
OUT

ol o
SWEEP OSCILLATOR

CXT
AtC

o

TO RF OT'T COi.NECTOR

I

SP€CTRUT AIIALYZER U}IDER IEST
lrndc? Tqtt

(
{

LOW LOSS@AI CAaLE W|THStA COr*ecroes

Figurc 6-28. Baseline levefingtert setup.

(6) Adjust R1069 for a triangular waveform across
the screen. See Figure6-g1b:
f/) ResetRl0tg throughRl061 to midrange.
(8) Sweep Band4 in 2 GHz increments. Set
the
Spectrum Analyzer as foltows for th€ first 2 GHz
portionof Band 4.
FREQUENCY
RANGE
FREQUENCY
FREQSPANiDtv
RESOLUNONBANDWIDTH
REFLEVEL
VERTICALDISPLAY
TrME/D|V
PEAK/AVERAGE
MAX HOLD

5.4-18.0 GHz
6.4 GHz
200 MHz
1 MHz
-20 dBm
10 dBiDtv
AUTO
Fully
Counterclockwise
On

l. Adjustthe slop€ of band 5 as follows:
(1) -Resetthe Sweep Oscillatorso it sweepsfrom
15 GHz to 21 GHz (MarkerSweepland set the out_
Plt 9o the power meter reads approximately
-10 dBm.
(2) Set R1070(Band 5 Stope)on the Mdeo processor board,fully counterclockwise.
(3) Set the SpectrumAnalyzercontrolsas follows:
FREQUENCY
RANGE
FREQUENCY
FREQSPAN/DIV
AUTORESOLN
REFLEVEL
MIN RF ATTEN
VERTICALDTSPLAY
TIMEID|V

15-2i GHz
15GHz
MAX
On
-1OdBm
O dB
10 dB/Dtv
50 ms

The UNCALindicatorwiil tight.
(9) Check that flatness is within +g.S dB. tf
flatnessis out of limits, activateSAVEA and WIDE
MDEO FILTER,and deactivateMAX HOLD. Reset
REFLEVELso the baselineis on the screen.
(10)
to compensate
.Adjust-levelingpotEntiometers
for abnormalitiesin tha SAVEA disptay.
(11) Recheck the 2eHz window for flatness.
Proceed checking the Band 5 flatness in 2 GHz
increments.

(4) Selecta 15 GHz markeron the SweepOscillator
and set the outputfor --10 dBm.
(5) Activate2 dBiDlV and set the REF LEVELsuch
that the signal amplitude is approximatety6 divisions. Set MANUAL PEAK for maximumresponse
or activateAUTO PEAK.
(6) Changethe SweepOscillatorto AutomaticInternal Sweepand set the SweepTime for 100 s or its
slowestsweep.

6-47

Malntenance-

494A/494Ap Servlce Vol. 1

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aftcr barcline lcvcling.

Figure 6-29. Typlcal basellne teveling response.

(7) ActivateView A, View B, and MAX HOLD. Note
the responseas th€ oscillatorsw€eps.
(8) Activate SAVE A and deactivate MAX HOLD,
then selectCW Marker on the SweepOscillatorand
r_noyethe signal to the upper end of band S (19_
21 GHz).
(9) Msualizean imaginarytine throughthe midpoint
of th€ SAVE A display and select a point on the
saved display (betweent9 and 20 GHz) that inter_
sectsthe imaginaryline.
(10) Switch VIEW A on and off as requiredwhite
rnovingthe CW Marker to the s€lectedpoint, then
switch MEW A ofi.
(11) Adjust R1070 until the CW Marker is at the 6
divisionlevelor maximum,whichEveroccursfirst.
(12) DeactivateSAVE A and repeat step I parts 6
through11 until the best overallflatnessis achieved.
10 MHr Reference Oscillator Accuracv
(Agingrate is 1 x 10-e)
The 10 MHz ReferenceOscillatoraccuracyis not a
performancerequirement;however, it must be checked
so th€ center frequency accuracycan be verified. Since
the Calibratoris tocked to the 10 MHz Osciilatorthis
procedureverifies accuracy by countingthe frequency
of the calibratorsignal.
a. connect the cAL ouT signal to the frequency
counter. (counters with a frequency range above 20i)
MHz may requirea 150 MHz low pass filterto €nsurea
stabletriggeron the 100 MHz CAL OUT signat).

6-48

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The Tektronix DC 510 must be modified to
accept an external oscillator reference.
Refer to the TM500ffM5000 Series Rear
Interface Data Book, Part No. 070-2088-04
f or modificationinstructions.
b. Connectthe frequencystandardto the Extemal
FrequencyStandardlnput of the frequencycounter.
c. Removethe protectivescrew from the oscillator.

lf the 10 MHz CrystalOscillator(th€ instrument) has not been powered-up for an
extended period, additionalwarm-up time
(in excess of the recommendedwarm-up
time tor making adjustments) may be
necessary before a final adjustment is
made. ln that case, several frequency
checks must be made before the final
adjustmentis made.
d. Adjustthe FrequencyAdj on the 10 MHz Crystal
Oscillatorslowlywith a smallscrewdriveror adjustment
tool until the frequency counter indicates 100 MHz
*10 Hz.
e. Replacethe protectiveserew in the oscillator,
and disconnectthe count€rfrom the CAL OUT connector.

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Malntenance- 494A/4g4ApService Vot. 1

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106l (low) through R1013 (high) leyete, actiustments

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Figure 6-30. Easelinelevelingadiumentand test point
locations.

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A- Scrler ol waveforms.Amplihrdeapproximately+5
dB
tbovc rnd belowbaaelingreterenc".--

B. Typlcalwrvclorm when dirsay bleaks up.

Flgure 6-31. Typical basetine compensation adjustrnent
displays.

Maintenance-

494A/4g4ApServtceVot.1

MICROCOMPUTER
SYSTEMMAINTENANCE

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Severalmaintenanceaids are built into the microcomputer syst€m. Th€se operating tssts dEmonstrate
correct performanceor indicate the location of a prob_
lem, if any.
The switch settingsthat set up two of these tests
are describedfirst. Theseare followedby descriptions
of the threetests.
In the first test, the microcomputerexecutesa self_
test that verifies,as much as possible,correct operation. RAM, ROM, and interfaceadaptersare checked.
Any failure found is indicated by LEDs on the GplB
board.
The secondtest forces the microcornputer
to cycle
through all of its addresses.This test requiresless of
the systemto run than does the first test, so it may be
used to troubleshootproblemsthat disablethe first test
mode.

Table 6-1O

SETTINGS
Switch
1

s1010
Open

2

Open

Closed €xcept in Option 41
instruments

3

Open

Closed except in nonprogrammableinstruments

4

Not used

5

Open

lesilist

The third test exercisesthe instrumentbus to iso_
late problemsin data transfer betweenthe microcomputer and the instrument.

Option Switches
S1050 on the Memoryboard selectsthe microcomputer system test modes, as well as selectingsom€
instrumentoptions. S1010 on th€ Z-Axis board selects
rnost ot the instrumentoptions exclusively.Table 6_10
shows the selections controlled by the individual
switchesof 51010and S1050.
The microcomputerr€ads these switches only at
power-up.Any changein a switch positiontakes effect
when the instrumentis next poweredup.

6
'7

Open
When set open (programmable instruments only)
causesinstrumentto output
tront-panel settings (no
waveform)when RESETTO
LOCAL is pressed in TALK
ONLY mode. When set
closed, causes the instrument to output both the
front-panelsettings and the
currentwaveform.

Closed

Open except in 7 & S c l o s e d - N o r m a l
Option
07 Operation
instruments
7 closed I open
Not
defined
7 open 8 closed : Longversion of the power-up self
test which reports on the
GPIBboard.
7 & 8 open - Instrumentbus

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Power-up Sell Test
Normal instrumentoperationis selectedby closing
switches #7 and #8 of Si050. At power-up,the pro_
cessor executessteps 1 and 2, the first part of step 3,
and steps 4 and 5 of the MicrocomputerSystemTest
(describednext). lf the first two steps in the test are
successful,any problemsin the other three steps are
reportedon the crt. Possibleerror messagesare:
"RAMXX TESTSBAD. PUSHA BUTTONTO CONT.'
'ROM XX TESTSBAD. PUSH
A BUTTONTO CONT."
"ROMXX MISPLACED.
PUSHA BUTTONTO CONT."
TIMER TESTSBAD. PUSHA BUTTONTO CONT."
6-50

a
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Cross-referencetables betweenthe ROM and BAM
numbers given in error messages(XX) and the circuit
numbersof the parts are givenin Table 6-11 and Table
6-12.
lf the entiretest is successful.
the instrumentinitializes and beginsnormaloperation.

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Maintenance-

Microcomputer System Test
.The microcomputersystemtest is chosenby setting
switch #8 ctosed and switch #7 ogen in S1O6O.
fni
displayis inoperativewhile this test is beingperformed.
The microcomputerreports th€ t€st results via the
LEDS
on the GplB board rather than on the GRT. lf a problem is encountered,the test stops and the problem
is
indicat€d by one of the LEDSon itre GptB Ooard. tf
no
problemis found,the systemtest takes two
minutes.
, The system test _doesnot begin normal operation
after the test is complete.
.. . A.ddrelsgsare specifiedas hexadecimalnumbersin
this description.
l. The microcomputerfirst veriftesthe check sum
of the system ROM portion of U30S0on the Memory
board. The check sum test uses no memoryexceptfor
U3050. The correct ROM must be instailed,the clock
on the Processor board must be present, and the
microcomputersystembus must be operatingcorrectty.
tf the conect check sum is not obtained,the routine
halts and lights DS1047on the GplB board. lf the test
stops but does not tight DS1O47,and everythingetse
seemsto be in order, the AddressBus Test (desiribeo
later in this section)shouldbe performed.
2. Tl'rg microeomputernext checks part of the pro_
cessorinterfaceto the instrumentUus'pln, U1010,on
the Processorboard. lf the test fails, the routinestops
and lights DS1050 on th€ GptB board. tf the test
succeeds,the processorassumesthat the instrument
bus interface is working, and displays PROCESSOR
SYSTEMTEST,PLEASEWA|T. on the trt.

Tabfe 6-11

u1010
u3020
ul030

The third part of the test is similar to the first part.
However,the memorycontentsare allowedto residein
memoryfor thirty secondsbefore being read back. The
resultsare reportedvia DS104g.
4. The microcomputernext performsa check sum
test of all ROMs.The checksum storedin eachROMis
comparedto the check sum formed by the successive
16-bit spirat sum of each byte in tne nOU, startingat
the third location in the ROM. The ROM numberco-ded
into each ROM will causean error if a ROM is installed
in the wrong location.
The Tektronix part number is also coded into each
ROM. lf the part number suffix and its complement,
which are stored in th€ fifth and sixth bytes of the ROM
header, do not read as complements,the microcomputer assumesthat no ROM is installedand does not
attemptthe checksumtest.
lf a bad or misplacedROM is found,the microcom_
puter pulses DS1049on the GplB board N+1 times,
where N is the numberof the ROM in error (e,g.,a bad
ROM #3 will cause four pulses; refer to Table Gi2).
MissingROMsare reportedas describedin part 6.

ROM

Table 6-12
TEST
ROM
Saakct

3. The microcomputernext checks RAM. The RAM
test containsthree parts. The first part performs a quick
test of all non-battery backed-up RAM (U10.10and
U3020 on th€ Memory Board). The microcomputer
loads the bit paftern 01010101into a RAM tocation,
reads the location,and compareswhat is returnedto
what was stored. The microcomputerthen repeatsthis
test with the pattern10101010.This step does not rely
on the RAM beinggood to execute.
. lf a readingerror occurs, the microcomputerstops
the test and pulsesLED DSlO4gon the GplB boardtire
numberof times correspondingto the RAM that failed
the test (referto Table6-11).
The second part of the test is a Moving Inversions
test of all RAM (volatile and non-volatile).This test
assumesthat a few byes of the RAM are good. lf a
RAM faits this test, DS1O4gon the Memory board is
pulsedas describedearlier.

4g4Ll4g4ApServiceVot. 1

0
1
2
3
4
5
6
7
I
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11
12
13
14
15
16
17

u3060
u3060
u1010
u1010
u1020
u1020
ul025
u1025
ul035
ul035
u3015
u3015
u3020
u3020
u3030
u3030
u3050
u30s0

DSl049

Board

A54Memory
A54 Memory
456 GPIB
456 GPIB

1
2
3
4

A56 GPIB
A56 GPIB
A56 GPIB
456 GPIB
456 GPIB
A56 GPIB
456 GPIB
456 GPIB
A56 GPIB
A56 GPIB
456 GPIB
456 GPIB
A54 Memory
A54 Memory

5

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12
13
14
15
16
17

6-51

Maintenance-

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494A/494ApService Vot. 1

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!. A" microcomput€rnext tests U2015,a timerchip
on th€ Procassorboard. lf any of the timers in U201b
result in timo d€lays that ar€ too short or too long, the
test stops with LED DS10Sgon th€ GptB boardtit.
6. The microcomputer resets the GplA, U2050, on
the GPIB board and checks to see that the GptA is not
addressed to talk or listen. The GplA is set to the
listen-only mode and checked to see that it is
addressedto listen. The GplA is then set to the talk_
only mode and checked to sEe that it is addressedto
talk. lf any part of this step falls, the test stops and LED
DSl052 on the GPIB board is ilt.

lf all steps in the test arE successfullycompletEd,
the microcomputer lights LED DS10S4 on the GptB
board. The LED is lit continuouslyif no empty ROM
sockets are found, or putsed the number of times
corresponding to the number of empty RoM sockets
found. lf the number of pulses is greater than the
number of absent ROMs, a ROM (or ROMs) was
missed in step 4. Look tor a problem on the chip-s€lect
line or on the D7 data bus line.
lf th€ microcomput€rsystem passes the t€st, but
does not controlthe instrum€flt,run the lnstrumentBus
Checkdescrib€dtaterin this section.

AddressBusTest
Select the address bus t€st by moving jumper
P3015 on the Processor board to th€ TEST position.
This forces the microprocessor(U1025)data linss to
hexadecimal5F. As a result, the microproc€ssorcontinuously executes a CLR B instruction, and rep€titively
cycles through all of itE address space. There shouldbi
a known pattern on the microcomputer address and
control lines and at th€ output of th€ address decoders.
This allows qualified servic personnel to corr€ct probl€ms that pr€vont the microcomputer from running its
self-t€st.
The spectrum analyzerwill not function while running this test.

Mlerocomputer Bus
As the microcomputer
cycles through its address spac€, it toggles the address
lines. The MSB, A15, has a period of approximately
1540ms. Each line, 414 through A0, has a periodhaif
that of the previousline. Thus, the LSB A0 has a period
of approximately4.7 ps. High-orderlines A15 through
A12 ara shown in Figure 6€2. lgnore the narrow pulses
that may be evident during the low portion of each
cycle.

6-52

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Figure6-32. A15throughA12ln mlcrocomputor
test node.

The data lines on the microprocessorside of U2025
on the Processor board are static; D7 and D5 are low,
the oth€rs are high. The TEST position of P3015 disables U2025. On the bus eidE of this buffer, the data
lines are driven by the various memory devices on the
bus as they are addressed.
Examlnlngthe data lines can locate shorted or open
lines; i.e., lines inactive at hlgh, low, or in-between
states or changingin unison, usuallyto indeterminate
logic lev€tsof +1 V to +2 V. A problem r€lated to a particular device may be evident only while that device is
addressed.

Memory Address Decoders - Address decoder
U2045 on the Memoryboard sets its outputs low in turn
to access blocks of memory space. The four main
block-selectorrtputsare shown in Figure 6-33.
U3025 on the Memory board decodes the RAM
addresses. Becauseof the power-upconditlonof the
bank select,only one of the non-volatileRAM chips will
be selected. The RAM seleotoutputsand their relationship to 6-ffi andl{ffi are shown in Figure 6€4 and
Figure6-35.
U3040and U3045on the Memoryboard decodethe
T/O-selectline and th€ selectline for S1050. Thesesignals are shownin Figure6€6.
lgnore the narrow pulses evident during the time
each outputis asserted.The pulsesresultfrom address
lines togglingbetweenmicrocomputercycles.

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Maintenance-

494A1494Ap
ServiceVot. .t

Processor Address Decoder _ Address decoder
U3035 on the processor board decodesseverd chip_
sel€cts. Y0, Y'1,y5, and y7 areshownin relation
to the
T/6-linein Figure6-37.

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4XXX

Itflu|ll

----lMm

oxxx

Ixxr

IilMU-

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u3025,
PIN12
5S4{5

Figure6-35. RAM select output in retationto-llXXX.

5565-75

Flgure 6-33. Four maln bloack select outputs ot
address
decoder U20tf5.

ililil1Iililt
fltilfiililil1ilililil
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SXXX

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lilfi-xilT;

axfr.

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0xxx

OPTIONS

U
u302s,
PIN6

swtTcH
SELECT
s@4-09

u3025,
PIN 4

Figure6-36.-Ip and 51050setecttinesIn relationto 0XXK
5@lL07

Figure 6-34. RAM select ouhut in relailon to dXXX.

GP|B Board Address Decoders
Address
decoderU1055on the GPIB board sets its outputslow
to select the GPIA, the GPIB address switch and the
bank latch. Y2, Y4, and YGare shownin relationto-TO
in Figure6-38.

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6-53

Maintenance-

494A/494ApServtceVol. 1

Instrument Bus Test

uo

woEm

It|l

Yr iffiI

[[I

t[I[

Y5 (70XXl

Y7 offii
556UX)

Flgurc 6-37.
-rlo.

Chlp relectr Y0, Yl, Y5, and y7 In retadon to

lf the microcomputer performs the power-up selftest, but fails to properly control the instrumeht, the
instrument bus interface may be faulty. Select the
instrument bus test by setting the option switch as
shown in Table 6-10.The microcomputercontinuously
writes to the instrumentbus in a repetitivemannertso
the instrumentdoes not operatenormally.
The pattern on the instrument bus toggles DATA
VALID and POLL and exercisesthe addressand data
lines. The addresslines changewhen DATAVALID ls
low and the data lines change when DATA VALID ls
high. However,if an assemblyon the bus is requesting
service because of the way it powered up, DBo-DB4
may continueto change after DATA VALID goes low. In
this case, an assemblyor assembliesmay respondto
the high stat€ of POLL and the changingstate of AB7
and attempt to report status.
The patternfor the upper addressand data lines is
shown in Figure 6€9. From addressor data line 7 to
linE 0, each line changesat twic€ the rate of the previous lin€, resultingIn 128 cycles on the LSB lines. ThE
initial pulse on the upper four data lines is not part of
the +2 pattgrn and is not repeated on the lower four
data lines. lt is possibleto discoveropen or shorted
lines by comparingthe patterns to those in Figure 6€9,
checkingthat they +t. Look for lines that stay high or
low, change together or at wrong times in the pattern,
or go to indeterminate
logic levels(1 V to 2 V).

TROUBLESHOOTING
ON THE
INSTRUMENT
BUS
lnstrument Bus Data Transfers

FlgureG-38. Chlp relects Y2, y4, and y6 in relation tilll6.

Clocks and Control Llnes - The 680g clock input
line should be a squarewave with a period of approximately0.293ps. The c 2 outputon pin 37 shoutdhave
a periodof approximately
1.17;rs. VMA, RESET,NMt,
and R/W shouldbe high. TFd instrumentbus powerup.

6-54

There are two commands and queries provided to
aid troubleshootingof circuit functionscontrolledby the
instrumentbus. Thesecircuitsget data from the microcomputeror respondwith data for the microcomputer.
The ADDR commandand ADDR query set and retum
the instrumentbus address for the DATA command.
The DATA command and DATA query set and return
data on the instrumentbus.

Becauseth€ DATA commandchangesthe
status of internal hardware, its use may
prevent normal spectrum Analyzer operation. Incorrect,settingsof some hardware
could causeinstrumentdamage.

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Malntenance-

These commandsand queries are transmitted
to the
Anatyzer with ihe pRtNT st#ment.
rne
!ryl*rn
upecrrumAnatyzerresp-onseto a query is input
into a
string variablewith the tNpUT statement.
A string variable is-formeclpVendinOth€ variablename
with a doilar
sign ($),€.9. A$, Xt$.
FOr thE GPIB PRIMARY ADDRESS, ENtEr
tIiE
'.'--' rear-panel
9"_g'g"l equivalentof the spectrr,
GPIBADDRESS
switchsettings. "n"lyi"r

4g4N494ApService Vol. 1

ADDR(instrumentbus address)command

HEX DIGIT - A character in the sequence 0
through 9 and A through F that representsa hexade_
cimal digit. The two digits (in ordei; torm a numberto
representa locationon the instrumentbus used by fot_
lowing DATA commands. lf a character is not a hexadecimaldigit or part of a pair of digits,it is not usedto
€xecutethe ADDRcommand,and an error is reported.

ADDR (instrument bus address) query

Responseto ADDRquery
r_----{-a

DATA (instrumentbus data) command

B.

419 chip selectoutputs from U1044 and
Uptton switch enablelineson the Memory
board.
4416-92A

Figure6-39. Insfument bus check.

HEX DIGITS- As with ADDR,a pair of digitsforms
a hexadecimalnumber.The numberis a data valueto
b€ sent on the instrumentbus to the locationspecified
by the last ADDR command.This allows internalspectrum analyzerparametersto be set for service:these
parameterscontrol functions by setting the status or
mode of spectrumanalyzercircuitassemblies.Up to .16
pairs of charactersare accepted.lf a characteris not a
hexadecimaldigit or part of a pair of digits, the data
byte formed by the pair is not executedand an error is
reported.Also, an error is reportedwhen data is sentto
an invalidaddress.

6-55

Malntenance-

o

494Alttg4ApService Vol. I

DATA(instrumentbus data)query
l \

\ -

F--{

2. Convert each group of four bits to a hexadecimal
digit. Hexadecimaldigits range from 0 to F in the
sequenc€0123456789A8CDEF.
0100- 4
1011- B (i.e..8+0+2+1-11,whichis hexadecimat
B)

oaraz }-.-

:^p0RjdglE*tF'
4416-08

3. Group the two hexadecimaldigits together, keeping their respectiveplaces.

Responseto DATA query

4 and B mak€the two-digithexadecimalnumber48

a4t$09

The infornationin Table6-13 is separatedby registers. The following information is related to the table
informationby leadingalphadesignators.

CombinedADDRcommand and DATA command
A. Variable Resolutlon (refer to diagram 20)

The address command may precede a data commandor queryto identifythe instrumentbus locationas
part of the same m€ssage.
Enors related to these commands are 41, invalid
DATA or ADDR argument contents, and 42, DATA
directionnot compatiblewith ADDRdirection.

InstrumentBus Registers
Registersprovide the link between the instrument
bus and microcomputercontrolledfunctions.The registers are definedhere in the same order as they appear
in the Diagramssection.The definitionsare providedto
help in constructingDATA commandsand interpreting
responsesto DATA queries.
The data is presentedhere as binary.In somecases
a data value occupies the entire register width; for
instance,a value in digital storage. tn other cases, a
single bit or group of bits in the registerforms a code;
for instance,the upper five bits in the sweep rate and
mode register indicate the sweep timeldivision.The
meaningof the data is not fully defined here; ref€r to
the d€scriptionof the circuit module in Section 5 for
details.
To use the binary codes presentedhere with the
DATA commandand query statements,you must convert_binary to hexadecimal.The binary code number
01001011
i$ used as an examplein the followingsteps.
1. Groupthe lower four bits and th€ upper four bits
(breakthe data byte in half).
0 1 0 0 1 0 1-1 0 1 0 01 0 1 1

6-56

The microcomputerwrites to two variableresolution
registers. The data MSB steers the other bits that are
definedinto the desiredregister.WhenDB7 equals1, it
steers DBo through DB2 to select the resolution
bandwidth.WhEn DB7 equals0, it steers DB6 through
DBo to selectthe amountof gain added in the VR s€ction and the band levelinggain (gainadjustmentrelated
to front-endresponsein each band).These two functions are addressedand set togetherby the same data
byte.
B. Log and Video Amplifier (refer to diagram 23)
There are two registers that receive data from the
microcomputer. One register controls vid€o offset (78)
and the other controlsthe displaymodes and the vertical scale factor (79).
C. Video Processor (reler to diagram 24)
Register 7C controls out-of-bandclamping,video
filtering,and leveling.
D. Digital Storage, Vertical (refer to diagram 25)
Registers7A and FA on the V€rticalDigitalStorage
board transfer displaydata to and from the microcomputer for spectrumanalyzerGPIB operations.Register
78 controlsdigitalstoragefunctions.
E. Z-Axis & RF Interface (refer to digram 28)
Register 4F on the Z-Axis & RF Interface board
enablesZ-axis and RF attenuatorcontrol. RegisterCF
reports powersupplystatus.
F. Crt Readout (refer to diagram 30)
Register5F controlscrt readoutand data steering.
Register2F acceptsdatafrom the microcomputer.

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- 4g4Al4g4Ap
Maintenance
ServlceVol.l
G. Sweep (refer to diagram 3l)
The microcomputerwrites to registers0F and
1F to
control sweep rate, mode. holdott, interrupts,
and
triggEring.

N. Front Panel(refer to diagram43)
Readingfrom F4 accessesthe keyboardencoder
andtheCENTER/MKR
FREQUENCy
controtencoder.

H. Span Attenuator (refer to diagram 32)
Registers75 and 76 controlthe spanattenuator.

Tabte 6-13
INSTRUMENT
BUS REGISTERS
DataBits
76543210
Description

l. lst LO Driver (refer to diagram 33)
Register72 controlsfunctionson the 1st LO Driver
board. RegisterZE is addedto makethe pEAKingcontrol programmable.
J. Preselector Driver (refer to diagram 34)
Register 77 controls functions on the preselector
Driver. The singlebit DB3 respondson the data bus
to
indicats that the board is instaileOwhen the microcom_
puter performsa read at F7.
K CENTER/MKR FREQUENCy Controt (reter
ro
diagram 35)
.R€gisjer70 is provid€d for control functionsand
register71 is providedfor data valuesfor center
fre_
quency DAC(s).A read, F0, returns the results
of a
comparisonof the DAC output voltageand a memory
voltage.
L. Auxiliary Synthesizer Control (refer to diagram
371
Register 7D accepts data to set the synthesizer
chip, U4041,to output 200 MHz to 220 MHz in 400 kHz
steps.Valuesof R, A, and N are givento determine
the
outputfrequencyas given by the formula
fout : (l/RXNP+A)
where R, the referencedivisionratio, is set at 5 and p
is the prescale value of 32. N values neededare
3.1
through 34, while A ranges from 0 to 31. (fable 6_14
showsthe fou, resultsfor givenN and A values.)
M. Phase Lock (refer to diagram 39)
,Register73 acceptsdatato preloadthe +2n counter
and control the synthesizer.Successivereads from
registerF3 obtainstatusand counteroutputs.
After the counter output register selectoris reset,
three read cycles return status bits and counterbits in
lhg To"l significantbyte and the remainingcounterbits
in followingbytes.

A. Variable
Resolution {3F}
Resolution Bandwidth

1xxxx001
1xxxx010
1xxxx011
1xxxx100
1xxxx101

I MHz Resolution Bandwidth
100 kHz Resotution Bandwidth
10 kHz Resolution Bandwidth
1 kHz Resolution Bandwidth
100 Hz Resolution Bandwidth
Galn, Levellng

00000xxx
00100xxx
00010xxx
00110xxx
00001xxx
00101xxx
00011xxx
00111xxx
01000xxx
01100xxx
0xxxx000
0xxxx001
0xxxx100
0xxxx101
0xxxx111

Band 1 Leveling
Band 2 Leveling
Band 3 Leveling
Band 4 Leveling
Band 5 Leveling
Band 6 Leveling
Band 7 Leveling
Band I Leveling
Band 9 Leveling
Band 10 Leveling
0 dB Gain
t0 dB Gain
20 dB Gain
30 dB Gain
40 dB Gain

B. Log & Video
Ampllfier
Video Olfset {78}
DB7-DBO LSB - 114dB
Total range - 63.75dB
Modes and ScaleFactorO9)
lxxxxxxx
Pulsestretcheron
0xxxxxxx
Pulsestretcheroff
xlxxxxxx
ldentifyoffseton
x0xxxxxx
ldentifyoffsetoff
xx0lxxxx
Lin
xxl0xxxx
Log
xx00xxxx
Full-screendeflection
DB3-DBO Log verticalscalefactor in
dB/div

6-57

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Maintenance- 494A/494ApServiceVot. i

Table 6-13(cont)
Data Bits
76543210

Data Bits
7654321

Description

C. Vldeo
Processor(7C)
011xxxxx
001xxxxx
1l1xxxxx
010xxxxx
xxx0000x
xxx0001x
xxx1001x
xxx1101x
xxx0011x
xxx1011x
xxx1111x
xxxxxxxl
xxxxxxx0

Out-of-bandclamp - ns
clamp
Out-of-bandclamp- g;6rt
upper5 div
Out-of-bandctamp- 66rO
lower div
Out-of-bandclamp- qlgmt
lower5 div
Mdeo filter off
Videofilter30 kHz
Mdeo filter 3 kHz
Videofilter300 Hz
Videofilter 30 Hz
Mdeo filter 3 Hz
Mdeo filter 0.3 Hz
Base-linelevelingon
Base-linelevelingoff
Horlzontal
Board

xlxxxxxx
xxlxxxxx
xxxlxxxx
xxxxlxxx
xxxx0xxx
xxxxxlxx
xxxxx0xx
xxxxxxlx
xxxxxx0x
xxxxxxxl
xxxxxxx0
Extended Address
2-O

Digital

Storage

Digital
Storage
Acquisition
Enable
Digital Storage Acquisition Disabl€
Extended Address 2
Extended Address 1
Extended Address 0
B-SAVE A on

B-SAVE A otr
VIEWB on
VIEWB off
VIEWA on
VIEWA off
SAVEA on
SAVEA off
Subaddressbits for Port 7A giving
subaddresses
Z-0.
Addressing 7A.6 transfers the
bus to the Vertical Digital
Storageboard.
7A.0

DB1-DB7
DBO

6-58

t

SecondaryMarkerpositionbits
SecondaryMarkertrace bit

a

Horlzontal Digital
Board (cont)

Storage

7A.1
DB8,DBg
DB1

SecondaryMarkerpositionbits
SecondaryMarkertrace bit
7A.2

DBl-7
DBO

PrimaryMarkerpositionbits
PrimaryMarkertrace bit
7A.3

DB8_9
DB1

PrimaryMarkerpositionbits
PrimaryMarkertrace bit
7A,.4

ADDRT-ADDRO

DigitalStorageaddressbits
7A.5

DB6
DB5

Transfersthe bus to the Vertical
DigitalStorageboard.
Determinesif bus transferis for
a single cycle or until it is
returned by the Vertical Digital
Storage board.

D84

DisableUpdateMarker

ADDRg,ADDRS

Loading ADDRT-o reloads th€
lastADDR9.8

7B

0xxxxxxx

t

Description

D. Digital Storage
(cont)

D. DlgitalStorage

l xxxxxxx

a

Table S13 (cont)

7A.7
DB4-7
DBO-3

PrimaryMarker intensitybits
SecondaryMarkerint€nsitybits
FA

DBO-7

DigitalStoragepositionbits
FB
Always low to indicatethat it is
from the Horizontal Digital
Storageboard

DBO& DBl

DigitalStoragepositionbits

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Maintenance-

Table &13 {cont)
Data Blts
76549210

Deseription

D. Digital Storage
(cont)
Ver$cal Digltal Storage Board
FA
DB7-DBO

Datavaluesfrom digitalstorage.
A writeto 78 initializesoutputto
begin at the left of the trace and
proce€dto the right
FB
Alwayshigh to indicatethat it is
frorn the Vertical Digital Storage
board
7A

DB7-DBO

Table &13 (cont)
DataEits
76543210
F. Crt Readout
Crt Controt (5F)
lxxxxxxx
0xxxxxxx
xlxxxxxx
x0xxxxxx
xxlxxxxx
xx0xxxxx
xxxxlxxx
xxxx0xxx
xxxxxxlx
xxxxxxOx
xxxxxxxl
xxxxxxx0

Spectrumchop enable
Spectrumchop disable
32 characters/line
40 characters/line
2lines
16lines
Max span dot on
Max span dot ofr
Address2F containsan address
Address2F containsdata
Readoutenabted
Reacloutdisabledto load readout
D84 A8 (addressbit 8)
oB2 A9 (addressbit 9)
Address/Data(2F)
DB7.DB6 l f D B l i n 5 F - 1 - A 7 , A 6 o f
address. With Ag and A9 in 5F,
they specify the line number
(0-F).
DB5-DBO l f D B I i n 5 F - 1
A5-40 of address. This
specifies the characterposition in a line.
D87 l f D B l i n 5 F - 0
1 - Characteris a space
0 - Characteris not a space
DBO l f D B l i n 5 F - 0
1-Skipaline
0: Don'tskipa tine
DB5-DBO l f D B l i n 5 F : 0

Data values for digital storage.
A write to 78 clearsthe address
counterso valuesare storedfor
points on the display startingat
the left and proceedingto the
right in order
7B

x1'lxxxxx
xl0xxxxx
x0lxxxxx
xxx'txxxx
xxx0xxxx

Peak/Averagecursor in knob
position
Peak/Averagecursor in peak
position
Peak/Averagecursor in Average
position
Max Holdon
Max Holdoff

E. Z-Axls & RF
Interfaee
Z-Axis & RF Attenuator{4F)
lxxxxxxx
0xxxxxxx
x1xxx1x1
x1xxx1x0
x0xxx1x1
x1xxx0x1
x1xxx0x0
x0xxx0x1
x0xxx0x0
xxlxxxxx
xx0xxxxx
xxxlxxxx
xxx0xxxx
xxxxOxxx
xxxxxxlx
xxxxxx0x

Baselineclipperon
Baselineclipperoff
0 dB RF attenuation
10 dB RF attenuation
20 dB RF attenuation
30 dB RF attenuation
40 dB RF attenuation
50 dB RF attenuation
60 dB RF attenuation
829 MHz 2nd converter
2 GHz 2nd converter
EXTMIXER
RF INPUT
100ms to switchattenuator
PowerSuppliesStatus(CF)
Fault
Suppliesokay

494A^l494Ap
Service Vot. 1

Charactercode (lower 6 bits
of ASCII)
G. Sweep
1F
lxxxxxxx
xlxxxxxx
xxlxxxxx
xxxxlxxx
xxxxxlxx
xxxxxxlx
xxxxxxxl

ExtendedAddress1
ExtendedAddress0
MarkerDAC/RampGenerator
TriggerSingleSweep
DisableSweepGate
DisableTrigger
Abort Sweep

Extended Address
1 and Address 2

Subaddressbits for Port 0F giving subaddresses3-0. Subaddresses0 and t havethe rest of
the control bits not on Address
lF. Subaddresses2 and 3
receive the 12 bits to set the
DAC.

6-59

I

Malntenance-

494A/4g4ApServlce Vol. 1

Table 6-13 {cont)
Data Bits
76549210

Descriptlon

G. Sweep

Holdoff, Interrupt, Trigger (0F.0)
xx00xxxx
xx0lxxxx
xxl0xxxx
xxxx00xx
xxxx0lxx
xxxxl0xx
xxxxllxx
xxxxxxlx
xxxxxxxl

Short sweep holdoff
Mediumsweepholdofi
Long sweep holdoff
Free run triggermode
Internaltrigger mode
Extemaltrigg€rmode
Line triggermod€
Enableend-of-sweepinterrupt
SingleSweepMode
Sweep Rato and Mode (0F.1)

xxx1101
xxx1O11
xxx1001
xxx0101
xxx0011
xxx0001
xxx1100
xxx1010
xxx1000
xxx0100
xxx0O10
xxx0000
xxx1100
xxx1010
xxx1000
xxx0100
xxx0010
xxx0000
xxx1111
xxx0111

20 ps Time/Div
50 ps Time/Div
100 ps Time/Div
200 ps Time/Div
500 ps Time/Div
1 rns Time/Div
2 ms Time/Div
5 ms Time/Div
10 ms Time/Div
20 ms Time/Div
50 ms Time/Div
100 ms Time/Div
200 ms Time/Div
500 ms Time/Div
1 s Time/Div
2 s Time/Div
5 s Time/Div
10 s Time/Div
Manual
External

0
0
0
0
0
0
1
1

Table 6-13 (cont)
Data Bits
76543210

lxxxxxxx
0xxxxxxx
xO0xxxxx
x0lxxxxx
xl0xxxxx
xxx00xxx

of U3032is +1
Gainof U3032is -1
x1,0 sweepdecadeattenuator
x0.1 sweepdecadeattenuator
x0.01 swe€pdecadeattenuator
l st LO maincoil output selectand
calibration
xxx0lxxx
1st LO FM coil output select and
calibration
xxxl0xxx
2nd LO output select and calibration
DB2 For futureuse
DBl, DBO Uppertwo bits of attenuationcode
l. 1st LO Driver
lst LO DriverFunctions(72)
lxxxxxxx
0xxxxxxx
xlxxxxxx
x0xxxxxx
xxlxxxxx
xx0xxxxx
xxxlxxxx
xxx0xxxx
xxxxlxxx
xxxx0xxx

MarkerDACvaluebits
0F.3 (U103s)

DB3-DBO

MarkerDACvaluebits
9F

xxx0xxxx

PollBit

H. Span Attenuator
Span Magnitude (75)
DB7-DBO

6-60

Lower 8 bits of 10-bit attenuation code (000 is max attenuation)

xxxxx
xxxxx
xxxxx
xxxxx
xxxxx0
xxxxxl

10
10
10
01
11
11

I

o

)
Span Magnitudeand Attenuator
(76)

0F.2 (U104s)
DB7-O

Descrlption

H. Span Attenuator
(cont)

o
o
o

Normalspan mode
spanmode
sweepvoltageto driver
Disconnect sweep voltage to
driver
Driveroff {for degauss)
Driveron
Filter on at driver output (for
unphase'locked
narrowspans)
Filteroff at driveroutput
Externalmixerdisconnected
External mixer connected (connected in bands 1-5 if external
mixer selected;always connected
in higherbands)
Internalmixerbiasfor Band1
Internalmixerbias for Band 2
Internalmixerbias for Band3
Internalmixerbias for Band4
lnternalmixerbias for Band 5
No inlernalmixerbias selected
PEAKingControl(7E)

0xxxxxxx
SteersDB4-DB0to upper latch
x0xxxxxx
SteersDBs-DBoto lower latch
DBs-DBO
1 sent to DB4 of upper latch disablesfront-panelPEAKingcontrol;
DB3-DB0 of upper latch and
DBS-DBOof lower latch form 10bit inputto DACfor programmable
peakingvoltage

t

o
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3

a
o
o
o
C
o
o
o
o
a
o
o
o
o
o
o
o
a
a
O
o

o

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o
o
C
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o
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O

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Mafntenanca-

Table 6-13(cont)
Data Bits
7654321A
J. Preselector
Driver (77)
0lxxxxxx
l0xxxxxx
00xxxxxx
xxlxxxxx

Descrlption

-conversion,g2g MHz ofiset
+conversion,829 MHz offset
829 MHz tF not usEd
Driver output filter on (for narrow
spans)
Driver output filter off
Preselectorswitch
LPF switch
lst LO FM coil not swept
1st LO FM coit swept
Driveron
Driver ofi (for degauss)
3rd harmonic1st LO conversion

x x0 X xxx X
x xx 1 xxx x
x xx 0 xxx x
x XX x lxx
x
x xx x 0xx x
x xx x xlx
x
x xx x x0x x
x xx x xxx
1
x xx
xxx
lst
LO conversion
K. CENTER/MKR
FREQUENCY
Control
Control (70)
lxxxxxxx
1st LO storagegateopen
0xxxxxxx
1st LO storagegateclosed
x0xxxxxx
Steers DAC data to 1st LO high
byte
xx0xxxxx
Steers DAC data to ist LO mid
byte
xxx0xxxx
Steers DAC data to 1st LO low
byte
xxxxlxxx
2nd LO storag€gate open
xxxx0xxx
2nd LO storagegate closed
xxxxx0xx
steers DAC data to 2nd Lo high
byte
xxxxxx0x
Steers DAC data to 2nd LO mid
byte
xxxxxxx0
Steers DAC data to 2nd LO low
byte
DAC Data (71)
DB7-DBO
Data for center frequencyDAC(s)
steeredby controlregister
CENTER/MKRFREQUENCyControl Read (F0)
D87
1st LO DAC stored voltage com_
parator
DBO
2nd LO DAC storedvoltagecomparator
L. Auxiliary
Synthesizer
Control (7D)
DB7-D84
synthesizerchip data(D3-D0)
DB2-DBO
Synthesizer chip
addresses
(A2-A0)
xxxxlxxx
VCOenable
xxxx0xxx
vco

494A1494Ap
ServiceVol. 1

Table6-13 (contl
Data Bits
76543210

DescripUon

L Auxlllary
Syntheslzer
Control (7D) (cont)
0101x101
0000x110
0000x111

This sectionsets R, the reference
divider to 5 yietding a 20O kHz
referencefrequency.

AAAA x 0 0 0

This section sets the value of A
from 0 to 31
LSB

000Ax001

N N N N x 0 t 0 This sectionsets N from 3.1to 34
0 0 NN x 01 1
0000x100
31-1111 32-0000

01

.r0

33*0001 34-0010
10
10
M. Phase
Control

Lock

Write (73)
lxxxxxxx
xxlxxxxx
xxxlxxxx
xxxxlxxx
xxxxxxlx
DB6
DB2
DBO

lxxxxxxx
xlxxxxxx
xxlxxxxx
DB4-DBO

Glocksdata on DBo into a tatch
Clearsthe counters
TransfersDBOserial data to control latch outputs
Resetsthe counteroutputregister
selector
TransfersDBo serial data to synthesizerN latches
Gate mode latch
NVRAMswitchlatch
Serial data for control of synthesizerN latches
Read(F3)-Most SlgnlficantByte
Enor voltage below a preset
amount
Error voltage above a preset
amount
Validcountis in counters
Upper five bits of counteroutput;
the remaining16 bits are in the
followingtwo bytes

N. Front Panel

Reading Data
Encoders(F4)
lxxxxxxx
0xxxxxxx
DB6-DBO

From

Swilch

CENTER/MKR
FREQUENCY
down
CENTER/MKR
FREQUENCY
up
Switch codes (see Figure 7-33 in
Section7)

6-6r

Malntsnance-

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494A/494ApServlceVol. l

o

Table6-14
AUXILIARY SYNTHESTZERVALUES AS A FUNCTIONOF N AND A
N

A

F*, Result

N

A

Fou,Result

N

A

Fou,Result

N

A

FooiResult

31
31
31
31
31
31
31
g1
31
31
31
31
31
31
31
31
31
31
31
31
31
31
31
31
32

I
I
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
28
27
28
29
30
31
0

200.0MHz
200.2MHz
200.4MHz
200.6MHz
200.8MHz
201.0MHz
201.2MHz
201.4MHz
201.6MHz
201.8MHz
201.0MHz
202.2MH2
202.4 MHz
202.6MHz
202.8MHz
203.0MHz
2O3.2MHz
203.4MHz
203.6MHz
203.8MHz
204.0MHz
2O4.2MHz
204.4 MHz
204.6MHz
204.8MHz

92
32
32
32
32
32
32
32
32
32
32
92
32
32
32
32
32
92
32
32
32
32
32
32
32

1
2
3
4
5
6
7
I
9
10
11
12
13
14
15
16
17
18
19
20
21
22
29
24
25

205.0MHz
205.2MH2
205.4MHz
205.6MHz
205.8MHz
206.0MHz
2O6.2MHz
206.4MHz
206.6MHz
206.8MHz
207.0MHz
207.2MH2
2O7.4MHz
207.6MHz
207.8 MHz
208.0MHz
208.2MH2
208.4MHz
208.6MHz
208.8MHz
209.0MHz
2O9.2MHz
209.4MHz
209.6MHz
209.8MHz

32
92
32
32
32
32
33
33
33
33
33
33
33
33
33
33
33
33
33
33
33
33
33
33
33

26
27
28
29
30
31
0
1
2
3
4

210.0MHz
210.2MH2
210.4MHz
210.6MHz
210.8MHz
2 1 1 . 0M H z
211.2MH2
211.4MHz
2 1 1 . 6M H z
2 1 1 . 8M H z
212.0MHz
212.2MH2
212.4MHz
212.6MHz
212.8MH2
213.0MHz
213.2MH2
213.4MHz
213.6MHz
213.8MHz
214.0MHz
214.2MH2
214.4MHz
214.6MHz
214.8MHz

33
33
33
33
33
33
33
33
33
33
33
33
33
34
34
g4
34
34
34
34
34
34
34
34
34
34

19
20
21
22

215.0MHz
215,2MH2
215.4MHz
215.6MHz
215.8MHz
216.0MHz
216.2MH2
216.4MHz
216.6MHz
216.8MHz
217.0 MHz
217.2MH2
217.4MHz
217.6MHz
217.8MH2
218.0MHz
218.2MH2
218.4MHz
218.6MHz
218.8MHz
219.0MHz
219.2MH2
219.4MHz
219.6MHz
219.8MHz
220.0 MHz

c

6
7
I
9
10
11
12
13
14
15
16
17
18

a

24
25
26
27
28
29
30
3l
0
1
2
3
4
5
6
7
I
9
10
11
12

I
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o
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Front-PanelRegisters
See Table 6-15.

Table6-15
FRONT.PANEL
REGISTERS
Writing Data to Shift Registersfor Lightsfi4)
DB3-1 - Initiallzesencoder at powerup
Writingto register74 loads data into shift registersthat drive all the lightson the front panel,includingthe one for
the crt graticule.Four 8-bit shift registersstore the data, requiringeight wlites of four bits each time (one bit for each
register)to updatethe front-panellights. This table showsthe order in whichdata is enter€dto controlthe lights.A o
turns on the light (exceptin the case of the crt graticule),and a 1 turns off the light.
Wrlte
Number
1
2
3
4
5
6
7
I

6-62

DB5
Not Used
Not Used
Not Used
Not Used
RECALL SETTINGS
GREEN SHIFT
Not Used
AF

DB4
MAX HOLD
M A R K E RM E N U
ADDRESSED
HELP
BLUE SHIFT
Not Used
MAX SPAN
PULSE STRETCHER

DB2

ZEROSPAN
REMOTE
10 dB/Drv
2 dB/DrV
IDENT
MIN NOISE
AUTO RESOLN
UNCAL

DB1
GRAT ILLUM
FINE
READY
LINE TRIG
SINGLESWEEP
FREE RUN TRIG
INT TRIG
EXT TRIG

DBO

TUNEMODE
UN
WIDE
NARROW
B_SAVEA
VIEWB
VIEWA
SAVEA

t
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Maintenance-

TAPE DATATRANSFERPROGRAM

I
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4g4ful4g4ApService Vol. 1

Macros stored in battery-backedup memorycannot
be down-loadedto tape. consequenfly,the macros will
be lost each time the battery is removedfrom
ttre f_Aemory
UoarO.
lf the battery on the Memory board is removed
while the
memorywill be lost' A Tektronix4041'seriescomputer, board is not.poweredup, data stor€d in battery-backedup
to the spectrumanalyzervia the GplB, will move
this datato a tape and back into memoryusingthe
"onn""t"a
tottowing
piogr"rn.

)

I

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a
I

lntegeral,sl ,tl,wl ,i,v,y,z,vl
Print "SpectrumAnalyzerAddressis: ,,;
lnput al
Print
Print#al:.ROS OFF"
Print "Savememoryon tape? ";
Inputb$
B$-seg$(b$,.t,1)
19q !j b$-"y" or b$-',y,,then goto 2000
190 Print
20O Goto 1000
109
119
PA
130
140
150
160
174

1000 ! This routinemovesdata from TApEto the spEcrRUM
ANALYZER
and Settingsare on the foilowingdata fites"
-I919 !1"t "Disptays
*(3060
1020 Print
x 9 for displays,1020x t0 tor settiigsl;
1030 Print
1040 Dir
1050 Print
1060 Print"Enternumberof first datafile,FlL,:,,;
1070 Inputtl
1080 Gosub9000
1090 Print"Writeover all Displaysand Settings(0),,,
1100 Print'Orwriteonlyin b1ank........
memory(1):,,;
1 1 1 0 t n p u yt $
11?9 lf y$:"0' or y$-,'1"then goto 11S0
,,,,,pleasl: ,,:
1130 pfint uuuO*"
Of ,,,,1
1 1 4 0G o t o1 1 1 0
1150 Y:vat(y$)
1160 Detetevar ig
1170 Dimi$ 700
1180 Print#al:"SET?,,
1190 lnput#al:i$
1200 w1-0
1210 Print#ai:"BVtEWOFF,'
1220 pilnt
1230 Print
124O For i:l to 9
1250 Gosub8000
1260 Gosub6000
1270 lf z-0 then goto I3O0
1280 Printw1;': Waveformfrom DataFileFtL';tl
1290 Goto1310
1300 Printw1:n: ........not written.FlL,,;tl;,,not used.,,
1310 Wl-w1+1

6-53

Maintenance-

4g4[l4g4Ap ServlceVot. 1

1320 T1-t1+1
1330 Nexti
13a0 S1:0
1350 Print
1360 Print
1370 Print
1380 For i-1 to 10
1390 Gosub5000
1400 lf z-0 then goto 1400
1410 Prints1;'- Settingsfrom DataFile";t1
1424 Goto 1440
14i10 Prints1;"-........ not written.FIL';TI;,.not used"
1440 S1-sl+1
1450 T1-t1+1
1460 Next i
1470 Print#al:i$
1480 Print
1490 Print
1500 Print
1530 Print
*rn
1540 Printo*r FINISHED
1550 Goto10000
2000 !This routinemovesdata from the spEcrRUM ANALYZERto TAPE
2010 Deletevar i$
2020 Dim i$ to 700
2030 Print#at:"SET?"
2040 Input#al:i$
2050 Dir
2060 Print
2070 Print'WARNING!This couldoverwriteexistingfiles!"
2080 Print'Enterthe Numberof the lasttape file: ',f
2090 Inputt1
2100 Gosub9000
2110 Print
2120 Print
2130 Print#a1:"BVtEW
OFF,'
2140 W1:0
2150 For i-l to g
2160 Gosub3000
2170 Gosub7000
2180 lf z-0 then goto 2210
2190 Printwl;': Waveformsent to FileFlL,,;tl
22A0 Goto2220
2210 Printwl;":.,...... skippedover.FlL";t1;',
is empty*
2224 Wl:w1f1
2230 T1-tl+1
2240 Next i
2250 Print#a1:i$
2260 | Settingsare sent to tape
2270 S1-o
2280 Print
2290 Print
2300 Print
2310 For i-1 to 10
2320 Gosub4000
2330 lf z:0 then goto 2360
2340 Printsl;"- Settingssent to FileFlL,,;tl
2350 Goto 2370
2360 Printsl ;"- ........skippedover.FlL";t1
;,'is empty.,'

6-64

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o
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I

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t

Mafntenance-

494A1494Ap
ServiceVot. 1

237A 51-sl+1
2380 T1-tl+1
2390 Next i
2400 Print#a1:i$
2410 Print
2420 Print
2$A Print"... FINISHED'.."
2440 Goto 10000
3000 ! AcquireWaveformand Settings.
3010 X? i.r 500 pointwaveform,t$ G towerreadout,
i
3020
lm$ is upperreadout,and €g is an er-i i"""ag"
3030 Deletevar eg,hg,lg,m$,x9
3040 Z-O
3050 Dimh$ to 1100
3060 Integerx9 (1000)
3070 Dim l$ to So,m$to 50
3080 Print #a1:"SAVEAOFF;DRECAL
A:",wl
3090 Print#al:"ERR?"
3100 Input#al:eg
3 11 0 E$*seg(e$,5;2)
3120 lf e$<>'62'then goto3190
3 1 3 0v-0
3140 X9:0
3150 M$-""
3160 L$*",'
3170 Goto 3280
3180 V-1
3190 Print#al:"UPRDO?"
3200 lnput#al:m$
3210 Print#al:"LORDO?'
3220 Input#a1:l$
3230 M$-seg$(m$,8,40)
3240 L$-seg$(l$,8,40)
3250 PTint#a1:NVFMWFID:A,ENCDG:BIN;CURVE?..
3260 lnput using"la,*Bo/o'dels'," #al :h$,x9
3270 Z-1
3280 Return
4000 ! Removememorysettings(S$)from SPECTRUM
ANALYZER
4010 Z-0
4020 Deletevar sg
4030 Dim s$ to 700
4040 Print#al :'RECALL,,:s1
4050 Print#a1:.ERR?,
4060 Input#al:eg
4070 E$-seg$(e$,S,2)
4080 lf e$<>'62" thengoto4120
a090 V1:0
4100 S$-"NULL"
4110 Goto4170
4120 Print#al :,,SET?,'
4130 Input#a1:s$
4140 Print#al:"ReS OFF"
4150 V1-1
4160 Z-1
4170 Open#1 00:"FtL"&str$(r1)&'{opE:REp,stz_1
020),,
4180 Print#100:v'l,s$
4190 Close100
4200 Return

6-65

Malntenance-

494[l4g4Ap ServtceVot. 1

5000 ! Retrievetaped settings (s$) and sendto memorytocations(s1)
5010 Z-0
5020 Deletevar s$
5030 Dim s$ to 6zt0
5040 Open#100:"FtL"&st6(t1)&'(ope-otd),,
5050 Input#100:v1,s$
5060 lf v1-0 then goto SiSO
5070 lf Y-0 then goto 5120
5080 Print#a1:"RECALL
";s1;,';ReSOFF;WAIT;ERR?,
5090 Input#al:e$
5100 E$:seg(e$,S,2)
5110 lf e$<>"62'thengoto51S0
5120 Print#a1:s$
5130 Print#a1:"STORE";s1;":ReSOFF,,
5140 Z-1
5150 Close100
5160 Return
6000 I Sendwaveform(X9)& readouts(M$,L$)to memorytocation(Wl)
6010 z:0
6020 lf v-0 then goto 6180
6030 lf Y-0 then goto 6080
6040 PriNt#A1:'SAVEAOFF;DRECNL
A:";Wl;',;ERR?,,
6050 Input#a1:e$
6060 E$-seg$(e$,5,2)
6070 lf e$<>"62" then goto 6190
6080 Print #al:"WA|T:TR|?"
6090 Input#a1:h$
6100 Print#al :"RDOUT'";69.t';r,
6110 Print#a1:'RDOUT',,;l$;"'"
6120 PriNt#A1:NVFMWFID:A,ENCDG:BIN;SIG;SAVEA
ON6130 Wbyteatn(mta,32+a1),x9,eoi
6140 Wbyteatn (unt,unt)
6150 Print#a1:'DSTOREA:...wl
6160 Print#a1:h$
6i7a z-1
6180 Return
7000 ! Storereadouts(M$,L$),and waveforms(X9)on TApE Fite(I1)
7010 Open#1 00:'FtL"&strg(tl)&,IopE-REp,St2_doOO).
7020 M$:m$
7030 L$-t$
7040 Print#100:v
7050 Print#100:m$
7060 Print #100:l$
7070 Print #100:xg
7080 Close100
7090 Return
8000 ! Retri€vesreadouts(M$, L$), and waveform(X9)from TApE
8010 ! From setectedTAPEFite [r1)
8020 Open#1 00:"FtL"&strg(tl
)&(ope-otd)',
8030 Deletevar x9,mg,tg
8040 lntegerx9 (1000)
8050 Dim m$ to SO,tgto SO
8060 Input#100:v
8070 Input#100:m$
8080 Input#100:t$
8090 Input#100:x9
8100 Close100

6-66

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Maantenance- I94Al4S4ApServiceVol. 1
8110 Return
9000 ! This routineshowsthe contentsof Memory
dispraysand settings
9010 Print"DisptayMemory',
9020 Print
9030 Print#al:,'ReS OFF'
9040 Deletevar sg
9050 Dim s$ to 660
9060 Print #a1:"SET?'
9070 Input#at:s$
9080 Wl-0
9090 For i:t to 9
9100 Print#at:,SAVEA:OFF;DRECAL
A:";w1
9110 Print#al:"ERR?"
9120 Input#a1:eg
9130 E$-s€gg(e$,5,2)
9140 if e$:"52' then goto 9170
9150 Print w1;"- Waveform"
9160 goto 9180
9170 Printwl;"*.........
9180 Wl:w1+1
9190 Next i
9200 ! NOTE:"RECALL"may recaila RQS_ON
9210 ! state,so this must be turnedotf atain by
ReS OFF
9220 Print
9230 Print "settingsMemory.'
9240 Print
9250 51-0
9260 For i-l to 10
9270 Print#a1:"RECALL',;st;',;ReS
OFF;WA|T,,
9280 Print#al:,,ERR?"
9290 Input#al:e$
9300 E$-seg$(e$,5,2)
9310 lf e$-'62" then goto 9g4O
9320 Print sl:"- Settings,,
9330 coto 9350
9340 Printsl;"- ........'
9350 S1-sl+1
9360 Next i
9370 Print
9380 Print#a1:sg
9390 Return
10000End

6-67

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Secton 7 -

494A1494ApService,Vot. 1

THEORYOF OPERATION
This sectiondescribesthe spectrurnanalyzer
circuitry. The section beginswith a functionaldescriptionof
the maiorcircuitblocks' This is fotloweJ6y'ror"
detaileddescriptionsof the circuitrywithin each block.
while readingthese descriptions,refer to
the corespondingblock or schematicdiagramin volume2 of
the
serviceManual' The description'tittes
use ir,e oi"grar nam-esand numbersfor easy reference.
The FunctionalBlock diagram,locatedat
the front of the Diagramssectionin Volume 2. shows how the
majorsectionsin the instrumentrelateandihe.paths_of
*o.1 r-"pr signals. Block diagramsshowingmore

L::*;ffi?#:llr:*tions

rollowttreFunctiinat
Brockoiagr;;. Gircuitschematicliasrams
ror6wthe

Adjacentto each schematicis a third level of
block diagram,a circuit
parts locationillustration,and
cross-reference
look-uptables.The third level block diairam'snows board
the functionof the Lornpon"nt"shown
on the schematic' The parts locationillustration
ano tooi-uf t"or". aid in findingcomponentson eitherthe
schematicor circuitboard.

FUNCTIONAL
DESCRI
PTION
What lt Does
The spectrumanalyzeracceptsan electricalsignal
as its input and displays the signal,sfrequency
com_
nn:t:.9n a crt. Signatscan beapptieddirecilyto the
RF fNPUTor throughan externalmixer.
The displayof the input signatappearson the
crt as
a graph where the horizontalaxis is'frequ€ncy
and the
v.ertjcalaxis is arnptitude.The disptaycan be ptotted,
i,
desired,by connectinga chart recorderthrougn
rear_
panelconnectors.The displaycan also
be transmitted
digitallyvia a |EEE4gg GeneiarpurposeInterface
Bus
(GPIB)to a GptB-compatible
ptotter.
The programmableversion can be operatedeither
front-panetcontrots,or remotetyvia rhe
T:H"lll.*jih
\rFtE wtrnan easy_to_use
programming
language.
How lt Works
The Spectrum Analyzer operates as a swept,
narrow-bandreceiver. The crt beammovesnorizontatty
as a range of frequenciesis spanned. When a
fre_
quency componentof an input signatis
detected,the
beamis deflectedverticallyas a fuiction oi inprt power
at that frequency.
Frequencyis measuredby countingthe local oscillator lrequencies
againsta reference.Amplitudeis measured by catibratingthe REFERENCELEVEL and
RF
attenuator.A master microcomputerperforms
control,
storage,signal processing,and communications
func_
tions.

First, Second, and Third Converters
Swept-frequencyanatysis is achievedby a triple'the
conversion superheterodynetechnique. Each of
three frequencyconvertersconsists of a rnixer,a local
oscillator,and appropriatefilters. Onlyone frequencyis
converted in each mixer to pass through bind_piss
filters to the detector. This frequencycan be changeO
by tuning the local oscillator trequencyin the first or
second convErters.The third converteruses the fixed
100 MHz calibratorsignal as a stable local oscillator.
An externalsourcemay also be used as a referencefor
the 100 MHz calibratorand third converter.
The first converter. usually referred to as the front
end,. converts the input signal frequencyto an intermediatefrequency(tF) of either g2g MHz or ZO72MHz,
dependingon which band is in use. The internalmixer
converts signals over the input range of 10kHz to
21 GHz. Externalmixers may be used for signalsinto
the millimeterwavelengths.When the internalmixer is
used, a preselectoror low-pass filter is insertedin the
signal path to reduce unwanted signalsor imagesand
spuriousresponses.
One of two second converters is automatically
selected for each band so the input fr6quencyrange
does not overlap the first lF frequency. Each second
converterhas its own local oscillator(LO),mixer, and
filters. Both down-convert
the signalto 110MHz which
is sent to the third converter.
The third converteramptifiesthe 110MHz lF signal
and converts it to the final intermediatefrequencyof
10 MHz. The third converter passes the signalto the

7-1

O

Theory of Operation- 494A/494ApService, Vol. 1

mainlF sectionfor processingand detection.
lF Section
This section processes the signal for frequency
resolution. Several functions are performed here:
bandwidth filtering, amplitude calibration and logarithmicconversion,and signaldetection.
The 10 MHz lF signal is processedthroughone of
sev€ralband-passfilters selectedby the RESoLUTIoN
BANDWIDTHcontrol. In the auto mode the microcom_
puter will sel€ctthe best combinationof bandwidthand
sw€eptime for the selectedspan, unlessoverriddenby
the operator.
Weak signals can be amplifiedby a set of switchable amplifiersso the dynamic display range (v€rtical
window) ls shifted up or down. The REFERENCE
LEVELcontrolselectsth€ gain and inputRF attenuation
to frame this windowbetweenthe referencelev€lat th€
top of the displayscreenand the bottomof the display.
A levelingcircuit helps provide flat frequencyresponse
across the range. The signal is amplifiedby a logarithmicamplifierto producethe verticalsignalcalibrat€d
in dB/div.
The detector produces a voltage that corresponds
to th€ input signal strength in decibels. The detector
outputis then sent to the verticalchannelof the display
sectionto drive the verticalaxis of the crt and display
the signal.
Display Section
The display section draws the signal on the crt
screen. Vertical deflection of the beam (y axis) is
increased as th€ output of the amplitude detector
increases.The horizontalposition(X axis) of a signalis
controlled by th€ frequency controt section and
correspondsto the frequency of the detectedsignal.
The Z axis, or brightness,is controlledby th€ INTEN_
SITYcontroland the Z axis blankingcircuits.(However,
markerbrightnessis actuallycontrolledby stoppingthe
digital storage sweep for a period of time to brighten
the spot.)
As the spectrumanalyzer spans from low to high
frequenciesthe beam sweeps from left to right. When
the spectrumanalyzertunesthrougha signalfrequency,
a vertical deflectionshows the strengthof the signal.
The result is a signal displayedat a position on the
span that correspondsto its frequency,or in other
words,the displayshowsamplitudeas a functionof freguency.

7-2

The video amplifier scales the detector output for
vertical deflectionin dB/div or performs a log/linear
conversion,depending on the vertical display mode.
The video processor provides additional bandwidth
filteringit eitherthe wide or narrowfilter is selected.
The display section also provides crt readout to
show control settings and measurementdata. This
readoutis basedon data from the microcomputer
which
is reading the settings of the front panel controls or
data on the instrum€ntand GPIB buses.
Digital storage circuits provide two functions;they
provide a flicker-free display at slow sweep rates, and
they store the display for later viewing. Up to nine
different displays with their readouts can be stored in
the battery-poweredmemory. The stored display data
can then be transmittedthrough the IEEE-488port to a
plotter,or for programmableinstrumentsto GPIB compatiblecontrollersor instruments.
Frequency Control Section
The spectrumanalyzersweepsthrougha frequency
range that is set by the frequencycontrol section. The
CENTER/MARKER
FREQUENCYcontrol sets the frequencythe l st and 2nd local oscillators.
The output of a sweep generator is scaled by a
span attenuatorto sw€ep a range or span of frequencies. The output of the span attenuatordrivesthe lst
LO for wide spans and the 2nd LO for narrow spans.
The output sweep also deflects the crt beam across the
horizontal axis as the local oscillatorsar€ swept so the
displayis a spectrumof power versusfrequency.
The frequency control section also tunes the
pr€selector so it tracks the signal frequency being
detectedoverthe 1.7 to 21 GHz range.
Counter and Phase Lock Section
The Counter, Harmonic Mixer, and Auxiliary Synthesizer form the nucleus of the frequency control
hardware. Both the l st LO and 2nd LO frequ€nciesare
controlledvia the firmware-basedcontrol loop. Oata
from the Counter is used as feedbackto control the
oscillatorfrequency. Accurate signal frequencymeasurement is possible by countingthe frequencyof the
3rd lF.
The Phase Lock system stabilizesthe 1st Lo frequency. This minimizes display jitter and increases
resolution.

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Theory of Operation- 4g4A/4g4ApServlce,Vol. .l
Digital Control Section
Operational modes and internal functions
spectrumanalyzerare selectedand controlled of the
from the front panel. The modesanOtunctions directly
that are
selectedare processedand activatedby the
instrument
mastermicrocomputerwhich tarksand iisten"
to ail
cuits over the instrumentbus. ttre progiammable cir_
ver_
sion can also be remotelycontrolledfrim
an external
controilerthroughthe IEEE_4gg
(GplB) connector. This
connectorinterfacesto the instrument
microcomputer
throughthe GptB.
Front panel control and sel€ctordata is processed
by a front panel CpU that interrac"" *itt
the master
microcomputerover the instrumentbus. The
master
microcomputerreceivesand sendsall of its
information
over the instrumentbus to th€ intemal circuits.
The
programmable
version communicateswith other instrum€ntsthroughthe GplB connector. The programmable
controllanguagecorrespondsto tront_panel
controfs.

Power Supply Section
The power supply s€ction provides regulateddc
power and forced air cootingfor all circuits within
the
instrument.The switchingsupptyis capabteof providing regulatedvoltagesover a wide range of input line
frequenciesand voltages. The coolingsystemconsists
of an intake on the bottom of the cise, air passages
within the instrument,a fan, and a rear panel exhaust.
Air is routedto all sEctionsof the instrumentin proportion to th€ heat generatedby circuitswithin thoie sections. Internaltemperaturevariationsare minimizedto
providereliableoperation.
Other Sections
Interconnectionsbetween assemblies are made
through a common Mother board. Most circuit board
assembliesplug into the top side of the Motherboard.
Assemblieson the RF deck are connectedto the bottom side of the Mother board throughcables and con_
nectors.

7-3

Theory of Operation -

4g4Ll4g4ApService, Vot. 1

DETAILEDDESCRIPTION
The followingdescriptionis arrangedby sectionsor systems;such as lst Converter,2nd Converter,etc.,
followed by circuit analysisof the circuiiswithinthat section. Each systemor section is introducedwith a
descriptionof the system using the sectionblock diagramfound in ihe oiagrams section of the Service
Manual,Volume2. This is followedby a descriptionof Lach cireuitboard or miajorcircuitwithinthe system.
The appropriateblock or schematicdiagramnumberis includedin the text h6adingsfor each section or
part.

1ST CONVERTER
(Diagram2)
SECTTON
The 1st Converter consists of the 0-60dB step
Atenuator, PreseleCtor,lst Mixer, .lSt LO, power
Divider, Transfer Switch, 2.OT2GHz DirectionalFilter.
Diplexer,and two 4.5 GHz Low-pass Filters. Externai
circuits that control or drive the assemblieswithin the
l st Conv€rter are: the preselector Driver, 1st LO
Driver, Counter and phase Loek system, and the RF
Interfaceboard.

The spectrum analyzer uses two intermediatefreguencies(2472MHz and 829 MHz) to preventbasetine
rise caused by local oscillator f€edthroughand crossover of intermodulationproducts. The 2072MHz lF is
selectedfor band I and for bands 5 and above. The
829 MHz lF is select€dfor bands2-4.

RF Interface Circuits (Diagram28)
The 1st Converterconvertsthe incomingRF signals
to the lst lF. lncomingsignals are applied througha
calibrated0-60 dB decade attenuator(AT10)to a fitter
select switch (S12). Signats in band t (t Ok|-tz to
1.8GHz) route through a Limiter (A10) and 1.gGHz
Low-PassFilter (FLl0) to the .tst Mixer (A12). Signats
in bands 2 through S (1.7 to 21 GHz) route througha
tunable Preselector (FL12) and a g dB Attenuator
(4T11)to the mixer.

The RF interfacecircuits receiveinstructionfrom the
microcomputerand produce control signals for the RF
Attenuator, the Transfer Switch, and the lF Select.
TheseRF controlcircuits are located on the Z-Axis/RF
Int€rfaceboard (A70) and their operationis described
underthe z-Axis board part of th€ Displaysection.

lst Converter(Diagram12)

The RF signals mix with the output from a tunable
localoscillator(A16)to generateproductsat one of two
intermediatefrequencies,dependingon the bandin use.
The 1st Mixer output goes to DirectionalFilter FL16
through Transfer Switch S1B. The transfer switch
allows input from the EXTERNALMTXERinput,except
in Option 07 and 08 instruments.In Option 0Z anO0g
instruments, the EXTERNAL MTXER capability is
deleted.

RF Input

The EXTERNALMIXERinput permits an externallF
source (externalmixer) to be connectedto the instru_
ment. The lF signalsfrom external mixers are routed
through the Transfer switch to the DirectionalFilter.
This feature allows much higher input frequenciesby
usingwaveguidemixers.

The RF input signal goes through a 0-60 dB Step
Attenuator(AT10)consistingof relay-controlled
10d8,
20 dB, and 30 dB sections. The relaysare actuatedby
controlsignalsfrom the RF Interfacecircuit.

The direetionalfilter separates the 2OTZMHzand
829 MHz intermediatefrequenciesfor the 2072MHz
2nd Converter(A18)or 829 MHz 2nd Gonverter(A23).
The 2072MHz lF is apptiedthrough a 4.5 GHz Low_
Pass Filter (FLl1) to the 2072MHz 2nd Converter.The
829 MHz lF is fed througha Diptexer(A14)and another
4.5GHz Low-PassFitter(FL1S)before it is apptiedto
the 829 MHz lF stages.
7-4

TheRFINPUT50() connector
acceptsthe inputsignals in bands 1 through 5. Higher frequenciesrequire
external waveguide mixers that use the EXTERNAL
MIXERinput,alongwith the LO outputs.
Option 07 instrumentshave a75A input in place of
the EXTERNALMIXERconnector. TransferSwitch S13
selectsbetweenthe 50O and 75O inputs.

PreselectorCircuits
Coaxialswitches311 and 512 are relaysthat select
eitherthe low-passfilter (FLl0) and Limiter(A10)or the
Preselectorand 3 dB attenuator(AT11)for the RF signal path. The relay coils are driven by circuitryon the
PreselectorDriver board. The low-pass filter path is
used for band 1, and the Preselectorpath is used for
bands2 through5.

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Theory of Operation -

_ The 2GHz Limit€r(A10) operatesfrom 100kHz to
2 GHz. lt has a lineartwo-porttransfercharacteristic
of
unity (-1 dB) until the input exceeds+5 dBm.
Above
this point, the internai detEctor OioOes
conduct,
reflecting part of the RF input energy
back to the
source.. A:
lhe input level rises, the-Limiter reflects
more signal,.limiting
the amountthat can pass through
the mixer, thus protectingthe mixer from
being over_
driven.
The 1.gGHz Low-pass Fitter (FL10) strips
incoming signal of any frequen"y cbmpon"nts the
above

1.9911.andpassesdtt treiueniy

1.8 GHzto FitterSetectorswiicnSi2."olnion"nt.o"ro*
The presetector(FL12) is a 1.7-1gGHz yttrium_
lron-Garnet(ylG) filterthat providesnigh setectivity
anO
y1S"-jl"qyency rejection. Tuning c-urrent,which is
near 500 mA at 21 GHz, is provideJby the preselector
Driver (A42) circuits. The presele"ior op"rates
on
bands 2, g, 4, and S. Becausethe preselector
is sensitive to outputtoadimpedance,a g dB Attenuator(AT11)
is insertedbetweenthe pr€s€lectoroutputand
one port
of the FitterSelectswitchto hetpisotateoutput
loading.

4g4Al4g4ApServtce,Vot l

1st Local Oscillator
The lst LO (A16) is a ytG (yttrium-tron-Gamet)
oscillatorthat has a tuning range of 2.072 to 6.4 GHz.
The oscillator assembly includesthe interface circuit
board that couples operatingand tuning voltagesfrom
the l.st LO Driver, Span Attenuator,and Error Amptifier
circuitsto the oscillator.
The +15 Vl voltage providesoperatingbias for the
p,l"jl1!or.- The_suppty is protected and iecoupted by
VRl 010,Cl 0t 6, and L1011. Th: s9c9ndsuppty,+t S t2:
is not used in this instrument.VRlolg anctVR1019
clamp transientvoltagesfrom the tune voltage coil. lt
atso protects the driving circuits from the transients
inducedwhendegaussing.
When the FM coil is used to sweep the osciilator,
relay K101S closes and couptesC1d12 and C1014
across the tune coil, The capacitorstower the noise
bandwidthof the main coil drivingcircuit while the FM
coil is in operation. The heater provides temperature
stability.

1st Mixer
The 1st Mixer {A12)circuit consistsof a single
bal_
anced mixer,a coupler,and a g0ophaseshifter.
A balanced mixer inherentlyhas less conversionloss
com_
Par€d to an unbalancedmixer, and local oscillator
feedthroughto ths RF port is minimized. The
locat
oscillator input is split through a broad-band
multisection coupler whose outputeare equal in power
but
9p deoqegs.out of phase. an aOOiitonat
tiO degree
phase shift is cascadedwith the appropriate
signal to
create a 180 degree phase differencettrat is
ipptied
across a pair of series-connected
Schottkydiodes.The
result is that the diodesare alternatetyswitcned
on and
off as the local oscillatorcycles.
The node betweenthe two diodes is isotated
from
by about O0dB so the RF input is
11"-,,1^"j
!O
^ilpu.
apptteo to this node. The blocking capacitor
at the
input connector permits broadbandsignal application
from the RF port, whileblockingthe dc'diodebias
from
g.etting.
to the RF port and the ipectrum analyzerinput.
Mixer bias is suppliedfrom the ist LO Driverboard
via
the 829 MHz lF circuits,4.5 GHz Filter,Diplexet,
Direc_
tional Filter,and TransferSwitch. Bias returnis through
assemblyA11 to ground.
Excludinglossesin the lF filteringcircuitry,the fun_
-Conuener
dam€ntalconversionloss of ths l st
is about
14 dB, and the thirdharmonicconversionloss is about
24.d8. The.Schottkydiodes are mountedin a
mixer
suo-assembty(A12A1)so that they can be
easily
replaced.

Power Divider
The Power Divider(A13)splits the output of the 1st
LO (YlG osciilator)to isolatethe 1st Mixei from thg tst
!O OUjP,qT .front-panet connector. Basicaily, the
Power Divider is two multi-sectiondirectionalcouplers
that are cascaded to produce two ports having equal
power. The isolationbetweenoutputports is 15 dg or
mors at the op€rating frequency. The power Divider
also providesan improvedload to the local oscillator.

Transfer Switch
The Transfer Switch (S13) is a three-port coaxial
relay that selects 1st lF signals from either the 1st
Mixer or from the EXTERNALMIXERinput. This allows
the use of an externalmixer by by-passingthe lst Converter circuitry. The function is controlledby circuitry
on the RF Interfaceboard. lt is autornatically
actuated
when waveguidebands ars selectedor the front-panel
EXTMIXERpush buttonis pressed.
ln Option07 and 08 instruments,the externalmixer
capability is detet€d. In those instruments, W125
directlyconnectsthe 1st Mixer outputto the Directional
Filter. In Option 07 instruments,the transfer switch
selects between the 50O and 7SO inputs to feed the
Step Attenuator.

7-5

Theoryof Operation-

4g4A/494ApService,Vot. 1

Directional Filter

2072MHz lF Filters

The DirectionatFitter (FL10)couptesthe 2072MHz
signalto the 2nd Convertervia low-passand band-pass
filters FLl1 and FL14. As mixing products iass
through FL16, they induce a selected current into a
one-wavelengthdistributed dng, which couples the
2072MHz lF signatout to the tow-passfitter FLl t. The
remainder of the intermodulationproducts pass on
through since the ring is excited only with ZiOZZl/r{z
signals. The bandwidth of this Dirirctional Fitter is
approximately45 MHz. The unfiltered signals are
passedon to the Diplexer.

The 2072MHz signal, from the Directional Fitter,
passes througha 4.5 GHz Low-PassFilter {FL11}.The
signal is then sent through a 15 MHz band-passfilter
(FL14) which reiects intermodulationproducts either
side of the 2072MHz lF.

7-6

Diplexer and Filter
The Diplexer (A14)passes the 829 MHz tF signal
from the mixer output through a low-passfilter (FL15)to
the 2nd Converter. The Diplexerand DirectionalFilter
provide a broadbandimpedancematch to the l st Mixer
lF port. This match contributes to thE overall flatn€ss
and frequencyresponseof the analyzer.

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Theory of Operafon -

4g4A/494ApServlce,Vot. i

2ND CONVERTER
SECTTON
(Diagramg)
Two 2nd ConvErtersystgms are used in the spec_
trum analyzer. One converts207ZMHz to 110 MHz
and the other convertsg2g MHz to 110 MHz. The con_
verter used is determinedby the frequencyband being
conveted. The lF selectionfor each banOis snown in
Table7-1 along with the band frequencyrangeand the
local oscillatorfrequencyrangE. two 2iO lFs are used
by the analyzerfor the followingreasons:

o lf the lst tF is inctuded in the frequencyband
being converted,it is possiblefor some input signals to pass un-convertedthroughthe lst c6nvert6r
to the 2nd Converter,appearingat ttre lst lF. The
resultingspurioussignat would cause the baseline
level on the screento rise and obscurereal signat.
Two 2nd converters avoids the problem by usiig a
1st lF not in the band beingconverted.

I With two lF'S, lF feedthroughin band 2 and higher
orderspursin bands3 and 4lan be eliminated.

. Because of the limited tuning range of the
719MHz LO, the lower lF cannoibe used above
band4.

The 2072MHz 2nd Convertermixes the 2072MHz
from the 1st Converterwith the output trom a 21g2 MHz
phase-locked2nd local oseillator. This local oscillator
is sweptand tuned over a 4 MHz range. The 2A72MHz
input tF signal is passed through a four-cavitybandpass filt€r (FL14)to ailow onty the 2OZ2MHz.tsi tf signal to pass through a1d pr€vent other signals, geierated within the 2nd Converter, from getting
back to
-combines
the lst Converter. A diode mixer
the
2072MHz lF input and the local oscillatorsignatsto
generatethe 110MHz lF output which then passes
through a 110 MHz fow-pass fltter to reject any higher
ordersignalsfrom the mixer.
The 829 MHz 2nd Converteruses a phase-locked
voltage controlled oscillator to produce the Z1gMHz
signal that is mixed with the g29 MHz first tF signat.
The swept 2182MHz 2nd Local Oscillatoris usectas a
referencefor the phasetockedoscillator.The 719 MHz
oscillator can be disabled upon command from the
microcomputerin the tF selectionprocess. The phase
lock circuit maintainsa constant relationshipbetween
the two local oscillatorsas the 719 MHz oscillatoris
sweptand tunedover a 1.33MHz range. A four section
coaxial band-passfilter is used before the mixer to
excludeany RF signalsother thanthe d€slredg29 MHz.
Again,a diode mixer is used to mix the g29 MHz input
and local oscillator signals to produce the 110 MHz
secondlF output.

Tabte7-1
2NDCONVERTER
IF SELECTION
Band

Range

1
2
3
4
5
6
7
I
I
10
11
12

50 kHz-1.8GHz
1.7-5.5GHz
3.0-7.1GHz
5.4-18.0
GHz
15.0-21.0
GHz
18.0-26GHz
26-40.0GHz
40.0-60.0
GHz
50.0-90.0GHz
75-140.0GHz
110-220
GHz
170-325GHz

2nd LO Range

2182 r.2.25MHz
719 *0.75 MHz
719 *,0.75 MHz
719 *0.75 MHz
2182x.2.25MHz
2182 *.2.25MH?
2182 *,2.25MH2
2182 *.2.25MHa
2182 *.2.25MH2
2182 *.2.25MH2
2182 *.2.25 MHz
2182 *.2.25MH2

lst lF
2072MHz
829 MHz
829 MHz
829 MHz
2072MHz
2072MHz
2072MHz
2072MHz
2O72MHz
2072MHz
2072MHz
2072MHz

7-7

Theory ot Operation-

494A/4g4ApServlce,Vot. 1

COUPLING HAT

COUPLINGLOOP

FREOUENCYDETERMININGGAP

F I L T E R TOP

J

cAvrrYPosr+

l+

FtRsr cAVrry

INTER-cAVttt*ott"raoND
cAvrry
2727-707A

Figure 7-1. Ctpsr section of a four-cavltyfiltee

Selectionbetweenthe two 2nd lF signalsalso takes
place within the 829 MHz convertersystem. A diode
switchingnetwork connectsthe activej10 MHz 2nd lF
signalto the outputto drivethe grd Converter.

2472MHz 2ND CONVERTER
(Diagram12)
The 2072 MHz 2nd Converter converts the
2O72MHz signal output from the 1st Convener to
110 MHz for eventualapplicationto the grd Converter.
The assemblyconsists of a four-cavityfilter connected
to a narrow band mixer through an external cable, a
110 MHz low-passfilter, and a mixer-biasing
circuit.

This filter has a 1 dB bandwidthof 15 MHz and an
insertionloss of 1.2 dB. Eachend resonatorls capacity
coupled to external circuits through a coupling hat
pluggedinto a 3 millimeterconnector.Intercavitycoupling is provided by coupling loops that protrude from
the machinedfilter top. The resonantfrequencyof each
cavity is determinedprimarilyby the depth of a gap in
the undersideof the filter top, and is fine tuned with a
tuningscrew on the side of each cavity. All of the tight
machiningtolerancesare confinedto the top. Thus,the
main cavity milling need not be a high precisionpart.
When properly tuned, using a network analyzer,the
filter return loss is greaterthan 25 dB from either end
(in a 50 ohms system). Figure7-1 shows a cross sectional view of the filter, and Figure 7-2 shows the
equivalentelectricalcircuit.

Four-Cavity Filter
The four-cavityfilter (FL14) is a low-loss narrowband fifter that only pass€s lhe 2072MHz IF signal to
the mixer. Any other frequenciesare reflectedback to
the lst Converterand terminated. In addition.the filter
prevents the converter LO and mixer products from
enteringthe 1st Converter.

7-8

Mixer Circuit
The mixer circuit consists of a single-balanced,
two-diodemixer, a bias circuit for th€ mixer, a delay
line,and a 110 MHz low-passfilter.

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Theory of Operaton - 4g4A/4g4ApService, Vol. .l

RF INPUT

j--"ou"'-'T'oo"---l
RF OUTPUT

+FoI

Q+r

h

TUNINGSCREW

,

CAVITY 1

CAVITY 2

lh

I

CAVITY 3

CAV!TY 4

2727-1o2A

Figute 7-2. Equivalentcircuit of the four-cavity filter.

2072MHz RF from.the four-cavity fitter (FL14)
enters the mixer, where it is switchedon anOoff at
a
2.182MH2rate by the the mixer diodes. Both mixer
diodes are tumed on and off by the 2lg2 MHz 2nd
LO
signal. The difierence frequency of 110MHz
is
separatedfrom the other mixer productsby a low-pass
filter for use as the tF output. Attnougnth! diodes
are
connectedfor opposite polarity, both are tumed on
at
the same time becauseof ths 1g0 degree phase shift
delay.line in.the input path to one of t[e diodes. Note
that the diodesare matchedand must be replacedas
a
pair lf one fails.
At the output of the mixer. the two inductorsand
one capacitorform a low-pass filter that passes unat_
tenuated110MHz signat to the g2gMtiz 2nd Converter,via coaxialconnectorplg2. Dc_blocking
capacitors at the three inputs to the mixer, keep tne diode
bias from being applied to the RF and locat oscillator
lines.
The bias circuit, which consists of operational
amplifierUl014 and the associatedcomponents,
establishes th€ bias for the mixer diodes and atso provides
the meansfor effectivelyswitchingthE mixer oif
lunder
control of the microcomputer). When the mixer
is
active, each diode has approximately2 mA of forward
bias. For this condition,the tF SELEbTsignalfrom the
Z Axis/RF lnterface circuits
lappti-eO through

feedthroughcapacitorC182) is low. This causes the
outputfrom U1014Ato be at +14 V and the outputfrom
U10148to be -14 V. DiodesCR1O14
and CR101gare
therebyreverse-biased.Thus,the seriesresistancesof
potentiometerR1019 plus resistor R1014, and poten_
tiometer Rl010 plus resistorR1017,provideforuvard
bias to the diodes. The potentiometersare set to balancethe bias levels.
In op€ration where the mixer is not active,the lF
SELECTsignal is high. This reversesthe statesof the
Ul0'14outputsand foruvardbiasesdiodesCRl014and
CR1018. With these diodes conducting, resistors
R1014,R1016,R1017,and R1018form two voltage
dividersthat set the reversebias, to the mixer diodes.
at 5 V. This effectivelyturns the mixer off and attenuatesthe 110 MHz signalby about55 dB.

PrecisionExternalCabtes
The externalcablethat connectsthe four-cavityfilter
output to the mixer RF input (W140)and the external
cable that connectsthe 2nd LO to the mixer LO input
W222) are both criticattengthcabtes.

7-9

Theory of Operation -

494A/494ApServtce,Vot. 1

Fllter to Mlxer RF Input Cable. Several products
and harmonicsof the local oscillatorand RF input frequencieswill exit the mixer via the RF input port of th€
mixer. The image (RF input minusthe 2nd LO) and the
sum (RF input plus the 2nd LO) are two significantpro_
ducts. There is enoughenergyin these two signalsto
warrant efforts to r€coverthat energy.
Onfy the RF signal at 2072MHz can pass through
the four-cavity filter. Thus, any other signal frequeniy
that is applied to th€ filter (that is, signils exiting thi
mixer via the RF port) is reflectedback to the mixlr by
the filter. lf the cablebetweEnthe filter and the mixeris
the correct length,the most slgnificantreflectedsignals
(i.e., the image and th€ sum) can be returnedto the
mixer in phase and convert€dinto additional€nergyat
the intermediatefrequency. This technique is called
"image enhancementmixing,,and typically improves
conversionloss by approximately3 dB at the design
frequencies.
The image frequency,in this instance,is very near
the RF frequency. A very sharpcut-offfilter is required
to pass the RF, yet refl€ctthe image. The four_cavity
filter performsthis function.

2nd LO lo Mlxer LO Input Cable. The image and
sum products are also present at the LO port of the
mixer. These signals leave the mixer via the cable to
the 2nd LO and are reflectEdback to the mixer by the
LO .The oscillatorsresonatorappears highly reflective
to the image and sum signalsbecauseit is tunedto the
LO frequency. Again, the length of the cable from the
LO to th€ mixer LO port is adjustedso the lmage and
sum signals are rEflectedback to the mixer, in the
proper phase, for re-conversionto suppty additional
energyat the lF frequency.

2182 MHz PHASELOCKED2nd LO
(Diagrams13 and i4)
The 2182 MHz phase locked2nd LO assemblycon_
tains a tunable microwaveoscillator,frequencyrefer_
ence, and phase lock circuitry. A two-sectionhousing
containsthe circuitry. Microwavecircuitry is packaged
within the machinedaluminumportion of the housing.
Low frequency phase lock circuitry is within the mumetalcompartment,
In the microwaveor LO portionof the assembly,the
2182MHz MicrostripOsciilatorg€nerates2Ig2 MHz tor
the 2nd convertersand the 2nd LO internal reference
circuitry. The 2200MHz Referencecircuit receivesa
100 MHz drive signal from the grd convert€r crystal
oscillatorand produces100 MHz harmonics. The i2nd
harmonicor 2200MHz is mixed with 21g2MHz from
the microstrip oscillator in the 2Z0OMHz Reference
7-10

Mixer circuit. The differencefrequencyof 18 MHz is
then fed to the phaselock side of the module.
A phase/frequencydetector, on the 16-20MHz
Phase Lock circuit board, compares the 18 MHz
differencefrequency with a signal from a linearized
varactor tuned, 18MHz voltage controlled oscillator.
The det€ctor output tunes the 2182 MHz Microstrip
Oscillator such that the differencefrequency exactly
matchesthe frequencyof the 18 MHz referenceVCO.
Sweep and tune signals from the Span Attenuator
and Cent€rFrequencyControl circuitstune the 18 MHz
VCO. The output voltage from the phase/frequency
detector forces the Microstrip Oscillator to tune the
same amount.
2182 MHz Microstrip Osciltator (Diagram 14)
This oscillatorconsists of a printed 1/2 wavelength
resonator driven by a common-emitt€r feedback
amplifier(01021). The base of Q1021 is capacitivety
tapped into the resonator. The resonatorserves as a
tuned phase inv€rterand impedancetransformer,connected betweenthe base and coll€ctorof Q1021. Part
ot the base feedback capacitanceis provided by a
bendabletab (C'1021).This allows line adjustmentof
the total feedback. This feedback RF signal is
detected, by the base- emitter junction of Q1021, to
produce a changein bias voltagethat is relatedto the
amount of feedback. The base voltage can be monitored at TP1015 with a high impedance voltmeter
without significantlydisturbingthe oscillator.
The dc collectorvoltage and current for Q1021 is
regulated by an activ€ feedback circuit containing
transistorQ2021. Voltageat the junctionof R2023and
L2023is a functionof Ql021 collectorcurrent. This voltage is sensedby Q2021,which alters the base current
to Q1021 thereby regulatingthe collector current and
maintaining+10 Vdc on the resonator. Decouplingand
control of bias loop dynamicsare providedby C2104.
Resistor R2016 swamps the negativebase resistance
of Q102'l to provide stabilization. ResistorR2015protects th€ base- emitter junction of Q1021 trom exc€ssive reversebias in the eventthe +12 V supplyfails.
The oscillator is tuned by varactor diode CR1028,
connectedto one end of the resonator. Decouplingfor
the varactoris providedby the low-passelementsin the
tune fine. Bendabletab C1022can be used to fine tune
the oscillatorcenterfrequency.
Three output taps are coupled to the resonator
through printed capacitors under the resonator. One
output supplies2182MHz througha 6 dB attenuatorto
the HarmonicMixer in the 829 MHz 2nd Converter.The
other two output taps coupl€ LO power through 6 dB
attenuatorsto bufferamplifiersQl031 and Ql0'll. The

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Theory of Opera{on -

amplifiers provide approximatety +10 dBm
to the
2072 MHz 2nd Converterand +g dBm to the Reference
Mixer.
Sinc€ the two buffers are..nearlyidentical,only the
'Oain
2nd Converterbufferis described.
is provicledby
Q1011. printed elements provide input and ortpui
imp:91199matching..Out-of-banddampingis provided
by R1011in serieswith a t/4 wavelengihsnortedstub.
Dc is btockedby G1014and C101t. i t1+wavetength
open stub is used at the output to reflectone of the
2;d
Converter'simage freguenciesat 4ZS4MHz (the other
buffer does not use nor need this stub). Collector
bias
for Q1011is providedthrough Rtfiz; 11011,
the 1/4
wavelength shorted stub. and R1011. The 114
wavetengthshorted stub is groundedthrough C2Oi1
(C2011,Cl0lg, and L1011 aie also used for
decoupling). Coilectorvottageis determinedby divider
R101g
and R2013; this controts the dc te6dback to
the
collector-basejunctionof eloll.
The bias networkis
decouptedfrom the RF path by L1014. DiodeCR2013
protectsthe baseof el01 1 from excessivereverse
bias
if the +12 V supptyfails.

2200 MHz Reference Board (Diagram t4)
_ Th," circuit generates harmonics of the 100MHz
input. The 22nd harmonicor 2200MHz is used by
the
ReferenceMixer. The input 100 MHz signalls apptieO
through€^matching,network lconsistiig of LiOg4,
L1025, C1096, C1029, and Clb2S) to i oinerential
amplifier (01024 and e2024). The €mitters of this
ampfifierare ac coupled through C2026,reducinglow
frequency gain and ensuring balancedoperation. A
snap-ofrdiode (CR2014)is driven by the amplifier,via
transforner T2015, to generate muitipteharmonicsof
the 100 MHz signatinctudingthe 22ObMHz reference.
The outputpassesthrougha 3 dB attenuator,for isolation, to the ReferenceMixer circuit.

t
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22A0 MHz Reference Mixer (Diagram i4)
Signals from the 2200 MHz Referencecircuit are
filtered by a printed 22AOMHz bandpassnner. OioOei
CR1011and CR1012are the switchingelementsof a
single-balanced
mixer. The microstripLscillatoroutput
is appliedto CR1011and through a 1/2 wavelength
derayrineto cRl012. The derayrineshifti the osciilator
signal 180 degrees so both diodes switch together.
Mixing the 2200MHz with the osciilatorZ1g2Mfiz sig_
nal producesthe differencefrequencyof 1g MHz. This
18 MHz signatis fed througha 3Z MHz tow_pass
fitter
to th€ 16-20MHz phaselock circuit. The low-passfilter
pley9lls
llwanted products, such as 82 MHz (product
of 2100MHz and 21g2MHz), from passinginto the
phaselock circuit.

4g4Ll4g4ApServlce, Vol. 1

16-20 MHz Phasetock Board (Diagram 13)
This board contains regulated pow€r supplies, a
16-20MHz (18 MHz nominal)voltagecontrolledoscillator with linearizing circuitry, and a phase/frequency
detector circuit. lts main function is control of thi
2182 MHz Microstrip Oscillator. Th€ entire circuit board
is housed in a magnetic shield to reduce spurious
efiects of external ac fields. All power supply and control inputs enter thg circuit board via feedthroughcapacitors in the housing wall. All connectionswith the
1ic^loyave circu_rlryare through feedthroughcapacitors
c2200 through c22a4. in the floor of the ho=using.
The +15V, -lSV, and +gV supplyinputsare reregulateddown to +12V, -12V, and *5.2 V by regulators using operationalamplifiers. lC U2O2Sprbvidesa
stable -6.2 V referencethat is fittered by R201g and
C2015and amptifiedby U20t6B to produte the -i2V
supply. fC U20168 uses emitter-foilowere2024 to
increasethe current capabilityof the supply. Resistor
R2013 ensures sufficient base drive, wiriie collector
resistor R2025 r€duces pow€r dissipation in e2024.
DiodeCR2019protectsthe base-emitterjunctionduring
power supply shutdown. Feedback resistors R2016
and R2017 set the gain of U2O16Band control the
-12 V, +12 V, and *5.2 V supptyvottages.
-12V suppty is apptiedto invertingamptifier
..^-fE
U2016A to produce the +12 V supply, and inverting
amplifierU1017to producethe +S.2V suppty. The output circuitryfor the +12V and +5.2 V suppliesare similar to the -12 V suppty.
Differentialampliffer V2072A accepts th6 2nd LO
sweep voltages. One input sensesthe sweep voltage
while the other input sensesthe groundpotentiatat the
Sweep board. Sweep sensitivityis adjustedby selecting resistor R2070. fn wide spans, the sweep signal
passesthrough parall€lresistorsR2AE2and R20g3. ln
narrow spans, R2082 may be switched out by 02094,
which reducesthe weep sensitivityby a factor of ten.
Whenthe TTL signatto 02026 is high, e2076 is tumed
off, R2086holds the gate of e2094 to -lS V. e2094 is
turnedoff, and R2082is switchedout. This reducesthe
sweep sensitivity. When the TTL signal is low, e2026
saturateswith the collector stighflyabove 0 V, O20g4
turns on, and full sweepsensitivityis restored.
AmplifierU2072Bacceptsthe 2nd LO tune vottag€.
the Tune board sensesthe ground potentialof the 1620 MHz Phase Lock board and floats the tune voltage.
Tunesensitivityis adjustedby selectingresistorR2Ol2.
The sweep and tune signals combine at the summing node input of a non-linearshapingamplifier.The
non-linearityof the shapingamptifiercompensatesfor
the non-lineartuning of the referenceoscillatorvaractor
to give a lineartuningcharacteristicfrom 16 to 20 MHz,
The shaping function is produced by a resistor-diode

7-11

Theory of Operation -

4g4ful4g4Ap Servlce, Vol. 1

afray in the feedback loop of inverting amplifier

ul073A.

All of the amptifier's feedback is through R1072
when the output swings to the negativelimit. As th€
output voltage swings less negative, it sequentially
passes the tap-point voltages of a series of voltage
dividersconnectedb€tween0 V (the summingnode at
pin 12) and a negativereferences€t by e1047. lf the
ot tput becomespositivewith respectto a givendivider
tap, a correspondingdiode in U2059 forward biases
and connectsthe output to the tap, which createsadditional feedbackthrough one leg of the divider to the
summingnode. This causes R2051,then R2052,then
R2053 (as so on through R20S6)to be connectedin
parallel with R1072 as the amptitieroutput becomes
le$s negativs. This progressivelyincreasesthe feedback,whichcausesthe gain of Ul073A to decrease.
Another series of dividers connectedbetweenthe
amplifier's output and a negative vottage reference.
causesthe diodes in U1059to sequ€ntlaltyconduct as
the output becomes more positive. ResistorsR2O6O,
then R2061,then R2062 (as so on through R206S)are
sequentiallyadded in parallel with the existing feedback. Soft diode turn-on characteristicsand a large
numberof breakpointsresult in smooth gain changes.
The nonlinearamplifier'svoltage-gaincharacteristicis
controlledby the shaperreferencevoltage,which is set
by R2049. Altering R2049 wiil make the breakpoints
either closer together or further apart; in practice,this
resistoris sel€ctedto correctthe tolerancevariationsof
th€ 18 MHz VCO varactor.
The fomrard drop of the shaper diodes gives
Ul073A an offset voltage. Temperature correction
diodes CR1086, CR1087, and CR1OBBcorrect this
ofiset over a wide temperaturerange by summing a
co.rectionvoltage through R1074. These diodes also
compensatefor the lack of s€ries diode drop across
R1072 and eliminate offsets at the summing input of
Ul0738. SelectingR1070 providesfine adjustmentof
the VCO's center frequency. lC U107gBis an inverting
amplifierthat increasesthe shaperoutputvoltageswing
to a level that can control the varactor of the 1g MHz

vco.

A differential amplifier with weil-defined timiting
characteristicsis used for the 1g MHz VCo. Emitter
degenerationis Lsed to control loop gain. Transistors
02096 and Q2087 form the differentiatpair of transistors, with the emitters coupled through C2091.
Transformer T2092 provides ac feedback for the
collector-basejunction of 02096 and also creates the
maiorityof the resonatorinductance.The total resonator inductancemay b€ adjustedby trying differentcombinations of connections between taps on inductor
Tl 091 and transformerT2092. Thesetaps allowcoarse
adiustmentof the VCO centerfrequency.The capacitor
of the resonatoris varactorCR1089. CapacitorC10gg

7-12

complet€s the resonator ac path and acts as a dc
bloc( which allows a bias voltageto be impressedon
the varactor. Resistor R2092 and capacitor C2090
damp the 02096 collector, which prevents hightrequencyinstabilityin the oscillator. TranslstorQ2087
provides a bufieredoscillatoroutput.
A discrete two-stage amplifier provides an unsaturated voltage gain of approximat€ly 43 dB for thg
18MHz signal lrom the 22A0MHz ReferenceMixer
board. Transistor Q1041 ls the common-emitterfirst
stage while Q1042 and Q1043 form the difierential
second stage. Th€ differential stage limits the output
swing to 0.8 V to prev€nt over- driving the following
ECL circuitry. Dc bias is malntainedby Q1041,which
has dc collsctor-basefeedback via R1O46and the
Rl043/R1048 vdtage divider. Transistor Q1043
receivesits base bias through R1042. Each transistor
operateswith 5 mA of quiescentcurrent.
ECL line receiversU2041Dand U20418amplifyand
bufier the 18 MHz signalsfrom the ReferenceMixerand
the VCO, respectively. These two signals are then
applied to the phase/frequencydetector for comparison.
A pair of ECL D-type flip-flops, U2031A and
U20318, comprisethe phase/frequencydetector. The
flip-flops drive a common reset lins with a wired-AND
output. The clock input of u20318 is driven with the
signal from the 18MHz VCO, and the clock input of
U20314is drivenwith the signalfromthe 18 MHzsignal
from the RefereneeMixer.
Both flip-flops are configured to r€set together
wheneverboth are set. lf they are clockedwith signals
that exactly match in trequency and phase, then both
flip-flops set simultaneouslyand then almost immediately reset. lf the R€ferenceMixer signal has a slight
phase lead, U2031A will remain set longer than
U20318. lf the ReferenceMixer signal has a slight
phaselag, U20318will set first and remainset the longest. The signalthat has the phase lead will causethe
associated flipflop to be set a grgater p€rcentag€of
time than the lagging flip-flop. lf there is a frequency
differencebetweenthe two inputs,the flip-flopwith th€
higherinput frequencywill be set more of the time than
the other flip-flop, The ratio betweenthe filtered output
signalsof the two flip-flopsindicateswhetherthe Reference Mixer signal leads, lags; or differs in frequency
from the 18 MHz VCOsignal.
The outputs of the flip-flops are low-pass filteredby
Cl031 and C1028 and applied to differentialamplifier
U1031. U1031 comparesthe outputs of the flip-flops
and producesan output that controlsthe tuningof the
2182MHz microstrip oscillator. The phase-lockloop
bandwidthis controlledby R1026,C1029,Rl027, and
C1026. The gain slope breaks to -l2dB/octave for
frequenciesbetow16 kHz. ResistorsR1033and R1034

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Theory of Operation -

4g4[l4g4Ap Servtce,Vot. 1

divideand offset lhe output of U1031so the
tune voltage rangesbetween0 and -12.5 V.
The outputof divid-erRl0gg/R1Og4is apptied
to
varactorof the 2192MHz microstriposcillaior(2nd the
LO).
This closes the phase-locktoop, tuning if," ZnO
LO so

!l"l-j!
9t9JrVtracksthe IB'MHZvto. when the
18 MHz VCO is

tuned, Ul0gt simuttaneousty
tun€s the
microstriposcillatoran equal amount. Withinthe toop
bandwidth,the 2nd LO performanceis OeiermineO
Uy
the 18 MHz VCO instead of the microstriposciilator,
giving a significantimprwement in frequency
stabitity
and reductionof phasenoise.

SERIES
RESONATOR
fo : 829 MHz

SERIES
RESONATORlo = 829 MHz

500

OUTPUT

PARALLEL

829 MHz 2nd CONVERTER
(Diagrams15 and 16)

RESONATORfo : 829 MHz
44.t695

Flgure7-3. Stmpllfieddlplexerdiagram.
The 829 MHz 2nd ConvErterassembty(A23)
downconvertsthe lst Converterband 2-4 g2g irtHz lF signal
to 110 MHz to drive the 3rd Gonverter.lt also provides
the switchingto select either the 2Ot2 MAz 2nd Converteror the 829 MHz 2nd Converter. The lF circuits
in
the signal path are shown on diagram 16, tF Section.
The local oscillatorcircuits are sh-ownon diagram
15,
LO Section.
lF Section (Diagram 16)
The 829 MHz lF circuitsincludean inputdiplexer,an
amplifier, a band-pass filter, a mixer, and a
diode
switch.

829 MHz Diptexer_.The 829 MHz Diptexer(A23A4)
passes signats at 929 MHz with approximateiy
f Ofi
rninimumattenuationand 200 MHz' pass-band. Frequencies outside the pass-band but betvyeen
about
50 kHz to 2 GHz are terminatedin 50O loads with a
matchof at least 10 dB. Figure Z-3 shows a simplified
schematicof the diplexer.
At 829 MHz, the series resonatorsprovide a low
irnpedancepath from input to output. fnl inputis from
the 1st Converterthrough low_passfilter FL.l5 and
P231. Signal loss across the SOO resistors is
insignificantbecauseof the low impedancepatharound
these r€sistors. The paraltetresonantcircu'ltto ground
appearsas an open circuitat 929 MHz.
At frequenciesabove or below the pass-band,the
s.eries.
r€sonatorsapp€ar as large reaciances,shifting
the primarysignalflow throughthe 50O r€sistors. The
out-of-bandimpedanceof the parallelresonantcircuitis
now small comparedto S0O. Thus, the 50O resistors
are.essentiallygroundedat their junction,terminating
boththe inputand outputports of the diplexer.

A wide bandwidthis used to minimiz€loss in the
resonant circuits and eliminateadjustments. Relative
bandwidthsof the series and parailelresonantcircuits
are optimizedto providereasonablematchat the band
edgEs.
As shown in the schematicdiagram,the diplexer
contains componentsnot shown in Figure 7-3. The
50o terminationsare actuallytwo pairsbt i00O resis_
tors, Rl014-R1015and Ri011-Ri0t2, connect€din
parallel to reduce load inductance. Small capacitors,
C1010 and C1013,are connectedacross each load to
improve impedance match at frequenciesabove the
pass-band. The inductor in the parallelresonatoris a
printed l€ngth of transmissionline that is tapped to
establishthe correct bandwidth. one end of this inductor is groundedthrough four capacitorsso that dc bias
from the lst Local OscillatorDrivercan be introduced
to the lst Mixer (A12) or the EXTERNALMIXERinput
through this diplexer. Severatcapacitorsare used in
paraflelto minimizeinductanceand circuit e degradation. A low-pass filter is includedin the bias line to
minimizeany noise from the 1st LO driver.
The diplexerdrivesthe 829 MHz Amptifierthrougha
1.2GHz Low-PassFilter that consistsof three shunt
capacitorsand two series inductors. Cutoff frequency
for this filteris 1.2 GHz.

829 MHz Amplitier. The 829 MHz Amptifier (A2SA5)
provides about 18 dB of signal gain at g2g MHz. The
amplifier consists of two similar cascaded amplifler
stages, Q1017 and Q1025, and a 3 dB pad. The overall
noise figure is approximately 2.8 dB. The gain stages
are stable amplifiers that are designed for use in a
50 ohm system.

7-13

o

Theory of Operaton -

494A/4g4ApService, Vol. 1

Since the amplifiersare nearlyidentical,the following descriptionapplies to both amptifiers.The ac and
dc signalpathsare treatedseparat€ly. Figures74 and
7-5 are simplifieddiagrams of the ac and dc signal
paths.

+ 1 2V

=

'PRINTED COMPONENT

Figure 7-4. Equivalent ac circuit of an B2g MH: amptifier.

f n th€ ac circuit(Figure7-41,C1,L1, and L2 form the
input matchingnetwork. (tn the first stag€, L1 is actually the series inductance of dc-blocking capacitor
cl016 at the input of the amplifier.)The coilectorcircuit
is matchedto 50o by L4 and c2. To a large extent,L3
controlsthe gain of the stage. High frequencystability
is enhancedby Rl and R2.
In the dc circuit (Figure 7-5), negative feedback
through the voltage divider, consistingof RO and R4,
sets the collectorvoltage as a fixed proportionof the
-12 V reference supply. Collector current is determined by R5. Current requirementsfor the first stage
are less than the requirementsfor the second because
the first stage requires less intermodulationdistortion
performance. Diode clamps are provided for each
amplifier (CR1013 and CR1022 at the bases of the
amplifiersin the actual circuits)to protectthe transistor
againstreversebreakdownof the base-emitterjunction
in casethe +12 V supptyfaits.
In the actual amplifiers(not shown in Figures 7-4
and 7-5)Ll 014 and Cl 014 at the baseof e1 017, Cl 0.tg
at the collectorof Q1017,L1021and Cl023 at the base
of Q'1025,and Cl013 at the collectorof Q1017decouple the signalpath from the bias network.
The 3 dB pad (R1026,R1027,R102B,and R1029)
helpsmaintaina wide-band50O interfacebetweenthe
second amplifierstage and the 829 MHz Bandpass
Filteron the 829 MHz 2nd Converterboard.
Test point J1029 at the outputport of the 3 dB pac,
is used for checkingamplifierperformanceand to aid in
adjustrnentof the 929 MHz band-passlilter on the
829 MHz 2nd Converterboard (A2347).
7-14

2?27-1A6A

Figure7-5. Equivalent
dc circultot an 829MHzamplifiee
829 MHz 2nd Converter. Down-conversionlrom
829 MHz to 110 MHz lF occurs on the 829 MHz 2nd
Converter board (A23A7). The board contains a
829MHz Band-PassFilter,a 1.3 GHz Low-PassFilter,
a 3 dB pad, a 450 MHz High-PassFilter, a singlebalancedmixer,and a 300 MHz Low-PassFilter.
The 829 MHz Band-Pass Filter blocks unwanted
inputs,primarilythe 609 MHz image signal. lt consists
of four, quarter-wave,coaxial type resonators,mounted
on the 829 MHz 2nd Converterboard. The end resonators are tapped near their grounded end to facilitate
input and output couplingof the filter. lnter-resonator
coupling is provided by printed "through-the-board"
capacitorsthat connectb€tweenthe resonatorsat their
high impedanceend. A bendabletab is locatedat the
high impedanceend of each resonatorfor fine adjustment of resonantfrequency. The bendabletab acts as
a small, variable capacitor to ground, making fine
adjustments of resonant frequency possible. When
properlytuned, the filter presents at least 12 dB input
returnloss and about2 dB insertionloss at 829 MHz.
The 1.3 GHz Low-PassFilter blockshigh trequency
signals that would otherwasebe admitted at the re'
entrant frequencies of the band pass in excess of
2 GHz. The functionof the 1.3 GHz Low-PassFilteris
sharedby the 1.2 GHz Low-PassFilter on the 829 MHz
Diplexerboard.

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Theory of Operation-

_ The 3 dB pad helps ensurea consistent5Oo interface for the 829 MHz Band-passFilter.
. T!" 450 MHz High-passFilter btocks the tower lF
signalsgeneratedwithinthe mixer.
. The mixer generates several intermodulationproducts of the 829MHzRF and 71g MHz LO signats.
The
mixer diodes are transformerdriven Oy a targe
amplitucre{+12dBm) 719 MHz signartrom t'he rocit
osciitator.
.This large signal driveJ the diodei in and out of
conduction,switchinglhe.loweramplitudeg29
MHz sig_
nal on and off at a 71g MHz rate, to generate
the
mixer
producJ:: Onty the differencetrequeicy
of 110 MHz is
passedthroughthe A00MHz Low-pasj filter.
The sum
product of 1548MHz, is reflectedback
to th€ mixer by
the 829 MHz Band-passFilter, in-phasewith LO
harmonics,to increasethe energyof ine 110 MHz
signal.
A..printedde-layline, Uetweenitre S2gMHz Band_pass
Filter and 1.3 GHz Low-passFilters,
the phase
delay, The net rssult of this ,'image
"ontrot"
enhancem€nt,,
is
low conversionloss and good intJr-modulation
distortion performance. The O dB pad reduces the image
enhancementeffect and permitsthe use of non-critical
line lengthsand filter characteristics.
Overallconversion
loss,from 829 MHzto 1.10MHz,is aboutg.5dB, including 2 dB from the 929 MHz Band-passFitterand g
dB
from the attenuator.

4g4[l4g4Ap SeMce, Vot. 1

829 MHz 2nd Converter. Becausethe 7l g MHz LO is
also turned off by the state of the lF sELECTline,isola_
tion for the 829 MHz 2nd Converteris nol critical wlien
the converteris inactive. The switchand amplifierlogic
is summarizedin TableZ-2.
Tabte Z-2
SWITCHAND AMPLIFIERSELECTION
lF Select
Llne

Serles
Swltch

Shunt
Ampllfier

1 1 0M H z
lF Source

High

On

otr

829 MHz 2nd Conv.

Low

otr

On

2O72MHz2nd Conv.

The diodes are used as the basic switch el€ments.
They present only a few ohms of series resistanceto
RF signalswhen fonrvardbiased,with currentof several
milliamps. When reverse biased, the diodEs present
€s_sentially
an open circuit. The control signal from
02015 is connectedin a series path through the four
diodes (CR2011,CR2012,CR201g,anO CAtOtSl anC
inductorsL2011,L2019,and L2019. Thus,only a small
currentis requiredto fonarardbias all four diodes. This
bias currentis also used to turn off el01 1.

110 MHz lF Select The 110 MHz lF Selectcircuit
{1?3161selects the 110 MHz tF signat from eitherthe
829 MHz 2nd Converteror the 2OlZ-UAz2ndConverter
for transmission
to the 110MHz tF Amptifier.

DiodesCR2012and CR2013are incorporat€dinto a
pi+!pj_matching network,consistingof L2011, L2O1O,
and C2012. Thereforeboth switchesshuntthe signalat
moderatelyhigh impedancepoints. In addition,when
the switch diodes are turned on, parallel resonance
between L2011 and CzAl2 presentsvirtuallyan open
circuit to signals passed by switch CR2O11. Switch
diode CR2013is tocated at th€ high impedancenode
created by the series resonanceof L2019and C2017.
DiodeCRl015direcilyshuntsthe outputfrom el01 l.

The 110 MHz tF signatfrom the 929 MHz 2nd Con_
y919r-boa( is apptieddirecflyto thE selectcircuit. The
1'f0 MHz lF signalfrom the iaZZu{z Convert€rboard
is appliedto the selectcircuitvia p233 and a controiled
amplifier(Ot012/Oi011). Switchingbetweenthe
two
lgft:_ is done by CR2011,CRtOt2, CR2013,and
cR1015.

Transistor Q1011 operates as a common-ernitter
ampfifierfor the 110 MHz tF signatfrom the 20Z2MHz
2nd Converter. lts gain and impedancematch are controlledby feedbackresistorsR101i and Rl012. Resistors R1013and R1018attenuatethe output by approximately 6 dB for enhancedcontrol of impedancematch
and stabilitycharacteristics.

DiodeCR2011is turnedon whenthe tF SELECTline
to the 110MHz lF SElect is low. Thls steers the
110 MHz lF signal,from the g29 MHz 2nd Converter
1119:-to the_outputport. At the same time CR2012,
CR2013,and CR't01Sturn on and el011 turn off to isolalg_theoutput port from any spurioussignalsfrom the
2072 MHz 2nd Converter.

Transistor Q1012 maintainsa constant dc current
through01011. Dc Coilectorcurrentfor 01011is set at
approximately15 mA. Collectorcurrent from e1011
developsa voltageacross Rl017. Transistorel012
then comparesthis voltagewith the fixed voltageof the
voltagedivider,Rl015 and R1016.Any variationin the
collector current of Ql 011 is sensed by e1012, and
ofiset by a resultant change in the base curent of
Q1011

The 300 MHz Low-pass Filter btocks LO, RF, and
higherfrequencyproducts.

Whenthe lF SELECTtinegoes high,etOtl turnson
and CR2012,CR201g,and CBl01Stirn otr to ailowthe
110 MHz lF signal,from the 2O72MHz2nd Converter,
to be apptiedto the output port. Seriesdiode CR2011
also turns off to prevent signal loss into th€ inactive

When th€ control current from e2015 (throughthe
switchingdiodes)developsa voltageacross Rl017 that
exceeds the control limits of 01 012, it effectively
removes the base-bias from e101i and turns el 01I
7-15

Theory of Opera$on-

t
t

4944/4g4Ap Servtce,Vol. I

off. Negativecurrent.suppliedthroughRl014, €nsures
that Q1011 is turned off. Diode CRt011 protects the
base of 01011 from excessivereversebias. Voltage
across R1017 is approximately
9.4 V when e1011 ls
turned on and approximately4.4V when it is off.
Overall gain is approximately 12.9dB when the
amplilieris turnedon.
The 110 MHz lF signalis transmittedvia p2g2 to the
110 MHz lF Amplifiershownon diagram17.

LO Section (Diagram'15)
The 829 MHz 2nd Converter LO generates the
719 MHz frequencythat is mixed with the 929 MHz tF
to produceth€ 110MHz lF signat. ln the following
description,the circuitsare referredto as the 71g MHz
LO. The 719MHz LO consistsof a phaselock loop, a
719 MHz outputcircuit,and a 2nd LO front paneloutput
circuit.

PHASE/FREOUENCY
DETECTOR

Phase Lock Circult The phaselock circuitreceives
referencefrequencyinputs and uses phase/frequency
detectiontechniquesto use those signals in controlling
the outputfrequencyof the 719 MHz oscillator. The circuit consists of a voltage controlled oscillator (VCO),a
phase/ frequencydetector,a harmonicmixer, and various amplificationstag€sand power splitters. Whenthe
719 MHz LO is enabled,the 2182MHz LO output fr€quency is used as a swept r€f€rence to d€rive the
719 MHz frequency. The VCO is controlled so that the
third harmonic of its output frequency is a constant
differencefrom the 2182MHz reference.This control is
accomplishedby the phase lock loop. Refer to Figure
7-6 for a simplifiedblockdiagram.
In the phase lock loop, the harmonic mixer generates a frequencythat is the difierencebetweenthe
swept 2182 MHz input referenceand the third harmonic
of the VGO output frequency. ldeally,this differenceis
25 MH4 which in tum. is compared with the 25 MHz
that is divideddown from the 100 MHz oscillatoroutput
supplied from the 3rd Converter. This comparisonis
done by the phase/frequencydet€ctorwhose outputis
a correctionvoltage that drives the VCO and shiftsthe
oscillatorfrequencyin the directionto hold the nominal
output frequencyat 719 MHz. This completesthe loop
that causesthe vco to track the 2182 MHz reference.

COMPENSATION
AMPLIFIER

OSCILLATOR

25 MHz DIFFERENCE FREOUENCY

829 MHz
HARMONIC MIXER

Figure7$. Block diagramof the phasetock loop in the 829 MHe2nd Converter.

7-16

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Theory of Operation-

Becausethe grd harmonicof 719 MHz is locked
to
the 2182MHz reference, the tuning range ot
tne
719 MHz osciilatoris onty one third oithe tuning
range
of the reference.Since.th:rgnge is 4 MHz, ttre ringe-ot
'
the 719MHzosciilatoris 71g Jt.gg trlnz.
The 719 MHz VCO (O20i4) uses a Cotpitts
configuration,with a printed circuit quarter-wavelength
transmissionline resonator,to achieve high specir"t
purity and good thermatstability. Correction
voliageis
appliedto varactorctiodeCRldlt (which is connected
at the midpointof the transmissionline resonator)
to
vary ths r€sonantfrequencyof the transmissionjine
ov€r a 1.5 MHz range. A tunabletransmissionline(atso
printed)adjacentto the printedresonatorcompensates
for variationsin componenttolerancesand resonator
dimensions-This adjustabletransmissionline is cut, at
factory calibration,to the correct length for proper VGO
operation.A scale with minor divisions everyiMHz
is
printednext to th€ adjustabreline to aid in caribration.
The outputfrom the oscillatoris extract€dnearone end
of the quarter-wavelengthline through two printed
inductorsand applied to output amplitiersthrough
a
powersplitter.
The 719MHz VCO is enabtedor disabted,under
microprocessorcontrol,dependentupon the frequency
band.beinganatyzed,by the tF SELECTline. Whenthis
lin€ is low, e2017 is cut off, which turns e2016 otr.
This, in turn, cuts off transistor e8015 (which is the
current source for oscillator transistor e20t+;, tnus
disablingthe 719 MHz oscillator.
From the oscillator,the *6 dBm 719 MHz output
signalis applied,throu-gha power divider consistingof
resistors Rl021, Rl022, and Rl02O, to tsolation
amplifierQ1021. From the other side of this power
9iut9gr,the signat is apptied to an output amptifier
(02021)for transmissionto the 929 MHz 2nd Converter
Mixer circuit. A second isolation amplifier (OgO21),
in configuration,
providesisotationbetweenthe
Il.e^n!i911
719 MHz oscillatoroutput and any undesiredHarmonic
Mixer products.
The 829 MHz HarmonicMixer producesnot only the
required 25MHz differencefrequency,but also many
higher order intermodulationproOucts. Two of these
frequencies,744 MHz and 6g4 MHz, are 25 MHz from
the 719 MHz oscillator frequency. The isolation
amplifiers,01021 and e3021, provid6sufficientattenua_
tion in the reversedirectionto preventthese products
from gettinginto the 829 MHz mixer to produie spuri_
ous signals.
To provide maximum reverse attenuationin each
amplifier circuit, external RF feedback is kept to a
m,inimum.An output matchingLC network, consisting
of capacitorC1025plus a printedinductorfor e1021,
and capacitorC3021plus a printedinductorfor e3021,
presentsan optimumload impedanceto the collectorof

4g4ful4g4ApServlce,Vol. 1

each transistorto allow maximumpowertransferto the
attenuatorthat precedesthe harmonicmixer. An input
LC matching network consisting of capacitors Ct0'23,
919?,plus a printedinductorfor al02i and capacitors
C3023, CgA22,ptus a printed inductor for e302i, estab_
lishesthe 50 ohm inputimpedanceto each transistor.
A 3 dB attenuatorconsisting of resistors R3021,
R3022, R2021, and R3023, at the output of isoiation
amplifier Q3021, provides a non- rehective source
impedanceto the mixer. Withoutthe attenuator.mixer
conversionloss couldvary from unitto unit.
The 829 MHz HarmonicMixer, consisting of diode
CR2021, inductor L2A14, and a half-wavelength(at
2182 MHzl transrnissionline, produces thE difference
frequencybetweenthe third harmonicof the 719 MHz
9:9,11?tolfrequency (nominalty 2157MHz) and the
2182 MHz reference frequency. Note that the
2182MHz sfgnal is supplied trom tfre 21g2MHz 2nd
Local Oscillatorthroughcoaxialconnectorp237 and the
power divider, consistingof resistors R1021, R1029,
and R1022.to a 112wavelengthtransmissionline. The
VCO input to the mixer switchEsdiode CR2021at a
719 MHz rate, The 2182MHz referenceacts as the RF
and is appliedto the diode from the transmissionline.
The resultant 25 MHz int€rmediate frequency is
diplexedfrom the mixer throughth€ 1OOMHz tow-pass
filter consistingof capacitorC3014and inductorL{jfi4.
(DiodeCR2021is mountedon printedcircuit boardcut_
outs to relieve any nec€ssity of bending the diode
leads. Lead bending may fracture the diode case.)
fnductorL2014providesa bias return path to allowthe
diodeto switchat a 719 MHz rate.
From the 829 MHz Harmonic Mixer, the signal is
appliedthroughthe above mentionedlow-passfilter to
cascaded amplifiers Ul053 and Ui0448. These
amplifiersboost the €2 dBm mixer output signalto a
level appropriateto drive the phase/frequencydetector.
lC amplifier(U1053)containstwo differentialamplifiers
in cascade; amplifier lC U1044 contains only one
differentialamplifierand acts as a bufier. When the
loop is first acquiringlock, such as at power-on,the
nominal25 MHz lF may be as high as 34 MHz. Two
stages of amplificationare necessaryto ensureenough
gain tor the phase/frequencydetector to drive the lF
back to 25 MHz; the bufferis necessaryto provideECL
levelsto the detector.
The secondinputto ths phase/frequency
detectoris
the 100 MHz signal,from the referenceoscillatorin the
3rd Converter,via two amptifierstag€s, U1022Aand
U10228, and a divide-by-fourcircuit, U1036A and
U10368. The 100MHz signat is divided down to a
25 MHz
reference for
application to
the
phase/frequencydetector. Two stagesof amplification
are used to isolatethe 100 MHz referencebus from signals generatedin the local oscillatorsectionof the 2nd
Converter. This stable25 MHz referencesignalis used

7-17

o

Theory of Operaton -

to lock the difference trequency from th€ Harmonic
Mixer to 25 MHz.
The phase/frequencydetector output is a voltage
that is proportionalto the phase difierencebetweenthe
25 MHz refer€nceand the lF signal from the g29 MHz
HarmonicMixer. This correctionvoltageis thenapplied
to the 719 MHz VCO to lock it to the reference.
The detector circuit consists of two D-typeflip-flops,
U2U7A and U2047B, and a differentiatariiptifiei stage
used as a NAND-gate(U1044A).The 25 MHz referenie
signal, from the frequency divider, is apptied to the
cfock input of flip-flopU204tA; the nominat25 MHz signal from the 829 MHz HarmonicMixer is appliedto the
clock input of flip-flop V204ZB. The rising €dg€ of the
input signalto each flip-flopcausesthe e(bar) outputs
to return to the low level only after both flip-flopshave
been clocked.
lf the frequencyout of the g2g MHz HarmonicMixer
is below 25 MHz, or if its phase lags that of the 25 MHz
reference, the Q(bar) output of ftip-flop U2047Awitl
remain high longer than the a (ba0 outputot u20478.
lf the frequencyout of the HarmonicMixer is above
25 MHz, or if its phase leads, the oppositewill occur.
When the two flip-flops are clocked at the same frequency and phase, the two outputs will be high for the
sam€ amountof time. The e(bar) outputsare applied
to a compensationor differentialamplifierU3059,that
determineswhich outputis high for the longertime.
CompensationamplifierUg05gprovidespart of the
loop gain to ensure that the 719 MHz oscillatorwill
track the sweep of the 2192 MHz referenceoscillator.
The compensation amplifier also limits the loop
bandwidthto 100 kHz to make certainthat the loop wilf
not oscillate. Note the differentialinputsto the amplifier
each include a low-pass RC filter to attenuatethe
undesired high frequency clock pulses from the
phase/frequency
detector.

7-18

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4g4A/4g4ApService, Vol. 1

The nominal swing of the U3053 output is from
+12V to -12V. Since the compensationamptifieris
capable of considerablymore output than is neededto
control the oscillator,a voltage divider is used to limit
the outputand reduceamplifierrelatednoise. This voltage divider, consisting of resistors R2053, R2054,
R3051,and R3052,reducesthe possible*12V swing
to +5 V to +12 V, as reguired by varactor diode
CR1011.Nominalvoltageswing in a lockedconditionis
+6.75 to +7.5 V. Thus, dependent upon whether the
HarmonicMixer frequencyis above or below 25 MHz,
the correctionvoltageswing, appliedto diode CR1011,
is more than nominalto correct the oscillator frequency.
2nd Local Oscillator Oupuf Circult A portion of
each 2nd LO output signal is sent to the front panel 2nd
LO OUT connector. This output provides signal for
externalaccessoryequipment,such as a trackinggenerator. Each local oseillator(719MHz and 2182 MHz)
output is applied through power dividers to a power
combinerfor applicationto th€ 2nd LO OUT connector.
The 719 MHz oscillatorfrequencyis appliedfrom a
power splitter(R3027,R3028,R3029)through a 1 GHz
fow-passfilter (C3025,C2024,C1023.C1021, and three
printed inductors),to the power combiner (R2024,
R2025, R2026),and the front panel 2nd LO OUTPUT.
The 2182MHz oscillator signal is applied through a
power splitter(R1021,R1022,R1023),a 2.2 GHz bandpass filter (consistingof coupled1/4 wavelengthprinted
lines) to the power divider (R2024,R2025, R2026)and
the front panel2nd LO OUTPUT.
Both 2nd local oscillatorsignals, 2182MHz and
719MHz, are present at the front panel when the
829 MHz 2nd Converteris selected.
719 MHz Output Clrcult The 719 MHz 2nd Local
Oscillatorsignal is applied is applied through divider
resistors R2021, R2023, and R2A24 to isolation
amplilier Q2021. 02021 boosts th€ signal level from
about 0 dBm to +12 dBm to drive the 829 MHz mixer.
The output of the amplifierincludesa 3 dB attenuator
(consistingof resistors R2027,R2028,and R2029),to
ensur€ a 50 ohms non-r€flectivesource impedance.
The signallevelat test point J2026is typically-6 dBm.

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Theory of Operation_ 4g4Al4g4ApService, Vol. 1

3RD CONVERTER
(Diagram4)
The 1t0MHz tF Amptifier(A32)and 3rd Converter
(A34) down converts the ttO MHz ouiput
signat from
the 2nd Converterto 10 MHz for the VariaUieResolution
circuits. A 100 MHz crystat controlledoscillator provides.thethird LO signal.This oscillatoris phase
locked
to either a precise internal10MHz reference
or an
external1, Z, 5, or 10 MHz reference.The 100
MHz LO
signaris appliedto the mixer and is oistriouteo
through
output amplifiersto many other circuitsthroughout
t6e
instrumentas a referencesignal. The 100 MFz
signal
and its harmonicsare also availablefor external
use at
the front-panelCAL OUT connectorfor irequency
anO
100 MHz amplitudecalibration.
The 110 MHz signal is amplifiedin a three_stage
.
gain
btockand apptiedthrougha band_paisfitter and
a
low-passfitter. From the toiv_passfil6r, the signal
is
appliedto the converter,which consistsof a
mixer, an
oscillator,and variousoutputamplifiers.

110 MHz tF AMpLtFtER(Diagram17)
-lnitial gain for the analyzer is provided by the
110 MHz lF Amplifier. Thi; gain compensates
for
conversionlosses in the thre€ mixers. Typicalgain
for
the amptifieris 2t dB. The amplifie,
of three
stagesof amplificationand an attenuator.
"onjirts
The first two
mixers in the RF syst€m ofier no high_frequency
gain;
therefore,it is importantthat this ariptifiei exhibit low
noise characteristics. lt must atso be relatively
free
from third-orderintermodulation
distortion.
. Signalinput is appliedthroughan impedancernatching b.and-pass
fitter(L2044anOCSZS)
to'a paraileltuned
circuit. The signal is injectedinto the paraltet-tuned
cir_
cuit through a tap in the inductorand taken out at
the
high impedanceside through variablecapacitorf;2A47.
Inductive input provides for
to high
impedancewithin the tuned circuit;
"onu"riion
the extra capacltor
on the output providesfor conversionback to 50 ohms
pr'.m."ry.tuning capacitor, C325, adjusts
l.Iil_"]:_I!:
tn€ resonant point; the output capacitor, C20C7,is
adjust€din combinationwith bSZSt6r good impedance
match at 110MHz. This is done wiih a return loss
bridge. The nominalreturnloss is 35 dB. The e of the
input filter is approximately20.
- From the input fitter,the signatis appliedto e4053,
which is the first stage of impliRcaiion. This is a
broad-bandfeedback amplifier to provide good input
and output impedanceand controliedgain. All feed919! is through reactive componenti (transformer
T3054),not resistivecornponents.Thus,the impedance
and gain can be controlled without significantnoise
problems.

The second amplifierstage, e40g7, is essentially
..
the same as the first, with oniy minor bias differences.
Gain through each of these itages is approximately
9 dB. The output is appliedthrough a 3 dB attenuator,
to..preservethe impedancefigure, to the bridged .T;
adjustableattenuator. The 3 dB attenuatorconsistsof
resistorsR2039,R2038,and R2043.
From the 3 dB attenuator,the signal is capacitively
goupled through C2Ogl to the aOyustabte
attenuator.
This attenuator uses two ptN diodes, CR3030 and
CR1029,in the mode when the resistanceto RF signal
by the current through the diodes.
lolv is c_ontrolled
Refer to Figure T-7 to aid in understandirigtt e foflowing
description.
ff resistorR1 in Figure7-T were set to infiniteresis_
tance and resistor R2 were set to zero resistance,the
RF signalpath would be throughR2 to ground,to produce infinitesignal attenuation.lf resistor Rl were set
to zero resistanceand resistor R2 were set to infinite
resistance,the RF signalpath would be throughRl to
th€ load, to producealmostno attenuation.This, basically,is.how the adjustableattenuatoroperates,except
that resistors R1 and RZ are actually plN diodes and
the RF path resistancethrough theie diodes is controlled by the current throughthe diodes in an inverse
proportion(higher current results in less resistanceto
RF).

Figute 7-7. Bridged 'T' attenuator equlvalent clrcuit

Resistors R3035 and R20gO on the detail€d
schematic diagram establish a constant current of
approximately
2 mA from the 15 V supplyto the diodes.
This current is dividedaccordingto the bias on the
diodes. The bias, in turn,is establishedby gainadjustmentR1015,fromthe +15 V suppty.lf Rl015is set low
(nearground),diode CR30g0is reversebiasedand the
2 mA flows through diode CR1029. This routesthe RF
signafthrough resistors R2092and R3029and capaci_
tor C2029, with the impedance characteristicsof

7-19

o

Theory of Operaton -

494A/4gdApService, Vot. 1

CRl029 addedfor maximumattenuation.
lf Rl01 5 is set higher(nearer+i 5 V), diodeCR3030
is forward biased and starts to conduct. Since the
2 mA supply current is relativelyconstant,this subtracts
from the currentthroughCRl02g. Thus,the impedance
of the diodes is relativelyconstant,which resultsin a
good impedance match over a broad range. The RF
signal path is determined by the exact amount of
curent through CR3030;part of the RF signal path is
through CR3030 to th€ output amptifier ind part is
through R2032 and diode CRlO2g to ground. This
resultsin reducedsignalattenuation.
lf R1015is set to the positivetimit,the entire2 mA
flows through CR3030. This routes the RF signal
through CR3030 (which exhibits titil€ resistance with
high current) to the output amplifier with almost no
att€nuation.Cl-heinsertionloss is approximatelyI dB.)
_Fromthe adiustableattenuator,the signalis applied
to the linal amplifier09018. This stage ts a broad'-6and
feedback amplifier that supplies relativelysubstantial
outputcurrentand exhibitsgood intermodulation
distor_
tion performance.This is providedprimarilythroughthe
large curr^ent
.capacity,by negativefeedbackthiough
resistorR3014,and emitterdegenerationthroughreslstor R4029. These resistorsare sized to providea r€asonablygood impedancematch at 110 MHz. Nominal
gainof the stageis 13 dB.
With Gain potentiomet€rRi0i5 set for maximum
gain (least attenuation),
the gain of the 110MHz tF
Amplifieris approximatety
26dB to 27d8. R.t01Sis
normallyadjustedfor total gain of 21 dB.
Th€ outputsignalfrom the 110 MHz tF Amplifieris
appliedthroughthe 110 MHz band-passfitter FL36and
low-passfilter FL37to the 3rd Converter.

110 MHz FTLTERS
(Diagram17)
The 110 MHz band-passfitter (FLg6)determin€sthe
widest resolutionbandwidthof the analyzer,provides
i-I1g-g-rejection to prevent the mixer fiom producing
10 MHz outputsfrom input signalsof 90 MHz, and also
limitsthe noise spectrumthat appearsat th€ 1OMHz lF
circuits. The low-passfilter (FL3Z)that follows turther
reducesharmonicsand spurs from the 2nd Converters.
Both filters are sealedunitswith no internalservicing.
The band-passfilter consistsof four helicalresonators that are tuned with multi-turntrimmer capacitors.
For purposesof impedancematching,the fittei is sym_
metrical.

7-20

Adjustment of the filter for minimurnattenuationis
performedby setting the trimmer capacitors. Insertion
loss is approximately4 dB to 4.5 dB. From this filter.
the 110 MHz signal is appliedto the separatelow-pass
filter. There is no adjustment for the low-pass filter.
The signalthen feedsthe 3rd Converterboard.

3rd CONVERTER(Diagram17)
The 3rd Gonverterconsists of a 100 MHz crystat
oscillatorand a mixer. lt outputsth€ 3rd lF of 10 MHz,
for the Variable Resolution (VR) circuits, and a stable
100 MHz referencefor other circuits within th€ instrument.
100 MHz Oscillator
A Colpitts oscillator is formed by Q2038, yg03g,
L1041, C1038, and related compon€nts. Y3038 is a
100 MHz crystal that op€rates in a series resonant
mode in the fEedbackloop of the oscillator.The oscillator output couples through C2042 to differential
amplitier 4204402441. The two separateoutputs of
approximately2V peak-to-peakamplitudego to three
hybrids(mixer U3051,distributionamplifierU30il1.and
cafibratorU2022)on the 3rd Converterboard.
lnductor L3041, varactor diode CR3039,and crystal
Y3038 form a series resonator that tunes th€ oscillator
approximately*1 kHz. The RPL VOLTS TUNE tine
varies from 0V to +12V, changingCR3039'scapacL
tanceto phaselock the oscillatorto the ReferenceLock
source. RPL GND is tied to ground in the Reference
Lock module.
Mixer
At mixEr U3051, 100 MHz enters on pin 2 and is
amplifiedto drive a ring diode mixer. 110 MHz enters
on pin 10 and is mixed with the 100 MHz to yield mixing
products at 10 MHz and 90 MHz. The 1OMHz signal
pass€sthrougha low-passfilter and is sent to the Variable Resolution Input circuat, while the unwanted
90 MHz signalis terminatedwithinthe mixer,
Distribution Amplilier
U3031 distributes a 100 MHz signal to other
modulesin the instrument. The input level on pin 2 is
typically 2 V peak-to-peak,while the output level is
0 dBm into a 50 ohm load.

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Theory of Operation -

Calibrator
u2022 and relatedcomponentsregulat€a 100
MHz
signatto -20dBm for the front-panetill
bUf connec_
tor. VRI 0S1 serves as an aecurate6.2 V
reference,
which is dividedto approximately1.e V anOapplied
to
pin 6 of U2022. The exact tevetii set
by R1041the Cal
Leveladjustmsnt.
The 100MHz signal_enters pin 1 and passes
through a pin diode variableattenuator. The signal
is
th€n amptifiedand passed througha low-pass
fitter to
removeany harmonics. The signalthen enters
a peak
detector-and comparator wnere the peak amplitude
of
the 100 MHz signalis comparedto the 1.2 V reference
pin
on
6. An operationalamplifier then adiusts the
att€nuationlevelof the pin dlodeto maintaina constant
signatlevel. The outqq of this operationaiampliRer
can
be measured on Tp301l. A small
of the
fortion
1^0-0
MHz signal is attenuated tnrou'gh RzO.ll
to
-20dBm. R1021and R1022suppfy
Uia-s-current
p€ak detector circuits. fne vottale on pins to the
7 and g
shouldtypicailybe +5 V.
c2023, C2011, and related componentsform
a
high-passfilter to allow harmonicsof iOOMn.
to pass
throughto the front panet. The nna resuttis a calibrator signal rich in harmonicswith an accurate100
MHz
amplitude.
In Option0Z instrum€nts,the CAL OUT signalgoes
a set of-relayswitches. tn 50O moOe,the out_
thr:ugh
put goes straight to the CAL OUT connector.
In the
750.mode, the outputis routed througha 50O_to-ZsO
matchingpad and the output is +ZOOg-mV.

REFERENCE
LOCK(DiagramS0)
The ReferenceLock module (A36)
consists of a
'(A3erc),
10 MHz crystat osciilator
reference
".tlblg
detector,
frequency
phaie/frequency
.synchronizer,
detector,and tune window
detector. Eittrertne internal
10 MHz referenceor an external1,2,5,or 10 MHz
reference frequencyis routedthroughthe referencedetector
1o-^tlg-frequencysynchronizer. The local oscillator,s
100 MHz output is divided by 100 and apptiedto one
inp.ut a pha.se/frequency
dbtectorwtrich'tomparesit
-of
with the i MHz reference frequency. Th€ resultant
error signal is amplified by the tune amplifier and
applied, as a correctivevoltage, to the voltage con_
trolled3rd LO.

4g4Ll4g4ApService,Vot. 1

External Reference Detector
_ Buffer amplilier02014 convertsExtemalReference
signals,within the range of -iS dBm to +15 dBm, into
TTL compatiblelevel. When an ext€mal signal,within
!!e tgvet rangE, is apptied, it triggers muttivibrator
U20468.. The output of U2046BenaOlesext€rnatsignat
control NAND gate U20g2D,and disablesthe inte-rnal
signalcontrolgate U2032A.lt also disablesthe internal
10 MHz referEnceosciltatorby turningel0g1 on, which
biasesQ1033off, and r€movesthe +5 V" supplyfor the
osciltator. The output of U20468,pin 9i is sent to the
processor, on the EXT REF line, to indicate
that an
externalreferencefrequencyis in use. Duringa diag_
nostictest, the microprocessorcan also pultthe INTEi_
NAL SHUT-DOWNline down to turn the lnternatReference Oscillatoroff and check for loop unlock. lJ2Og2B
gates either the 10 MHz from the internalgate u2o32A,
or the external referencefrom ltZOgZD,to ihe frequency
synchronizerU2046A.

Frequency Synchronizer
MultivibratorU2046A,synchronizes
its 1 MHz output
with any of the allowed input frsquenciesby edge_
triggeringthe time-out period. The I MHz ouiput frequencyis set by the timingcomponentsR2039,c2o3g,
and adjustmentR2042. With a 10 MHz signatappliedto
U2046A,adjustrnentRZO4Zis set for a lrrs period, with
65 ns betweenthe fallingedge at Tp2046and the next
fallingedgeat Tpl044.

Phase/Frequency Detector
The 100 MHz from the 3rd Local Oscillator is
clividedby 100 and convertedto a TTL level by prescaler U2020. The I MHz from U2020, is fed to the
clock input of D-typeflip-flopU1O44A.The 1 MHz from
U2946A,is appliedto the clock input of D-typeflip-flop
U10448. The two ftip-flopsand NAND gaie UZOO2C,
form the Phase/FrequencyDetector. R1Og4,Rl0gS,
and C1037,along with it's counterpart,on the outputof
U1044A,form a low-passaveragingfilter for the outputs
of the flip-flops. When the two input frequenciesare
equaland in phase,the compositeoutputof the averaging filter is +2.5 Vdc.

7-21

Theory of Opera0on -

t

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4g4[l4g4Ap Servlce, Vot. 1

O
Tune Amplilier
Thg FET-inputoperationatamptifier (Ui034) takes
..
the output of the phasefrequencyd€tector, amplifies
tJre gqgr and supplies an appropriate tune vottage to
the 1O0MHz voltage controlled oscillator. The tun€
ampliller, with feedback components c1031, c1o3g,
Rl028, and Rl029, determinethe toop transfercharacteristics. The toop dc gain is very high which takes
advantaggof the high accuracy of tire internal or external references.The loop ac aain (determinedby ClOgl)
rolls off very quicklyso any phasenoise, on an external
referencesignal,is not amplified.

Lock Detector
U1012 is used as a tune volts window detector.
R1013,R1012,and R1011set the upper threshotdat
11 V6s,and the lower thresholdat 2 Vo". As long as the
tune volts stays within these limits, d trigtroutput tells
the processorthat the 3rd Lo loop is locked. A low
output from Ul012, indicatesthat the referenceoscilta_
tor frequencyis beyondthe Ord LO's tune range. This
REF LOCK status line, along with the othEr two proc€s_
sor interface lines, is routed through thE Swe€p board
for processor interrupt generation. The processor
r€ads the lines and displays their status on th€ crt
r€adout.

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7-22

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Theory of Operation-

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4g4ful4g4ApServlce, Vot. i

lF SECTTON
(DiagramS)
The lF section receivesthe lO MHz lF signal
from
the 3rd converter, establis_hes
the system resolution,
levels the gain across the frequencyi"ng.,
logarithmi_
cally arnplifiesthe signal,and Oetecisthe-signai
to pro_
duce the videooutputto the Display
"""itn.
System
bandwidth
resolution
is selectable
3 MHz to 10 Hz. This s.etectionis pe;orm€d from
by the
VariableResotutioncircuits and is
over the
instrumentbus. Generally,two sets"6niiot"O
oi Ritersar€ used
to establisheach bandwidth. A uano-pasi
filter is also
includedat the circuitsoutput.
Significantgain is al.s: prgvided by severatstages
amplificationwithinthe VariableResoiution-circuit of
block.
Other gain steps are also provided by-switching
gain
blocks in or out of tle^ signal path. ffiese gain
blocks
-10,
provide
+10, *20, or +dOdB ot aOOitionat
gain
when switchedin combination.
..Logarithmicamplificationof the signalis requiredto
calibratethe graticulein dB/division.-Tti. i" performed
:.."y".n stage amptifiert-hatproOucesLn output pro!y
portional
to the logarithmof the input. thus, tne screen
displacementcan be selectable tor ttre
amount of
change per division, and can Ue projortional
to the
input level
irilt" 10dB/div
'displar"r.nt
.change. For exampl"i
display mode, each division of
on the
screen represents a signal level change
of 10 dB
regardressof whetherit is at the top or 50ttom
of the
screen.
The detectorfollowsthe logarithmicamplifier proto
positive-going
outputsilnat that is apptieO
9t"9 "
to the
displaysectionas the V|DEOsignat.

VariabfeResolution
(Diagrams19, 19,104;Id,'and 21)
The VariabteResotution(VR) assembty(A6g)
and
the 10 Hzl100Hz Bandpass Firter aiiJmOty
inOSy
establishthe resolutionbandwidthand provideipproxi_
41
dB
of
system gain. The Vi assembiyconTa.tely
sists of two sets of filters plus gain stages.
The
1.0Hl100 Hz BandpassFitterissem-Oty
acts as part of
the VR circu.its,but is physicailyin a seiarate assembty.
Since the input to the VR circuits'is nominalty
at
-35-dBm and the Log Amptifier
input ,"quir"" *6 dBm
for full screen,the VR circuits mi.,.t prduiOe
the gain
difference. The VR suppties30 dB oi aOJifionat
and. 10dB of gain reductionfor alt verticat lain
disptay
modes.
Physically,the VR assembly contains two subassembliesthat connect together and plug onto
the
instrumentMother board. The input
are in one
"ir",lit-i

sub-assemblyand the output circuits and digital interface are in the other. Each of the sub-assembliesconsists of boards that plug onto a four_layerVR Mother
board with a ground plane on both outside layers.
pow€r supply and control voltages travel throughOnly
th6
VR Mother board. All signatconiectionsare by joaxial
cable.
VR Input (Diagram 19)
The VR Input circuit receivesthe _3S dBm I0 MHz
signal from the Ard Mixer through J6g3. This signal
goesthroughan amplifierand an attenuator.
The signal is applied to broadband feedback
amplifier01029, which is biased for a large output
current (approximately50 mA) to reduce intermodulaperformanceis provided primarily
I_o-1
I:t:ni9n. This
through
the large currentcapacityby negativefeedbaci
through resistor R1025 and by emittei degeneration
resistorR1023.
A 6 dB attenuatorat the output of amplifierelo2g
providesa clean 50 ohm output to the lst Filter Select
circuit.
1st Filter Setect (Diagram t9)
The 1st Filter Select circuit operateswith the 2nd
Filter Selectcircuit through banks of switchedfiltersto
set the overallsystembandwidth. Data bits 0, 1, and 2
from the data bus are applied to decimal decoderlC
U4035(it providesa low signalon the appropriateoutput pin to enablethe selectedfilter). Bandwidthsetections are 10 Hz to 1 MHz in decadesteps, and 3 MHz.
The data bits select a bandwidthfiltei accordingto
Table7€.
Table 7-3
BANDWIDTHSELECTION
Bandwidth

3 MHz
t MHz
100kHz
10 kHz
1 kHz
1 0 0H z
1 0H z

DBO DBl
1
00
1
11
0
10
1
10
0
0'l
1
01
0
11

DB2

Filters are selected by diode switching. Series and
shunt diodes are at the input and output of each filter,
The instrument allows only one filter to be selected at a

7-23

t

Theory ol Operation-

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494A/494ApSewice, Vot. 1

time. When a filter is selected,the series diodes are
biased on and the shunt diodes are biased off. The
diode conditionsare opposite for the filters that are not
selected. Sincethe switchingoperationis th€ samefor
all ftlters,the followingdescriptionfor the 100 kHz filter
selectionappliesto all filters.

The 10 kHz filter uses a pair of two-polemonolithic
crystal filters that ar€ interconnectedby variable shunt
capacitor C2030. Input and outprrt impedances are
matched with broadband transformers T2025 and
T3040. A 3 dB pi attenuator is included at the filter
inputto help matchthe loss of the other sections.

When the 100 kHz filter is sel€cted, line 2 from
U4035will be low. This tums on switchingtransistors
Q3015and Q3055. With input switch 03015 turnedon,
the current path is through R4012, R4010, L4010,
CR3013,L3015, R3015, and e3015. This current is
determinedthe resistors in this seriescircuit. The voltage drop across the resistors is enoughto turn the
seraesdiode on and reversebias shuntdiode CR3012.
The same case exists for the lilter output switch.
03055. SEries resistors establishthe current to forward biasCR3063and reversebiasCR3062.

The 1 kHz resolutionfilter consists of a singletwopole monolithiccrystal filter, matched to the 50 ohm
impedance with broadband transformers T2035 and
T2040. A 2 dB attenuatoris also included at the filter
input to h€lp matchthe loss of the oth€r filters.

Thereforethe signal from the VR Input circuit, via
jumper B, is applied through the sel€ctedtilter to the
10 dB Gain Steps circuit via jumper K. Nominalloss
through the lilter circuit is approximately6 dB, with
slight variationsamongthe filt€rs. The 1st FilterSelect
output level is nominally-25 dBm. Any differencein
gain betweenthe filters is compensatedfor later in the
2nd FilterSelectcircuits.
In the non-selectedfilter sections,the inputand output switchtransistorsare tumed off by the high outputs
from decimaldecoderU4035. The collectorsare pulled
toward -15V through the resistors that forward bias
th€ shunt diodes in the input and output. Since one
filter is always selected, the voltage drop across the
common input and output resistors back biases the
seriesdiodes.
A filter is not used in the 3 MHz sectionbecausethe
wide bandwidth filtering takes ptace in the 110 MHz
filters betweenthe znd and 3rd ConvertErs.Insteadof
a filter, a 6 dB attenuatoris containedin the 3 MHz
selectioncircuit. This attenuatorhelps matchthe lEvels
of the various bandwidthsby simulatingthe insertion
loss of the other sections.
The 1 MHz filter section consistsof a pi attenuator
and an LC band-passfilter. The attenuatoradjuststo
match the level of the 3 MHz section. Gainis adjusted
for bothbandwidthsin the 2nd FilterSelectcircuit.
The 100 kHz filter is a doubte-tunedLC circuit
designedfor a good time-domainresponseshape. The
filter is tun€d with compositevariablecapacitorsconsisting of small air variables paralleledwith switched
fixed capacitors. A third variable capacitor may be
adjustedto establishthe desiredbandwidth.For Option
07 instruments,a similar 300 kHz filter replac€s the
100 kHz filter.

7-24

The loHzfiAA Hz filter, A69, is contained in a
separateassemblywith switchingdone on this board.
One set of switchingtransistorsenablesthE filter path
when either the 100 Hz or 10 Hz bandwidthis selected.
Another switch selects between the two bandwidths.
Decimal decoder U4035 selects 100 Hz bandwidthby
pulling output 5 (pin 6) low, and selects 10 Hz
bandwidth with output 6 (pin 4. The filter path is
selectedwhen eitheroutput5 or 6 are low.
Diode pair CR1030turns on 01025 at the input to
forurrardbias diode CR1011. Diode pair CR4055tums
on Q4050 at the outputto fonilard bias diode CR4061.
Diodespairs in CR1012and CR1020providelimiterand
clamp action at the filter input to remove RF excursions
causedby the dc switching.
The filter has a bandwidthof 100 Hz when its input
port is low (-15V) and 10Hz when high (+15\4.
TransistorQ1027does the switching.When100H2 is
selected.output 5 (pin 6) of decoder U4035is low and
output 6 is high. This turns transistor Q1025on, forward biasing CR1011 and reverse biasing CR101O.
This applies the lF signal to the filter input. This also
biases 01027 off, placing -15 V at the filter input to
select the 100 Hz bandwidth. (04040 also switchesthe
output, but is not effectivein this instrumentsinceA69
only requiresswitchingat the input).
When output 6 of U4035is low and output5 is high,
Q1027 and Q4040 are on in addition to Q1025 and
04050. This selectsthe filter path and applies*15 V to
the input and output ports, switching the tilter to the
10 Hz mode.
100 Hz and 10 Hz Bandpass Filter (Diagram 19A)
The 100 Hz and 10 Hz bandwidthsare providedby a
dual-bandwidthfilteringassembly(A69). The signal is
convertedfrom 10 MHz down to the 250 kHz centerfrequency of the filter. Filtering at 250 kHz makes the
bandwidtha much higherpercentageof the filter center
frequencythan if filteredat 10 MHz. The ltlteredsignal
is then convertedback up to 10 MHz.

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Theory of Operalion - 4g4A/lg4Ap Service, Vol. 1
- -. The.assemblyconsistsof four subassemblies:
1st
Mix-er(A69A't), Bandpass Fitter (A69A2),2nd Mixer
(A69A9), and Local Osciilator (A69i4).
These
subass€mbliesare on individualciriuit boards contained in shielded compartmentswithin a metal cas€
mountedabove th€ crt.

lst Mlrer. The lst Mixer (A6gA1)is the input
mixer. lt converts the l0 MHz lF signal down
to
250 kHz. An input filter reducesthe signil skirts before
going to the mixer. The buffered9.ZSi4Hz Local
Oscillator (LO) mixes with
19 MHz signat,
producingthe
-bandpass
lhe
250 kHz mixer outputthat drivesttre
filter.
- The input signal consists of the 10 MHz lF signal
with a dc control signal also riding on the line. Ttre Oc
control signal selects the 10 Hz or 100 Hz lilter. The
10 MHz signal couples through a capacitor and
transformerto feed the input filter. The dc control signal feeds through a resistor and capacitorto isolate ttie
10Ir4Hzsignaland providea cleandc signalto the filter
switcheson the BandpassFitterboard(469A2).
Input filter Y2025 is a monolithicsecond-ordercrystal fflt€r with a i kHz bandwidth. The tilter limits tarje
signals outside the bandpass before they enter the
mixer. This reduces th€ intermodulationOistortion
(lMD)in the circuit. The l0 MHz signaldriv€sthe fitter
at about-20 dBm signatlevet.
The filter drives high level mixer USO20,built from a
monolithicring of MOSFETswitches. Differentiatpair
05020 and Q5025 buffers the g.7SMHz LO signal and
drives the mixer at the LO input. The buffer provides
oppositepolarityhigh amplitudesquarewaves to drive
the mixerdifferentialLO inputs. The squarewave helps
providelow mixer lMD. A potentiomet€radjustsrnixer
bias to help provide low IMD and low mixer insertion
loss. The adjustmentis madefor best conversiongain.
The main power suppliesalso enterthis board. The
power suppty is re-regutatedto +1S V to avoid
117V
loading the existing +.1SV suppty. The _1 5 V suppty
acts as the referencesupply for th€ +1S V regutaior
whichconsistsof US010B,e5010, and eS015. hesistors R5125and R5'l27 act as a voltagedivider to set
the outputvoltage.

Bandpass Fitter. The 250 kHz signat
producedby
-ampiified
the previous mixer is filtered and
in the
BandpassFilter board (A69A2). The filter consists of
thr€e nearly identical stages. Bandwidthis changed
from 10 Hz to 100 Hz with transistorswitchesin each
ijaS.". The controlsignalfor this switchingcomesfrom
the lst Mixer board (A69Al).

The filtEr sectionsconsist of crystalsin series with
the signal path. Each crystal is driven from a low
impedance source. Resistive loading then sets the
bandwidthof each section. Ttre switihing transistors
connectsmaller resistorsin parallelwith the filter load
resistorsto reducethe bandwidth.
Each crystal is embeddedin a balancednetwork.
The balancEadjustmentcompensatesfor the effects of
crystal parallelcapacitance.This improvesfitter stopband attenuationand shapesymmetry. each stagealio
containsa variablecapacitorin series with the Lrystal
to provide a fine frequency adjustment with a tuning
range of about 15 Hz tor each stage.
_ lach amplifierconsistsof a feedbackcircuitusinga
JFET and a PNP, providing voltage gain of about trio.
The stage is completedby drivingan emitterfollowerto
providethe low output impedanceneEdedto drive the
next crystalor the outputmixer (2nctMixer). The vatues
of the f€edbackresistor and the input resistorsdeter_
minethe stagegain.
The 250 kHz signal from the mixer drives a smatl
attenuator and the transformer Tgoi 6. The attenuator
terminatesthe mixer and transformers. The balanced
output from T3016 contains crystal y2o2o and the Fre_
guencyadjust capacitorson one side and the Balance
adjustmentcapacitoron the other side. Load resistor
R4163 terminates the crystal network When 10Hz
bandwidthis selected,Q4159turns on, ptacingR9162
in parallelwith load resistor R4l69. This raises the e
and reducesthe bandwidth. lt also increasethe insertion loss, so Q2159 also switcheson, placingR3162in
parallelwith R4027to increasethe gain and overcome
the addedinsertionloss.
Series network R2145 and C2150 provide positive
feedbackfor the amplifier. This looks inductiveand so
compensatesfor the capacitance an the impedance
seen at the amplifierinput. Capacitor Cg14g, across
feedback resistor R3160, rolls ofr the amplifier gain
above250 kHz to prevent10 Mhz feedthrough.
Emitter follower Q4145 provides a low impedance
drivefor the next filter stage.
The secondstag€filter uses Q4140to invertthe signal for BalanceadjustmentC4045. Other than that, the
operationof this stageis identicalto the first. The third
stageis identicalto the second.
2nd Mker. The 2nd Mixer (A694A)converts the
filtered signal trom 250 kHz back up to 10 MHz. The
mixer in this circuit is a MOSFETring (U5022)like that
used in the 1st Mixer stage. Less LO voltageis needed
because IMD requirementsare less stringent in this
stage. A potentiometeradjusts mixer gate bias. The
adjustmentis madefor best conversiongain.

7-25

Theory of Operation-

494A/494ApServlce, Vol. 1

After mixing,the l0MHz output signal is fittered
with a second monotithic crystat fitter (y2020). This
filter is importantto the systemoperation. Withoutit, a
large signal at 9.75MHz woutd be presentin the wide_
bandVR amplifiersthat foltow.

Local Osclllator. The Local Oscillator assembly
(469A4)providesthe 9.75MHz squarewave LO signali
needed for mixing. This is derived from a 19.SMHz
9ry_sFl oscillator by using a duat D-type flip-flop in
divide-by-two circuits. Since both sections are avail_
able, one is used for each mixer. This providesexcellent isolataon.One output drives the buffer amptifierto
!he.11 Mixer (A69At),and the other dir€cflydrivesthe
2nd Mixer (A69A3). A +5 V regutatoron this board
powers the flip-flops.

10 dB Gain Steps (Diagram 20)
The 10 dB Gain Steps circuitprovidessystemgain,
a 10 Hz gain adiustment,a 10 dB switchabti gain itep,
and the front-paneloverall gain (AMpL CAL) control.
The circuit consists of three stages of amplification.
The nominalinput signallevelfrom the 1st FilterSelect
carcuit is -25 dBm for a resolution bandwidth of
100 kHz. (All levels listed in this descriptionrelate to
the 100 kHz resolution.)
The input signat is apptied through impedance
transformerT4019to the first amplifierstageconsisting
of a differentialpair, 03016 and e2027, drivingemitter
follower 01036. The signalfeeds back to the base of
Q2027throughdividerR2034and R20S1.Signatoutpui
resistor R2035presentsapproximatetyS0 ohms output
impedanceto the next stage.
Gain of th€ input stageis the samefor all resolution
bandwidths€xcept 10H2. When 10Hz is selected,
Q2015connects10 Hz Level control R2025and R3029
acrossR2031.
Tle lst stage output drives commonemitter stage
02043. Gain of this stage changesby +10 dB when
Q4039 is switchedon. Data bit 0 froni the gain steps
decoder circuit on the VR Mother board #2 {A6gA2)
controls this galn step. When the bit is high, emitter
resistor R2048sets the stage gain. When low. e40gg
saturatesand shuntsR2049with R3039and 10 dB Gain
adjustmentR3035. This increasesthe stage gain by
10 dB.
The output of Q2043 drives the input of the third
amplifierstage. This stage operatesthe same as the
first stage except the gain is adjustableby the front
panel AMPL CAL screwdriver control. plN diode
CR1053and resistorR1056shunt resistorFt1060to

7-26

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control the gain of this stage. The AMPL CAL control
biases CR1053. The amount of current through the
diode determinesits high-frequencyresistance.As the
current through the diode increases.the resistance
decreasesand the gain of the stage increases. Gain
rangeis approximately14 dB.
Outputimpedanceof the stage is 50 ohms as set by
resistor R1064. Nominal output level is -1 dBm for a
full screen display. This level may be as high as
+9 dBm when MIN NOISEis active. In the MtN NOTSE
mode, '10dB of att€nuationis removedfrom the instrument input step attenuator.vR Inputsignalsare higher.
H€nce,10 dB of gain is removedfrom th€ VR.
20 dB Gain Steps Circuit (Diagram 20)
This circuit provides gains of -8 dB, +2 dB,
+12 dB, and +22 dB in precise10 dB steps. The nominal -1 dBm input is supplied through pin P from the
10 dB Gain Steps circuit. This signal is applied to a
chain of three amplifiers,each using emitterdegeneration. A change of the emitter resistancechangesthe
amplifiergain. The gain step decoderon the VR Mother
board #2 suppliesthe switchingsignalsthat s€lectthe
amplifiergain. These ampliftersare similarto the 10 dB
Gain Step amplifier previously described. On this
board, the first two amplifiers are cascaded for the
20 dB step and the third amplifierprovidesthe additional10 dB step.
The nominalgain of the compl€tecircuit is -8 dB,
with th€ gain steps switched off. This provides a nominal -9 dBm output. In this condition.controlpins V and
Y are high,biasingQ2018,Q204{ and Q1062off.
For the 20 dB gain step. 02018 and Q2042turn on
(pinV is low), increasing the gain of the first two
ampfifiersby 10 dB each, for a 2OdB gain step. Potentiometer A2029 (20 dB Gain) adjusts the first stage
(O1025)gain shift while the secondstage(Q1035)gain
shift is fixed at about +10 dB. The adjustmentallows
settingthe gain step to exactly+20 dB.
For the 10 dB step, pin Y is low, saturatingQ1062.
This raises the gain of the third amplifier(Q1043)by
10 dB, as set by R2060.
Gain of the 20 dB and 10 dB gain step circuitsis
controff
ed by data bits 0, 1, and 2. Data is latchedon
the output of decoder U3017 on the VR Mother board
#2. When the bits are high. transistor04035, 03035,
and Q4037 switch on. The resultantlow out turns on
the respectivegain step circuit. Table 74 shows the
state of bits 2, 1, and 0 and the gain shiftsobtained.
The output signal from the 20 dB Gain Stepscircuit
is appliedthrougha coaxialcableto the VR Band Leveling circuit.

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Theory of Operatlon -

4g4Al4S4Ap Servlce, Vol. 1

Table 7-4
GAIN STEP COMBINATIONS

Galn Required
ru ots
20 dB
30 dB
40 dB

Data Biis

2

1

0

0

0
0
0

1
0
1
1

1
1
1

1

Band LevetingCircuit (Diagram20)
- The two amplifiers,in the VariableResolutionBand
Levelingcircuit,conect gain variationsthroughthe front
end. These band-to-bandvariations are due to the
differentmodulationproducts out of the lst Converter
and lossesthroughthe preselector.
Nominalsignal input tevel for band 1 at 100 kHz
resolution,in the Min Distortionmode, is _12 dBm.
This decreasessornefor the higherbands. The output
level is about -2 dBm. This output level is kept con_
stant by using the microcomputer to adjust the
amplification
throughthis circuitfor eachbanct.
The two amplifierstageson this boardare similarto
llre 10 dB gain steps circuits. A stage consists of a
three-transistorcircuit using a diffeiential pair connectedto an emitter-follower.The gain is controlledby
alteringthe feedbacknetwork.
first stage (e2015, e2019, and e1025) has a
.The
gain
range of 13.5dB by controilingthe bias of ptN
diode CR2021in the feedbackloop. Bias for this diode
depend-son-a voltage divider network consistingof an
array of variablaresistors on the VR Mother board #2,
468A2, with the dividernetwork setectedby the microcomputer.
(e1031,e1o3g,and e1041)is
. Jh" second.stage
similar,.exceptthe gain changeis a one step changeof
approximately12.5dB. This gain step occurs in the
higlrelbands(4 throughi1). tf required,gain changeis
activatedby the microcomputerthrough user-selected
diodesand transistore2046.
The spectrumanalyzer is normallycalibratedwith
the band 1 gain control resistor set for rninimumgain.
Gain is then added as requiredfor the higher
bands.
-banO
Data bits 3 through6 select gain for each
selection.
The output from this board is appliedthrough con_
nectorEE to the 2nd Filter Selectcircuit.

468A5
Pin N (10 dB)
0
1
0
0

468A6
Pin V (20 dB)

1
0
0
0

PinY (10
1
1
1
0

VR Mother Boards {Diagram 18)
The circuits on the VR Mother boards provide
addressand data decoding,band levelingcontrol,and
plwer supply and controlsignalinterfacingto the other
VR boards. The VR Motherboard #1 (A6SA|)provides
decoupledpower suppliesand interfacelines to the VR
Input (A6849), lst Fitter Setect (A68A4),10 dB Gain
Steps(A68A5),and 20 dB GainSteps(A6gA6)boards.
The VR Mother board #2 (A6gA2)providesaddress
and data decoding and gain controf for the Band Levefing circuit. The VR Mother board #2 providespower
supply voltages and control lines to the VR Mother
board #1 (A68A1),Band Leveting(A68AZ),2nd Fitter
Select(468A8),and the VR post Amptifier(A6gA9).
Address and data valid lines from the instrument
address bus are applied to address decoder U4O2Z.
Data bit 7 is appliedto the decoder,sselect inputA as
a supplementaladdress bit. This bit selects either an
address to latch data for th€ resolution bandwidth
selection or an address to latch data for gain step
selectionand band identification.
Data latchesu3010 and u3017 monitorthe data bus
at the sel€ctedaddress. Latch u3010 stores the filtEr
s€lect data that controlsth€ lst and 2nd Filter Select
circuits.
U3017 latches the gain selection and band
identificationdata. Latcheddata bits 0, 1, and 2 (output
pins 2, 5, and 6) switch transistorse4095, e3035, and
Q4037to controlthe gainswitchingcircuitsin the 1OdB
and 20 dB Gain Step circuitsthroughVR Motherboard
#1.
The output on pins 15, 16, 19, and 12 ol U3017
(correspondingto data bits 3, 4, 5, and 6) are apptiedto
band decoder U3023, an op€n collector decoder. lf
band 1 is selected,pin 1 of u3023goes low and if band
2 is selectedpin 2 goes low, etc. This output in conjunction with a 7.5 V referencesource (providedby
operational amplifier U30388 and driver transistor
03036) produces a voltage at the output of a operational amplifier,U3038A. This voltage is indicativeof
the gain that must be set for each band so the level
remainsconstantat the outputfor all bands.

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7-27

Theory of Operation -

49{A/4g4Ap Service, Vol. I

The output of u3038A is apptiedthrough edge connectorpin BB to the gain controlplN diode in the Band
Levelingcircuit. For example;when band 1 is selected
(U3023pin 1 low), current through Band 1 Gain potentiometer,R2031,and the emitterof e3036 sets the voltage throughR2033to the summinginput of operational
amplifier U3038A. The increas€d output of U303gA
increasesthe current through band levElingplN diode
CR2021and increases the gain of the stage according
to the setting of Band 1 Gain pot€ntiometerR2031. In
similar fashaon, the other potentiometers (R9034,
R3030,R3019,3A22,R3024,R3026,R3032,R302g,and
R3028)allow adjustmentof the current for each of the
other bands.
An additionaldiode may be added to each decoder
output,for bands 4 through10, to transmitthe low. via
edge connectorpin OD, to the gain control transistor,in
the Band Levelingcircuit, and increasethe gain more
lor these bands. These diodes are CR3022,CR3O23,
CR3024, CR3025, CR3031, CRg027, and CR3026.tf
needed these diodes are installed during instrument
calibration.
The +5 V regulatorcircuit, U9041,suppliesa noisefree +5 V source for the VR system. This ls required
becauseof noise in the +5 V main supply.
2nd Filter Select Circuits (Diagram 2l)
Circuits on the 2nd Fitter Setect board (46gAg)
operatein conjunctionwith the circuits on the lst Filter
Select board (A68A4) to set the overall systern
bandwidth. Banksol filters are select€dunderthe master microcomput€rcontrol. Data bits 0, 1, and 2, lrom
the data bus, are applied to decimal decoder U9070
(which outputs a low on th€ appropriateoutput pin to
enable th€ selected filter). Bandwidth selectionsare
10 Hz to 1 MHz in decadesteps,plus3 MHz.
Filter selection is accomplished as previously
describedfor the 1st Filter Selectcircuit except for the
3 MHz,1 MHz,and 100 Hzl10Hz selections.
The input signal,from the Band Levelingcircuitvia
jumper EE, is routed through the selectedfilter to the
Post VR Amplifiercircuit, via jumper JJ. Nominalloss
throughthe filter circuit is approximately12dB, with
internal adiustment compensation for variations
between the filters. The output level is nominally
-12 dBm.
The filter for each bandwidthrangeslrom no filter at
all to a temperature compensatedcrystal filter. An
important difference between the i st and 2nd filter
selectcircuits is the additionof a gain adjustmentin all
except the 100 kHz circuit. This adjusts the amountof
att€nuationthrough the other filters and matches the
outputlevel to that of the 100 kHz filter. since the Band

7-28

Levelingcircuit furnishescompensationgain to obtain
equal signal levels for all bands, this adjustmentcompensatesfor variationsbetweenthe filters.
The 3 MHz and 1 MHz bandwidthsignals use the
same path through this board. No filter is required
here, becauso of filtering in previous stages. When
€ither 3 MHz or 1 MHz is selected, the signal goes
through a simple attenuator with a gain control for
matchinglevelswith th€ other sections. Pins 2 and 9 of
U3070are tied togetherto selectthe 3 MHz/l MHz path
for eitherbandwidth.
The 100 kHz filter is a double-tunedLC circuit
designedfor a good tima-domainresponseshape. The
filter is tuned with compositevariablecapacitorsconsisting of small air variables paralleledwith switched
fixed capacitors. A third variable capacitor may be
adiustedlo establishthe desiredbandwidth.For Option
07 instruments,a similar 300 kHz filter replaces the
100 kHz filter.
The 10 kHz filter uses a two-polemonolithiccrystal
filter. The impedances at the input and output are
matchedto 50 ohm by T5047 and T7050. An attenuator
that containsGain adjustmentR3039is includedat the
filter inputfor filter variationcompensation.
The 1 kHz filter is also a two-polemonolithiccrystal
with impedance matching transformers T40/,4 and
T:7043. A Gain adjustmentis also part of th€ attenuator.
The 100 Hzll0 Hz filter is a temperaturecomp€nsatedhigh-Q crystal filtsr. The actual filter
bandwidthis about 200 Hz. This filter augmentsthe
filter in the 1st Filter Select circuit and reducesnoise
producedin the interveningstages. Freq AdjustR4025,
in a voltagedividercircuit,sets the centerfrequencyof
th€ crystalfilter.
The 100Hzl10Hz path is selectedby Q2020and
08035throughdiodescRl017 and cR8016on the input
and output respectively.when 10 Hz is selected,pin 7
of U3070goes low turningon Q2020and Q8035. When
100H2 is selected,pin 6 of U3070 fonarardbiases
cR3068,thus enablingthe path.
Gain control R3015 adjusts the 100 Hz level. The
10 Hz level is set by a controlon the 10 dB Gain Steps
board (A68A5),as previouslydescribed.
Post VR Amplifier Circuit (Diagram 21)
The Post VR Amplifiercircuit providesthe final VFt
system gain to bring the signalto the requir€d+6 dBm
output level and providesthe final band-passfiltering.
The circuit consistsof two stag€sof gain followedby a
filter.

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Theory of Operadon- 4g4A/4g4ApService, Vol. 1
.. fn9 input signat.at a nominal_14 dBm, is applied
through toroid transformer T1041 to the
Oaii of
common-emitteramplifier el040. Gain adjustment
Rl0i!0, in the emittercircuit. sets the posi Vn impfin"i
gain. The output is transformercoupled,
by Tt0i0, to
the base of feedback amptifier OiOSO. ihis circuit
include.semitt€r d€generationthrough resistor
RlOg4
and collector-to-base
feedbackthroulh resistorRl041.
The collectorfeedbackhelps to prorid" a well-deftned
output impedanceof 50 ohms. input impedance
is a
function of transformer T1040 ana relistor
R1042
acrossthe primarywinding.
Fro.mthe finalamplifier,the-signalis apptiedthrough
.
a band-pass filter with about 2 O-einserton toss.
The
*6 dBm outputsignatfrom th€ fitter is afptied
through
coaxialconnectorJ6g2 to the Log Amplinii.

LOc AMp and DETECTOR(Diagram22)
The Logarithmic (Log) Amptifier and Detector
acceptsinput signalsfrom the Vi circuits. The
signals
are amplifiedso the output is proportionalto the
1-ogarithm of the input. The output ii ttrenappliedto
a linear
detector which outputs a video signal. By controlling
the compressioncurve_characteristi-c",
OBctranfE
in th€ input signallevel r€suttsin an equal
"""hincrementof
changein the output. In the 10 clBldivmode,each
division of displacementon the screenrepresentsa
10 dB
changeof inputsignallevel.
Log Amplifier Circuits
Tlgr". circuitstogarithmicaily
amptifythe inputsignat
,
from the VR circuitsand apply the output signalto-the
Detectorcircuit. The Log'Amplifier consistsof seven
ac-coupledamplifierstages. Each stage has two gain
valuesthat dependon signalamplitude.-In additionlhe
first three stag€s have an extra automaticallysel€cted
gain value. The combinedcircuitsprovidehighgain
for
lowJevel signals and low gain for high-level-ignals.
For.the,outputsignalto be ploportionalto the log;ithm
of the_input,more gain is reguiredfor a chang-efrom
-80 dBm to -79 dBm than
a changefrom _1 dBm to
0 dBm. For a given stage of the cir:cuit,the gain starts
at approximatelyl0 dB for a low{evel signal and
decreasesto unity as the input signal level increases.
In _thefirst three stages, the gain becomestess than
unityas th€ signalamplitudeincreases.
^ _lnput signaf levels nominalfy range between
-84
dBm and *6 dBm. As the signattev-etincreases.
the gain decrease begins with the final stage and
proc€eds,in succession,_backthrough the remaining
six stages to the first. Each stage initially produced
approximately10 dB of gain. That gain was reduced
to
unity, so the total gain reductionis Z0 dB. With further
increasesin input signaflevel, three more gain change

st€ps take place. The gain of th€ first three stages is
reduced.betow unity approximately7 dB for each itage.
This reduction starts with the first stage and procee-ds
to the third, to provide an additionatgain reduction of
approximatety
20 dB.
- As the Input signal increases from _g4 dBm to
19 d?r, the gain throughthe amptifierdecreasestoga_
rithmically so that the output signal is exactly proportional to the logarithm of the input. This ii accomplished through a system of seiies diode limiting in
each stage, with a second set of diodes for extra timiting in each of the first three stages.
The followingdescriptionof a simplethree-stagelog
amplifier,with one gain step in each stage, proviOls ai
aid
-to understanding the concept of a logarithmic
ampfifier.Figures7-g, T-9, and 7-10 show an example
amplifierand illustrat€its operation. The gain of each
stageis.3.16(10d8) up to an outputlevel-of1V peak,
then unity for output tevetsgreaterthan t V peafi tnai
is,. each stage uses one breakpoint. That breakpoint
voltageis used for ease of illustration;the actualbreakpointvoltageis significanfly
lower.
The amplifier is shown in Figure 7-g. The source
has a step att€nuatorthat allows the input signalto be
incrementedin 10 dB steps. Table 7-5 shows the progressionof gain reductionabove 1 V at each ampiifier
output. Note that with each input level change of
10 dB, the output change at point 4 is 0.694V. The
gain curv€ for one stage is shown in Figure 7-9. Also
note that when the level at point 1 is increasedbeyond
1.V, it is beyond the togging range of the ampiifier.
Similarly,if th€ inputlevelis decreased10 dB betowthe
minimuminpul level, the output incrementis different.
A curveof the loggingrangeis shownin Figure7-10.

POINT 1

POINT 2

POINT 3

POINT 4

44 16-99

Flgure 7{.

Block diagram of a tfrree stage log ampllfier.

7-29

Theory of Operation -

494A1494Ap
Servlce,Vot. 1

Table 7-5
PROGRESSION
OF GAINREDUCTION
Input
Level

Point
1

Point
2

,

Point
3

Poinl
4

0.316

0.1
- - 0'216
0.316

BeyondLoggingRange
x-10 dB
X Level
X + 1 0d B
X+20 dB
x+30 dB
x+40 dB
X+50 dB

0.00316

0.01

0.01

0.316

0.0316

0.1

0.1
0.316

___r
l_ 0.68a
1.0

3.16

0.1
0.316
1-0.684-1
1.0

0.316
r-0.684

1.€

1- 0.684-_-1

1.0

=__1
1_ 0.684
1.684

o
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o
o
o
o
o
o
o

1.684

1_ 0.684
2.368

BeyondLoggingRange

t
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t
LIN
VOLTS
OUT

END OF AMPLIFIERDYNAMIC RANGE

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Figure 7-10. Curve showing end-ol-range for a log amplifier.
44r&100

Figure 7-9. Log amplifaer gain curye rhowlng break polnts.

7-30

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. The 10 MHz input signalfrom the VR circuitsdrives
input preamptifiere2075, in th€ tog lmftiner circuits
on A62A1. The input preamptifierir"nsier" the
S0O
input signal to the high_impedance
input of the first
amplifier stage. The input signal is ilso apptied
to
transistor01 07S,a common-baseamplifierthat acts as
a bufierto supplythe l0 MHz lF signatto the rear_panel
connector.
Frgm the input preamplitier,the signat is apptied
..
through seven cascadedstages each cinsisting'ot
an
emitter follower driving a common base amptifier.
Resistorsbetweenthe emitterfollowerand the common
base sectionsdeterminethe gain. Diodesswitch various resitorsin or out of the circuitto vary the gain
for
different input levels. All of the
are similar,
except that the first three stages "t"g"Jan extra set
of
diodesfor an additionalgain itep."ontaii
All stages have maximum gain for low amplitude
input signals. As the input amptitudeincreases,the last
stageswitchesto a lower gain. For furtherincreasesin
input amplitude,additionalstages decreasegain
back
to -the first stage. Then the second set of gainswitching diodes switches into the first, second, and
third stag€sto reducethe gain for the larggstsignals.
Typically,when the inputlevelto the emitterfollower
in th€ last stage is less than 60 mV peak-to-peak,the
transistorconductsenoughto maintainfonrvardbias on
series limitingdiodes. The 10 MHz signatpath at that
level is throughboth diodes,a capacitjr, ani a resistor
networkto the commonbase sectionof ihe stage. The
gain
.of the stage under these conditionsis ipproximately10 dB.

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- As the input signalvoltageincreases,more current
llows through the left diod€ to increasethe reversebias
of the right diode. This sharplyreducesthe stagegain
to unity. The signalcurrentthen flows only in the lower
path aroundthe diodes.This changetakes ptace
during
the positive-goingportionof each cycte. tne opposite
occurs during the negative_going
pdrtion of the signal
above the minimum input level. As the input signal
increasesbeyondthe point at whichthe gain of the final
stage decreasesto unity,the same sequince occurs in
the precedingstage.and in succession,backto the first
stage.

4g4Ll4g4ApServtce,Vot. l

Signal levels above this point activatethe second
tier of gain reductionin the first three stages. These
stages each incorporate a second set of diodes that
r€duces the gain by another 7 dB. In the first tier of
gain reduction. reduction started at the last stage and
proceededto the first; in the secondtier, the reduction
starts at the first stage and proceedsto the third.
In the first three stages, the lower diodes are forward biased untit the second tier of gain reduction.
With a further increase in input signai level, limiting
occurs in the same manneras previouslydescribedand
results in less than unity gain through the stage
(approximatety 112r. The one-two-th6e reducrion
sequenceis establishedby the valuesof the pull_down
resistorsat the cathodesof the diodepairs.
Detector Circuit
This circuit demodulatesthe 10 MHz output of the
Log Amplifier,producingthe VIDEOsignal that drives
the VideoAmplifiercircuits. The detectoiconsistsof an
operationalamplifierwith a diode detectorin the feed_
back path. A low-pass filter at the output, shown on
diagram23, filtersthe RF from the dEtectlOsignal.
The operationalamplifiEris madE up of common
emitt€r amplifier01012 and a differentialamplitierthat
consists of Q2010and e20l8. The summingnode for
the n€gativeinput is the base of e1012 (the positive
input is at the groundedemitt€rof el012).
The differentialamptifier's high impedanceoutput
allows it to rapidly changeduringthe periodwhen both
detector diodes are effectivelyopen circuited;that is,
when the outputis near 0 V. Whenneitherdiode is conducting,it is necessarythat the output change rapicfly
throughthat zone.
Figure 7-11 shows a simptified ac-equivalent
schematicdiagramof the detectorcircuit. Two detector
diodes are used, but only the negativehalf cycle is
taken as the output. Ac couplingis used on both sides
of the detector diodes to prevent ternperature
coefficient effects of the operationalamplifier from
affectingthe detectoroutput.
The detector output signal is appliedto the Video
Amplifier. A low-pass filter shown on the foilowing
diagramcompl€testhe detectorby filteringthe remaining RF.

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Theory of Operation-

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Theory of Operation-

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4g4ful4g4ApServtce,Vot. I

DISPLAYSECTTON
(Diagram6)
FUNCTIONAL
DESCRT
PTION
The display section consists of the followingmajor
blocks:
o VideoAmplifier
o Mdeo Processor

characteristicto lin€arfunction. In either mode, base_
line compensationfrom the Vid€o processoris applied
to the video signalto compensatefor any unflatnessin
the front-endresponse.The pulsestretcircircuitat the
output of the Video Amplifieratters narrow pulses so
data can be acquired and disptayed by the Digital
Storage logic. Signalamplitudeoffset ciicuits provide
displayoffsetfor the "ldentify,,mode
operation.

. DigitalStorage
o DeflectionAmplifiers

Log Mode Circuits

. Z-Axis

The log mode circuits process the VIDEO signal
from the Log Amplifier,and they add ofrsetfor selecting
that segrnent of the log amplifier gain curve to be
displayed. The circuitsalso select screendisplaygain
steps from 1 dB/divto 15 dB/div.

r CRT Readout
. The Video Amplifierprocessesthe detectedlF sig_
nal through appropriateamplifiers for log and tineir
displays, and provides pulse stretching for narrow
pulsedsignals.
The Video processor provides band leveling to
corr€ct front-end unflatnessthrough the bands, video
filtering for noise averaging,out_;f_bandblanking to
clamp the display to the basetinewhen the sweep is
outside the range of the selected band, and video
markercapabilityfor use with a TV sidebandadapter.
Tl" Digitat Storage digitizes th€ video and sweep
.
signalsand stores the data in memory. Storeddata is
thsn converted to analog signals for ttre Deflection
Amplifierand Z-Axiscircuits.
The DeflectionAmplifierprovidesthe drive voltages
for the cRT. This includes vertical and horizontal
deflectionsignals as well as readout charactersfrom
the CRT Readoutboard.
The Z-Axis circuits receive and decode data from
the microcomputer;accept control levels ,rom the
front-panelbeam controlsand generateunblankingsig_
nals to control the displayappearance,brightnesslaid
focus; detect power failure;monitorthe inJtrumentvol_
tage supplies;and recordthe elapsedoperatingtime.
The CRT Readout circuits generate the
alphanumeric
charactersfor the display.

VIDEOAMpLtFtER(Diagram23)
Video signals, from the log amplifier and ctetectorin
the lF section, are received by the Video Amplifier. In
the logarithmic mode, the signals are amplified linearly
and applied to the Video processor. In the linear mode,
exponential amplification converts the logarithmic
aain

The detectedVIDEOsignat,the VTDEOI correction
signal, an offset signal, and reference current are
summedat th€ input to operationalamptifierU4050. A
lowpass filter removes l0 MHz from the detected
VIDEO signal. The VTDEOI signat is adjustedon the
Video Processor board (A40) as compensationfor
front-endunflatness.The signalis equal and opposite
in amplitude to the unflatness. Th€ lnput Ref Level
adjustment,Rl 012, sets the reference level. Signal
converter(DAC)
9{"9t is suppliedby digitaf-to-anatog

us160.

The DAC convertsthe microcomputercommandsto
an offset signal that selects the location on the log
amplifier curve tor the disptay (see Figure 7-12). In
dB/div or log display modes, a change in th6 Vertical
POSITIONcontrol produces an effect after the log
amplifier that is the sam€ as a signal level or gain
change before the log amplifier. Instead of using a
large amount of linear gain before the log amplifier,the
output of the DAC effectivetyofisets ths disptay up or
down along the log curve. This offs€t produces the
same effectas varyingthe pOSITIONcontrolexceptthe
display positiondoes not change,only the signal level
requiredto reachthe referencelevelchanges.
This processallowsthe lineargain to changewhile
the top of the screenis kept constant,and it must also
allow any 16 dB segment(in th€ 2 dB/div mode)to be
displayed. Nominally,the log amplifier operates with
+6 dBm equivalentreferencelevel at the top of the
screen.
The outputol U4050is equivatentto 20 mV/dB. Futl
screenis 2.2 V, as set by lnput ReferenceLevelpotentiometerR1012. From U4050the signalfeedsthe log
mode gain circuil and the lin€armode gain circuit. The
digital controlcircuitselectsbetweenth€ log and linear
modecircuits.

7-33

Theory of Operaton -

494[l4g4Ap Servlce,Vol. 1

*

TH|S 16 dB
SEGMENT
MAY BE MOVED
TO ANY POSITION
ON LOG CURVE

LIN

ouT

*10 dBm

80 dB Total

dB IN

4416-1t3

Figure 7-12. Selecdon ol display positlon on lhe log scale.

Log mode amplifierU4030tineartyamptifiesthe signal. (fhe log conversiontook placein the Log Amp circuit.) At 2.2 V input, the output of amptifierU40S0is
0 V. This is the only voltageat which the feedbackcircuit switchingnetwork resistorsof amplifierU4030can
be switchedwithont changingthe outputvoltage. The
switchingnetworkis describedlater in this discussion.
When the log mode is selected,the output signal
from U4030is appliedthroughFET e5035to the output
amplifier. Output Reference Level potentiometer
Rl030, in the input circuitto U5030,adjuststhe output
level for a full screen display after Input Reference
Level potentiometerR1012 is set for no changein the
output of U4030when switchingbetweenthe 10 dB/div
and 2 dBldiv modes.
The gain switchingnetwork switchesresistorsin or
out of the fe€dbackpath of amplifierU4090. The network consists of Q4035, e4090, e4155, and e4150,
and associatedresistors. The FET switches(controlled
by data bits 0, 1, 2, and 3 from the instrumentdata bus)
switch in feedbackresistorslor U4030in combinations
determinedby the four data bits.
Linear Mode Circuits
The linear mode circuits accept the logarithmically
scaled output from U4050 and rescalethe signal level
to linear values. Sincethe input signalsare logarithmically scaled,the signallevel is exponentiated
to operate
the systemin the linearmod€. High gain is requiredat
the top of the screen and low gain is requiredat the
bottom of the screento offset the characteristics
of the
Log Amplifiercircuits.

7-34

In th€ linear mode, FET switch Q5150 is on. enabling the linear mode signal path; and Q5035 is off,
disabling the log mode path. The output from
preamplifierU4050 is also appliedto linear mode operational amplifierU4070, with a successiveresistor network switched into the feedback path. From this
amplifier, the output signal is applied through FET
Q5150 to the summing node at the input of output
amplifierU5030.
With a *6 dBm input to th€ Vid€oAmplifier,the output of U4070 is 0 V. This is the level that represents
the top ot the screen. At that level,the foedbackpath
is only through resistors R4118 and R5112. Diode
CR4125and R4122 are only activawhen neededto limit
negative excursions. The other feedback resistors
(switchtransistoremitt€r r€sistors)ar€ not in the path,
because the switch transistorsare biased off by the
dividernetworkat the transistorbases.
As the displaymovesawayfrom full screen,th€ output voltage of U4070 increasesand turns transistor
O4120on. This places R4124in parallelwith the tixed
feedbackresistors,thus reducingthe gain. As the voltage output increases,transistors04125, Q4065.and
04060 start to conduct in sequence, adding their
emitter resistors across the feedback path. This
effectivelyreduces the gain of U4070 exponentially.
The transistor characteristicssmooth the step transitions, producing a smooth exponential gain curve.
Diode CR41'l 5 providesternperaturecompensationfor
the switchingtransistors.The Lin Mode Balancecon'
trol, R1025,sets the U4070 output level to match the
log modeoutput.
Pulse Stretch Circuit
The pulse stretch circuit consists of FET switch
Q5026 and the associated components. When the
pulse stretch mode is not sglect€d{data bit 7 on the
instrum€ntdata bus is low), pin 13 of U4020Cpulls
down to -1 5 V, and Q5026 biases off. This removes
C5024from the circuit and also suppliessufficientnegative bias to keep CR5025fonvardbiased. With CR5025
on, the feedback loop for U5030, through Q5025and
R5033is closed so the signaloutput will fall as fast as
its rise.
when the pulse stretch mode is selected(databit 7
high), the open collector output of u4020c (pin 13) is
allowedto float. This turns Q5026on which completes
the path for C5024to ground. During signal rise time,
C5024chargesthrough the low impedanceof CR5025.
The feedbackpath for U5030is still closed which providesa fast rise time.
When the output of U5030 begins to fall, CR5025
turns off and the signalfall time is now a functionof the
RC time constantof R5031and C5024.since the f€ed-

Theory of OperaUon-

back loop for U5030is now open. DiodeCR5035turns
on to preventU5090from slewingtoo far negative.
ldentily Circuit
This circuit provides a vertical offset on alternate
t9 help identifytruE and fatsesignats. Whenthe
lllcg:
'ldentify"feature
is in op€ration,it allolvsthe operator
to distinguishbetweenresponsesthat result from signals at.the desired spectrumanalyzerinput trequenjy
(true signals)and those that are produced by'othe?
spuriousor harmonicconversions(falsesignats;.fatse
signalsshift horizontallyon alternatetrac6s while true
signalsremainin position.
The horizontaloffset is accomplishedelsewherein
the instrumentby movingthe 1st and 2nd LO frequency
an equal and opposite amount, relatedto the ist LO
harmonicused, or by moving the lst LO twice the lF
divided by the harmonic number (N), on every other
sweep. The result is that any conversionpioducts
causinga false responsewill shift a significantamount
horizontallyon the displaywhile true signalswill remain
closeto eachother.
The identifyoffset circuit describedhere shifts the
alternateor'ldentify" sweepvefiicallyas a furtheraid to
identifyth€ true signals. The microiomputersets DB6
high during'ldentify"sweep so the open collectoroutput of U4160A(pin 1) goes from -15V to open. This
remov€sthe current normaltyflowingin R5154, R51SS,
and R5158 from the summing node of U5030 and
causesa shift in the VIDEOil outputlev€t.

494A1494ApService,Vot. I

vtDEo PROCESSOR
(D|AGRAM
24)
The Video Processor performs four functions. The
ftrst is compensationfor flatness variationsin front-end
response. The secondis vldeo filtering,whichprovides
the selection of six video bandwidths(90 kHz, O kHz,
300 Hz, 30 Hz. 3 Hz, and 0.3 Hz) under control of the
instrumentmicrocomputer.The third functionis out-ofband blanking,which blanksth€ upp€r and lower ends
of the local oscillator swept frequ€ncyrange to provide
a selectedwindow for the display. This functionis also
controlled by the microcomputer. The fourth is the
capability to genEratea negative-goingditch markeron
the video display for interfacingwith a 1405 TV Sideband Adapter.
Interface with 1405 TV Sideband Adapter
The TEKTRONIX1405 W SidebandAdapter is a
specializedtracking generator that is used with the
SpectrumAnalyzerto analyzethe responseof a television transmission system. The Spectrum Analyzer
monitorsthe RF outputof the transmitterwhilethe sideband adapterdrivesthe video input of the system. The
video input may be at the transmittersite, the headend
of th€ studio-transrnitter
link, or the video switcherin
the studio. ThE sidebandadapter must be connect€dto
the lst LO of the SpectrumAnalyzerby a short length
of coaxialcable.
Th€ system in Figure7-13 depicts a TV transmitter
operating on Channel 10 with a video carrier at
193.25MHz. The sidebandadapteris tunedto Channet
10. The Spectrum Analyzer is tuned to 195.25MHz
with a span settingof 1 MHz/Div(for purposesof iilustration,the sweep is assumedto be haltedat the center
frequencyof the analyzer).

The digital control circuit providesthe control sig_
nals that select the various Video Amplifierfunctioni.
Addresses78 and 79 are decodedby U6160and sent
throughinverterU6170as clock or enablingsignalsfor
gainlatchu5010 and modetatchu4010.

The sidebandadapterapplies a2MHz signalto the
AM modulatorof the video transmitter. Th€ modulator
producesa lower sidebandat 191.25 MHz, a carrierat
193.25MHz, and an upper sideband at 195.25MHz.
This signal is amplified,filtered,and combinedwith the
FM aural signal. The compositesignal is sensedby a
RF pickup and appliedto th€ RF Input ot the Spectrum
Analyzer.

Gain latch lc u5010 is an g-bit latch that suppties
commanddata to the 8-bit DAC, USl60, to offset the
Log Amplifieroutputsignat. ModetatchU4O1O
is an 8_
bit latchthat suppliescommanddata throughthe comparatorsin U4020and U4160to selectthe resistorsin
the dB/div switchingcircuitand to sel€ctidentify,pulse
stretch,and log or linearmode.

The 1st Converterappli€s the compositesignalto
the 'l st mixer. The compositesignal is mixed with a
2.26725GHz signalfrom the 1st LO, formingthreeproducts. The subsequentstages of the analyzeraccept
onfythe 2.072GHz productand rejectthe rest. For frequenciesused in this example,the acceptedproductis
the differencebetweenthe 1st LO and the uppersideband of the TV signal.

Digital Control Circuit

7-35

Theory of Operaton -

4g4Al4g4ApService,Vol. I

ToVid@Pcq

RF ln

'l

95.25 MHz/Uppsr Sdeband
t93 25 MHz/Cars
19t.25 MHzIL@d Sirebad

trA8X€R/VtO€O
rcll
-2.5 6lt

LOAO
Oisglay MaA6

h

Z-Ax6 o(rl

ffi
rffi

?.26525GHz
lst lF + fV Carrs

i\r

o.TsMHr

i\o-

r.zsMHr

i\\o*

sprre

i\o-

3.5sMHz

i\-..rsMHz
i\'o-

4.75 MHz
Ert. l.Voui

!@_f9sEs9Ll9l
5(n+fi

Figure 7-13. Functonal dlagramrhowing the Spectrum Anafyzcrand 1405TV SldcbandAd.picr System.

The product is converted twic€ more, amplifi€d,
liltered,log amplified,and detected. This detectdOsignal is applied either directly to the video amplifiersof
the crt or to digitalstorage.
The SpectrumAnatyzerlst LO signatis appliedto
the RF mixer of the sideband adapter. The
2.26525GHz signal from the tunable LO is subtract€d
from the 2.26725GHz signal trom the Spectrum
AnalyzerLO, yieldinga ZMHz product. This video frequencysignalis conditionedwith sync and blankingsig_
nals and applied to the video input of the T\/
transmitt€r.
Whenthe SpectrumAnalyzeris sweeping,the video
signal starts at 3 MHz, lalls to 0 Hz, and rises up to
7 MHz. During this intervat,the analyzerdisplaysthe
lower sidebandas it movestoward the carrier,diiplays
the carrier,and then displaysthe upper sidebandmov_
ing away from the carrier. Sincethe SpectrumAnatyzer
and 1405 TV SidebandAdapter system is similar io a
trackinggeneratorsystem,it rejects nolseand uncorrelated signal. This allows normal in-serviceuse of the
transmitterby adding a tow tevel (1 to 3 tRE units)cw
signal to the video or by using fuil levetswith a ilTS
inserter.
7-36

The sidebandadapter can lnsert frequencymarkers
at preselected deviations from the carrier frequency.
Six selectablocrystal oscillators have their outputs
mixed with video signal and appliedto a Z-Axis circuit.
This circuit producestwo n€gativepulsesas the video
signal sweepsthrough tho crystal oscillatorfrequency.
These pulses are applied to the spectrum analyzer
mark€r input, whers they appear on the crt as two
notch€s on either side of th€ marker frequency. The
sidEband adapter allows the width and depth of th€
notchesto be adjustedwith the width and Intensitycontrols.
Video Marker
The Z-Axis signal from the 1405 SidebandAdapter
connects to the MARKER input on the spectrum
analyz€rrear panel. This negative-goingsignal flows
through the Accessories and Mother boards to the
Video Processor board. Here, the signal drives the
ernitterof Q4060and turns the transistoron, pullingthe
VIDEO OUT line down. This produc€sa notch in the
video signalof the displayto signifythe locationof the
markeron the display.

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Theory of Operaton -

Video Leveling
. -A^mjnor slopein frequencyresponse,causedby the
1.86GHz low-passfilter in the front end, is corr€cted
with band I Slope adjustmentR1012. Wirenoperatng
in band 1, contacts6 and 7 of U3025are closed;therJ
forq a portion of the PRESELECTOR
DRTVEsignat is
applied to the VIDEO I output signal, providiig
the
ofiset necessaryto correct slope difference.

Video Leveler Circuits
. Mdeo levelingcomp€nsatesfor analyzerfront-end
microwave circuit characteristics that cause unflat
response. band 4 (5.4 GHz to 1g GHz). Since band 4
ln
is a multipliedband, any unflatnessis ac"entuatecl.
Levelingis accomplishedthroughprogrammableperturbation of the disptaybasetine[trai is opposatein direc_
tion to the flatnesserror. As the signai power output
decreases,the baselinerises an equil amountto com_
pensate,and as power output increases,the
baseline
falls an equalamount.
perturbationis producedby
.The
a normalizerintegrated
that produces19 evenly
spaced valu€s of the -circuit
input voltage, with each valui
correctedto compensatefor unflatness.

The PRESELECTOR
DRTVEsignatfrom the tst LO
drivercircuitsis appliedto a translationcircuitthat consists of two currentdrivers(U3O45Aand hatf of e303g,
plus U30458 and the other half of e303g).
The
PRESELECTORDRIVE signat is direcfly r€tated in
amplitudeto displayedanalyzerfrequency.The nominal
+10V to -10V gxcursion voltage versus frequency
9urve1in maximumspan, relates to the full bandwidth.
This 20 V maximurnexcursion is scaled to a precise
current(from 1 mA at +10 v to o currentat _10 v) that
is appliedto the normalizerlC to generatethe baieline
perturbation.Actual signal scaling is done by current
driver U3045A/Agmg. The outpui signatis apptiedto
the normalizerSWp lN input, pin 5 of U20g9. The
second current driver, Ug04SB/Og03g,generates a
2 mA referencecurrent for the normalizer] Horizontal
Freq adiustmentRl069, in the input translationcircuits,
shifts the 19 evenly spaced points up or down in frequencyto compensatetor unflatness.

?

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NormalizerlC U2039operatesas a shaperand contains 19 transistorsthat turn on and off in sequenceas
the current input to pin 5 decreasesfrom 1 rnA to 0.
Each collector is connected to a potentiometerthat
allows outputtrimming. potentiometerR1061 is active
with no current,and R1013is acfiveat I mA. The trim_
ming operationis describedlater.

4g4AJ4g4ApService, Vol. 1

From the normalizer,the outputis appliedthrougha
jumper switch to bufferamptifierU2OS5B,which his a
gain of five, then to offs€t amplifier U2OSsA. This
amplifierhas a gain of two, but its primarypurposeis to
offset the 0 to +5 V (normal),0 to -5 V-(invert),buffer
output to the levels requiredby th€ Log Amplifiercircuits. The range requiredby the Log Amplifieris O to
. J-0V. The output voltage is a seriss of linear interpo_
lations of th€ voltag€ betwe€n adjacenttrimming reiis_
tors at the outprrts of the normalizer. Compensation
adjustmentR1065sets corect interpolation.
Jumper ptug p2060 setectsthe input side of buffer
amplifi€rU20558 and proper ofiset vottagefor U2055A.
This provides the meansto invert the buffer output dur_
ing the instrumentadjustmentprocedure.The adjustment procedure is described in that section of this
manual.
As previouslynoted,only band4 requiressignificant
compensaflon.Selectionof band 4 is indicatedby data
bit 0 switchingto a 1 (seethe Lev€lingtabte at tire top
right_cornerof Diagram24). When DBOis a 1, pins b
and 2 ot switch U2015 are connected,and the output
from offset amplifier U205SAis supplied out as the
VIDEOI signat.
Minor compensationis required for Band 1, to
correct a minor slope causedby the 1.8 GHz low-pass
filter and 2 GHz limiter. When pins 6 and 7 of switch
U3025are connected,the PRESELECTOR
DRTVE
signal
is ofrset by R4023 and R4011and Band Stopeadjustment R1012 to provide an attenuated negative-going
ramp to the VIDEOI outputline. Switch Ug02Sis controlled by inverter 04025. O402S is activated by data
bit 6 going low. As shown in the Video Blankingtable
on the schematicdiagram,DB6 is 1 except when Band
1 is selected.

Video Filter Gircuits
Video filtering provides selection of onE of six
bandwidths,under microcomputercontrol.As shownin
the Vid€o Filter table on Diagram24, dataits 1 through
4 select any of six bandwidths:30 kHz, 3 kHz, 300 Hz,
30 Hz, 3 Hz, and 0.3H2. Either wide or nanow-band
filtering is selected at the front panel (Wide band is
definedas 1/30th of the selectedresolutionbandwidth
and narrow is defined as 1/30fth of the resolution
bandwidth). The microcomputermakes the selection,
based on such factors as sweep rate and total dispersion. With no video filtering(all data bits are 0), the
videosystembandwidthis 500 kHz.

7-37

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Theory of Operation- 4g4A/4g4ApServtce,Vol. 1

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EXT VIDEOSELECT

f

MARKER/VIDEO15

VIDEO FILTER
OUT
6,11

t
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INTERNAL VIDEO

RC FILTER
u20158

OATA BIT 1

Flgure 7-14. Simplllied diagram of a video filter.

Tabte 7-6
FILTERCOMPONENT
COMBINATIONS
Bandwldth

DB2

DB3

DB4

30 kHz
3 kHz
300 Hz
30 Hz
3Hz
0.3 Hz

0
0
0
1

0
0
1
0
0
1

0
't

I
1

R2023 c3026

1
0
1
1

Two signal inputs (EXT MARKER/V|DEO)can be
appliedto the video filter circuits. ThE EXTViOeOsignal, from the rear-panelMARKERI VIDEOconnector.is
appliedto pin 15 of switch U306gAthroughedge con_
nector pin 53. The INTL VTDEOsignal,from the Video
Amplifiercircuits(via the front-panelLOG CAL control),
is appliedto pin 2 of U3063Athrough edge connector
pin 51. Note that the internalvideo sectidnsof switch
U30634 are normallyheld energized(pins 2 and three
connected,pins 15 and 14 disconnected)
by the +5V
supprythrough R3064. tf the EXT vtDEo sELECTtine
(from the rear panel ACCESSORIES
TNTERFACE
connector,throughedge connectorpin 55) is grounded,the
externalvideo sectionsof UO063Aare de-energized.

7-38

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X
X
X
X
X
X

R2021

R2022

x

X
X

X

X
X
X
X

x
x

X

X

x

c2016

X
X

X

Wh€n this occurs, the EXT VIDEO signal is applied
through, or around, the filter to becorne th€ VIDEO
FILTEROUT signal at edge connectorpin 57. This is
shown in the simplifiedschematicdiagramof Figure714.
As shown in Figure 7-14, when no tiltering is
selected(all data bits are 0), eitherthe internalor external signalis routedthroughU3062and aroundthe filter,
becausethe two sections of U30638 are selectedby
DBl. When DB1 is high, the video is routedthrough
the filter. Somefilter value will be setectedby bits 2, 3,
and 4. Thesedata bits control three sectionsof switch
U20158to add or deletefilter time constants.

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Theory of Operation-

The filter consists of resistors R2O2g,RZOZ1,
R2022
and capacitorsC3026 and C2016,
between
U3062and U2066. Tabte7-6 lists itre
"onn""t"O
tiiiei components
in thE circuitfor eachof the six OanOwiOttrs.
Databits 2,
4 are apptiedto switch U2O15B(pi-nsB, 16,
1:
and
9) "1!
which selects the components. frorir U2OOOB,
the
signal is routed through contacts Z ana
6 of switch
!9.qpp to.edgeconnectorpin 57 as th€ VtoEOFILTER
OUT signal.
Video Blanking
The video btankingcircuits allow selective
blanking
lower and upper ends of the locat osciilator
9l_!h"
range. Selectiveblankingis requiredbecause
the local
oscillatgrsw€epsthe fuli span-regardlessot
the band

s_y:tem
is desisn;cto
op"n
IT,r-.:,].P.,:9:?
a.otsptay
windowonly during
"tr""tiu"ry

the time for
-*iiro"orput"r,
display. Data
bits 5, 6, and 7, under coritrol of the
selectthe appropriateamosntof displayfor eacn
end.

Video blankingand the PRESELECTOR
DRTVEsig_
.
nal (which provides frequency information,in
rorm) are located on the ViOeo processorvoltag-e
board.
yg.0g3.incorporates a disabte function rhat,
::1,:h_
wnen provicteda tow input, opens all switch
s€ctions
regardless of individual section input. This
feature
allows the VTDEOFTLTEROUT signat to
be easity
blankedat wiil.
The disablefunctionis controlledby a combination
of outputs from comparators U30154 anO
UgolsB.
comparatorsare from the PRESELEC_
I11ttlq.these
TOR.DRIVEsignaland a combinationof vottage
dividers that are switchselectedundercontrolof
dai=a
bits 5,
5, and 7. The PRESELECT_OR
DRTVEsignatis applied
from edge connectorpin 54 through OiiiJer
resistors
R4013and R4012to the invertingiriput oi UgOtSR,
anO
throughdividerresistorsR4014inO'Ra0tito
the non_
invertinginput of U3O15B.These dividersrectuce
excursionof the drivE.signalfrom (+10V to _10V)the
to
(2.5V to -2.S V), which is the maxlmuminput
tevetto
the comparators.
Input to the non-invertinginput of U3015Ais
from
divider resistorsR9011,RgOld and selectedr€sistor
R4015. The inctusionof R4015 is controlted
by DB7
throughpins 2 and 3 of U9025. The junctionof divider
resistors R3011 and Rg0l2 is connectedto ground
throughR401Sfor band 2.
Inputto the invertinginput of Ug0158 is from divider
resistorsR4018,R4012,and selectedresistorRgO2g.
The inclusionof 83023 is controlleOOy OeO
through
pins 10 and tl of U3025. The junctionoi
Rg0t anO
R3012 is connectedto +S V ttrr6ugnRO0rSwhen
it is
selected.This switchingarrangementof negative
and
positive levels for comparisbn with
the reduced
PRESELECTOR
DRIVEsignat enabtesthe iop and bot_

494Al4g4ApService, Vot. i

tom extr€mesof the frequencyexcursionto be blanked.
The blanking is activated by the disable function of
switch U3063, which is controlled by the microcomputer.

DlclTAL STORAGE(Diagrams25 and 26)
The Digitat Storage circuits provide the abitity to
store and process a signal before displayingit. fnis
allows flicker-free displays, Even at tire'stow swesp
rates required for narrow resolution bandwidth meajurements. Digitizingthe signal also allows signalprocessingand markergeneration.
processingincludesdetectingpeak amplitudes
.- - Th-"
(Max.Hold),storing a signat (SaveA),'subtractingone
signal from another (B-Save A), signal averiging
(Averaging),and signal comparison(View A anOVei
g)t These operations use two
memory banks to
independently
store two completesignalstirat are Each
digitized at 500 points across the lweep. Therefore,
two signals may be observed simultaneoustyor processedin separateways.
The markers are used in a variety of ways. There
ar€ two waveform markers that th€ user sets for various measurements. In addition, an update mad<2
x2
x2
)<2
x2

x3
x3
x3
x3
x3
x3
X3

x3
X3

x3

x4
x4
X4

x4
x4
x4
X4

x4
x4
x4
X5
X5

x5
X5
X5

x5
x5
X5

x5
X5

Y1
Y2
Y3
Y4
Y5
Y6
Y7
Y8
Y9
Yl0
Y1
Y2
Y3
Y4
Y5
Y6
Y7
Y8
Y9

00
01
02
03
04
05
06
07
08
09
OA
OB

0c

OD
OE
OF
10
11
12
13

Y1
Y2
Y3
Y4
Y5
Y6
Y7

20 ps TIME/DIV
50 ps TIME/DIV
0.1 ms TIME/D|V
0.2 ms TIME/DIV
0.5 ms TtME/D|V
1 ms TIME/D|V
2 ms T|ME/D|V
5 ms TIMEID|V
10 ms TIME/D|V
20 ms TIMEID|V
50 ms TIME/DIV
0.1 s TIME/D|V
0.2 s TIME/DIV
0.5 s TIME/DIV
1 s nME/DtV
2 s TIME/O|V
5 s TIME/D|V
AUTO
MNL
EXT
EXTTRIGGER
SINGLESWP
SAVEA
2 dBl
B-SAVEA
10 dB/
 SHIFT

RUN/STOP
RESET
(Selectplotter)

ASSIGN2
SIGNALTRACK

(PlotterB-A offsetentry)
(Disablecorrections)
(Greenshift/
Blueshiftcancel)
REFLVLENTRY

(Greenshift cancel)

Y8
Y9
Yl0
Y1
Y2
Y3
Y4
Y5
Y6
Y7
Y8
Y9
Y10
Y1
Y2
Y3
Y4
Y5
Y6
Y7

21
18
29
2A
25
26
1B
28
29
28
30
2C
24
20

MAX SPAN
- STEP
FINE
CAL
INTTRIG
BASELINECLIP
FREERUN
STEPENTRY
NARROW
LIN
(Calfactor display)
VIEWB
RECALL(display)
WIDE
(SpecialModesMenu)
ZEROSPAN
dB/Dtv
AUTORES
SPANiDTV
+ STEP
MrN NOTSE/DISTORT|ON REF LEVELUNITS
HELP
(Blueshifthelp)
GRATILLUM
READOUT
MAX HOLD
(Displayerrors)
PULSESTRETCHER
(Diagnosticmenu)
MARKERMENU
FREQSTARTSTOP
VIEWA
STOREDISP
 SHTFT
(Blueshiftcancel)

Y8
Y9
Yl0

27
2E
31

IDENT
TUNECF/MKR
75f,}a

2F
1C
1D
1E
1F

u

FREQ
MKROFF

2
4
3
7
kHz/-dBX

STEPSIZE
MKR * REF LVL
BW MODE
PEAKFIND

M K R1 + 2
dBlHz
(Greenshift hetp)
A MKR

5
1
6
I
HzldB
MHz/+dBX

MKR STARTSTOP
(Blueshift/
Greenshift cancel)

e Option 07 onty.

7-101

Theoryof Operatlon-

494A1494Ap
Service,Vol. 1

Table 7-24 (Continued)
FRONTPANELSWTTCH
MATRTX
TABLE
CODE/FUNCT|ON
ROW

coL

X6
X6
X6
X6
X6
X6
X6

Y1
Y2
Y3
Y4
Y5
Y6
Y7

X6
X6
x6

x7
x7
x7
x7
x7
x7
x7
x7
x7
K7

x8
X8

x8
x8
x8
x8
x8
x8
x8
x8

HEX
CODE

MAIN
FUNCTION


FUNCTION

DATA
ENTRY

MIN RF ATTEN dB
0
10
20
30
40
50
60

Y8
Y9
Yl0

32
33
34
35
36
37
38
39
3A
3B

RECALL
AF
COUNT

Y1
Y2
Y3
Y4

3C
3D
3E
3F

FREQUENCY
SPAN/D|V
FREOUENCY
SPAN/D|V
FREOUENCY
SPAN/D|V
FREOUENCY
SPAN/DIV

Y5
Y6
Y7
Y8

40
41
42
43

RESOLUTION
BANDWIDTH
RESOLUTION
BANDWIDTH
RESOLUTION
BANDWIDTH
RESOLUTION
BANDWIDTH

Y9
Y10

4A
45

PLOTa/RESETTO LOCALb
LINE

Y1
Y2
Y3
Y4

46
47
48
49

REFERENCE
LEVEL
REFERENCE
LEVEL
REFERENCE
LEVEL
REFERENCE
LEVEL

Y5
Y6
Y7
Y8
Y9
Yl0

(Not Used)
(NotUsecl)
(Not Used)
(Not Used)
(Not Used)
(Not Used)

astandard instrument. bP-version only.

7-102


FUNCTION

STORE(settings)
MKR - CENTER
COUNTRESOLN

PLOTb
MACRO MENU

BACKSPACE

SEND SROb
ASSIGN 1

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Theory of Operation-

4g4A/494ApServlce,Vol. 1

POWERSUppLy(Diagram10)
The Main power Supply furnishesall the regulated
voltagesfor the spectrumanalyzer,exc€pt the crt
highvoltage:uppty. The high-efficiency
desiin of the Main
Power Supply reduces total weight ind conserves
en_ergy.The power supplycircuitslre dividedinto
th€
primary circuits and the iecondary and fan
drive circuits.

primaryCircuits
(Diagram46)
power supplyprimarycircuitsconsistof
the fol_
. .ft"
rowing:the rine input circuit, wnicn rectifiesand
firters
the incomingline voltage;and the inverter,which drives
the primaryof the powertransformer.

Line Input Circuits
_^ Poweris appliedthroughtinefilter FLg0l, line Fuse
F301, and through FLgb2 (for additional normal
.
mode/commonmode EMt fittering)to POWERswitch
5300. The power is then sent thro-ughline s€lectorconnector J1091. The line filter plevents power-line
interferencefrom enteringthe power supply,and it also
preventsinternally-generated
signalsfrom radiatingout
the powercord.

ThermistorsRT209gand RT2097limit currentsurge
at turn on. After the instrumentwarms up, the current
demanddrops. The increasein temperaturedecreases
the resistancevalue of the thermistorsso they have
minimumaffecton the circuit.
Thermalcutout switch S2109opensif thE interiorof
the instrurnentreaches109"C to preventoverheatingin
case the coolingfan fails.
E1094 and E2095 are surge voltage protectors.
When the line selectorswitch is in the 115V position,
only E1094is connectedacross the line input. it a peak
voltage surge in €xcess of 230 V occuis across the
input,or if the instrumentis accidentallyconnectedto a
230 V source, E1094 will break down and demand
enoughcurrent to open the line fuse. Whenthe instrument is operatedwith the line selectorat 230v, E1094
and E2095operatein seriesto protectthe inputagainst
line surgesof approximately460 V peak.
, The voltage for the line trigger is taken across
CR3096. This 48 Hz to 440 Hz vottagedrives optical
isolatorU5043. The pulsating5 V outputis ac coupled,
then sent both to the Sw€ep circuit to provideinstru,
ment triggeringat ths line frequenciosand to th€ Z-Axis
board for the Power-FailDetectorcircuit.
Inverter Circuit

Line selector switch S302 allows instrumentopera_
tion trom €ither a lSV nominalor 230V nominalline
voltagesourcg. With S3O2is in the 115 V position,pins
1 and2 of p1091 are connectedto the input power,
and
rectifi€rsCR3096 and.CR4094operate'in ionjunction
with energystorage filter capacitorsC6101and C6111
as a full-wavedoubleqthus, the voltageacrossthe
two
vatueoJ the line vottage.
9lqacllol: is the peak_to_peak
With S302 in the 290 V position,pins 2 and 3 of p1091
are connectedto the input powerand CR3096,CR4O95,
CR3098,and CR4094operateas a bridge rectifier. As
a- result, the output voltage applieclto the inverteris
aboutthe same for 1lS V or 23b-Voperation.

BecauseG6011and C610.tdischargevery
slowly,hazardouspotentialsexist wiihintne
power supply for severalminutesafter the
POWERswitch is turned off. A relaxation
oscillatorformed by C51lg, R5l 11, and
DS5112, indicatesthe presenceof voltages
in the circuit until the potentialacrossihe
filtor capacitorsis belowg0 V.

The inverter consists of a multivibratorthat pro_
duces a rectangularshaped signal to drive the ramp
generatorand th€ inverterlogic circuits. The rampgenerator produces a low-level sawtooth ramp that is
applied to the primary regulator circuit. The inverter
logic circuitscontrolthe duty cycle of the inverterdriver
and the inverter output stage. The primaryregulator
circuit comparesthe +l 7 V supply output with a reference voltag€,then gates the inverterlogic circuitsoff
and on to control the inverter duty cycle and the
effective primary voltage. The inverter driver stage
amplifiesthe signal from the inverterlogie circuit and
drives the output stage, The output stage consistsof
two power switchingtransistorsthat drive the primary
of main power transformerT4021. The primaryoveicurrentsenseand soft start circuitsadd protection.

Multivibrator. U6059, a low-powerS55 tirner, is a
multivibratorthat operatesat approximately66 kHz and
90-7-"duty cycle. Oscillator frequencyis adjustedby
R6061. The rectangutar-shaped
outputsignatis appliei
throughR6052to the primaryof T6044in the rampgenerator and atsodirecttyto u6053,u6063A,u60638,and
u6069.

7-103

Theory of Operaton -

494A/494ApServtce,Vot. 1

u$36. PrN2

u603A
PIN 3

u6036,
P|l{ 7

Figure7-34, Primary.egutator Input and output waveforms.

Ramp Generator. The ramp generatorcircuit is a
gated sawtooth generator that consists of T6044.
Q5023, Q6034, Q5032, and related components. The
negative excursion of the rectangularshaped signal
from U6059 is coupled across T6044 to force e6094
into conduction.This foruvard-biases
e5032. lts coll€ctor moves toward +17 V to charge Csoggto this value.
06034 loses drive (since the pulse coupled across
T6044 has died away)and the two transistorscut off.
05023 acts as a constant-cunent drain to linearly
dischargeC5038. This signal is coupledacross divider
R5036/R6032,
then apptiedthrough C6Og9to the input
of comparatorU6036,which is part of the primaryregulator.

Prlmary Regulator. The primary regulator circuit
consistsof comparatorU6036and U6046,photocoupler
U6043,and relatedcomponents. The circuitvaries the
duty cycle of the driving signal for the inverter. The
+17 y is dividedby R6038and R6097to approximatety
+4.8V and apptiedto the invertinginput of U6036. Thi
+5 V referenceis apptied through R6022 to the noninvertinginput of u6036, where it is combinedwith the
ramp signal from the ramp generatorstage. The noninvertinginput receivesa sawtooth signal of approximately 500 mV peak-to-peaksuperimposedon a +S V
dc level.This is comparedwith the +4.9 V on the other
input, so the comparatorswitches with each sawtooth
cycle. Note in Figure 7-34 that as the level at pin g
(which corresponds to the +I7 V supply variations)
7-104

rises and falls, the duty cyele of th€ output waveform
variesaccordingly.
The output signal of U6036is appliedto opticalisolator u6043,which drivesthe inputof u6069,

lnverter Loglc. This stage consistsof steeringflipflop U6063B and dual quad input NAND gate U6069.
The flip-flop is connectedso it toggl€s to enable first
one gate then the other. The sguare-wavgoutput from
the multivibratordrives the clock input of U60638. The
signalalso enables each gate to ready it for the other
signals that arrive later. The output state of U60638
determines whether the upper or lower section of
U6069will be ready for the enablingsignal.
Assumethat the Q output of U60638is holdingpin
2 of U6069high. This meansthat the complementoutput of the latch is holdingthe oppositeside of the gated
pair disabled. When the output of U6043moves high,
U6043controlsthe duty cycle of the inverter,the upper
section of U6069 produces a low state. This causes
currentto flow through half the primaryand Q6078only.
On the opposite cycle of the multivibratorsignal, the
latchis reset, so the lower half of U6069is enabledand
Q6077is now in the conductionpath.

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Theory of Operation -

494[l4g4Ap Servlce, Vot. 1

TRIGGERIN (PIN 2I

lmCONTIOL VOLTAGE = 6.6 v

tt(v1(
f

=140k.95 pF

l-----J
ll
F

.,o*.,P

oR AFIERCuRRENT.,,.,__I

l.- "o.*ro. o"enanon*l

2727-161

Flgure 7-35. Tirning waveformsfor soft-start clrcuit

Inverter Driver. The inverter driver consists of
transistorsQ6072and e6079, transformerT60g1,and
relatedcomponents.This is a push- pull amplifier
with
diode protectionin the collectorcircuitsto pr€ventdam,
age frorn voltagetransientsduringoperation.The
drive
signal is inducedinto.the two slcondary wlndings of
T6081and couptedto the outputstage.

^ 9utput Stage. This circuit consists of transistors
Q.2071and Q2061,series LG tank L10g1/C1063,and
transformer T4071. The output transistors are connected in a half-bridgeconfiguration.The two transistors drive the series tank, which acts as an energy
storage element and. an averaging circuit. Outp-ul
.
transfonnerT4071is driven
by tne tanf circuit,anctit, in
turn, drivesthe secondarycircuits.
Primaryregulation,-as
discussedpreviously,
occurs
when the duty cycle of the inverterdriver main switch_
ing transistorsis varied.Maximumduty cycle occurs at
low input line (90V) and fulty toadedoutput. At maximumduty cycle,bothtransistbrsare off for only 1Ao/o
of
the period, or l.Sps. This short interval allbws any
stored base chargeto deplete,so there is no chance
both transistors will conduct at the same time.
Minimumduty cycte occurs at high input tine (132V)

and minimumloaded output. At minimumduty cycle,
each transistor is off for approximately6 ps, or 4O;/oot
the total period.

Soft'Start and Prlmary Over-CurrentClrcuits. The
soft-start circuit consists of U6053and associatedcomponents. Soft-start graduallyincreasesthe switching
transistofs duty cycle at turn-onor after over-current
shutdownto preventexcessivetranslstorcurrentdue to
chargingoutput capacitors. R€fer to Figure 7-35 for
timingwaveforms.

The primary over-currentcircuit protects against
secondary shorts that could destroy the switching
transistors. T2080 s€nses the collector current in
Q2071and createsa vottageon pin 5 of U60468. lf the
bias on pin 5 surpassesthe 2.5 V referenceon pin 6, at
approximately 6 A through e2OT1, the output of
U60468sets U6063A. U6063Ais a D-typeflipflop used
as a timer to shut down the inverterlogic for approximatety1 s and to reset the soft-startcircuit.

7-105

Theory of Operation -

4g4Ll4g4ApService, Vot. 1

Secondary& Fan DriveCircuits
(Diagram47)
The secondarycircuits includethe rectifier_filter
circuit, which rectifies and filters the secondaryvoltages;
the voltage reference circuit, which furnistrei a stiOte
and precisereferencefor the regulators;and the regulator circuits,which control the voltage and currEntlor
the suppliesthat requirepreciseregulation.
The Fan Driver board (A30Al) contains the Fan
Driver circuit, which furnishes the appropriate drive
current for the fan motor. lt also contains the OverVoltage Protection circuit, which shuts down the +5 V
supplyin case of over-voltage.
Reclifler-Filter Circuits
TransformerT4071 has three secondarywindings.
The first furnishes current to the +3OOV and +100 V
supplies; the second furnishes current to the -7 V,
+7 V, and +9 V supplies;and th€ third furnishescurrent
to the +17V and -17 V supplies.The linearregulated
supplies (+5 V reference, +5 V, -5 V, +iS t, and
-1 5 V) derive their cunent from the rectifier-filter
circuits.
The ac voltage from pins 7 and g of T4071 is
qp]i"_q to_ a bridge rectifier composed of CR3053,
CR3056, CR3055, and CR3054. The output of this
rectifteris filtered, then appliedto the r€mainderof th€
lnstrumentas the +100 V supply.
. The +300 V supplyis derivedby stackinga 2X multiplier on the +100 V suppty. CR3O52,
CRiO42,CR1O34,
CR1022and associated capacitors,compose this circuit.
- The ac voltag€ from pins 9 and 10 supplycurrentto
full-wave rectifier CR4061/CR4062. The output is
fltered and sent to the rest of the instrumentas the
*9 V supply. Two other taps off the samewinding(pins
11 and 12) supply current to the bridge rectitierihat
consists of CR4063, CR40S7,CR40S3,and CR4065.
The output dividEs across filter capacitorsC9051 and
C4051 to become the +7 V and -7 V supplies. The
+7 V supply is only used on the Main power Suppty
board; the -7 V suppty is used by other circuits in ihi
instrument.
. .The third winding of T407.1(pins 13, 14, and 15) fur_
nishes current to full-wave bridge rectifier CR5052,
CR5062,CR5065,and CR5055. The output is divided
to bEcometh€ +lZV and -17V supplies.The -lZV
s.upflyl: used onty on the Main power Supply board;
the +17 V supplyis used both on the Main eower Sup_
ply boardand elsewherein the instrument.

7-106

+5 V Voltage ReferenceSupply
The +17V is divideddown by a voltage dividerto
Zener diode VR6026. The 6.2 V from VR6026is divided
across R6029, R6028, and R6023. CR5031provides a
regulatedsourceof bias to VR6020after +15 V comes
up. The +5 V REF adjustment,R6028,is set by monitoring the +15v supply and setting it tor a precise
+15.00v.
Regulator Circuits
The +15V, -15V, +5V. and -5V are regulated.
Sinceall four regulatorsare basicaltythe same,onlythe
+5 V regulatoris described. Significantdifferencesare
discussedfollowingthis description.
U2O37A,the voltage regulator part of the circuit,
compares the +5 v^g. and +5 v sENsE voltages,
amplifies the difi€r€nce,and applies the change to
driver transistorQ2023. The changeis amplifiedby this
stage and appliedto the base of seriss-passtransistor
Q2024to change its conductionand correct for the original changeto the +5 V. The +5 V sense samplesthe
+5 V at a distributionpoint on the Mother board. This
signalcompensatesfor voltage(lR) lossesto that point.
U20i!78 is the curent limiter portion of the regutator. The amplifierdet€cts the voltage differentialacross
the current sensing resistor R2017,which is in seri€s
with the output load. When the overloadthresholdis
reached,as set by R2017,R2039,R3032,and R3031.
U20378 removes bias current from driver transistor
02023 and Q2024. The negativebias on R3031ailows
the limiter to rernainactive under short circuit conditions.
The +15 V regulatoris identicalto the +5 V regula,
tor, except that the ounent limiter, U2O37Dsupplies
additionalpositivebias for Q2031when it is not active.
The -15V regulatoris virtuallyidenticalto the +5V
regulator. The -5 V regulatordiffersfrom the othersin
that a driver stage is not required,so the preamplifiers
clrives€ries-passtransistorQ5013 directly.
*5 V Over-Voltage Protection Circuit
Zener diode VR1015 and SCR 01010 form the
over-voltage protection circuit. lf the +5 V supply
exceeds +6 V, th€ potential on the gate of 01010
biases it into conduction.This forces the +5 V oupply
to ground potential;it remainsat ground potentialuntil
the mains poweris turnedoff and turnedon again.

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Theory of OperationFan Drfve Circuit
The fan drive circuit provides a temperaturecontrolled current drive to the fan motor. if,e
circuit pro1y:?: " thr€e-phase_driveculent of approximatety
240 Hz operating freguency. The actuar
ctrive circuit
operates as a ring counter.
TransistorsOl03g and e1044 form a vottag€
regu_
by th€rmistor RT2O4S. The value of
!:tlT- _c_ontrotted
RT2045varies inverselywith tf," int"in"i
temperatureof
the anatyzer. The therinistor and ,".Gioi nzo+2
fix the
turn-onvoltageat the emitterof e1044 ai approximatety
-13 V. The voltage goes
mor€ positive as'tire andyzt,Jr
warms up.
The ring counterconsistsof three stages.
Because
of circuitimbalances,whenthe anrtyzer-is-nrst
powered
up one-of the stages beginsto con'ductbefore
the oth9r1 Tfie stag€s consastof e1025 .nJ-etOzO, ,itt
RlGlt/C1092 and RtOzZClOle as- ine'
trequencye2025 anO-'-btOtg, with
99t^"ITjli.nS_-components;
R1033/C1033and R2Ot9/Ct01g as the
frequency_
$t^"Tjl'lg,components; and e2030
*itt
R20141C2012and R2016/C2O18as "nO-OZOZO,
ite rrequencydeterminingcomponents.

4gtA/4g4Ap Servlce, Vot. 1

Assume that the stage with e1025 anct e1020
begins to conduct first. The collector vottageof
e1025
is near -1T V, which fixes that point as the most nega!y"-^rl _a_rlng consisting ot itrOgz, R1029, niOig,
R2036,R2034,and RiO36. Sincethe emi*er vottage
of
the threecontroltransistors(OfO2O,el01g, anOOiOeO;
is the same, the voltage division around ihe resistive
ring is such that el0lg and e2020 remain cut ofi.
{he1 the capacitivecharge that hotds etO2O in conduction bleeds off, the transistor cuts off and th€ next
stage can begin to conduct. Operationof the other
two
s.!ag,es is prevented until the RC cornbination
discharges. The fan motor inductanceworks in conjunctionwith the RC componentsto regulate
the switch_
ing of the stages.
This ring-counteraction builds up slowly until the
circuit producesa three-phasedrive signatof approximat€fy 240 Hz. Th€ inductanceof the m-otorcoils iound
off the othenrvisesharp comers of the drive signal; so,
the current waveformal p2O2Opins 1, 2, and 3 looks
s-imilarto the output of a half-wave rectiher. The fan
drive signals are phased approximately120 degrees
apart.

7-107

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Sectlon 8 -

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494[l4g4Ap Servlce,Vot. I

OPTIONS
This section describesthe optionsavailableat
this
time for the spectrum analyzer. Ct.ng""
.in
specifications,.if
any, are describedin this section.Contaet your local Tektronix Field Office or representativ€
for additionat information and ordering instructaons
(unlessothenriseindicated).
Optionsare usuailyfactory installed;however,field
kits are availablefor some options. Contact your
local
Tektronix Field Office or r€presentativefor information
on fiEldkits and their installation.
Options A1-AS

lA1 |
}IORTH AMERICAN
120V/154

(power Gord Options)

EUROPEAN
220Yl104

There are five int€rnataonalpower cord options
offered for the spectrum analyzer, The physical
.
descriptionsof the cord plugs ar; iltustrateC-inRgure
8-1.. For ordering purposes,refer to the Replaceable
MechanicalParts list in th€ ServiceManual,Votume
2,
for th€ Tektronix part Number.
Option Bl (service Manuals)
Option81 includesa set of servicemanuatswaththe
instrument.
Options Ml-M3
(Extended Service and Warranty Options)

ut(
2.rcV/134

| ^'J
AUSTRALIAN
2&Vl10A

There are three extended service and warranty
options ofiered for the spectrum analyzer tnat
96
beyond the basic one-year coverage
{see Table g_i).
Contact your focal Tektronix Field dtric; or representative for additional information about your specific
requlrements.

EXTENDED
sERv'clTlt'D8;ARRANTy
opl oNs
Two routine calibrations to publistled
specifications;one each in years two and

Four

routine calibrations to

NORTH AMERICAN
240V115A

swtss

220v1104

Figure 8-1. Intemational power cord options.

published

specifications;one each in years two,
three, four, and five of product ownership,
plus four yearsof remedialservice

8-1

o

Optons -

4944/494Ap Servlce, Vol. 1

Option 07 (75O Inpur)

Option 08 (Delete External Mixer Input)

Option 07 provides an optional 7SO input and *20
dBmV calibratorin additionto the standard50O input
and +20 dBm calibrator. Also, a 300 kHz Resolution
Bandwidthfilter replacesthe 100 kHz fitter. The 7SO
input replaces the €xtemal mixer capability. Table g-2
lists the changesand additionsto the standardinstrumsnt electrical characteristics. These characteristics
apply to the 75o Input except for the 3@ kHz 50 o
Input sensitivity.

Option08 deletesthe ext€malmixer capability.The
frequencyrange is 10 kHz to 21 GHz.

Table 8-2
OPTION 07 ALTERNATE SPECIFICATIONS

Characlerlstic

SupplementalInformaton

Input lmpedance
R€tumLoss
5 MHz to 800 MHz
800 MHz to 1000MHz

75(}
17 dB (1.35:1VSWR)
13 dB (1.6:1VSWR)with
>10 dB attenuation
+78 dBmV, 100 Vo. maximum
(dc f peak)

MaximumInputL€vel
CenterFrequencyOperatingRang€
StaticResolutionBandwidth
FrequencyResponse
5 MHz to 1000MHz
CoaxialInput

1 MHz to 1000 MHz
Within 2ao/ool selected bandwidth

300 kHz resolutionfilter replacesthe
standardinstrument100 kHz filter.
*2.0 dB about the midpointbetween Frequency response is measured
two extremes
with )10 dB RF attenuation.
The response figure includes the
effects of:
. inputvswr
r gain variations
Variationsin displayflatnesscontribute
about 1 dB to the responsefigure.
Typically <3 dB down from the
5 MHz r€sponse,
-68 dBmVto +89 dBmV

1 MHz to 5 MHz
Reference Level Range

+99 dBmVis achievablein
the reducedgainmode.

Calibrator
Output
(cAL OUT)
Level

+20 dBmV *0.5 dB
at 100MHz

100 MHz comb of markers provide
amplitude calibration.
Phase locked to frequency
reference.

Outputlmpedance

8-2

75o nominal

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Optons _ 494Al4g4ApServtce,Vol. 1

Tabtc B-2(Continued)
OPTION07 ALTERNATE
SPECIFICATIONS
Characterlstc
Sensitivity
75O INPUT
5-1000 MHz

Performanc€Requlrement
Eguivatenttnput Noi"t
10 Hz 100 Hz 1 kHz
-85

5OOINPUT
300 kHz Resc
tion Bandwidth

10 kHz

300 kHz I MHz 3 MHz

-66
-s6
-41
-36 I -31
EqulvalentInput Nolso In dBm vs. Band

-76

land 1 Band 2 Band 3 Band 4a Band 4b

-90

Supplemental Information

-84

-u

-70

-65

Band 5
-65

ent maximum input
for each resolution
easuredat 25" C with:
. 0 dB anenuation(MinAtten0 dB)
o NarrowMdeo Filteron
. V€rticalDisptay2dBlDiv
o Digital Storageon
o Max Hold off
o Peak/Averagein Average
. 1 sec Time/Div
o Zero Span
. Inputterminatedin characteristic
impedance

tS.4GHzto l2 GHz. bl2 GHz
to 1g GHz.
Options 21 and 22 (Waveguide Mixers)
Option 21 includesa set of hrvohigh-performance
waveguidemixers (18 to 40 GHz). Optio-ni2 includesa
set of-threehigh-performance
waveguidemixers (1g to
60 GHz). Both options also includJan interfacecable
and a diplexerassembly. SEeTableg-Ofor characteristics. For ordering purposes, refer to the back of the
Replaceable Mechanical parts list in the Service
Manual,Volume2, for the Tektronixpart Number.

Tabte &3
OPTIONS21 AND 22 CHARACTERISTICS

The characteristics
in Table8€ for Options
21 and22 assumethat the waveguidemixer
is connect€dto a continuouswave signal
source and that PEAKIAVERAGE is
adjusted for maximum signal amplitude.
The signal must be stable (not frequency
modulated more than the resolution
bandwidth);otherwise,frequencyresponse
performancecannotbe met.
Table 8-3 (Continued)
OPTIONS21 AND 22 CHARACTERISTICS
CharacterisUc

SENSITIVITY
EquivalentInput Noise at
1 kHz ResBW

PHYSICAL
Weight
Option21

Option22

Descrlpton
With standard accessories,except
manuals.
Adds 10 oz. (0.28kg)
Totafof 48lbs, I oz. {22 kg) for stanion21.
Adds 13 oz. (0.37 kg)
Total of 48 tbs, 11 oz. (22.1 kg) for

STANDARD
ACCESSORTES

DiplexerAssembly
Adapter;tnc to sma
Cable;semi-rigid
Cable.sma to sma

8-3

O

Optione -

494A/494ApService, Vot. 1

Option 39 (Sitver Battery)

Option 42 (110 MHz lF Outpur)

. Option 39 provides a silver battery for the
instru_m€nt'sbattery-poweredmemory. The battery life
at +55"C is 1-2 years and 2-5 years at +2SoC. W€
recommendremovingthe silver batteriesduring longterm storage.

Option42 providestor a rear-panel110 MHz tF signal with a bandwidthgreEterthan 5 MHz, which makes
the spectrum analyzer suitable for broadband sweptrEceiver applications. Table 8-5 lists the electrical
characteristicsof the 110 MHz output.

Option 41 (Digitat Radio)

Oplion 45 (MATECO)

Option41 inctudesthe followingteaturesto provide
extra measurem€ntcapabilitiesfor Digital Microwave
Radio. Table 8-4 tists the changes troh tne standard
instrument.

This option providesthe spectrumanalyzerwith the
software/firmware nec€ssary to meet Modular
Automated Test Equipment Compatibitity Options
(MATECO). A MATECO Programmers Manual is
includedas an accessorywith this option.

o A wider bandwidthpresel€ctorprovidesbettersignal symmetryin the digitalradio bands.
o A narrowvideo fitter(approximately
1/3000thof the
resolutionbandwidth)improvesamplitudevariation
analysisat specificfrequencyspansthat are unique
to the digitalradio measurements.
o

Option 52 (North American 220V,
Option 52 provides a North American 22O V
configurationwith the standard pow€r cord. The fuses
are replacedwith 2A slow blow.

llprovcd frequency span/div accuracy at s
MHz/div span providesaccuratesignal bindwidth
measurements.

Table 8-4
OPTION 41 ALTERNATE SPECIFICATIONS

Gharacteristic
FREOUENCY
FrequencySpan/Div
Accuracy

SupplementalInlormation

5 MHz/div,within *1%

At center frequency of 6 GHz and 11
GHz

Measuredover th€ center6 divisions
of
Video Filter
Narrow

3O Hz (1i3000th)with 100 kHz reso-

PreselectorFilter Bandwidth
1.7 GHzto 5 GHz
5 GHz to 16 GHz

Hz to 2'l

8-4

3OMHz minimum
35 MHz minimum

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Opdons _ 494A/4g4ApServlce,Vol. 1

Tabte 8-5
OPTION42 ELECTRICAL
CHARACTERISTICS
Characteristic
tu Mnz tF gutput
CenterFrequency

goesanoffi
B"ndp""" C[ptJ--

symmetry
"ooultn"Gffi

quency

Power Output
Band1
Band5

PerformanceReguirement

SupptementalInformation

1 0 8 . 5M H zt o 1 1 1 . 5M H z
)5MHz
< 0.5 dB
t1.0 MHz

(0dBm
) -40 dBm

With -30 dB input and signatat futl
screen.
In MIN DISTORTION
modeonty.
1 dB compressionof output
) 0 dBm.

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Appendix A -

GLOSSARY
gtossary is presented
.._-Il"^^1"_l':,*ing
understandthe terms as they aie used as an aid to
in thi" do"urn"nt
and with referenceto spectrumanatyzers.

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Llne Display. The display produced on
a spectrum
anatyzerwhen the resolution'bandwidih
i" t"." than the
spacingof the signarampritudesof the
individuarfrequ€ncycomponents.

I

Llne SpectruT.A spectrumcomposed
of signal
tudesof the discretefrequencycomponents. ampli-

t

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4g4Al494Ap Service, Vol. 1

GENERALTERMS
Center Frequency. That frequency
which corresponds
to the centerof a frequencyspan,expresseO
in hertz.
Baselinecftpper (rntensrfier).A
meansof increasing
the brightnessof the signatretativ"
i;l;; basetinepor_
tion of the display.
dBc. Decibelsreferencedto carrierlevel.
1_8i.. .A unit_to express power level in decibelsreferenced
to 1 milliwatt.
dBmV. A unit to express voltage levels
in decibels
referencedto 1 millivolt
dBpV. A unit to express voltage levels
in decibets
referencedto 1 microvolt.
Efrectlve.Frequency_.T:1g.".That range
of
over which the instrument performanie frequency
is specified.
The lower and upperlimits are
n".tr.
"if.""r"t:in
EnvelopeDisplay.The displayproduced
on a spectrum
anatyzerwhen the resotutibnbino*iOt
ii greatertnan
the spacingof the individualtrequenci
"o,ipon"nt".
Freguency Band. A part of effectjve
frequencyrange
over which the freouencycan be adlusted,
Lxpressedin
hertz.
Full
.Span (Maximum Span). A rnode of operation in
which the spectrumanatyzer
tr"qu"n"y
band.
"""n, "n "ntir"
lnterm-odulation
Spurious Response (lntermodulation
Distortion - tMD). An..unwanre; ;d;i;*
anatyzer
responseresultingfrom the mixingof
the nth order fre_
quencies,due to non-linearelemints
ot in"
analyzer, the resultant unwanted ,".fonr"spectrum
being
displayed.

Markers. The instrumentusesthreetyp€s of

markers:

WaveformMarkers. _ Whenthe Markerfunction
is enabled, it provides a movable cursor
with
readout of frequencyand amplitudeat the
marker
position. Whenthe delta markermode is
enabled,a
second marker allows operations and
readout
between the two_ marker positions. (Also
see
WaveformMarkerTerms.)
UpdateMarker. - Marks the currentsweepposi_
tion in a digitat storage disptay as the disptiy
is
beingupdated.
Video Mark
9{"_rryl VTDEOIMARKERinpul from a Tektronix
1405 TelevisionSideband Analyzer. The Video
Markersmark frequenciesof intereston the televisionsignal.
MaximumSafe Inputpower
WITHOUTDAMAGE...Themaximumpower apptied
at the input whichwill not causedegiadation
oi the
instrument
characteristics.
WITHDAMAGE.The minimumpower appliedat the
'
inputwhich will damagethe instrument.
Pulse Sfetcher. A pulse shaperthat producesan out_
put pulse, whose duration is greater than
that of the
inputpulse,and whoseamplitudeis proportional
to that
of the peakamplitudeof the inputpui"e.'
ScanningVelocity. Frequencyspan divided by sweep
timeand expressedin hertzpir second.
Signal ldentitier. A means to identifythe spectrurno,
the inputsignalwhenspurious,esponsesare possible.
Video. The term is used heregenerallyto meana sig_
nal afterthe detectorstage. lt can also be usedmore
specificallyto meana baseband(zerocarrierfrequency)
television
signal.
VideoFilter.A post detectionlow_passfilter.
Zero Span.A mode of operationin whichthe frequency
spanis reducedto zero.

A-1

I

Gfoesary-

494[l4g4Ap Service,Vol. 1

FREQUENCY
TERMS
DisplayFrequency.The input frequencyas indicatedby
the spectrumanalyzerand expressedi; hertz.
Frequency Span (Dispersion).The magnitudeof the
frequencyband displayed,expressedin-hertz or hertz
per division.
FrequencyLlnearityError.The error of the relationship
betweenthe frequencyof the input signal and the frequencydisplayed(expressedas a ratio).
FreguencyDrlft Gradual shift or change in displayed
frequency over the specified time Oue to internal
changes in the spectrum analyzer,and expressed in
hertz per second, where other conditionsremain constant.
lmpulse Bandwldth.The displayedspectrallevel of an
applied pulse divided by its spectral voltage density
levelassumedto be flat withinthe pass_band.
ResidualFM (lncidentalFM). Short term displayedfrequencyinstabilityor jitter due to instabilityin th-espec_
trum analyzerlocal oscillators,givenin terms of pLakto-peakfrequencydeviationand expressedin hertz or
percentof the displayedfrequency.
Shape Factor (Skirt Selectivlty).The ratio of the fre_
quencyseparationof the two (60 dBi6 dB) down points
on the response curve to the static resolution
bandwidth.
Static (Amplifier)ResolutlonBandwldth.ThE specified
bandwidthof the spectrumanalyzer'sresponseto a cw
signal, if sweep time is kept substantiailylong. This
bandwidthis the frequencyseparationof two pointson
the responsecuryerusually6 dB down, if it is measured
eitherby manualscan (true static method)or by usinga
very low speedsweep(quasi-staticmethod).
Zeto Pip (Response). An output indication which
correspondsto zero inputfrequency.

AMPLITUDETERMS
Detlectlon Coeflicient. The ratio of the input signal
rnagnitude to the resultant output indication. Tne ratio
may be expressed in terms of volts (rms) per division,
decibels per division, watts per division, or any other
specified factor.
Dlsplay Reference Level A designated vertical position
representing a specified input level. The level may be
expressed in dBm, volts, or any other units.

A-2

Display Flatness. The unwanted variation of the
displayed amplitudeover a specifiedfrequencyspan,
expressedin decibels.
Relative Display Flatness. The display ftatness
measuredrelativeto the displayamplitudeat a fixed
frequencywithin the frequencyspan, expressedin
decibels.

Display flatness is closely related to frequency response. The main difference is
that the spectrum display is not recentered.
Display Law. The mathematical law that d€fines the
input-output function of the instrument.
The following cases apply:
Llnear - A display in which the scale divisions are a linear function of the input signalvoltage.
Square law {power} - A display in which
the scale divisions are a linear function of
the input signal power.
Logarithmic - A display in which the scale
divisions are a logarithmic function of the
input signal voltage.
Dynamic Range. The maximum ratio of the levels of
two signals simultaneouslypresent at the input which
can be measured to a specified accuracy.
Display Dynamic Range. The maximum ratio of the
levels of two non-harmonically related sinusoidal
signals each of which can be simultaneouslymeasured on the screen to a specified accuracy.
Frequency Response. The unwanted variation of the
displayed amplitude over a specified center frequency
range, measured at the center frequency,expressed in
decibels.
Gain Compresslon. Effect seen at an input level where
the analyzer circuits have less gain than their small signal values. This is usually specified at the 1 dB
compression point in terms of the input level requiredto
reduce the gain by 1 dB.
Input lmpedance. The impedance at the desired input
terminal. Usually expressed in terms of vswr, return
loss, or other related terms for low impedancedevices
and resistance-capacitance parameters for high
impedance devices.

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Glossary_ 4g4Al4g4ApService,Vol. 1
Sensitvity. MeasureoJ a.spectrurnanalyzef
s abilityto
display minimumreversignars,
-ifei in vorts or
decibets. Intermediate.tr"qu"n"V
"*pi".J"o bandwidth,
displaymode,and any other innueniinji"'.to*
must be
given.
Spu.rious Response. A respons€ of
a spectrum
_.
analyzerwhEreinthe displayed'frequency
is not related
to the inputfrequency.
Hum Sidebands. Undesired responses
cr€ated
within the spectrum analyzer,
on the
display, that are separated trom
"pp"urlng
the desired
response by the fundamentalor harmonic
of the
power linefrequency.
Noise Sldebands.Undesiredresponse
caused
noiseinternalto the spectrurnanalyzerappearingby
on
the displayarounda desired,".ponr".
Resldual Response. A spurious response
in
absence.ofan inputsignal. (Noiseund:r.ro pip the
are
excluded.)

DIGITALSTORAGETERMS

View (Display). Enables viewing of contents of
the
chosenmemorysection(e.g.,'.VidwA, displays
the
contents of memory A; ',ViewB" displaysthe contents
of
memoryB).
Max Hold (peak Mode), Digitallystored display
mode
which,at eachfrequencyaddresi,comparesthsincoming signal level to the stored level and retains
the
greater.ln this mode, the displayindicates
the peak
lev€l at each frequency after several successive
sweeps.
Scan Address. A numberrepresentingeach horizontal
data position increment on a direited Ueam type
display. An address in a memory is associatedwith
eachscanaddress.
Volatile/Non-volatile
Storage.A volatilestoragesystem
is one whereany total loss of power to the systemwill
result in a loss of stored information. Non-volatite
I"Tory is not subjectto the instrumentpower supply
for its storage.

WAVEFORM MARKER TERMS

DigitatfyStored Disptay-A.disptaymethodwhereby
displayedfunctionis held_.in'a'digitalmemory. the
tne
displayis generatedby readingthe dita ouf ot
mernory.

Live Trace. Any combination of the A trace and/or the
B trace when SAVE A is off.

Digltally-Averaged Display. A disptayof
the average
value of digitized data computedby combining
serial
samples.

Active Trace. Live Trace or the B-SAVE A trace (a
trace recalled into B is not an active trace).

MultipleDisptayMemory.A digitailystored
disptayhav,
in_g_
multiple memory sectionswtrictr
b" displayed
separatelyor simultaneously.
""n
Clear (Erase).presets memory to a prescribed
state,
usuallythat denotingzero.
Save. A functionwhich.inhibitsstorageupdate,
saving
existingdata in a sectionof a multif,le,i"rory
1".g,,
SaveA).

Inactive Trace. SAVE A trace or a trace recalled into
the B display before the sweep is started.
Primary Marker. The marker displayed in the Single
Marker mode whose frequency and/or position is
when tuning with the CENTER/MARKER FRE_
gllseo
QUENCY control. When two markers are displayed, the
brightest marker is the primary marker.
Secondary Marker. The "second,, marker; displayed
only in the Delta Marker mode.

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A-3

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REVISIONINFORMATION
Manual Part No. 07G556O-00 Flrst prtnilng
hduct

Revleed

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ManualInsertStatus

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CHANGEREFERENCE
SEP1987
FEB1988
MAY1988
JUN 1988
MAY1990
JUN1990
SEP1991

c11887
M63911

c2lsge
M66071
c21590
C2l590REVISED
c1-991

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Page 1 of 1

Effective
Effective
Effective
Efiective
Effective
Effective
Effective

JAN 1987

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Tektronix.

MANUALCHANGEINFORMATION

Cornnt|ncd to Ercdl€E

Date:9-1-87
Product:See list
INSTRUMENT
494N494APOp€rators
494N4944P Service1

ChangeReference:
C11887
ManualPartNo:Seelist
gN 8010227and
up

Part No.
070-s557-01
070-5560-00

Feplaca sanshlvlty table In the speclflcailon secilon wlth the tabte betow.

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SENSmV|TY
Equivalent Input Noise in dBm vs. ResohrtionBandwidth
Frequency Range

Band1

10kHz-1.8 GHz

Bands2& 3

1.7GHz-7.1 GHz

10Hz

1 kHz

10 kHz

-134

-12s

115

-105

-95

€5

-80

-12s

- 11 9

-109

-99

-89

:19

-74

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10OkH2f

3 MHz

Band 4

5.4 GHz-12 GHz

- 1 1I

-105

-95

-85

-75

€5

-60

Band4

12GHz-18 GHz

-107

-100

-90

-80

-70

€0

-55

Band5

15 GHz-21 GHz

# -106

-99

-89

-79

-69

.59

-54

Band5'

18GHz-27 GHz

- 11 6

-108

-100

-90

-80

-70

-65

- 1 11

-103

-95

-85

-7s

€5

-60

Band7'& 8.

25.5GHz-€0 GHz

Band9.

50 GHz-€0 GHz
(1 kHz Bandwidlh)

Typically-95 dBm at 50 GHz,degradingto -85 dBm at 90 GHz.

Band10'

75 GHz-140 GHz
(1 kHz Bandwidth)

Typically-90 dBm at 75 GHz,degradingto -75 dBmat 140GHz.

Band11'

11OGHz-ZZ0GHz
(1 kHz Bandwldth)

,
Band12'

170GHz-825 GHz
(1 kHz Bandwidth)

Typkafly-80 dBm at 1'l 0 GHz,degradingto -65 dBm al220 GHz.
Typlcally-70 dBmat 170GHz,degrading
to -55dBmat 325GHz.

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1 MHz

1O0Hz

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productGroup:26

' SpecifiedusingexternalTEliTRONlX
WavequideMixers.
b Option07 replacesthe 100kHzfilterwith 300
a
kHz fitter.
# Revised8-25-87

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Tektronix"
Cdmfrittsd to Erca{ence

Date:2-22-88
Producl:seelist
Inslrument
4941Pservice1
495/Pservice1
49?NAPservice1
494AIAPservice't

MANUALCHANGEINFORMATION
ChangeReference:
M63911
ManualPartNo: seelist

Manual
070-4416-00
070-5084-00
070.5565-00
070-5560-00

productGroup:26

Efr/sN
8011156
8,020228
8010702
8010383

ReplaceDeflectionAmplifiers Gainand Freguency Besponsein the AdjustmentProceduresection
with procedurebelow.

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3. AdjuslDeflection
Ampli{ier
Gain,Frequency
Response,
andreadoutGainandoffset.
(C3080,C3060,C1030,C1040,R1055,R1066,R5020,andR5030on the Deflection
Amplifier
board).
A. Connectthetestequipmentas shownin figure5-4.Setthe TIME/DIVto 1 ms. Positionthe traceon
the bottomgratiarleline.
B. Setthefuncliongenerator
for a 500H2sinewave
controls
signal,withan amplitude
of 0 to + 4V.
Connecta jumperbetweenpins1 and5 (ExtVideoSelectandGroundrespectively)
on the ACCESSOFIIESconnector.Deactivate
VIEWA andV|EWB, andsel TRIGGERING
to tNT.
C. AdjusltheVertGain,R1066(Figure5-2)for a fuilgraticute
screendisptay.
D. Disconnect
the500H2signallromtheMARKERA/IDEO
input.Removethejumperbetweenpins1
and5 of theACCESSORTES
connector.ResetTriggering
lo FREERUN.
E. SetTIME/DIV
to MNL.MonitorTP2on theSweepboard(Figure5-2)witha vollmeter
(DigitalMultimete4. SETTHEMANUALSCANcontrolfor0.0V readingon thevoltmeler(TP2),Sel lhe horizontal
POSITION
controllo centerthe CRTbeam(dot).
F. ResettheMANUALSCANcontrotfor
a readingof +5V alTpz.
G. AdjustHorizGain,R1055(Figure5-2)to positionthe crt beamto the rightgraliculeedge
(1Oth
graticule
line).
H. Resetthe MANUALSCANcontrolsuchthatthe crt beam(dot)moveslo the leftedgeot the graticule
andcheckthalthe voltageat TP2 is now-5.0V+ or - 0.2V.
l. Disconnect
the vollmeter,
and
setTlMgDlVto AUTO,changethetesloscilloscope
to EXTTBIGGER,
applylhe Readout
CIf signalatTP1038on theCRTFleadoul
board(Figure5-5)to thelestoscillosmpe
ExtTriggerinput. Setthe testoscilloscope
Time/Divto 2us.

Page1 ol 5

Product: see list

Date:2.22-88

Chg.Ref.M63911

J. Setthe SpectrumAnalyzercontrolsfor a lriggeredsweep,thenswitchthe sweepoft by activating
SINGLESWEEP,and ensureREADOUT
is on.
K. Monitorlhe drains(metaltabs)of 04040 or Q4030,on lhe dellectionAmplifierboard,withtestoscilloscope.See Figure5-6
L. AdjustC1040for bestfrequencyresponse(noovershootor roll off) as viewedon the test oscilloscope.
M. Monitor
the Drains(metaltabs)of Q4020or Q4010,on the Amplifier
board,withthetesl oscilloscope.
N. AdjustC1030(Figure5-6torthe bestresponse).
O. Monitorthe Drains(metaltabs)of 02090or Q1090,on the Deflection
board,withthelest
amplifier
oscilloscope.
P. AdjustC3080for bestresponse.
Q. Monitorthe drains(metaltabs)ofQ1070or Q2070,on the Deflection/amplifier
board,withthetest
oscilloscope.
R. AdjustC3060lor bestresponse.
S. Disconnect
the test oscilloscope.
Checklhe appearance
of the letter"2" in GHZof the frequency
readout,and if necessary,readjustC3060and C3080(verticaloutput)for the straightest
top on the letter
"2". Note:The oscilloscope
probemay alterthe responseand alterremovingthe oscilloscope
probe,
adjustment
will be necessary.
T. SettheVERTICALDTSPLAY
to LlN,TIME/DIV
to MNL,the REFLEVELfor 100uv,withthe MANUAL
SCANconlrolsetfully clockwise.
U. AdjustC1030and C1040for thebestREFLEVELreadout(straightest
lettersandnumerals).Posilion
the MANUALSCANbackandforthbetweenlhe clockwiseand countercloskwisepositionandcontinueto
adjustC1030and C1040for bestresponse.
V. AdjustR5020,R/O GAINand R5030,R/OOFFSETfor bestplacementof the readoutcharacters(top
and bottom)dependingon whetheror not the crt hasa lull graticuleor a reducedgraticule.
Note: Setthe firsltwo rowof readoutcharactersiustabovethe top graticulelineandset the lastrowof
readoutcharacters
iust belowthe bottomgraticulelineon Reducedgraticuleinslruments.

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Page2 of 5

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Product:see llst

date:2-22-88

Chg.Ref:M6391r

Replacethe descriptionfor the Deftection Amptifiers(Diagram27) with the tottowing.
DEFLECTION
AMPLIF|ER
(Diagram278)
Referlo ihe blockdiagramadjacenlto Diagram27aswellastheschematic
diagram.TheDeflection
Amplifier
receivesverlicalsignalinlormation
tromtheverticalsectionoflhe DigitalStorageof theVideoProcessoi,
and
horizonlalorsweep
board.TheReadoul
dataforthedisplaycomestromtheCR1Readout
circuits.
Theoutput
of the DeflectionAmplifierdrivesthe crt dellectionplates.The amplitierscontainlhe switchingcircuits
necessary
lo performtheselectionfunctionsandtheyalsocontaintheamplifierstagesneededto productthe
defleclionplatedrivesignals.
HorizontalSection
SignallinesHORIZONTAL
SIGNAL(fromlhe digitatstorage
pin 49) and
circuitsthroughedgeconnector
Sweep(fromtheSweepcircuitthroughedgeconnector
pin51)areapptied
to switChU7O55A.
U705s,under
conlroloftheSTORAGE
OFFsignal(fromthedigitalstorage
circuitsthroughedgeconnectorpin
7),setects
HORIZONTAL
eitherthe
S|GNALorSWEEPinput.
TheSWEEP
signatis
setectedwhenthe
STORAGE
OFF
line is pulledlow. ResistivedividerR7065and R7070reducethe selectedsignaltrom 1V/divto o.Sv/div.
U7073bufferstheselectedsignal.Thesefected
signalgoesoutto theHORTZ
OuT rear-panet
via
conneclor
pin 1 and2 on P6100,P6090andpin48 of theedgeconnector.
U7073apptiesthe signatto switchU70558.
TheHORIZR/OOFFsignal,tromtheCrtReadoulselectsbetweenthesetwosignati.WhenR/Ois floating
or pulledhigh,theswitchtransmilsthesignallrombufferU7073to lhe shaper.Whenthe tineis puledtow,
it selectsthe HORIZONTAL
R/Osignat.
U7055 appliesthe signal to a shaper networklo compensatelor non-linearityin the crt deflection
characteristics.
This networkconsislsof resistorsR5059,R5058,R50S7,R4061,iaosg, and R5062,plus
diodesCR4052,
CR4051
TheHORIZONTAL
, CR4958,andCR4056.
POStTtON
vottage,
fromthefrontpanel
via edgeconneclorpin 47, throughresistorR5056,is appliedto the shapercircuitso tne shapeconection
lactorrelateslo the crt deflection.
Theshapedsignalis thenappliedlhroughpreamplifier
U2055to the deftectionamplitiercircuits.HORTZ
gain
adjuslmentR1055,calibrateslhe amountof gaincompensation
requiredfor properdeflectionsensitiviiy.
The horizontaldetlectionamplilierconsistsof two circuitssimilarto each other,one for each horizontal
deflectionplate.One circuitis an invertingamplitier,the otheroperatesin-phase.Inputsto U2030of the
invertingsidearethroughthe paraltelcombination
ol resistorsR1039and R1038andcapacitorC1040.The
seriesconneclionof resistorR1038 and variablecapacitorCl040 provideshigh-frequency
response
compensatio
n- capacitor c2047controtshigh{requency
feedback.
fnpullo lhe non-inverting
sideof theamplifieris throughresistorR1025to u2030. R1o?'zandR2020setthe
dc levelfor the feed-backloop to the plus inputsideof the amplifier.VariablecapacitorC1030provides
adjustment
to sel lransientgain.Highfrequencyfeedbackis controlledby capaciiorC20tO.Gain
ol each
amplifiersectionis approximately
20.(Horizontaldellection
per
sensilivityof
lhe crtis approximately
21.3v/div
side.)
Signalswith
a lowrateof changedrivetheoulputFETtransistorsthrough
R3038,astherateol riseincreases,
the drop acrossR3040increasesand when it reaches0.6V,either03047 or e3046 biasedon. These
providehighcurrentdrivefor theoutputlransislors.
transislors
Whenthesignalrateol changeis low,04030
drivesthecrtdefleclionplatesandQ4040providesbiascurrenlfortheamplitier,Asthe rateor riseincreases,
thesignaltothegateof 04040.04040provides
ptate,and
theposilivedriveto thedeflection
949?1couples
04030providesthenegativedrive.Eachoutputtransislorcanprovidea 200Vexcursioninapproximately
1ps.

Page3 of 5

Product: see llst

Dale:2-22-88

Chg. Ref: M63911

The standingcunenton the horizontal
by a resistivedividerR4046,R3045,
amplifierMosletsis established
and R5038as lollows.The baseof Q5040is set 3.5voltsnegativewilh respectto the +300volt supply.The
voltagedropacross85045is then3 voltsandthe resultingemittercurrenlis 2.0ma.Currentfromthe-15V
sourcethroughresistorR2041setsthe output level.FeedbackresistorR2049sets this outpul levelat
142volts.DiodesCR2040,CR3040,andVR4030providetransientvoltageprotectionduring
approximalely
turnon andunderfaultcondition.
Capacitor
C2031withresistorR2035shapethephaseresponseof U2030.
Operation
ot the left drive(non-inverting)
sectionis basicallythe sameas the rightdrive(inverting)section.
VerticalSection
arerouled
DigilalStorage
VIDEOFILTEROUTfromtheVideo
Processor,
andVERT|CALS|GNALfromlhe
Notethat
board.
Storage
Digital
throughswitchU60554,undercontrolof the STORAGEOFFsignalfromlhe
thevideofilterout signalis butferedby U7065to preventa changein loadtransientsf romaftectingthesignal
anda lowselects
level.A highontheSTORAGE
VIDEOFILTEROUTSIGNAL,
OFFlineselectsthebuffered
the VERTICAL
SIGNAL.U6065invertsthe selectedsignalandclampsit to ground.Boththe VIDEOFILTER
andpositivevohagesabove
OUTandtheVERTlCAL
SlGNALarespecilied
at0.SVtdivwith
0Vforthebaseline
thebaseline.
The signalis re-inverted
andolfselby buflerU6073so cenlerscreenrepresents0V.BufferU6073supplies
a sampleof thiscenteredsignallothe rear-panel
VERTOUTconnectorvia pins1 and2 ol P7075andedge
pin46.The outputof u6073is alsoappliedthroughswitchu60558,whentheR/OOFFlineis high,
connector
to the verticalshapercircuit.WhenR/O lineis low,the VERTICALR/Osignalis appliedto the shaper.
The Verticalsection shaper R4062,R4065, R4077,R4069,R4063 and CR4063,CR4064,plus the
preamplifierV2062, operateslhe same as the horizontalsection.04078 limitsposiliveexcursionsto
approximately
onedivisionabovethetopof the crtscreento protecttheoutputstagesfrombeingoverdriven.
The verticaloutputstagesare similarto the horizontalstages,withthe exceptionof highbiascurrent.The
outputstageproducesapproximately
current,resislorsR3108 andR2086
SmA.To correctforthisincreased
are lowerin valuethan theircounterpartsR5032and R5045in the horizonlalseclion.
levelseiby dividerR6020
U6024compares
lhe signallevelfromthebaseline
clamp,U6065,wilha relerence
and R6024.This producesthe cLlP signallorthe z-Axls interlacecircuit.when the VIDEOFILTEROUT
signalis morenegativethanthe referencelevel(approximately
1 divisionabovebaseline),it pullsthe CLIP
linelow.R7035pullsthe CLIPLINEhighif the signalis morepositivethanlhe referencelevel.
VariableresistorsR5020and R5030can be usedto adjustthe relaliveverticalpositionof the character
readoutsandependently
of the vedicalsignal gain adjustmentRl066. 85020 is adjustedlor vertical
displacement
characters.Wilhthe advanceol the reducedgraticulecrt,R5020and R5030can be adjusted
to positionthe readoutcharaClers
outsideol the graticulearea.

Page4 of 5

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Product:see llst

Chg. Ref: M63911

Replacetigure 5-6in the Adjustmentprocedure sectionwith thefollowingdiagram

Defiectron
Arnplif
ier

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HorlZontal freqJency response

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Figure5-6. Deflection
Amplifiertestpointsand adjustments

Page5 ol 5

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-^l-.r--

-

Conmined to Erca$eno

Date:5-1G-Bg
Product:See List

INSTRUMENT
49UP Seruice1
492P/6Service1
4941PServicet
4951PServicel
496/PServiceI
492NAPService1
492B|BPService1
494NAPService1
2753PService1
27541P
Servicei
27551PServicet
2755NAPServicel
2756PService1

ITIANUAL
CHANGEINFORMATION
GhangeReference:
C2t5lgg
ManualPartNo:SeeList
productGroup: ZO

MANUAL
070,3783-01
07a-4232-O0
070-4416-00
070-5084-00
070-3481-00
070-5565-01
070-5565-01
070-5560-00
070-6306-00
070-6097-00
070-6032-01
070-6032-01
070-6318-00

PERFORMANCE
CHECKPROCEDURE

NOTE
performing
lhe accuracycheckat 10 dB/Dlvmodeon someinstrument
Ih".n
options,the last .t0dB stepof
DisplayDynamicRangemaynot appearto meetspecification
whenthe 10 KHz ResolutionBandwithFilteris
used' Thisis observed.
as noiseinierrering
withthe signalwhenthe ExternalAttenuatoris setto g0 dB. The
signalwillappeartoo high,and noisecan 6e seenon either
side. lf this is the case,thenchangethe sparvDiv
to 10 kHz'the resoulution
BandwidthFilterto 1 kHz,andthe video Fitterto wlDE. Then resetthe External
Atlenuator
lo 0 dB, readiustthe signalGeneratoroutpulto FULLscFEEN and retestthe 10
dB/Dlvmode.

)

Page1 ol 1

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Tektronix.
Cottrti.d

MANUALCHANGEINFORMATION

to Ercrltono

Date:$01€8
Product:See list

ChangeRelerence:M66071
ManualParl No:Seelist

INSTBUMENT

PARTNO.

494NAP
49YP
2753P
27541P
2756P
4928/BP
2755NAP

Operators
Operators
Operators
Operators
Operators
Operators
Operators

070-5557-01
070-5082-00
070-6305-00
070-6096-00
070-6317-00
070-5552-01
070-6031-01

494A/AP
495/P
2753P
2754tP
2756P
4928/8P
2755NAP

Service1
Service1
Service1
Servicet
Service1
Service1
Servicet

070-5560-00
070-5084-00
070-6306-00
070-6097-00
070-6318-00
070-5565-01
070-6032-01

Efi/SN8010100
produciGroup: 26

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ADD:

oPTtoN43
Option43 providesa reducedgraticuleray tube. Thisoptionatsoenablesthe maindisptayreadout
characters
to be positionedoutsidethe grdiculearea.

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Tekt"fp"n[X.

MANUAL CHANGE INFORMATION

Date: 5/u9o

Change Reference:C2lSgO
ManualPart No. 070-5s60-OO

Product: 494N4g4Ap Service Vol. 1

In section4 - PERF)RMANCE)HECK pRocEDURE

Replace header secfian with the foltowing:
11. Check Resolution Bandwidth and Shape Factor
(bandwidthis within 2oo/oot the selectedLandwidth
for
all butthe'l0 Hzfilter;.10Hzto 1 MHz in decadesteps,
and 3 MHz; shape factor is 7.5:.t or less _
60 dB
bandwidthfor the .t0 Hz filreris s150 Hz)
Change step i. to read as follows:
i.
. Repeatthe processto checkthe resolutionbandwidth
and shape lactor for the 10 kHz, 1 kHz, and 100
Hz fihers.
j. To checklhe60dBbandwidthof
the 10 Hzfitter,setthe
SpanrDivro 50 Hz, and the REFEHENCE
t_EVfL lo _20
dBm. Push AUTO RES, VTDEOFTLTERWlOe,
and ser
PEAK AVERAGEto average.
k. Checkthat the 60 dB bandwidthis <150

Hz.

change stepr r as foltows:

product Group: 2E

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Tektfgnl;.

MANUAL CHANGB INFORMATION

Date: 6/1190
Product:494N494ApServiceVot.1

ChangeReference:
CA59A(revised)
ManualPart
No.070-5560-00

productGrOup:2E

The followlng is a revision of change Reference:c2ls90 datectslztgo.
ln section 4 - PERFORMANCEcHEcK pRocEDIJRE changeas foilows:
Replace step 5 wlth the fottowlng.
5.

CheckCenterFrequencyStabitity
[Driftis50 Hzlminor lesswith1st LOlocked(SPAN/DtV
<200kHz for band 1 and bands5 through12, and
SPAN/DlVs1
00kHzforbands2through
+)lfter t hour
ol warmuptimein a stableambienttemperature].
a. Applythe Catibralor
signalrothe RF tNpUT.
b. Setthe SpectrumAnalyzercontrolsas {ollows:
CENTERFREOUENCY
SPAN/DIV
RESOLUTION
BANDWIDTH
REFLEVEL
MINRF ATTENdB
VERTICALDISPLAY
TRIGGERING
VIEWAandVIEWB
TIME/DIV

100MHz
50 Hz
100Hz
-20 dBm
0
2 dB/DIV
FREERUN
On
AUTO

g. check that the total driftover 60 secondsis within+1
divisionof the referencesignal.
h. DeactiveEOS conectionby selecting
WIDE VIDEO FILTERthen B-EOS CORRECTTONMODE
TOGGLE'
l. Enable FrequencyConeclions by selectingPULSE STRETCHERthen selecring.6=D TSABLE/
ENABLE FREOUENCYCORRECTIONS'.

F€Hc€|ffi
uilEntna,
-20ogr

ffiREffi
IM(EN

tw
*

SHIFT>PULSESTRETCHER
rhenseleciing
"6=D|SABLE/
ENABLEFREOUENCY
CORRECTIONS".
f. Observethedriftof thedisplayed
signalin relationto
the relerencefor 60 seconds.SeeFigure4_4.

SPAW
frl

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tl

.-

1""

Drift

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:\

'/N

c. Aclivatethe End Of Sweep(EOS)correctionby
selecting

WIDEVIDEOFtLTERrhen
"3=EOS
CORRECTION
MODETOGGLE.
d. Tune rhe CENTERFREOUENCY
ro establisha
referenceat the intersection
of two graticulelines and
activateSAVEA. See Figure4-4.

Ff,€q,€Td

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GF
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ODB

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fLE

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WA

Figure4-4. Centerfrequenry drift wilh 1st LO locked.

o

Change stepll as follows:

Replaeestepl7 wtth the tollowlng:

6. CheckReslduatFM

11.CheckResolutlonBandwldlhand ShapeFactor
(bandwidlhis within2O%ot lhe selectedbandwidth
exceptfor 10Hz.Shapefactoris 7.5:1or lessexceptlor
10 Hz. 10 Hz bandwidth
<150Hz @ -60 dBc.

[Within7 kHz over 20 ms with the 1st LO unlocked
(SPAN/DIV
>200kHzfor band1 andbands5 rhrough
12andSPAN/DIV
>100kHzfor bands2 rhrough4)1.
[Within(5 + N)Hzover20 ms withrhe 1st LO locked
(SPAN/DIV
s200kHzfor band1 andbands5lhrough
<100kHztor bands2 rhrough
12andSPANiDIV
4)1.
Change'f-" to read as follows:
f, ll SAVEA wasusedin parte, de-activate
SAVEA and
VIEWB.ActivateZEROSPAN,setTIME/DIV
ro 20 ms,and
set CENTERFREQUENCY
controlto posirion
the display
nearcenterscreen
asshowninFigure4-5B.UseSAVEAto
f reezethedisplayforeasein measuring
FM.Forthe
example
in Figure4-5,the verticalamplitude(gp) overeach20 ms
sweepinleryal(1 div.)can varyby no morethan7 kHz(O-7
div)
nEfg*
cv€!
IegEE
-2308M

'lO0MHz
CENTERFREOUENCY
l MHz
SPAN/DIV
RESOLUTION
BANDWIDTH 3 MHz
-20 dBm
REFLEVEL
VEHTICALDISPLAY
2 dB/DIV
MINNOISE
Activated
PEAI(AVERAGE
FullyClockwise
TIME/DIV
AUTO
FREERUN
TRIGGERING
b. Measure 6 dB bandwidthfor each ResolulionBandwidth as follows:

(2) Select'7 - ENTER BANDWIDTHNUMBER"
(3) Enter "6" with the keypadand terminatewith "dB'.

Sror =-9!$

or to Ktkrvrnicd

(4) Activate BAND WIDTH mode pushbutton(BANDWTDTH).
(5) From the inlormationdisplayedon lhe CRT, record
the 6 dB bandwidthin Table 44.
NOTE

2-6ilv/

A

rHI'

10DS
RF

lru

aE€n&€wR
udiltryR
-aD8rl

ol,8
E€O
uc

t T
ET
6C

Span Arcurary is not a lactor
when using the bandwidthmode.

looxHz
ru€O
AB

CffiFBEU*Y

ftEruM
3Ailm

(6) Check that the recordedvalue for the 6 dB
bandwidth is within the limitsas specifiedin Table
44.

atMr

r*sn&uw
ar.6aaJz

a,|tg
G

verucrt dlvlJon

(1) Set the Spectrum Analyzercontrolsas follows:
SPAN/DIV
RESOLUTIONBANDWIDTH
VERTICALDISPLAY
WIDE VIDEO FILTER

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IODB

ffi

B

dttut

A1E

Fico
asE

(7) Using the values in Table 4A, measure the 6 dB
bandwidlh lor all remainingRESOLUTIONBANDWIDTH settings(except10 Hz).
c. Measure the 60 dB bandwidthfor each Resolution
Bandwidthas follows:

tttl
7 tHr:0.7
ttll

iF
olc

sEo
FLE|

ts!@i
tailfr

Flgure 4-5. Typlcal dlsptay for measurlng resldual FM

t
)

a. ApplytheCALOUTsignaltotheRF INPUT.Setthe
Spec{rum
Analyzercontrolsas follows:

(1) Activate MARKER MENU pushbutton.

c€,frE; mEqrcrw
Kqft€d
roos!il||}tz

UG

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l MHz
3 MHz
1OdBIDIV
Activated

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(2) AcrivareMARKER MENU pushbutton.
(3) Select "7 - ENTER BANDWTDTH
NUMBER"
(4) Enter'60" with the keypadand terminatewilh "d8".
(5) ActivateBAND WIDTH mode pushbutton(BANDWTDTH).
(6) From the informationdisplayedon the CRT, record
the 60 dB bandwidthin Tabte4A.
(7) Using the values in Table 44, measurethe 60 dB
bandwidrhfor allremaining RESOLUTIONBANDWIDTH setrings(excepr 10 Hz).
d. Usingthe valuesrecordedin Table44forthe 6 dB and
60 dB bandwidth,calculateand recordthe shape factor for
each RESOLUTTONBANDWTDTH(excepr10 Hz)
e. Checkthat each FiESOLUTIONBANDWTDTHshape
factor is less than or equal to lhe specificationin Table 4A.
f. To check the 6OdB bandwidthof the 1OHz filter, set
the Span/Divlo 50 Hz, and the REFERENCELEVEL to _20
dBm. Push AUTO RES, VTDEOFILTERWIDE, and ser
PEAK AVERAGEto average.
g. Check lhat the 60 dB bandwidthis s150 Hz.
h. Aftercompletionof thetest, deactivateBANDWIDTH
MODE.

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uq|.E

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q'E*ffi
reiu|d

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KUf,!

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re@

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)r{

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t I{r

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fxmfiofl
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, ! { d

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/

it..
aN

Ert

F f f : c E
l n q M *

A. Measuring6 dB down bandwidth

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-E

.:=!ry
s

Fl!

IE

^fru

B. Measuring6OdB down bandwidth
and computingshape factor

Figure 4-9. Displaysthat illustratehow bandwidthand shape factor are determined
using markers.

1-3

RESOLUTION
BANDWIDTH

6 dB BANDWIDTH
LIMITS

3 MHz
1 MHz

60 dB Bandwidth
RESOLUTION VERNCAL FREOUENCY 60 dB MEASURED
BANDWIDTH DISPLAY SPAIVDIV
BANDWIDTH

CaleulatedShape
Factor (60 dB/6 dB)

SHAPE FACTOR
SPECIFICATION

3 MHz

10dB/

l MHz

<7.5:1

1 MHz

1 0d B /

1 MHz

<7.5:1

100kHz
'10kHz

1 0d B /

100kHz

<7.5:1

t0 dB/

5 kHz

<7.5:1

1 kHz

10dB/

lkHz

<7.5:1

100Hz

1 0d B /

1 0 0H z

<7.5:1

1 0H z

N/A

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Change step 12as follows:

t

12. CheckCalibratorOutput
(-20 dBm r0.g dB)

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a.Applyan external
100MHzsignalto lhepowermeter
througha 3 dB attenualor
anda 50e iable.Setthegeneraror
outputlevellor a readingol -20 dBmon the powermeter.

VERTICALDISPLAY
NARROWVIDEOFILTER
TIME/DIV
PEAI(AVERAGE
VIEWA andVIEWB
'Selea

3 test frequencies

Test Freq. 1:
Tesl Freq.2:
Test Freq.3:

Change step l7 as follows:
PARTI

a. Conneclthetestequipment
as shownin Figure4_14.
Setthe SpectrumAnalyzercontrolsas follows:
TeslFrequenry'
200kHz
100kHz
-30 dBm
0
On
2 dB/DIV
On
AUTO
FullyClockwise
On

'SeleA
3 testlrequencies
TestFreq.1:
TestFreq.2:
TestFreq.3;

1OkHz - 1.8 GHz
1.8-18GHz
18-21GHz
PARTIII

Change'a." ta readas follows:

CENTERFREOUENCY
SPAN/DIV
RESOLUTION
BANDWDITH
REFLEVEL
MtNRF ATTENdB
MINNOISE
VERTICALDISPLAY
NARROWVIDEOFILTER
TIME/DIV
PEAIVAVERAGE
VIEWA andVIEWB

2dBtDtv
On
AUTO
FullyClockwise
On

1OkHz- 1.8GHz
1.8-18
GHz
1g-21GHz
PARTIT

Change "b." to read as follows:
b. Connectthe test equipmentas shown in Figure4-15.
Set the SpectrumAnalyzercontrolsas {ollows:

CENTERFREOUENCY
SPAN/DIV
RESOLUTION
BANDWDITH
REFLEVEL
MINRF ATTENdB
MINNOISE
VEBTICALDISPLAY
NARROWVIDEOFILTER
TIME/DIV
PEAIOAVERAGE
VIEWA and VIEWB

Test Frequency*
200kHz
1 MHz
-25 dBm
50
On
2 dB/DtV
On
AUTO
FullyClockwise
On

'Select3 testfrequencies
TestFreq-1:
TestFreq.2:
TestFreq.3:

10 kHz- 1_8GHz
1.8-18GHz
't8-21GHz

Change'b."to readas follows:
b. Connectthetestequipment
as shownin Figure4-14.
Setthe SpectrumAnalyzercontrolsas follows:
CENTERFREOUENCY
SPAN/DIV
RESOLUTION
BANDWDITH
REFLEVEL
MINRF ATTENdB
MINNOISE

Test Frequency'
200 kHz
100 kHz
-25 dBm
30
On

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POWERMETER

ANALYZERUNDERTEST
SPECTRUM
SIGNALSOURCE

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ADAPTER

ADAPTEF
POWEBDIVIDEB
POWERSENSOR

ADAPTEF

LOW LOSSCOAXCABLEWITHSMACONNECTORS

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Figure 4.14. RF attenuator test equipment setup,

Change step 14 as follows:
14. Check Frequency Response
(Responseabout the midpoint betweenlwo exlremes
measuredwith 10 dB of RF attenuationand peaking
optimizedin the applicablebands for each cenrer
lreguency setting is as lollows:
B a n d 1 : + 1. 5 d B f r o m 1 0 k H z t o 1 . 8 G H z
Band 2'.r2.5 dB from 1.71o5.5 GHz
Band 3: f2.5 dB from 3 to 7.i GHz
Band 4: +3.5 dB from 5.4 to 18 GHz
Band 5: +5.0 dB from 15 to 21 GHz)
(Responsewith respectto 1OOMHz is as follows:
Band 1 : .t2.5 dB from I O kHz to 1.8 GHz
Band 2: +3.5 dB from 1.7 to 5.5 GHz
Band 3:13.5 dB from 3 to 7.1 GHz
Band 4:14.5 dB from 5.4 to 18 GHz
Band 5: +6.5 dB from 't5 to 21 GHz)
The folfowingproceduretest displayflatness(peakedat
center of test frequency range, typically 1 dB greater than
Trequencyresponse, see specificationTable 2-2)

1-6

lf any range segmentf ailsto meetthe specification,set
the FREOUENCY to the center of the range in question,
apply a marker at the centerf requencyof the range,and repeak with the MANUAL or AUTO PEAKING.Decreaselhe
FREOUENCYSPAN/DlVto displaythat rangeand recheck
the response.
The responseat eachcheckpointaboveband 1, should
be peaked with the MANUAL PEAK control.
a. Checklrequencyresponsefrom0.01GHzto 21 GHz
(Band 1 through5)
{1) Conneclthe CAL OUT signalto the RF INPUT,and
performthe CAL routine.
(2) Set the SpectrumAnalyzercontrolsas lollows:
C E N T E RF R E O U E N C Y 1 0 0 M H z
SPAN/DIV
500 kHz
RESOLUTION
3 MHz
-20d9m
REFLEVEL
2 dB/DIV
VERTICALDISPLAY
10
MIN RF ATTENdB
AUTO
TIME/DIV
PEA}VAVERAGE
Fully Counterclockwise

,

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cHANcE
INFoRMAnoN
TercfgnixoEcEu.E^pE MANUAL
CETvitTTEDT

Date: l1_Sep_gl

Product: See List .

ChangeReference:

ManualPart No.: See Lisl
DESCRIPTION

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)

Prodrrct Group 2E

Effectivefor Alt SertalNumbers:
492PGM
494NAP
495/P
497P
2753tP
2754tP
2755tP
2755NAP
2756P

070-7556-00,ServiceVotume1
070-5560-00,ServiceVolume1
070-5084-00,ServiceVotume1
070-7679-00,ServiceVolume1
070-6306-00,ServiceVolume1
070-6097-00,ServiceVotume1
070-6032-01,
ServiceVolume1
070-6032-01,ServiceVotume1
070-6318-00,ServiceVolume1

Makethe fotlowlngchanges In your ServtceVolume
i manuat:

Section2 - Specification
Changethe 1 dB Compression
specificafion
as shownbelow.
Measuredin Min Noisenrodewith
no RF attenution.

o
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C1-991

Section4 - performanceVerification
Addthe toilowingequipmentto the Equipment
Requiredtabre.
PowerSptitter(FemateSMA
Connectors)
20 dB Attenuator
(SMAConnec_
tors)

TEKTRONIX
PartNo.015-0565-00
(1 dB Compression
check).
TEKTRONIX
PartNo.015-1003-00
(1 dB Compression
check).

Replacethe 1 dB compressionPointperformance
verification
procedure
withthe followingprocedurg;

Check1 dB Compressionpoint

,,t i :i;lv

:,;

0 dBmin MINNOTSEmodefor Bands1 through5.
a. Connectthe testequipmentas shownin the followirqfigure.

O

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Page 1 ot 2

Product: See Llst

Date:11

Ref. C1-991

Spectrum Analyzer Under Test

a
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Test equlpment,setuplor checklng I dB lnput compresslonpolntb. Sefectlhe followingsettingsfor the specirumanatyzer:
FBEQUENOY

103MHz

FREQUENCYSPAN/DIV
1 MHz
RESOLUTIONBANDWTDTH1 MHz
-40 dBm
REFERENCE
LEVEL
MINRF ATTEN
0dB

VERTICALDISPLAY
VIEWA/B
TIME/DIV

aIDIV
On
AuTo

-40 dBm.
c. set the generatoroutputamplitudeto approximatety
d.

PressSAVEA to storethe 100 MHzsignalamplitudeon the screen
fivedivisions).
{approximately

e . .Set|he REFERENCE
LEVELto OdBm.
f.

Adiustlhe signalgeneratoroutputfor a full-screen
display(approximately+6 dBm intothe powerdivkler).

g. Setthe REFERENCE
LEVELto -40 dBm.
h. Checkthat the amplitudeditlerencebetweenthe 100 MHz peakson

the activeand SAVEA tracesdoes not exceed1 dB.

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Page 2 of 2

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o
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;
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