UBS Axcera DT325B 350-Watt VHF Low Band Digital Transmitter User Manual title page DT325B
UBS-Axcera 350-Watt VHF Low Band Digital Transmitter title page DT325B
Contents
- 1. Axciter Modulator User Manual Part 1
- 2. Axciter Modulator User Manual Part 2
- 3. Compiled Exciter Users Manual
Compiled Exciter Users Manual
INSTRUCTION MANUAL
DT325B
350 Watt Digital VHF
Low Band Transmitter
AXCERA, LLC
103 FREEDOM DRIVE P.O. BOX 525 LAWRENCE, PA 15055-0525 USA
(724) 873-8100 • FAX (724) 873-8105
www.axcera.com • info@axcera.com
350-Watt Digital VHF LB Transmitter Table of Contents
DT325B, Rev. 0 i September 12, 2008
TABLE OF CONTENTS
Section Page
CHAPTER 1 INTRODUCTION
1.1 Manual Overview...................................................................................1-1
1.2 Assembly Designation Numbers ..............................................................1-1
1.3 Safety..................................................................................................1-2
1.4 Contact Information...............................................................................1-2
1.5 Material Return Procedure ......................................................................1-2
1.6 Warranty for Axcera Products – Limited One-Year Warranty.......................1-3
CHAPTER 2 SYSTEM DESCRIPTION
2.1 System Overview ..................................................................................2-1
2.2 Exciter Driver Chassis Assembly Description.............................................2-1
2.2.1 Control & Monitoring Power Supply Module Assembly.......................2-2
2.2.2 Upconverter and Downconverter Module.........................................2-2
2.2.3 Adaptive Equalization Circuits........................................................2-3
2.3 VHF Low Band Amplifier Tray..................................................................2-3
2.4 Control and Status.................................................................................2-6
2.4.1 Front Panel Display Screen............................................................2-6
2.5 System Operation..................................................................................2-6
2.5.1 Principals of Operation..................................................................2-6
2.6 Maintenance .........................................................................................2-8
2.6 Module Replacement .......................................................................2-8
2.7 Customer Remote Connections ...............................................................2-9
CHAPTER 3 INSTALLATION AND SETUP PROCEDURES
3.1 Site Considerations................................................................................3-1
3.2 Unpacking and Installation of the Cabinet and Trays .................................3-4
3.3 Input and Output Connections to the Transmitter .....................................3-5
3.3.1 Main AC Connection to the Transmitter System ...............................3-5
3.3.2 Input Connections to the Transmitter System..................................3-5
3.4 Setup and Operation Procedures.............................................................3-7
3.4.1 Driver/Amplifier Modules front panel LEDs ......................................3-7
3.4.1.1 Axciter Upconverter Sled Module front panel LEDs..................3-8
3.4.1.2 Controller Module front panel LEDs .......................................3-8
3.4.2 Front Panel LCD Screen for Driver/Amplifier Chassis Assembly..........3-8
CHAPTER 4 CIRCUIT DESCRIPTIONS
4.1 Control Monitoring/Power Supply Module .................................................4-1
4.1.1 Power Protection Board.................................................................4-1
4.1.2 System Controller Board ...............................................................4-2
4.1.2.1 Schematic Sheet 1 ..............................................................4-2
4.1.2.2 Schematic Sheet 2 ..............................................................4-3
4.1.2.3 Schematic Sheet 3 ..............................................................4-3
4.1.2.4 Schematic Sheet 4 ..............................................................4-3
4.1.2.5 Schematic Sheet 5 ..............................................................4-4
4.1.3 LCD w/Switches Board..................................................................4-4
4.1.4 Switching Power Supply Assembly .................................................4-5
4.1.5 RF Output of Driver/Amplifier Chassis Assembly ..............................4-5
350-Watt Digital VHF LB Transmitter Table of Contents
DT325B, Rev. 0 ii September 12, 2008
TABLE OF CONTENTS (continued)
Section Page
4.2 VHF Low Band Amplifier Tray..................................................................4-5
4.2.1 Phase Shifter Board......................................................................4-6
4.2.2 Filter/Amplifier Board....................................................................4-6
4.2.3 VHF Low Band Amplifier Board.......................................................4-7
4.2.4 Overdrive Protection Board............................................................4-7
4.2.5 3 Way Splitter Board ....................................................................4-7
4.2.6 VHF Low Band Output Amplifier Pallets...........................................4-7
4.2.7 3 Way Combiner ..........................................................................4-8
4.2.8 AGC Control Board .......................................................................4-8
4.2.9 +28 VDC Switching Power Supply..................................................4-9
4.2.10 Current Metering Board...............................................................4-9
4.2.11 Operation of the VHF Amplifier Tray .............................................4-9
4.3 External Boards...................................................................................4-10
4.3.1 Triple Peak Detector Board..........................................................4-10
4.3.2 Isolation Relay Board..................................................................4-11
CHAPTER 5 DETAILED ALIGNMENT PROCEDURES
5.1 System Preparation ...............................................................................5-1
5.2 Module Replacement..............................................................................5-1
5.3 VHF Amplifier Tray.................................................................................5-1
5.3.1 AGC Control Board .......................................................................5-1
5.3.2 Phase Shifter Board......................................................................5-2
5.3.3 Filter/Amplifier Board....................................................................5-2
5.3.4 VHF Low Band Amplifier Board.......................................................5-2
5.3.5 Overdrive Protection Board............................................................5-2
5.3.6 3 Way Splitter Board ....................................................................5-2
5.3.7 VHF Output Amplifier Pallets..........................................................5-2
5.3.8 3 Way Combiner Board.................................................................5-3
5.4 Calibration of the Output Power of the VHF Amplifier Tray .........................5-3
5.5 Setting Up the Output Power of the Transmitter .......................................5-3
5.5.1 Setting Up of AGC 1 .....................................................................5-3
5.5.2 Setting Up of Overdrive Threshold..................................................5-4
5.5.3 Axciter Relay K2 Sample Values.....................................................5-5
5.5.4 Upconverter/Downconverter Adjustment ........................................5-5
5.6 System Calibration of Forward & Reflected Powers using the Driver/
Amplifier LCD Display ............................................................................5-5
5.6.1 Forward Power Calibration.............................................................5-5
5.6.2 Reflected Power Calibration...........................................................5-5
APPENDICES
APPENDIX A DT325B w/AXCITER SYSTEM DRAWINGS
APPENDIX B DRIVER/AMPLIFIER CHASSIS ASSEMBLY DRAWINGS
APPENDIX C VHF LOW BAND AMPLIFIER TRAY DRAWINGS
350-Watt Digital VHF LB Transmitter Table of Contents
DT325B, Rev. 0 iv
LIST OF FIGURES
Figure Page
1-1 Brady Marker Identification .............................................................1-1
2-1 Driver/Amplifier Chassis Assembly Front View ...................................2-1
2-2 Rear view Driver/Amplifier Chassis Assembly ....................................2-9
3-1 1 kW Minimum Ventilation Configuration...........................................3-4
3-2 Front and Rear view Driver/Amplifier Chassis Assembly......................3-4
3-3 AC Input Box Assembly...................................................................3-5
3-4 Rear view Driver/Amplifier Chassis Assembly ....................................3-6
5-1 Axciter Upconverter/Downconverter Main Screen...............................5-4
350-Watt Digital VHF LB Transmitter Table of Contents
DT325B, Rev. 0 v
LIST OF TABLES
Table Page
2-1 DT325B Assemblies and Trays.........................................................2-1
2-2 Controller/Power Supply Front Panel Display .....................................2-2
2-3 Controller/Power Supply Front Panel Status Indicators .......................2-2
2-4 Controller/Power Supply Front Panel Control Adjustments ..................2-2
2-5 VHF Amplifier Front Panel Tray Control Adjustments ..........................2-4
2-6 VHF Amplifier Tray Sample..............................................................2-4
2-7 VHF Amplifier Tray Switches............................................................2-5
2-8 VHF Amplifier Tray Fault Indicators ..................................................2-6
2-9 (A2) Driver/Amplifier Remote Connections............................... 2-9
3-1 Rear Chassis Connections for Digital Driver/Amplifier Chassis..............3-6
Digital Driver/Amplifier System LCD Controller Screens
3-2 Menu 01 Splash Screen #1..............................................................3-9
3-3 Menu 02 Splash Screen #2..............................................................3-9
3-4 Menu 10 Main Screen ..................................................................3-9
3-5 Menu 11 Error List Screen ............................................................3-9
3-6 Menu 12 Transmitter Device Data Access Screen ..........................3-10
3-7 Menu 13 Transmitter Configuration Access Screen.........................3-10
3-8 Menu 20 Error List Display Screen..................................................3-10
3-9 Menu 30 Transmitter Device Details Screen ....................................3-10
3-10 Menu 30-1 System Details Screen..................................................3-11
3-11 Transmitter Device Parameters Detail Screens Table........................3-11
3-12 Menu 40 Authorized Personnel Screen............................................3-12
3-13 Menu 40-1 Transmitter Set-Up: Power Control Screen......................3-12
3-14 Menu 40-2 Transmitter Set-Up: Model Select Screen .......................3-13
3-15 Menu 40-3 Transmitter Set-Up: Upconverter Channel Select Screen..3-13
3-16 Menu 40-5 Transmitter Set-Up: Serial Address Screen .....................3-13
3-17 Menu 40-6 Transmitter Set-Up: System Forward Power Calibration ...3-13
3-18 Menu 40-9 Transmitter Set-Up: System Reflected Power Calibration..3-13
3-19 Menu 40-13 Transmitter Set-Up: Min Forward Power Fault Threshold 3-14
3-20 Menu 40-14 Transmitter Set-Up: Max Reflected Pwr Fault Threshold .3-14
3-21 Menu 40-19 Transmitter Set-Up: Remote Commands Control Screen.3-14
4-1 Innovator DIP Switch Settings for SW2.............................................4-3
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-1
Chapter 1
Introduction
This manual explains the installation,
setup, alignment, and maintenance
procedures for the DT325B 350-watt
digital VHF low band transmitter. It is
important that you read all of the
instructions, especially the safety
information in this chapter, before you
begin to install or operate the unit.
1.1 Manual Overview
This instruction manual is divided into
five chapters and supporting appendices.
Chapter 1, Introduction, contains
information on safety, the Axcera method
of assigning assembly designation
numbers, maintenance, return
procedures, and warranties. Chapter 2
describes the transmitter and its system
control and status indicators and remote
control connections. Chapter 3 explains
how to unpack, install, set up, and
operate the transmitter. Chapter 4,
Circuit Descriptions, describes the circuits
that make up the trays and assemblies in
the transmitter. Chapter 5, Detailed
Alignment Procedures, provides
information on adjusting the system
assemblies for optimal operation.
Appendix A contains the system
specifications sheet. Appendix B
contains the system drawings and parts
lists. Appendix C contains the assembly
and subassembly drawings and parts lists
for the exciter/driver chassis and
modules. Appendix D contains the
drawings and parts lists for the VHF Low
Band Amplifier Tray and the assemblies
and subassemblies that make up the
tray.
1.2 Assembly Designation Numbers
Axcera has assigned assembly numbers,
Ax designations such as A1, where
x=1,2,3…etc, to all assemblies, modules,
and boards in the system. These
designations are referenced in the text of
this manual and shown on the block
diagrams and interconnect drawings
provided in the appendices. The Block
Diagrams, Interconnects, Schematics,
Assembly Drawings and Parts Lists are
arranged in increasing numerical order in
the appendices. Section titles in the text
for assembly or module descriptions or
alignment procedures contain the
associated part number(s) and the
relevant appendix that contains the
drawings for that item.
The cables that connect between the
boards within a tray or assembly and
that connect between the trays, racks
and cabinets are labeled using Brady
markers.
Figure 1-1 is an example of a Brady
marked cable. There may be as few as
two or as many as four Markers on any
one cable. These Brady markers are
read starting furthest from the
connector. If there are four Brady
Markers, this marker is the transmitter
number such as transmitter 1 or
transmitter 2. The next or the furthest
Brady Marker is the rack or cabinet
number on an interconnect cable or the
board number within a tray. The next
number on an interconnect cable is the
Tray location or number. The Brady
marker closest to the connector is the
jack or connector number on an
interconnect cable or the jack or
connector number on the board within a
tray.
Figure 1-1 Brady Marker Identification
Drawing
1.3 Safety
The DT325B transmitters manufactured
by Axcera are designed to be easy to use
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-2
and repair while providing protection
from electrical and mechanical hazards.
Listed throughout the manual are notes,
cautions, and warnings concerning
possible safety hazards that may be
encountered while operating or servicing
the transmitter. Please review these
warnings and familiarize yourself with the
operation and servicing procedures
before working on the transmitter.
Read All Instructions – All of the
operating and safety instructions should
be read and understood before operating
this equipment.
Retain Manuals – The manuals for the
transmitter should be retained at the
transmitter site for future reference. We
provide two sets of manuals for this
purpose; one set can be left at the office
while one set can be kept at the site.
Heed Notes, Warnings, and
Cautions – All of the notes, warnings,
and cautions listed in this safety section
and throughout the manual must be
followed.
Follow Instructions – All of the
operating and use instructions for the
transmitter should be followed.
Cleaning – Unplug or otherwise
disconnect power from the equipment
before cleaning. Do not use liquid or
aerosol cleaners. Use a damp cloth for
cleaning.
Ventilation – Openings in the cabinets
and tray front panels are provided for
ventilation. To ensure reliable operation,
and to protect the unit from overheating,
these openings must not be blocked.
Servicing – Do not attempt to service
this product until becoming familiar with
the equipment. If in doubt, refer all
servicing questions to qualified Axcera
service personnel.
Replacement Parts – When
replacement parts are used, be sure that
the parts have the same functional and
performance characteristics as the
original part. Unauthorized substitutions
may result in fire, electric shock, or other
hazards. Please contact the Axcera
Technical Service Department if you have
any questions regarding service or
replacement parts.
1.4 Contact Information
The Axcera Field Service Department can
be contacted by phone at 1-724-873-
8100 or by fax at 1-724-873-8105.
Before calling Axcera, please be prepared
to supply the Axcera technician with
answers to the following questions. This
will save time and help ensure the most
direct resolution to the problem.
1. What are the Customers’ Name
and call letters?
2. What are the model number and
type of transmitter?
3. Is the transmitter digital or
analog?
4. How long has the transmitter
been on the air? (Approximately
when was the transmitter
installed).
5. What are the symptoms being
exhibited by the transmitter?
Include the current front panel
meter readings and the status of
LEDs on the front panels of the
trays. If possible, include the
meter readings before the
problem occurred.
1.5 Material Return Procedure
To insure the efficient handling of
equipment or components that have been
returned for repair, Axcera requests that
each returned item be accompanied by a
Return Material Authorization Number
(RMA#).
The RMA# can be obtained from any
Axcera field service engineer by calling
the Axcera Field Service Department at 1-
724-873-8100. This procedure applies to
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-3
all items sent to the Field Service
Department regardless of whether the
item was originally manufactured by
Axcera.
When equipment is sent to the field on
loan, the RMA# is included with the unit.
The RMA# is intended to be used for the
return of the unit to Axcera. In addition,
all shipping material should be retained
for the return of the unit to Axcera.
Replacement assemblies are also sent
with the RMA# to allow for the proper
routing of the exchanged hardware.
Failure to close out this type of RMA# will
normally result in the customer being
invoiced for the value of the loaner item
or the exchange assembly.
When shipping an item to Axcera, please
include the RMA# on the packing list and
on the Axcera-provided shipping
container. The packing slip should also
include contact information and a brief
description of why the unit is being
returned.
Please forward all RMA items to:
Axcera
103 Freedom Drive
P.O. Box 525
Lawrence, PA 15055-0525 USA
For more information concerning this
procedure, call Axcera Field Service at
1-724-873-8100 or by fax at
1-724-873-8105.
Axcera can also be contacted through e-
mail at info@axcera.com and on the Web
at www.axcera.com.
1.6 Warranty for Axcera Products –
Limited One-Year Warranty
Axcera warrants each new product that
it has manufactured and sold against
defects in material and workmanship
under normal use and service for a
period of one (1) year from the date of
shipment from Axcera's plant, when
operated in accordance with Axcera's
operating instructions. This warranty
shall not apply to tubes, fuses,
batteries, or bulbs.
Warranties are valid only when and if
(a) Axcera receives prompt written
notice of breach within the period of
warranty, (b) the defective product is
properly packed and returned by the
buyer (transportation and insurance
prepaid), and (c) Axcera determines, in
its sole judgment, that the product is
defective and not subject to any misuse,
neglect, improper installation,
negligence, accident, or (unless
authorized in writing by Axcera) repair
or alteration. Axcera’s exclusive liability
for any personal and/or property
damage (including direct, consequential,
or incidental) caused by the breach of
any or all warranties, shall be limited to
the following: (a) repairing or replacing
(in Axcera's sole discretion) any
defective parts free of charge (F.O.B.
Axcera's plant) and/or (b) crediting (in
Axcera's sole discretion) all or a portion
of the purchase price to the buyer.
Equipment furnished by Axcera, but not
bearing its trade name, shall bear no
warranties other than the special hours-
of-use or other warranties extended by
or enforceable against the manufacturer
at the time of delivery to the buyer.
NO WARRANTIES, WHETHER
STATUTORY, EXPRESSED, OR
IMPLIED, AND NO WARRANTIES OF
MERCHANTABILITY, FITNESS FOR
ANY PARTICULAR PURPOSE, OR
FREEDOM FROM INFRINGEMENT,
OR THE LIKE, OTHER THAN AS
SPECIFIED IN PATENT LIABILITY
ARTICLES, AND IN THIS ARTICLE,
SHALL APPLY TO THE EQUIPMENT
FURNISHED HEREUNDER.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-4
F WARNING!!!
× HIGH VOLTAGE Ø
DO NOT ATTEMPT TO REPAIR OR TROUBLESHOOT THIS EQUIPMENT UNLESS
YOU ARE FAMILIAR WITH ITS OPERATION AND EXPERIENCED IN
SERVICING HIGH VOLTAGE EQUIPMENT. LETHAL VOLTAGES ARE PRESENT
WHEN POWER IS APPLIED TO THIS SYSTEM. IF POSSIBLE, TURN OFF
POWER BEFORE MAKING ADJUSTMENTS TO THE SYSTEM.
« RADIO FREQUENCY RADIATION HAZARD «
MICROWAVE, RF AMPLIFIERS AND TUBES GENERATE HAZARDOUS RF
RADIATION THAT CAN CAUSE SEVERE INJURY INCLUDING CATARACTS,
WHICH CAN RESULT IN BLINDNESS. SOME CARDIAC PACEMAKERS MAY BE
AFFECTED BY THE RF ENERGY EMITTED BY RF AND MICROWAVE
AMPLIFIERS. NEVER OPERATE THE TRANSMITTER SYSTEM WITHOUT A
PROPERLY MATCHED RF ENERGY ABSORBING LOAD ATTACHED. KEEP
PERSONNEL AWAY FROM OPEN WAVEGUIDES AND ANTENNAS. NEVER
LOOK INTO AN OPEN WAVEGUIDE OR ANTENNA. MONITOR ALL PARTS OF
THE RF SYSTEM FOR RADIATION LEAKAGE AT REGULAR INTERVALS.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-5
EMERGENCY FIRST AID INSTRUCTIONS
Personnel engaged in the installation, operation, or maintenance of this equipment are urged to become
familiar with the following rules both in theory and practice. It is the duty of all operating personnel to be
prepared to give adequate Emergency First Aid and thereby prevent avoidable loss of life.
RESCUE BREATHING
1. Find out if the person is
breathing.
You must find out if the person
has stopped breathing. If you
think he is not breathing, place
him flat on his back. Put your ear
close to his mouth and look at his
chest. If he is breathing you can
feel the air on your cheek. You
can see his chest move up and
down. If you do not feel the air
or see the chest move, he is not
breathing.
2. If he is not breathing, open
the airway by tilting his head
backwards.
Lift up his neck with one hand
and push down on his forehead
with the other. This opens the
airway. Sometimes doing this will
let the person breathe again by
himself.
3. If he is still not breathing,
begin rescue breathing.
-Keep his head tilted backward.
Pinch nose shut.
-Put your mouth tightly over his
mouth.
-Blow into his mouth once every
five seconds
-DO NOT STOP rescue breathing
until help arrives.
LOOSEN CLOTHING - KEEP
WARM
Do this when the victim is
breathing by himself or help is
available. Keep him as quiet as
possible and from becoming
chilled. Otherwise treat him for
shock.
BURNS
SKIN REDDENED: Apply ice cold water to burned
area to prevent burn from going deeper into skin
tissue. Cover area with a clean sheet or cloth to
keep away air. Consult a physician.
SKIN BLISTERED OR FLESH CHARRED: Apply
ice cold water to burned area to prevent burn from
going deeper into skin tissue.
Cover area with clean sheet or cloth to keep away
air. Treat victim for shock and take to hospital.
EXTENSIVE BURN - SKIN BROKEN: Cover area
with clean sheet or cloth to keep away air. Treat
victim for shock and take to hospital.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-6
dBm, dBw, dBmV, dBµV, & VOLTAGE
EXPRESSED IN WATTS
50 Ohm System
WATTS PREFIX dBm dBw dBmV dBµV VOLTAGE
1,000,000,000,000 1 TERAWATT +150
+120
100,000,000,000 100 GIGAWATTS +140
+110
10,000,000,000 10 GIGAWATTS +130
+100
1,000,000,000 1 GIGAWATT +120
+ 99
100,000,000 100 MEGAWATTS +110
+ 80
10,000,000 10 MEGAWATTS +100
+ 70
1,000,000 1 MEGAWATT + 90 + 60
100,000
100 KILOWATTS + 80 + 50
10,000 10 KILOWATTS + 70 + 40
1,000 1 KILOWATT + 60 + 30
100 1 HECTROWATT + 50 + 20
50 + 47 + 17
20 + 43 + 13
10 1 DECAWATT + 40 + 10
1 1 WATT + 30 0 + 77 +137 7.07V
0.1 1 DECIWATT + 20 - 10 + 67 +127 2.24V
0.01 1 CENTIWATT + 10 - 20 + 57 +117 0.707V
0.001 1 MILLIWATT 0 - 30 + 47 +107 224mV
0.0001 100 MICROWATTS - 10 - 40
0.00001
10 MICROWATTS - 20 - 50
0.000001 1 MICROWATT - 30 - 60
0.0000001 100 NANOWATTS - 40 - 70
0.00000001 10 NANOWATTS - 50 - 80
0.000000001 1 NANOWATT - 60 - 90
0.0000000001 100 PICOWATTS - 70 -100
0.00000000001 10 PICOWATTS - 80 -110
0.000000000001 1 PICOWATT - 90 -120
TEMPERATURE CONVERSION
°F = 32 + [(9/5) °C]
°C = [(5/9) (°F - 32)]
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-7
USEFUL CONVERSION FACTORS
TO CONVERT FROM TO MULTIPLY BY
mile (US statute) kilometer (km) 1.609347
inch (in) millimeter (mm) 25.4
inch (in) centimeter (cm) 2.54
inch (in) meter (m) 0.0254
foot (ft) meter (m) 0.3048
yard (yd) meter (m) 0.9144
mile per hour (mph) kilometer per hour(km/hr) 1.60934
mile per hour (mph) meter per second (m/s) 0.44704
pound (lb) kilogram (kg) 0.4535924
gallon (gal) liter 3.7854118
U.S. liquid
(One U.S. gallon equals 0.8327 Canadian gallon)
fluid ounce (fl oz) milliliters (ml) 29.57353
British Thermal Unit watt (W) 0.2930711
per hour (Btu/hr)
horsepower (hp) watt (W) 746
NOMENCLATURE OF FREQUENCY BANDS
FREQUENCY RANGE DESIGNATION
3 to 30 kHz VLF - Very Low Frequency
30 to 300 kHz LF - Low Frequency
300 to 3000 kHz MF - Medium Frequency
3 to 30 MHz HF - High Frequency
30 to 300 MHz VHF - Very High Frequency
300 to 3000 MHz UHF - Ultrahigh Frequency
3 to 30 GHz SHF - Superhigh Frequency
30 to 300 GHz EHF - Extremely High Frequency
LETTER DESIGNATIONS FOR UPPER FREQUENCY
BANDS
LETTER FREQ. BAND
L 1000 - 2000 MHz
S 2000 - 4000 MHz
C 4000 - 8000 MHz
X 8000 - 12000 MHz
Ku 12 - 18 GHz
K 18 - 27 GHz
Ka 27 - 40 GHz
V 40 - 75 GHz
W 75 - 110 GHz
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-8
RETURN LOSS VS. VSWR
1.001 1.01 1.1 2.0
VSWR
0
-
10
-
20
-
30
-
40
-
50
-
60
-
70
R
E
T
U
R
N
L
O
S
S
dB
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction
DT325B, Rev. 0 1-9
ABBREVIATIONS/ACRONYMS
AC Alternating Current
AFC Automatic Frequency Control
ALC Automatic Level Control
AM Amplitude modulation
AGC Automatic Gain Control
AWG American wire gauge
BER Bit Error Rate
BW Bandwidth
DC Direct Current
D/A Digital to analog
dB Decibel
dBm Decibel referenced to
1 milliwatt
dBmV Decibel referenced to
1 millivolt
dBw Decibel referenced to 1 watt
FEC Forward Error Correction
FM Frequency modulation
Hz Hertz
ICPM Incidental Carrier Phase
Modulation
I/P Input
IF Intermediate Frequency
LED Light emitting diode
LSB Lower Sideband
MPEG Motion Pictures Expert Group
O/P Output
PLL Phase Locked Loop
PCB Printed circuit board
QAM Quadrature Amplitude
Modulation
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-1
Chapter 2
System Description, Maintenance and Remote Control Connections
Figure 2-1: Driver/Amplifier Chassis Assembly
Table 2-1: DT325B Major Assemblies and Trays
ASSEMBLY
DESIGNATION TRAY/ASSEMBLY NAME ASSEMBLY NUMBER
A24 Axciter Modulator 1305842
A2 Driver/Amplifier Chassis
Assembly 1310206
A2-A11 Backplane Board 1310080
A2-A1 Downconverter Module 1311157
A2-A5 Upconverter Module 1310226
A2-A4 Control/Power Supply Module 1310835 (220 VAC)
A3 VHF Low Band Amplifier Tray 1304363
2.1 System Overview
The DT325B is a complete VHF low band
solid-state digital television transmitter
that operates at a nominal average
output power of 350 watts.
The transmitter needs an AC input line of
220 VAC at 40 amps that connects to the
AC Distribution Panel which distributes
the AC through AC power cords to the
VHF exciter/driver chassis and the VHF
amplifier tray.
The DT325B consists of (A24) an Axciter
Modulator Tray, (A2) a Driver/Amplifier
Chassis Assembly and (A3) a VHF Low
Band Amplifier Tray. The assemblies and
trays are listed in Table 2-1.
2.2: Exciter Driver Chassis Assembly,
LXB, 220 VAC (1310206; Appendix C)
The chassis assembly is factory set for
operation using 220 VAC. All of the
modules, except the power amplifier
module and the power supply section of
the Control & Monitoring/Power Supply
Module, plug directly into a backplane
board. The backplane board (1310080)
provides module to module
interconnection as well as interconnection
to remote command and control
connectors.
NOTE: Information and drawings on the
Axciter Modulator Tray (1305842) and
the Upconverter Module (1310226) and
Downconverter Module (1311157) are
found in the separate Axciter Manual.
A
1
A
5
A4
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-2
2.2.1: (A4) Exciter Control/
Power Supply Assembly, LXB,
220VAC (1310835; Appendix C)
The (A4) Control/Power Supply
Assembly is made up of a System
Controller Board (1310089), a Power
Protection Board (1302837) and a LCD
w/Switches Board (1307977). The
Assembly also contains a switching
power supply that provides ±12 VDC to
the rest of the modules in the chassis
and +32 VDC to the Power Amplifier
module if needed.
The Assembly provides all transmitter
control and monitoring functions. The
Front panel LCD allows monitoring of
system parameters, including forward
and reflected power, transistor currents,
module temperatures and power supply
voltages.
Table 2-2: Controller/Power Supply Display
DISPLAY FUNCTION
LCD A 4 x 20 display providing a four-line readout of the internal
functions, external inputs, and status. See Chapter 3,
Controller/Power Supply Display Screens, for a listing of displays.
Table 2-3: Controller/Power Supply Status Indicator
LED FUNCTION
OPERATE
( green )
When lit it indicates that the transmitter is in the Operate Mode. If
transmitter is Muted the Operate LED will stay lit, the transmitter
will remain in Operate, until the input signal is returned.
FAULT
( red or green )
Red indicates that a problem has occurred in the transmitter. The
transmitter will be Muted or placed in Standby until the problem is
corrected.
DC OK
( red or green ) Green indicates that the switchable fuse protected DC outputs that
connect to the modules in the transmitter are OK.
Table 2-4: Controller/Power Supply Control Adjustments
POTENTIOMETER DESCRIPTION
DISPLAY CONTRAST Adjusts the contrast of the display for desired viewing of screen.
2.2.2: (A5) Upconverter Module
(1310226) and (A1) Downconverter
Module (1311157)
NOTE: More information and the
drawings on the Axciter Modulator Tray
(1305842) and the Upconverter Module
(1310226) and Downconverter Module
(1311157) are found in the separate
Axciter Manual.
The output from the Axciter modulator,
which is an 8-VSB IF signal centered at
44 MHz. that is -6 dBm in level, is cabled
to J68 on the rear panel of the
Driver/Amplifier Chassis Assembly. The
IF input is connected to the upconverter
module assembly through the backplane
board in the chassis assembly. The 44
MHz IF signal is upconverted to the
desired channel frequency by the
upconverter module. The resulting RF
signal is amplified and wired to a Pin
Diode Attenuator which adjusts the gain
of the module that is controlled by an
Automatic Gain Control circuit. The AGC
maintains a constant power out of the
upconverter, and also the transmitter,
that connects to the power amplifier
module. The gain controlled output of the
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-3
pin diode circuit is connected to the
output of the Upconverter Module,
approximately +10 dBm in level, at J23,
on the rear panel of the Driver/Amplifier
Chassis Assembly. This output is cabled
to the (A10) splitter and then the VHF
amplifier tray in the system.
2.2.3: Adaptive Equalization Circuits
The adaptive equalization circuits for the
system are contained in the Axciter
Modulator which controls the K2 relay
whose output connects to the
downconverter module mounted in the
Driver/Amplifier Chassis Assembly.
Two transmitter output samples are taken
from directional couplers located before,
pre-filter, and after the channel mask
filter, post-filter, that are applied to the
external K2 Relay. The switching of the
relay between the pre and post filter
samples is controlled by the Axciter
Modulator through J7 on the rear panel of
the tray.
The pre or post filter sample is connected
to J12 the Downconverter RF input jack
located on the on the rear panel of the
Driver/Amplifier Chassis Assembly. The
downconverted IF transmitter sample
output of the downconverter module at
J13, on the rear panel of the
Driver/Amplifier Chassis Assembly, is
cabled to J2 on the Axciter Modulator.
The signal is digitized by the Axciter
modulator and demodulated in non-real
time software. The result is analyzed to
calculate linear and nonlinear adaptive
equalizers to improve the transmitted
signal quality by compensating for the
nonlinear compression of the power
amplifier, and the linear distortions
(mostly group delay effects) of the channel
filter.
When a linear adaptive equalizer is being
calculated, the transmitter sample is taken
after the channel mask filter so that its
linear distortions can be “seen.”
When a nonlinear adaptive equalizer is
being calculated, the transmitter sample is
taken before the channel mask filter, so
that the distortion sidebands being
generated by the power amplifier can be
seen (the channel filter would remove the
out-of-band sidebands).
The Axciter modulator contains a standard
Personal Computer. The PC performs user
interface functions and the numerical
processing necessary for the adaptive
linear and nonlinear equalization. The PC
is not in the forward signal path; if it fails
the exciter will continue to generate a
signal with the most recently calculated
equalization.
2.3: VHF Low Band Amplifier Tray
(1304363; Appendix D)
The tray provides approximately 54 dB of
gain. The tray contains (A1-A1) the phase
shifter board 1198-1602 and (A1-A2) the
Filter/amplifier board 1198-1606, which
are mounted in the (A1) RF enclosure
assembly. The (A2-A1) VHF low band
amplifier board 1198-1605, the (A2-A2)
Overdrive protection board 1198-1601 and
the (A2-A3) 3-way splitter board 1198-
1608, which are mounted in the (A2) RF
enclosure assembly. The (A3-A1, A3-A2
and A3-A3) low band VHF amplifier pallets,
P400-VHF-L-18, 1304348 which are
mounted in the (A3) RF enclosure
assembly. The (A4-A1) 3-way combiner
board 1198-1626 and the (A4-A2 & A4-
A3) Low pass filter boards 1198-1628,
which are mounted in the (A4) 3 way
combiner enclosure. The tray also
contains the (A5) AGC control board
1306482, the (A8) Current metering board
1304362 and (A10) the +30 VDC
switching power supply assembly
PM3329B-5-1-R-2-E, 1301504.
The On Channel RF signal (0 to +10 dBm),
enters the rear of the Tray at the "BNC"
Jack J1. The RF connects to a phase
shifter board that provides a phase shift
adjustment of the RF Signal that is needed
to produce the maximum output during
the combining of multiple Amplifier Trays
in an Amplifier Array. The output of the
phase shifter is cabled to the
filter/amplifier board. The gain of the tray
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-4
is controlled by an external bias voltage
that connects to the AGC Control Board
and adjusts the AGC Pin Attenuator Bias
Voltage which is applied to the
Filter/Amplifier Board. The RF output of
the Filter/Amplifier Board is amplified by
the LB Amplifier Board and connected to
the Overdrive Protection Board. The
overdrive protection board provides a trip
point, 110%, for over power conditions
which will cut back the output power of the
Tray.
The RF Output of the Overdrive Protection
Board connects to the 3 Way Splitter
Board. The three RF outputs connect to
the three Low Band Output Amplifier
Pallets. Each amplifier pallet provides
approximately 18 dB gain. The RF signal
inputs to the Output Amplifier Boards
(+33.3 dBm) are amplified to +51.3 dBm
outputs at J2, which are connected to the
3 Way Combiner Assembly. The 3 Way
Combiner takes the three +51.3 dBm
combined inputs and combines them to
form the ˜375 Watt RF Output at J4 of the
Combiner which soldered to J2, the RF
Output Jack of the Tray.
The 3 Way Combiner Board provides a
Forward Power Sample and a Reflected
Output Power Sample that connect thru
low pass filters to the AGC Control Board.
The AGC Control Board provides detected
outputs that are used for front panel and
remote meter Indications of the forward
and reflected output power levels, AGC
Detector Voltage Level and also the VSWR
Cutback protection if the Reflected Power
level increases above the preset level.
Two voltages, +28 VDC from the internal
switching power supply and +12 VDC from
the Driver/Amplifier Assembly are needed
for operation of the Tray. The +12 VDC is
connected to a +5 VDC Regulator IC which
supplies the +5 VDC needed for operation
of the front panel mounted LEDs. The
(A10) +28 VDC Switching Power Supply
provides the +28 VDC to the Current
Metering Board. The Current Metering
Board distributes the voltages through
fuses to the Amplifier Devices on the
Filter/Amplifier, Low Band Driver Board
and the three Final Low Band Amplifier
Boards.
The Current Metering Board also supplies
sample outputs of the operating currents
of the amplifier devices in the Tray to the
front panel Current Meter. The Meter in
the (I1) position reads the current for the
(A3-A1) Low Band Output Amplifier
Board, (I2) for the (A3-A2) Low Band
Output Amplifier Board and (I3) for the
(A3-A3) Low Band Output Amplifier
Board. To read the desired current;
switch S2 to the proper position checking
that S1 is in the Current position. These
current readings can be used when
setting up the Idling Currents, no RF
Drive applied, for the devices. (I1, I2 &
I3) are set for 3 Amps max.
Table 2-5: VHF Amplifier Tray Control Adjustments
ADJUSTMENT DESCRIPTION
R2 – A7
Phase Adjusts the phase of the RF output by approximately 70°.
R3 – A6
Gain Adjusts the gain of the RF output when the amplifier control
board is in the AGC mode.
Table 2-6: VHF Amplifier Tray Sample
SAMPLE DESCRIPTION
J5
RF Front Panel Sample Forward power sample of the tray from the AGC control
board.
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-5
Table 2-7: VHF Amplifier Tray Switches
SWITCH FUNCTION
CB1
On/Off Circuit Breaker
Switches 220 VAC through a 15-amp circuit breaker-type
protection device. The switch lights if AC is present. The
AC is applied to the switching power supply in the tray.
Selects the desired % Forward Output Power, % Reflected
Power reading, AGC Voltage, Power Supply Voltage, or
Current
With Switch S1 in
Position Display
% Forward Reads the % Forward Output
Power of the tray (100%= 375
watts DTV)
% Refl (Reflected) Reads the % Reflected Output
Power (<5%)
AGC Voltage Reads the AGC level of the tray
(1 to 3 VDC)
Power Supply Reads the voltage from the
switching power supply
(+28 VDC)
S1
Switch, Meter
Current Uses Switch S2 to indicate the
current of transistor devices
Selects the current of the transistor devices on the low band
amplifier boards. S1 must be in the Current position.
With Switch S2 in
Position Display
I1
Reads the current of (A3-A1)
the low band amplifier board
(idling current=1.8 amps and
operating current=12-13 amps,
black picture)
I2
Reads the current of (A3-A2) the
low band amplifier board (idling
current=1.8 amps and operating
current=12-13 amps, black
picture)
I3
Reads the current of (A3-A3)
the low band amplifier board
(idling current=1.8 amps and
operating current=12-13 amps,
black picture)
S2
Switch, Meter
ID
Reads the current of (A2-A1) the
low band amplifier board (idling
current=3 amps and operating
current=3 amps, black picture)
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-6
Table 2-8: VHF Amplifier Tray Fault Indicators
INDICATOR DESCRIPTION
DS1
Overdrive
Indicates that the level of drive is too high. The protection
circuit will limit the drive level to the set threshold. The fault
is generated on the overdrive protection board.
DS2
Enable Indicates that the Enable supplied by the driver/amplifier
chassis assembly is present
DS3
Module Status Indicates that the forward power sample level is lower than
the set reference level
DS4
VSWR Cutback
Indicates that the reflected level of the tray has increased
above 20%; this will automatically cut back the output power
of the tray. The fault is generated on the AGC control board.
DS5
Overtemperature
Indicates that the temperature of (A13, A14 or A15) one of
the thermal switches is above 175° F. When this fault
occurs, the Enable to the switching power supply is
immediately removed.
2.4: Control and Status
The control and status of the
exciter/amplifier chassis assembly is found
by operating the front panel display screen
on the assembly. Detailed information on
the use of the screen is found in Chapter 3
of this manual.
2.4.1: Front Panel Display Screen
A 4 x 20 display located on the front of
the Control & Monitoring/Power Supply
Module is used in the transmitter for
control of the operation and display of
the operating parameters of the
transmitter.
2.5: System Operation
When the transmitter is in operate, as set
by the menu screen located on the
Control & Monitoring Module, the +32
VDC stage of the Power Supply in the
Control & Monitoring Module is enabled,
the operate indicator on the front panel is
lit and the DC OK on the front panel
should also be green. The enable and DC
OK indicators on the PA Module will also
be turned to green.
When the transmitter is in standby, the
IF Processor will be disabled and the
mute indicator on the front panel will be
red. Also, the +32 VDC stage of the
Power Supply in the Control & Monitoring
Module is disabled, the operate indicator
on the front panel will be extinguished
and the DC OK on the front panel should
remain green. The enable and indicator
on the PA Module is also extinguished.
If the transmitter does not switch to
Operate when the operate menu is
switched to Operate, check that all faults
are cleared and that the remote control
terminal block stand-by signal is not
active. Also check that a jumper or
external closed interlock is connected
from J30-5 to J30-15 on the rear of the
exciter/deriver chassis assembly.
2.5.1: Principles of Operation
Operating Modes
This transmitter is either operating or in
standby mode. The sections below
discuss the characteristics of each of
these modes.
Operate Mode
Operate mode is the normal mode for
the transmitter when it is providing RF
power output. To provide RF power to
the output, the transmitter will not be in
mute. Mute is a special case of the
operate mode where the power supply's
32 VDC section is enabled but there is
no RF output power, because of a fault
condition that causes the firmware to
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-7
hold the IF Processor module in a mute
state.
Operate Mode with Mute Condition
The transmitter will remain in operate
mode but will be placed in mute when
the following fault conditions exists in
the transmitter.
• Upconverter is unlocked
• Upconverter module is not present
• IF Processor module is not present
Entering Operate Mode
Entering the operate mode can be
initiated a few different ways by the
transmitter control board. A list of the
actions that cause the operate mode to
be entered is given below:
• A low on the Remote Transmitter
Operate line.
• User selects "OPR" using switches
and menus of the front panel.
• Receipt of an “Operate CMD” over
the serial interface.
There are several fault or interlock
conditions that may exist in the
transmitter that will prevent the
transmitter from entering the operate
mode. These conditions are:
• Power Amplifier heat sink
temperature greater than 78°C.
• Transmitter is Muted due to
conditions listed above.
• Power Amplifier Interlock is high
indicating that the amplifier is not
installed.
Standby Mode
The standby mode in the transmitter
indicates that the output amplifier of the
transmitter is disabled.
Entering Standby Mode
Similar to the operate mode, the
standby mode is entered various
different ways. These are:
• A low on the Remote Transmitter
Stand-By line.
• Depressing the “STB” key on
selected front panel menus.
• Receipt of a “Standby CMD” over the
serial interface.
Auto Standby Mode
The FCC requires that certain
transmitters automatically switch to
standby operation on loss of input. The
transmitter incorporates this feature as
a user configurable setting. When Auto
Stand-By On Modulation Loss is selected
in the set-up menus, the transmitter
temporarily switches to standby after
ten seconds of modulation loss. When
the modulated signal as reported by the
IF Processor module is again present,
the transmitter automatically returns to
Operate mode.
RF System Interlock
A RF System Interlock signal is provided
through TB30-5. When this signal's
circuit is completed to ground such as
through a wire between TB30-5 and
TB30-15, the transmitter is allowed to
operate. If this circuit is opened, the
transmitter switches to a Mute condition.
This circuit may be completed through
coax relay contacts or reject load
contact closures to assure the RF output
system is available to receive the
transmitter's output RF signal.
Operating Frequency
The transmitter controller is designed to
operate on UHF frequencies. The exact
output frequency of the transmitter can
be set to one of the standard UHF
frequencies, or to a custom frequency
using the software channel set-up menu
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-8
on the Controller Module. Since RF
performance of the transmitter requires
different hardware for different
frequency bands, not all frequency
configurations are valid for a specific
transmitter. The Power detectors in the
transmitter are frequency dependent,
therefore the detectors of the power
amplifiers are calibrated at their
frequency of use. The detectors for
System RF monitoring are also
calibrated at the desired frequency of
use.
2.6: Maintenance
The Transmitter is designed with
components that require little or no
periodic maintenance except for the
routine cleaning of the fans and the front
panels of the modules and the periodic
check of general tightness of hardware.
It is recommended that periodically, the
time interval depends on the amount of
movement the cabinet receives, all
mounting hardware, holding tray slides,
shelving and mounting plates inside the
cabinet are checked for tightness. All
screws and bolts that are accessible
should be tightened initially when the
transmitter is received and periodically
thereafter if the transmitter is moved by
vehicle. All coaxial connectors, hard-line
connections and hardware holding
combiners, splitters, or any other
mounted items should be checked and
tightened. Check the front panel
thumbscrews that hold the Exciter/Driver
Sleds, Amplifier Module and Power
Supply Sleds in place are tight. This is
especially important after the transmitter
has been transported.
The amount of time between cleanings
depends on the conditions within the
transmitter room. While the electronics
have been designed to function even if
covered with dust, a heavy buildup of
dust, dirt, or insects will affect the
cooling of the components. This could
lead to a thermal shutdown or the
premature failure of the affected
modules.
When the front panels of the modules
become dust covered, the top covers
should be taken off and any accumulated
foreign material should be removed. A
vacuum cleaner, utilizing a small, wand-
type attachment, is an excellent way to
suction out the dirt. Alcohol and other
cleaning agents should not be used
unless you are certain that the solvents
will not damage components or the silk-
screened markings on the modules and
boards. Water-based cleaners can be
used, but do not saturate the
components. The fans and heatsinks
should be cleaned of all dust or dirt to
permit the free flow of air for cooling
purposes.
It is recommended that the operating
parameters of the amplifier assembly and
transmitter be recorded from the LEDs on
the modules and the LCD system
metering on the control/monitoring
module at least once a month. It is
suggested that this data be retained in a
rugged folder or envelope.
2.6.1: Module Replacement
Module replacement on the products is a
relatively simple process. All modules
plug directly into the backplane board
except for the power amplifier module,
and in higher power units, the power
supply and power amplifier modules,
which plug into a blind mating
connector.
To replace a module, refer to the
following procedure. Loosen the two grip
lock connectors, located on the front
panel, at the top and bottom of the
module, counterclockwise until the
module releases. The Downconverter,
Upconverter and the Controller/Power
Supply can then be gently pulled from
the unit. After removal of the failed
module, slide the replacement module in
place and make certain it connects to the
backplane board. If the replacement
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-9
module does not slide in easily, verify it
is properly aligned in the nylon tracks,
located on both the top and bottom of
the module.
Note: Each Module has an assigned slot
and will not fit properly or operate in the
incorrect slot. Do not try to place a
Module in the wrong slot as this may
damage the slot or the connectors on
the backplane board. Each module has
the name of the module on the front,
bottom for identification and correct
placement. The Modules are placed in
the unit from left to right; (1)
Downconverter, (2) Blank panel, (3)
Blank panel, (4) Upconverter, (5) the
Controller/Power Supply and (6) a Blank
panel.
2.7: Customer Remote Connections
The remote monitoring and operation of
the transmitter is provided through
jacks TB30 and TB31 located on the rear
of the chassis assembly. If remote
connections are made to the
transmitter, they must be made through
plugs TB30 and TB31 at positions noted
on the transmitter interconnect drawing
and Table 2-9. TB30 and TB31 are 18
position terminal blocks that are
removable from their sockets to make
connections easier. Just grasp and pull
connector straight out. After
connections are made, replace the
connector and push firmly to seat the
connector in the socket.
Figure 2-2: Rear View Driver/Amplifier Chassis Assembly
Table 2-9: Driver/Amplifier Chassis Assembly Hard Wired Remote Interface Connections
to TB30 or TB31, 18 pos. Terminal Blocks Located on the Rear of the Chassis Assembly
Signal Name Pin
Designations Signal Type/Description
RMT Transmitter
State TB30-1 (Connects to isolation relay board.) Discrete Open
Collector Output - A low indicates that the transmitter is in
the operate mode.
RMT Transmitter
Interlock TB30-2
Discrete Open Collector Output - A low indicated the
transmitter is OK or completes a interlock daisy chain.
When the transmitter is not faulted, the interlock circuit is
completed.
RMT Transmitter
Interlock
Isolated Return TB30-3
Ground - Configurable ground return which can be either
jumpered directly to ground or it can be the “source” pin of
an FET so that the transmitter interlock can be daisy
chained with other transmitters. This signal does not
directly interface to the microcontroller.
TB30
TB31
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-10
Signal Name Pin
Designations Signal Type/Description
RMT AUX IO 1 TB30-4
Discrete Open Collector Inputs, Discrete Open Drain
Outputs, or 0 - 5 VDC Analog Input - When used as an
output, this line is pulled to +5 VDC with a 1.0 kO resistor
for logic high and pulled to ground for a low. A diode
allows this line to be pulled up to 12 VDC. When used as a
digital input, this line considers all values over 2 Volts as
high and those under 1 volt as low. As an analog input,
this line is protected by a 5.1 Zener diode.
RMT RF System
Interlock TB30-5
When this signal's circuit is completed to ground the
transmitter is allowed to operate. Typically, a jumper is
connected from TB30-5 and TB30-15. If this circuit is
opened, the transmitter switches to a Mute condition.
(See note at end of table)
RMT
Transmitter
Operate TB30-6 Discrete Open Collector Input - A pull down to ground on
this line indicates that the transmitter is to be placed into
the operate mode.
RMT
Transmitter
Stand-By TB30-7 Discrete Open Collector Input - A pull down to ground on
this line indicates that the transmitter is to be placed into
the standby mode.
RMT Power Raise TB30-8 Discrete Open Collector Input - A pull down to ground on
this line indicates that the transmitter power is to be
raised.
RMT Power
Lower TB30-9 Discrete Open Collector Input - A pull down to ground on
this line indicates that the transmitter power is to be
lowered.
RMT
System Reflect
Power TB30-10
Analog Output - 0 to 4.0 V- This is a buffered loop through
of the calibrated “System Reflected Power” and indicates
the transmitter's reflected output power. The scale factor
is 25 % / 3.2V.
RMT System
Forward Power TB30-11 Analog Output - 0 to 4.0 V- This is a buffered loop through
of the calibrated “System Average Power”. Indicates the
transmitter's Average power. Scale factor is 100 % / 3.2V.
RMT Spare 1 TB30-13 Remote connection to spare module - Use is TBD.
RMT Spare 2 TB30-14 Remote connection to spare module - Use is TBD.
Interlock Rtn TB30-15 Typically connected to TB30-5, which allows the
transmitter to operate.
+12 VDC TB30-16 (Connects to triple peak detector board, the isolation
relay board, and the VHF amplifier tray.) +12 VDC w/
2 Amp re-settable fuse
Rtn TB30-17 (Connects to the VHF amplifier tray.) Rtn
-12 VDC TB30-18 (Connects to isolation relay board.) -12 VDC w/ 2
Amp re-settable fuse.
Power Lower TB30-19 Discrete Open Collector Input - A pull down to ground on
this line indicates that the transmitter power is to be
lowered.
Rtn TB31-1,2,6-11 Rtn
RTN Ground TB31-12 (Connects to triple peak detector board.) Ground
System Reflect
Power TB31-13
(Connects to triple peak detector board.) Analog
Input - 0 to 1.00 V- This is the input of the “System
Reflected Power ” indicating the transmitter's reflected
output power. The scale factor is 25 % / 0.80V.
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-11
Signal Name Pin
Designations Signal Type/Description
System Forward
Power TB31-14
(Connects to triple peak detector board.) Analog
Input - 0 to 1.00 V- This is the input of the “System
Forward Power ” indicating the transmitter's Forward
output power. The scale factor is 100 % / 0.80V.
NOTE: The RMT RF System Interlock, at TB30-5, provides the customer with a means of
connecting the transmitter to protection circuits, for the loads, thermal switches,
combiners, or the antenna, in the output of your system, that will Mute the
transmitter if the protection circuit opens. If the interlock is not used in the
system, a jumper from TB30-5 to TB30-15, which is ground, needs to be
connected to TB30. This jumper provides the RF System Interlock, which allows
the transmitter to go to operate. Without the jumper, the transmitter will remain
Muted.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-1
Chapter 3
Installation and Setup Procedures
There are special considerations that
need to be taken into account before the
DT325B can be installed. For example, if
the installation is completed during cool
weather, a heat-related problem may not
surface for many months, suddenly
appearing during the heat of summer.
This section provides planning
information for the installation and set up
of the transmitter.
3.1 Site Considerations
The transmitter requires an AC input line
of 220 VAC with a rating of 30 amps
connected to the AC input box on the
cabinet. Make sure that the proposed
site for the transmitter has the voltage
requirements that are needed.
The DT325B is designed and built to
provide long life with a minimum of
maintenance. The environment in which
it is placed is important and certain
precautions must be taken. The three
greatest dangers to the transmitter are
heat, dirt, and moisture. Heat is usually
the greatest problem, followed by dirt,
and then moisture. Over-temperature
can cause heat-related problems such as
thermal runaway and component failure.
Each amplifier tray in the transmitter
contains a thermal interlock protection
circuit that will shut down that tray until
the temperature drops to an acceptable
level.
A suitable environment for the
transmitter can enhance the overall
performance and reliability of the
transmitter and maximize revenues by
minimizing down time. A properly
designed facility will have an adequate
supply of cool, clean air, free of airborne
particulates of any kind, and without
excessive humidity. An ideal environment
will require temperature in the range of
40° F to 70° F throughout the year,
reasonably low humidity, and a dust-free
room. This is rarely attainable in the real
world. However, the closer the
environment is to this design, the greater
the operating capacity of the transmitter.
The first source of heat in the building is
the transmitter itself. The fans designed
and built into the transmitter will remove
the heat from within the trays and
cabinets, but additional means are
required for removing this heat from the
building. Two blowers, one mounted on
the roof of each cabinet, are designed to
achieve this.
The second source of heat is other
equipment in the same room. The third
source of heat is equally obvious but not
as simple to calculate. This is the heat
coming through the walls, roof, and
windows on a hot summer day. Unless
the underside is exposed, the floor is
usually not a problem. Determining this
number is usually best left up to a
qualified HVAC technician. There are far
too many variables to even estimate this
number without detailed drawings of the
site showing all construction details. The
sum of these three sources is the total
amount of heat that must be removed.
There may be other sources of heat, such
as personnel, and all should be taken into
account.
Now that the amount of heat that must
be removed is known, the next step is to
determine how to accomplish this.
The options are air conditioning,
ventilation, or a combination of the two.
Air conditioning is always the preferred
method and is the only way to create
anything close to an ideal environment.
Ventilation will work quite well if the
ambient air temperature is below 100° F,
or about 38° C, and the humidity is be
kept at a reasonable level. In addition,
the air stream must be adequately
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-2
filtered to ensure that no airborne
particulate of any kind will be carried into
the transmitter. The combination of air
conditioning for summer and ventilation
during the cooler months is acceptable
when the proper cooling cannot be
obtained through the use of ventilation
alone and using air conditioning
throughout the year is not feasible.
Caution: The operation of air
conditioning and ventilation
simultaneously is not recommended.
This can cause condensation in
transmitters. For tube type
transmitters, this can be especially
serious if the condensation forms in
the tube cavity and creates
damaging arcs.
The following precautions should be
observed regarding air conditioning
systems:
1. Air conditioners have an ARI
nominal cooling capacity rating. In
selecting an air conditioner, do not
assume that this number can be
equated to the requirements of
the site. Make certain that the
contractor uses the actual
conditions that are to be
maintained at the site in
determining the size of the air
conditioning unit. With the desired
conditioned room temperature
under 80° F, the unit must be
derated, possibly by a substantial
amount.
2. Do not have the air conditioner
blowing directly onto the
transmitter. Condensation may
occur on, or worse in, the
transmitter under certain
conditions.
3. Do not isolate the front of the
transmitter from the back with the
thought of air conditioning only
the front of the unit. Cooling air is
drawn in at the front of all
transmitters and in the front and
back of others. Any attempt to
isolate the front from the rear will
adversely affect the cooling air
flow.
4. Interlocking the transmitter with
the air conditioner is
recommended to keep the
transmitter from operating without
the necessary cooling.
5. The periodic cleaning of all filters
is a must.
When using ventilation alone, the
following general statements apply:
1. The blower, with attendant filters,
should be on the inlet, thereby
pressurizing the room and
preventing the ingress of dirt.
2. The inlet and outlet vents should
be on the same side of the
building, preferably the leeward
side. As a result, the pressure
differential created by wind will be
minimized. Only the outlet vent
may be released through the roof.
3. The inlet and outlet vents should
be screened with 1/8" hardware
cloth (preferred) or galvanized
hardware cloth (acceptable).
4. Cooling air should enter the room
as low as practical but in no case
higher than four feet above the
floor. The inlet must be located
where dirt, leaves, snow, etc., will
not be carried in with the cooling
air.
5. The exhaust should be located as
high as possible. Some ducting is
usually required to insure the
complete flushing of heated air
with no stagnant areas.
6. The filter area must be adequate
to insure a maximum air velocity
of 300 feet per minute through the
filter. This is not a conservative
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-3
number but a never-exceed
number. In a dusty or remote
location, this number should be
reduced to 150 CFM.
7. The inlet and outlet(s) must have
automatic dampers that close any
time the ventilation blower is off.
8. In those cases in which
transmitters are regularly off for a
portion of each day, a
temperature-differential sensor
that controls a small heater must
be installed. This sensor will
monitor inside and outside
temperatures simultaneously. If
the inside temperature falls to
within 5° F of the outside
temperature, the heater will come
on. This will prevent condensation
when the ventilation blower comes
on and applies even in the
summer.
9. A controlled-air bypass system
must be installed to prevent the
temperature in the room from
falling below 40° F during
transmitter operation.
10. The blower should have two
speeds, which are thermostatically
controlled, and interlocked with
the transmitter.
11. The blower on high speed must be
capable of moving the required
volume of air into a half inch of
water pressure at the required
elevation. The free air delivery
method must not be used.
12. Regular maintenance of the filters,
if used, can not be
overemphasized.
13. Tube transmitters should not rely
on the internal blower to exhaust
cooling air at elevations above
4000 feet. For external venting,
the air vent on the cabinet top
must be increased to an 8"
diameter for a 50-W, 100-W and
1-kW transmitter and to 10" for 5-
kW and 10-kW transmitters. An
equivalent rectangular duct may
be used but, in all cases, the
outlet must be increased in area
by 50% through the outlet screen.
14. It is recommended that a site plan
be submitted to Axcera for
comments before installation
commences.
In calculating the blower requirements,
filter size, and exhaust size, if the total
load is known in watts, 2000 CFM into
1/2" of water will be required for each
5000 watts. If the load is known in BTUs,
2000 CFM into 1/2" of water will be
required for each 17,000 BTUs. The inlet
filter must be a minimum of seven
square feet, larger for dusty and remote
locations, for each 5000 watts or 17,000
BTUs. The exhaust must be at least four
square feet at the exhaust screen for
each 5000 watts or 17,000 BTUs.
The information presented in this section
is intended to serve only as a general
guide and may need to be modified for
unusually severe conditions. A
combination of air conditioning and
ventilation should not be difficult to
design (see Figure 3-1). System
interlocking and thermostat settings
should be reviewed with Axcera. As with
any equipment installation, it is always
good practice to consult the
manufacturer when questions arise.
Axcera can be contacted at 1-724-873-
8100.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-4
Figure 3-1: Typical 1 kW Minimum Ventilation Configuration
Figure 3-2: Front and Rear View of the Driver/Amplifier Reconnection Drawing
3.2 Unpacking and Installation of
the Cabinet and Trays
Thoroughly inspect the cabinet, the trays
and all other materials upon their arrival.
Axcera certifies that upon leaving our
facility the equipment was undamaged
and in proper working order. The
shipping containers should be inspected
for obvious damage that is indicative of
rough handling. Check for dents and
scratches or broken switches, meters, or
connectors. Any claims against in-transit
damage should be directed to the carrier.
Inform Axcera as to the extent of any
damage as soon as possible.
Remove the cabinet with the Axciter
system, driver/amplifier chassis and VHF
amplifier tray, also the harmonic filter,
bandpass filter, couplers and the
installation material from the crates and
boxes. Remove the straps that hold the
cabinets to the shipping skids and slide
the cabinet from the skid. Remove the
plastic wrap and foam protection from
around the cabinets. Do not remove any
labeling or tags from any cables or
connectors; these are identification
markers that make assembly of the
transmitter much easier.
If the trays are shipped in the cabinet,
remove the L-brackets, mounted on the
front panel rails, which hold the trays in
place during shipment. The trays are
mounted in the cabinet using Chassis
Trak cabinet slides. The slides are on the
sides of the VHF amplifier and the Axciter
modulator trays. Inspect the trays for
any loose hardware or connectors,
tightening where needed. Open the rear
door of the cabinet and inspect the
interior for packing material, carefully
removing any that is found. Slowly slide
each tray in and out to verify that they
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-5
do not rub against each other and have
no restrictions to free movement.
Adjustments to the position of the trays
may be necessary. To accomplish this,
loosen the cabinet slide mounting bolts
that hold the front of the slide to the
mounting frame of the cabinet and move
the tray up or down as needed to correct
for the rubbing.
The air intake to the transmitter is
intended for room air only. The cabinet
should be positioned with consideration
given to adequate air intake and exhaust,
the opening of the rear door, access to
the trays (including sliding them out for
testing), the main AC hookup, and the
installation of the output transmission
line. The cabinet should be grounded
using copper strapping material and
should also be permanently mounted to
the floor of the site using the holes in the
bottom of the cabinet.
3.3 Input and Output Connections to
the Transmitter
3.3.1 Main AC Connection to the
Transmitter System
Once the cabinet is in place, the
connection of the Main AC to the cabinet
is ready to be made.
Caution: Before connecting the
transmitter to the AC voltage, make
certain that all of the circuit breakers
associated with the transmitter are
switched off.
The main AC input circuit to the DT325B
is a 30-amp, 220-VAC line, using AWG 6
wire, inside of 1-1/4-inch conduits to
each cabinet assembly. The 220 VAC
input connections are made to the
terminal block TB1, which is part of the
AC junction box, mounted near the upper
right-hand, rear portion of the cabinet:
terminals 1 and 2 (220 VAC) and
terminal 3 (chassis ground). See Figure
3-3.
Figure 3-3: AC Input Box Assembly
Check that the AC power cords from the
Driver/Amplifier Chassis Assembly and
the Axciter Modulator Tray connect
directly to the UPS or to the AC outlet
assembly connected to the UPS in the
Cabinet. Check that the AC power cord
from the VHF Amplifier Tray connects to
the AC outlet assembly not connected to
the UPS in the Cabinet.
3.3.2 Input Connections to the
Transmitter System
Connect the SMPTE 310 input to J27
located on the rear panel of the (A24)
Axciter Modulator Tray. If an external 10
MHz reference is used, connect it to J9
located on the rear panel of the (A24)
Axciter Modulator Tray. If the external
10MHz is not used an internally
generated 10MHz is produced by the
Axciter Modulator for use in the
transmitter. Check that the DTV output
of the Axciter at J40 connects to J68, the
IF Input jack, on the rear panel of the
Driver/Amplifier Chassis Assembly. Check
that the 1GHz output of the Axciter at
J15 connects to J40 on the rear panel of
the Driver/Amplifier Chassis Assembly.
Check that the forward power sample,
pre-filtering, of the VHF amplifier tray,
from the (A16) pre-filter coupler
connects to J1, on the K2 relay. Check
that the forward power sample, post-
filtering, of the output of the transmitter
from the (A11) post-filter coupler
connects to J2, on the K2 relay. Check
that the selected output of the K2 relay
at J3 connects to the rear of the
driver/amplifier chassis assembly at the
SMA Jack J41. This sample is used by
the Axciter system in the adaptive
equalization process.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-6
Figure 3-4: Rear View of Driver/Amplifier Chassis Assembly
Table 3-1: Rear Chassis Connections for the Digital Driver/Amplifier Chassis Assembly.
Port Type Function Impedance
J1 IEC AC Input N/A
TB02 Term (NOT USED) Base Band Audio Input 600O
J3 BNC (NOT USED) Composite Audio Input 75O
J4 BNC (NOT USED) SAP / PRO Audio Input 50O
J5 BNC (NOT USED) CW IF Input 50O
J6 BNC (NOT USED) Digital IF Input 50O
J7 BNC (NOT USED) Video Input (Isolated) 75O
J8 BNC (NOT USED) Visual IF Loop-Thru Output 50O
J9 BNC (NOT USED) Aural IF Loop-Thru Output 50O
J10 BNC External 10 MHz Reference Input (From Axciter) 50O
J12 BNC (NOT USED) MPEG Input 50O
J13 BNC Downconverter IF Output (To Axciter) 50O
J68/
J15 BNC Digital IF I/P (From Axciter) 50O
J17 BNC (NOT USED) Video Loop-Thru (Isolated) 75O
J18 BNC (NOT USED) Visual IF Loop-Thru Input 50O
J19 BNC (NOT USED) Aural IF Loop-Thru Input 50O
J23 BNC Upconverter RF Output (To Splitter) 50O
J24 BNC IPA RF Input (Jumpered from J23) 50O
J25 N IPA RF Output 50O
J32 RJ-45 SCADA (Input / Loop-Thru) CAT5
J33 RJ-45 SCADA (Input / Loop-Thru) CAT5
J34 RJ-45 System RS-485 Serial CAT5
J40 SMA 1GHz Input (From Axciter) 50O
J41 SMA Downconverter RF Input (From K2 Relay) 50O
TB30
Termination Remote Control & Monitoring N/A
TB31
Termination Remote Control & Monitoring N/A
J1
J21
TB30
TB31
J32
J34
J33
J
10
J23
J13
J
68
J41
J40
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-7
3.4 Setup and Operation Procedures
The transmitter should initially be turned
on with the RF output of the coaxial
switch terminated into a dummy load of
at least 350W. If a load is not available,
check that the output is connected to the
antenna.
Check that the circuit breaker mounted
on the rear panel near the AC input jack
of driver/amplifier chassis assembly is
On. Check that the circuit breaker,
located on the front of the VHF amplifier
tray, is On.
On the driver/amplifier, switch the
Operate/Standby switch to Operate. The
VHF amplifier tray should go to operate.
Observe the power supply reading on the
front panel of the VHF amplifier tray. It
should be +28 VDC.
NOTE: If the transmitter does not switch
to Operate when the selected On Air
exciter is placed in Operate, check that
the protection interlock is present,
normally by jumpering TB30-5 to TB30-
15. The interlock or the jumper provides
the remote interlock needed by the
transmitter to allow it to switch to
Operate.
On the LCD screen in the driver/amplifier
chassis assembly, look at the % Output
Power indication, it should read near to
the level as stated on the final test data
sheet for your transmitter. If necessary,
adjust the output power of the
transmitter using the Driver/
Amplifier LCD display while viewing the
Power Control Screen in the Set Up Menu
and increase or decrease the level as
needed to attain 100% output power of
the transmitter. As the output power
level is being checked, observe the LCD
screen reading in the % Reflected Power
position. If the % Reflected Power is
very high, above 10%, a problem may
exist with the output coaxial lines and
they will need to be checked. A center
bullet missing from the coax lines or
loose bolts is a probable cause. Repair
as needed to attain a <5% reflected
reading.
The gain and phase control on the front
panel of the VHF amplifier tray was
adjusted at the factory to obtain an
output of 100% for the transmitter and
should not need to be readjusted. Refer
to the Test Data Sheet for the transmitter
to compare the final readings from the
factory with the readings on the tray after
the setup. They should be very similar.
If a reading is off by a significant amount,
refer to the power adjustment procedure
for the VHF amplifier tray in Chapter 5,
Detailed Alignment Procedures, of this
manual before trying to make any
adjustments.
If a dummy load is connected to the
transmitter, switch the main on/off circuit
breaker, for the system, Off. Remove the
dummy load and make all of the
connections needed to connect the
transmitter to the antenna. Switch the
main on/off circuit breaker On and the
Operate/Standby switch to operate. If
needed, adjust the output power, using
the Axciter LCD screen in the Upconverter
menu screen, to attain 100% output of
the transmitter.
If the transmitter is already connected to
the antenna, check that the output is
100%. If necessary, adjust the output
power, using the Axciter LCD screen in
the Upconverter menu screen, to attain
100% output of the transmitter.
3.4.1 Driver/Amplifier Chassis
Modules front panel LEDs
The following LED descriptions are
typical of the operating On Air Exciter.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-8
3.4.1.1: Axciter Upconverter Sled
Module LEDs on Front Panel
Status Indicators:
PLL: This illuminates Green when the
phase lock loop circuit is closed, Red if
unlocked.
STATUS: This illuminates Green if no
faults present, Red when a fault has
occurred in the upconverter.
AGC: This illuminates Green when in
Auto, Amber when in Manual.
3.4.1.2: Controller Module LEDs on
Front Panel
Status Indicators:
OPERATE - This illuminates Green when
transmitter is in operate.
FAULT - This illuminates Red when a
fault has occurred in the transmitter.
DC OK - This illuminates Green when the
DC outputs that connect to the modules
in the transmitter are present.
3.4.2: Front Panel LCD Screen for the
Driver/Amplifier Chassis Assembly
A 4 x 20 display located on the front of
the Control & Monitoring/Power Supply
Module is used in the Driver/Amplifier
Chassis Assembly for control of the
operation and display of the operating
parameters of the transmitter. Below
are the display screens for the system.
The ↑ and ↓ characters are special
characters used to navigate up or down
through the menu screens. Display text
flashes on discrete fault conditions for all
screens that display a fault condition.
When the transmitter is in operate mode,
the STB menu appears. When the
transmitter is in standby mode, the OPR
menu appears.
NOTE: The following screens are typical
of an operating Exciter but may be
different from the screens in your
system.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-9
Display Menu Screens for the Driver/Amplifier Chassis Assembly
Table 3-2: Menu 01 - Splash Screen #1
This is the first of the two transmitter splash screens that is shown for the first few
seconds after reset or after pushing the SPL button on the Main Screen. This screen will
automatically switch to the second splash screen.
Table 3-3: Menu 02- Splash Screen #2
This is the second of the two transmitter splash screens. This screen will automatically
switch to the Main Screen. The Model Number, Code Version Number and Firmware
Number for your system are displayed on this screen. Make note of these two numbers
when conferring with Axcera on software problems.
Table 3-4: Menu 10 - Main Screen:
This is the default main screen of the transmitter. When the transmitter is in
Standby, the 'OPR' characters appear in the lower right. By pushing the right most
button located under the display, the operator will place the Transmitter in Operate.
When the transmitter is in Operate the 'SBY' characters are displayed, the “OFF” is
replaced with 'ON' and the forward power values are displayed. Pushing the SPL button
will display the two splash screens.
If the ↓ key is activated the display changes to Menu 11, the System Error List Access
Screen. If the ↑ key is activated the display changes to Menu 13, the Transmitter
Configurations Access Screen.
Table 3-5: Menu 11 - Error List Access Screen
This screen of the transmitter shows the current number of errors, displayed in upper,
right of screen (0), and provides operator access to view Menu 20, the error list screens,
by pushing the ENT button. When ENT is pushed, Menu 20, the Error List Display
Screen is displayed. If the ↓ key is pushed the display changes to Menu 12, Table 3-6,
the Transmitter Device Data Access Screen. If the ↑ key is activated the display returns
to Menu 10, the Main Screen.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-10
Table 3-6: Menu 12 - Transmitter Device Data Access Screen
This screen of the transmitter allows access to various parameters of the transmitter
system. This is the entry point to Menu 30, the System Details Screens, by pausing the
ENT button. When the ENT button is pushed, Menu 30 is accessed. Go to Menu 30,
Table 3-11 for set up details. Before pushing the ENT button: if the ↓ key is activated
the display changes to Menu 13, Transmitter Configurations Access Screen. If the ↑ key
is activated the display returns to Menu 11, the Error List Access Screen.
Table 3-7: Menu 13 - Transmitter Configuration Access Screen
This screen of the transmitter allows access to various software settings of the
transmitter system. If ENT is pushed, go to Menu 40, Table 3-12, the access to
transmitter configuration and set up. Before pushing the ENT button: if the ↓ key is
activated the display returns to Menu 10, Main Screen. If the ↑ key is activated the
display returns to Menu 12, the Transmitter Device Data Access Screen.
Table 3-8: Menu 20 - Error List Display Screen
This screen of the transmitter allows access to the system faults screens. Fault logging is
stored in non-volatile memory. The transmitter's operating state can not be changed in
this screen. The 'CLR' switch is used to clear previously detected faults that are no
longer active. The ↑ key and ↓ key allow an operator to scroll through the list of errors
that have occurred. The ESC button is used to leave this screen and return to Menu 11,
Table 3-5, the Error List Access Screen. NOTE: Shown is example of a typical screen.
Menu 30 is entered by selecting ENT at Menu 12, Table 3-6.
Table 3-9: Menu 30 - Transmitter Device Details Screen
This screen allows access to the transmitter parameters of installed devices. The system
is configured to know which devices are present. Current values for all installed devices
are shown. If a module is not installed, only a "MODULE NOT PRESENT" message will be
displayed. The first screen displayed is Menu 30-1, Table 3-10, the System Details
Screen.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-11
Table 3-10: Menu 30-1 – System Details Screen
This is first screen of the details screens. The ↓ and ↑ arrows allow you to scroll through the
different parameters of each device as shown in Table 3-11. Each System Component is a
different screen. The proper modules will be programmed for your system.
Table 3-11: Transmitter Device Parameters Detail Screens
System
Component Parameter Normal Faulted
(Blinking)
D/C PIN ATTEN VOLTAGE ˜.6V N/A
OVERDRIVE FAULT ˜1.6V N/A
AGC MODE AUTOMATIC N/A
ADAPTIVE EQUALIZATION
STATUS RUNNING N/A
MEASURED SIGNAL TO NOISE ˜32.6dB N/A
PLL STATUS LOCKED N/A
SMTE310 INPUT STATUS OK N/A
DEMOD FUNCTION STATUS OK N/A
FX VERSION ˜1.013 N/A
Axciter Details
NB VERSION ˜0.029 N/A
D/C PIN ATTEN VOLTAGE ˜0.0 N/A
U/C PIN ATTEN VOLTAGE ˜1.6V N/A
AFC 1 LEVEL ˜0.06V N/A
INPUT STATUS OK N/A
OUTPUT STATUS ON N/A
AGC 1 LEVEL ˜0.32V N/A
AGC 2 LEVEL ˜0.00V N/A
PLL XXXMHz N/A
PLL STATUS OK FAULT
OVERDRIVE LEVEL STATUS OK FAULT
Upconverter
Details
CODE VERSION 1.6h or higher N/A
System Control
Details SUPPLY ENABLED FOR xxx HOURS N/A
Pushing the ↓ Down Arrow, after scrolling through all of the detail screens, will put you
back to Menu 30, Table 3-9. Push the ESC button to exit the Transmitter Device
Parameter Screens to Menu 12, Table 3-6, the Transmitter Device Parameter Access
Screen.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-12
Menu 40 (Table 3-12) is entered by selecting ENT at Menu 13.
Table 3-12: Menu 40 - Authorized Personnel Screen
This screen of the transmitter notifies an operator that they are only to proceed if they
are authorized to make changes to the transmitter's operation. Changes made within
the following set-up screens can affect the transmitters output power level, output
frequency, and the general behavior of the transmitter. Please do not make changes
within the transmitter's set-up screens unless you are familiar with the operation of the
transmitter. This screen is implemented in transmitter software version 1.4 and above.
Pressing ENT will put you into the Transmitter Set Up Screens for Menu 40.
A safeguard is added to the Set Up Menus in software version 2.5 and above. If a
change is made to a screen within the Set Up Menus, when you go to the next menu, a
new screen asks if you accept the change or want to return to the previous menu to
reconsider the changes made.
To accept the changes, the two buttons located under ACCEPT must be pushed
simultaneously.
To return to the previous Menu to make corrections, the two buttons located under the
RETURN must be pushed simultaneously.
Upon returning to the previous Menu the correct input must be entered and the above
procedure repeated, this time accepting the changes
Accept or Return to previous Menu Screen
Pushing these two buttons Pushing these two buttons
Simultaneously will accept Simultaneously will return you
the change. to the previous Menu.
Typical Set Up Screens are shown in Table 3-13 Menu 40-1 through Table 3-21 Menu
40-19 that follow.
Table 3-13: Menu 40-1 - Transmitter Set-up: Power Control Screen
This screen of the transmitter is the first of several that allows access to transmitter set-
up parameters. When + is selected, the Power will increase. When - is selected, the
Power will decrease.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-13
Table 3-14: Menu 40-2 - Transmitter Set-up: Model Select Screen
This screen is used to specify which components are expected to be part of the system.
By specifying the model number, the transmitter control firmware knows which
components should be installed and it will be able to display faults for components that
are not properly responding to system commands.
Table 3-15: Menu 40-3 - Transmitter Set-up: Upconverter Channel Select Screen
The choices of this screen are to the standard UHF / VHF channels. The + and – buttons
change the desired channel of the transmitter. The PLL frequency is set for custom
Offsets within the upconverter frequency. Any change to the channel is immediately set
to the Upconverter Frequency Synthesizer PLL circuit.
Table 3-16: Menu 40-5 - Transmitter Set-up: Serial Address Screen
This screen allows the user to set the serial address of the transmitter. The default
address is 5. This value and all other set-up parameters are stored in non-volatile
memory.
Table 3-17: Menu 40-6 - Transmitter Set-up: System Forward Power Calibration
This screen is used to adjust the calibration of the system's forward power. A symbol
placed under the '6' character is used to show major changes in the calibration value.
When the calibration value is at full value, the character will be full black. As the value
decreases, the character pixels are gradually turned off. The calibration value is a value
between 0 and 255 but the calibration value symbol only has 40 pixels. Therefore small
changes in actual calibration value may not affect the symbol's appearance.
Table 3-18: Menu 40-9 - Transmitter Set-up: System Reflected Power Calibration
This screen is used to adjust the calibration of the system's reflected power. Again a
calibration value symbol is used for this screen as on the previous screens.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure
DT325B, Rev. 0 3-14
Table 3-19: Menu 40-13 - Transmitter Set-up: Minimum Forward Power Fault
Threshold Screen
This screen is used to set the minimum forward power fault threshold. When the
transmitter is operating, it must operate above this value otherwise the system will shut
down with fault for 5 minutes. If after five minutes the fault is not fixed, the transmitter
will enable, measure the power and if less than this value it will again shut down for five
minutes.
Table 3-20: Menu 40-14 - Transmitter Set-up: Maximum Reflected Power Fault
Threshold
This screen is used to set the maximum reflected power fault threshold. When the
transmitter is operating, it must not operate above this value otherwise the system will
slowly begin to reduce the forward output power. If the system's reflected output power
exceeds the maximum reflected power threshold by five percent or more, the
transmitter will shut down with fault for 5 minutes. If after five minutes the fault is not
fixed, the transmitter will enable, measure power and if above this value plus five
percent it will again shut down for five minutes. If the system's reflected output power
exceeds the maximum reflected power threshold due to some condition like the
formation of ice on an antenna, the transmitter reduces visual forward power to a level
where the reflected power is less than this threshold. The transmitter will automatically
increase its output power to normal operation when the cause of higher than normal
reflected power is corrected.
Table 3-21: Menu 40-19 - Transmitter Set-up: Remote Commands Control
This screen is used to allow or deny the use of remote control commands. When
disabled, remote commands are not used. Remote commands are commands received
either through the rear terminal blocks or through serial messages.
Push the ESC button to exit the Transmitter Set Up Screens to Menu 13, Table 3-8, the
Transmitter Configuration Access Screen.
The same previous screens will be displayed by the back up exciter if it is switched to
become the On Air Exciter.
This completes the description of the menu screens for the Driver/Amplifier Chassis
Assembly and the Setup and Operation Procedures for the DT325B.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-1
Chapter 4
Circuit Descriptions
NOTE: Information and drawings on the
Axciter Modulator Tray, the Upconverter
Module and the Downconverter Module
are contained in the separate Axciter
Manual.
4.1 (A4) Control Monitoring/Power
Supply Module, 220VAC
(1310835; Appendix C)
The Control Monitoring/Power Supply
Module Assembly contains (A1) a Power
Protection Board (1302837), (A2) a 790
Watt Switching Power Supply, (A3) a
System Controller Board (1310089),
(A4) a LCD w/Switches Board (1307977)
and (A5) a LCD Display.
AC Input to the Amplifier/Driver Chassis
Assembly
The AC input to the Amplifier/Driver
Chassis Assembly is connected from J1,
part of a fused entry module, located on
the rear of the chassis assembly to J50
on the Control Monitoring/Power Supply
Module. J50-10 is line #1 input, J50-8 is
earth ground and J50-9 is line #2 input.
The input AC connects to J1 on the Power
Protection Board where it is fuse
protected and connected back to J50, at
J50-11 AC Line #1 and J50-12 AC Line
#2, for distribution to the cooling Fan.
4.1.1 (A1) Power Protection Board
(1302837; Appendix C)
The input AC connects through J1 to two
10 Amp AC fuses F1 and F2. The AC
line #1 input connects from J1-1 to the
F1 fuse. The AC line #1 input after the
F1 fuse is split with one line connected
back to Jack J1 Pin 4, which becomes
the AC Line #1 to the Fan. The other
line of the split connects to J4. The AC
line #2 input connects from J1-3 to the
F2 fuse. The AC line #2 input after the
F2 fuse is split with one line connected
back to Jack J1 at Pin 5, which becomes
the AC Line #2 to the Fan. The other
line of the split connects to J2. J1-2 is
the earth ground input for the AC and
connects to J3.
Three 150-VAC, for 115 VAC input, or
three 275-VAC, for 230 VAC input, MOVs
are connected to the input AC for
protection. One connects from each AC
line to ground and one connects across
the two lines. VR1 connects from J4 to
J2, VR2 connects from J4 to J3 and VR3
connects from J2 to J3.
+12 VDC Circuits
+12 VDC from the Switching Power
Supply Assembly connects to J6 on the
board. The +12 VDC is divided into four
separate circuits each with a 3 amp self
resetting fuse, PS3, PS4, PS5 and PS6.
The polyswitch resettable fuses may
open on a current as low as 2.43 Amps
at 50°C, 3 Amps at 25°C or 3.3 Amps at
0°C. They definitely will open when the
current is 4.86 Amps at 50°C, 6 Amps
at 25°C or 6.6 Amps at 0°C.
PS3 protects the +12 VDC 2 Amp
circuits for the System Controller, the
Amplifier Controller and the Spare Slot
through J62 pins 7, 8, 9 and 10. If this
circuit is operational, the Green LED
DS3, mounted on the board, will be lit.
PS4 protects the +12 VDC 2 Amp
circuits for the Modulator and the IF
Processor through J62 pins 13, 14, 15
and 16. If this circuit is operational, the
Green LED DS4, mounted on the board,
will be lit
PS5 protects the +12 VDC 2 Amp
circuits for the Upconverter through J62
pins 17, 18, 19 and 20. If this circuit is
operational, the Green LED DS5,
mounted on the board, will be lit
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-2
PS6 protects the +12 VDC 2 Amp
circuits for the Remote through J63 pins
17, 18, 19 and 20. If this circuit is
operational, the Green LED DS6,
mounted on the board, will be lit
-12 VDC Circuits
-12 VDC from the Switching Power
Supply Assembly connects to J5 on the
board. The -12 VDC is divided into two
separate circuits each with a 3 amp self
resetting fuse, PS1 and PS2.
PS1 protects the -12 VDC 2 Amp circuits
for the System through J63 pins 1, 2, 3
and 4. If this circuit is operational, the
Green LED DS1, mounted on the board,
will be lit
PS2 protects the -12 VDC 2 Amp circuits
for the Remote through J62 pins 1, 2, 3
and 4. If this circuit is operational, the
Green LED DS2, mounted on the board,
will be lit
The connections from J62 and J63 of the
Power Protection Board are wired to J62
and J63 on the Control Board.
4.1.2 (A3) System Controller Board
(1310089; Appendix C)
In this transmitter, control monitoring
functions and front panel operator
interfaces are found on the Control
Board. Front panel operator interfaces
are brought to the control board using a
26 position conductor ribbon cable that
plugs into J60. The control board
controls and monitors the Power Supply
and Power Amplifier module through a
16 position connector J61 and two 20
position connectors J62 & J63.
4.1.2.1 Schematic Sheet 1
U1 is an 8 bit RISC microcontroller that
is in circuit programmed or programmed
using the serial programming port J4 on
the board. When the microcontroller,
U1, is held in reset, low on pin 20, by
either the programming port or the
external watchdog IC (U2), a FET Q1
inverts the reset signal to a high that
connects to the control lines of U5, an
analog switch. The closed contacts of
U5 connects the serial programming
lines from J4 to U1. LED DS10 will be lit
when programming port J4 is used.
U2 is a watchdog IC used to hold the
microcontroller in reset, if the supply
voltage is less the 4.21 VDC; (1.25 VDC
< Pin 4 (IN) < Pin 2 (Vcc). The
watchdog momentarily resets the
microcontroller, if Pin 6 (ST) is not
clocked every second. A manual reset
switch S1 is provided but should not be
needed.
Diodes DS1 through DS8 are used for
display of auto test results. A test board
is used to execute self test routines.
When the test board is installed,
Auto_Test_1 is held low and
Auto_Test_2 is allowed to float at 5
VDC. This is the signal to start the auto
test routines.
U3 and U4 are used to selectively enable
various input and output ICs found on
pages 2 & 3 of the schematic.
U1 has two serial ports available. In this
application, one port is used to
communicate with transmitter system
components where U1 is the master of a
RS-485 serial bus. The other serial port
is used to provide serial data I/O where
U1 is not the master of the data port. A
dual RS-232 port driver IC and a RS-485
Port driver is also in the second serial
data I/O system. The serial ports are
wired such that serial data input can
come through one of the three serial
port channels. Data output is sent out
through each of the three serial port
channels.
Switch SW1, transmitter operation
select, is used to select either
transmitter operation or exciter/driver
operation. When the contacts of SW1
are closed, transmitter operation is
selected and the power monitoring lines
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-3
of the transmitter’s power amplifier are
routed to the system power monitoring
lines.
4.1.2.2 Schematic Sheet 2
Digital output latch circuits are used to
control system devices. Remote output
circuits are implemented using open
drain FETs, Q13, Q14, Q16, and Q17,
with greater than 60 Volt drain to source
voltage ratings.
Remote digital inputs are diode
protected, using CR6, CR7, CR8 and CR9
with a 1 kO pull-up resistor, to +5 VDC.
If the remote input voltage is greater
than about 2 Volts or floating, the FET is
turned on and a logic low is applied to
the digital input buffer, U9. If the
remote input voltage is less than the
turn on threshold of the FET (about 2
VDC), a logic high is applied to the
digital input buffer, U9.
Four of the circuits on page two of the
schematic, which include Q2, Q9, Q19
and Q21, are auxiliary I/O connections
wired for future use. They are wired
similar to the remote digital inputs but
include a FET, Q5, Q12, Q20 and Q22,
for digital output operations. To operate
these signals as inputs, the associated
output FET must be turned off. The
FETs are controlled by U10 and U12,
analog input multiplexer ICs.
4.1.2.3 Schematic Sheet 3
U13, U14, U15, U16, U17 and U18 are 3
state non-inverting transceiver ICs that
provide 2 way asynchronous
communication between data busses.
The ICs are used as input buffers to
allow the microcontroller to monitor
various digital input values. The digital
inputs to the ICs utilize a 10 kO pull-up
resistor. The buffer IC, U18, used for
data transfer to the display is wired for
read and write control.
RB1 is the connector to a Rabbit
Semiconductor RCM4300. This Ethernet
enabled controller polls the U1
microcontroller on the same serial lines
as a remote computer. The controller
only gets data and sets conditions
through the serial communications port.
Table 4-1: Innovator DIP Switch
Settings for SW2 located on the Exciter
Controller Board (1310089) in the Power
Supply/Controller Assembly
Switch
Position Function
SW2-1
0 = No Modulator in a translator
configured transmitter
1 = Modulator present in a translator
configured transmitter
SW2-2 0 = Normal
1 = Aural Upconverter not to be
installed
SW2-3 0 = Normal
1 = IP Processor not to be installed
SW2-4 0 = Normal
1 = Modulator not to be installed
SW2-5 0 = Normal
1 = Visual Upconverter not to be
installed
SW2-6 Reserved
SW2-7 Reserved
SW2-8 Reserved
NOTE: These switch positions are
factory set and should not be changed.
4.1.2.4 Schematic Sheet 4
U19 and U20 are digitally controlled
analog switches that provide samples
back to the microprocessor. Each
analog input is expected to be between
0 and 5 VDC. If a signal exceeds 5.1
VDC, a 5.1 Volt Zener diode clamps the
signals voltage, to prevent damage to
the IC. Most signals are calibrated at
their source, however two dual serial
potentiometer ICs are used to calibrate
four signals, System Average Power,
System Aural Power, System Reflected
Power and the Spare AIN 1. For these
four circuits, the input value is divided in
half before it is applied to an op-amp.
The serial potentiometer is used to
adjust the output signal level to between
80 and 120% of the input signal level.
Serial data, serial clock and serial pot
enables are supplied by the
microprocessor to the dual serial
potentiometer ICs. Serial data to the
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-4
second serial potentiometer is
transferred through the first IC. The
wiper position of the digital
potentiometer circuit is used to set the
gain of the op-amp. Lower digital
values for the wiper settings increases
the gain of the op-amp. If N=0 then
Gain=6.0 and if N=255 then Gain=3.00.
If the Vin=1.0 at spare_Ain_1 and
N=128 then U21A out=4.0V with
gain=4. J62 and J63 are two 20
position connectors that provide the +12
VDC and –12 VDC power through the
Power Protection Board. The ±12 VDC
generated by the switching power
supply connects to J62 and J63 after
being fuse protected on the Power
Protection Board.
4.1.2.5 Schematic Sheet 5
There are three dual element,
red/green, common cathode LED
indicators mounted on the front panel of
the sled assembly that are used. The
fourth is a spare. The used LEDs are DC
OK, Operate and Fault.
There are four identical circuits, one of
which is a spare, that drive the front
panel mounted LED indicators. The
levels on the 1, 2, 3 and 4 LED Control
Lines, for both the red and green LEDs,
are generated by the IC U11, shown on
sheet 2, as controlled by the DATABUS
from the microprocessor U1, shown on
sheet 1.
Each LED controller circuit consists of an
N-Channel MOSFET w/internal diode that
controls the base of an N-P-N transistor
in an emitter follower configuration. The
emitter of the transistor connects the
LED.
With the LED control line LOW, the
MOSFET is Off, which causes the base of
the transistor to increase towards +12
VDC, forward biasing the transistor.
With the transistor forward biased,
current will flow from ground through
the LED, the transistor and the current
limiting resistors in the collector to the
+12 VDC source. The effected LED will
light.
With the LED control line HIGH, the
MOSFET is On, which causes the base of
the transistor go toward ground
potential, reverse biasing the transistor.
With the transistor reverse biased, no
current through the transistor and LED,
therefore the effected LED will not light.
A third color, amber, can also be
generated by having both transistors
conducting, both control lines LOW. The
amber color is produced because the
current applied to the green element is
slightly greater than the red element.
This occurs because the current limiting
resistors have a smaller ohm value in
the green circuit.
There are four voltage regulators, three
for +5 VDC, U26, U27 & U28, and one
for +7 VDC, U25, which are used to
power the Control Board. +12 VDC is
applied to U25 the +7 VDC regulator
that produces the (+7V), which is
applied to the LEDs mounted on the
board. The +7V is also connected to the
input of U26 a precision +5.0 Volt
regulator. The +5.0Vdc regulator output
is used to power the analog circuits and
as the microcontroller analog reference
voltage (+5Vdc). Another two +5 Volt
regulator circuits U27, (+5V), and U8,
(+5Vserial), are used for most other
board circuits.
4.1.3 (A4) LCD w/Switches Board
(1307977; Appendix C)
The switch board provides five front-
panel momentary contact switches for
user control and interface with the front-
panel LCD menu selections. The
switches, SW1 to SW5, complete the
circuit through connector J3 to
connector J2 that connects to J1 on (A5)
the 20 Character by 4 line LCD Display.
J3 on the switch board is also cabled to
the (A3) System Controller Board.
When a switch is closed, it connects a
logic low to the system controller board
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-5
that supplies the information from the
selected source to the display. By
pushing the button again, a different
source is selected. This occurs for each
push button. Refer to Chapter 3 for
more information on the Display Menu
Screens.
4.1.4 (A2) Switching Power Supply
Assembly
The power supply module contains a
switching power supply, a terminal
blocks, V1, V2 & V3, for distributing the
DC voltages, and a 3 position terminal
block to which the AC Input connects.
Jack J1 connects to the Control Board
and supplies DC OK, at J1-4 & 3, and AC
OK, at J1-2 & 1, status to the control
board. A Power Supply enable connects
from the control board to the power
supply at V1B-6 & 7. The power supply
is configured for three output voltages
+12V, -12V, at the 10 position terminal
block, and a main output power of +32
VDC at J50 pin A (+) and J50 pin B
(Rtn). The power supply is power factor
corrected to .98 for optimum efficiency
and decrease in energy consumption.
For safety purposes all outputs are over
voltage and over current protected. This
supply accepts input voltages from 85 to
264 volts AC, but the power entry
module, for the exciter/amplifier chassis,
must be switched to the proper input
voltage setting, for the transmitter to
operate.
4.1.5 RF Output of Driver/Amplifier
Chassis Assembly
The RF output from the upconverter at
the upconverter RF output jack J23, a
BNC connector. The RF is cabled to the
“S” input Jack on the (A10) 2 Way
Splitter. One output of the splitter
connects to the VHF Amplifier Tray. The
other output of the splitter connects to
the triple peak detector board for
metering, ALC and monitoring purposes.
NOTE: Information and drawings on the
Axciter Modulator Tray, the Upconverter
Module and the Downconverter Module
are contained in the separate Axciter
Manual.
This completes the description for the
Driver/Amplifier chassis assembly.
4.2 (A3) VHF Low Band Amplifier
Tray (1304363; Appendix D)
The VHF low band amplifier tray is
adjusted at the factory for use as a
digital RF amplifier tray. The tray has
approximately 55 dB of gain at the
frequency of the VHF low band channel
and will take the typical +4 dBm DTV
input and amplify it to an output level of
approximately +55.8 dBm. As a DTV
amplifier, the tray is calibrated for 350
watts average power that is equal to a
100% meter reading. The tray is made
up of the boards and assemblies listed in
Table 4-1.
Table 4-1: VHF Low Band Amplifier Tray Boards and Assemblies
MAJOR ASSEMBLY
DESIGNATOR BOARD/ASSEMBLY NAME DRAWING NUMBER
A1-A1 Phase shifter board (mounted in
[A1] an RF enclosure assembly) 1198-1602
A1-A2 Filter/amplifier board (mounted in
[A1] an RF enclosure assembly) 1198-1606
A2-A1 VHF low band amplifier board
(mounted in [A2] an RF enclosure
assembly) 1198-1605
A2-A2 Overdrive protection board
(mounted in [A2] an RF enclosure
assembly) 1198-1601
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-6
A2-A3 3-way splitter board (mounted in
[A2] an RF enclosure assembly) 1198-1608
A3-A1, A3-A2 and A3-A3 Three low band VHF amplifier pallets
(mounted in [A3] an RF enclosure
assembly)
P400-VHF-L-18
1304348
A4-A1 3-way combiner board (mounted on
[A4] the 3 way combiner enclosure) 1198-1626
A4-A2 & A4-A3 Low pass filter board (mounted on
[A4] the 3 way combiner enclosure) 1198-1628
A5 AGC control board 1306482
A8 Current metering board 1304362
A10 +30 VDC switching power supply
assembly PM3329B-5-1-R-2-E
1301504
4.2.1 (A1-A1) Phase Shifter Board
(1198-1602; Appendix D)
The On Channel RF signal (+4dBm),
enters the rear of the Tray at the "BNC"
Jack J1 and is fed to J1 of the (A1)
Enclosure Assembly which contains the
phase shifter board and the filter
amplifier board. The input is cabled to
to J1 of (A1-A1) the Phase Shifter Board
(1198-1602).
The Board provides a Phase Shift
adjustment of the RF Signal that is
needed to provide maximum output
during the combining of multiple
Amplifier Trays in an Amplifier Array. A
front panel mounted Phase Shift
Potentiometer, R2 (A7), which connects
to J3 of the Board, controls the Phase of
the RF Signal.
If the Input Signal level to the Phase
Shifter Board falls below a preset level, a
High, which is an Input Fault, connects
from J5 of the board to J14 on the AGC
Control Board. When an Input Fault
occurs, the AGC Control Board generates
a Fault Output at J1, which is connected
to J4 on the Filter/Amplifier Board. The
Fault cuts back the RF Signal level using
the Pin Diode Attenuator Circuit located
on the Filter/Amplifier Board.
The output at J2 of the Phase Shifter
Board is directed to J7 the input jack on
(A1-A2) on the filter/amplifier board.
4.2.2 (A1-A2) Filter/Amplifier Board
(1198-1606; Appendix D)
The phase-controlled output (+4 dBm) at
J2 of the phase shifter board is directed
to J7, the input jack of the (A1—A2) filter
amplifier board (1198-1606) that is made
up of two circuits. The first circuit is a
channel filter that is adjusted for the
desired channel frequency and
bandwidth. The filtered output (+2 dBm)
is connected to the second circuit that
contains two amplifiers. The RF connects
through a pin-diode circuit to the
amplifier IC U1. The voltage applied to
J4, which is the external control jack of
the board, controls the amplitude of the
RF signal through the pin-diode
attenuator circuit. Jumper W1 on J5
should be between pins 2 and 3, which
provide external control, through J4, of
the gain of the board, as well as the
output level of the tray. R9 is the
manual gain pot that is in the circuit
when the jumper W1 is between pins 1 &
2.
The front panel mounted gain pot R3
(A6) connects to the AGC control board
and is used to adjust the AGC pin-
attenuator bias voltage that connects to
J4 on the filter/amplifier board. The RF
signal, after the pin-attenuator circuit, is
amplified by the second amplifier stage
Q1 to about +16.5 dBm; this signal is
connected to the output of the board at
J2.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-7
The RF output of the filter/amplifier
board connects to J2 of (A2) a RF
enclosure that contains the VHF low band
amplifier board, the overdrive protection
board and the 3-way splitter board.
4.2.3 (A2-A1) VHF Low Band
Amplifier Board
(1198-1605; Appendix D)
The Low Band VHF Amplifier Board takes
the +16.5 dBm input signal and amplifies
it to approximately +38.5 dBm Output.
The board contains a MRF151G Dual FET
Amplifier device.
The Input to the board is applied at J1
and is connected through T1 a 9:1 Balun
to the Sources of the parallel FETs, which
make up Q1. C1 is adjustable for
maximum signal to match the impedance
of the input to the Push-Pull Transistor
Stage. The Bias and collector voltage for
the Transistor, +45 VDC, is applied at E1,
which is bypassed by C18. The bias
voltage is regulated to approximately 20
VDC by Q2 and adjusted by R4 before
connecting to Q1. The output of the Q1
push-pull circuit connects to T2 which is a
4:1 Balun that transforms the signal back
to a single 50O impedance Output. The
Collector Voltage is applied at E1, which
is filtered and bypassed by L1, C12 &
C14. The Amplifier Stage has roughly 22
dB of gain and draws 5 to 6 Amps of
current. The RF output of the board is at
J2.
4.2.4 (A2-A2) Overdrive Protection
Board (1198-1601; Appendix D)
The RF output of the low band VHF
amplifier board at J2 (+38.5 dBm)
connects to J4 of (A2-A2) the overdrive
protection board (1198-1601). The RF
signal is through connected directly to J5,
the RF output jack of the board. A
sample of the RF on the board is applied
to a diode-detector circuit that consists of
CR1 and U1A. The gain of amplifier U1D
is controlled by detector gain pot R11,
which is set to +.4 VDC as measured at
TP1. The set output of U1D is connected
to the comparator IC U1B. The trip point
for the comparator is adjusted by R12,
typically set to 110% output power.
When the signal reaches that level, the
overdrive protection board will cut back
the output power of the tray and the red
Overdrive LED DS1 located on the board
and the red Overdrive LED DS1 mounted
on the front panel will be illuminated.
Typically, the output power level will
bounce down and then up and continue
bouncing until the output level is lowered
to the normal operating level (100%).
The red Overdrive LED DS1, the green
Module LED DS3, and the Enable LED
DS2 may blink on and off during the
bouncing of the output level; this is a
normal occurrence. The greater the
output level is above 110%, the larger
the bounce will be. The RF output of the
overdrive protection board (+38.3 dBm)
at J5.
4.2.5 (A2-A3)3 Way Splitter Board
(1198-1608; Appendix D)
The RF output of the overdrive protection
board at J5 connects to J1 on (A2-A3)
the 3-way splitter board (1198-1608).
The splitter board takes the +38.3 dBm
input and provides three +33.3 dBm
outputs at J2, J3 and J4 of the board.
These three outputs connect to J1, J2
and J3 on the (A3) final amplifier
enclosure.
4.2.6 (A3-A1, A2 & A3) VHF LB
Output Amplifier Pallets
(1304349; Appendix D)
The three RF outputs of the splitter board
connect to (A3) the Final Amplifier
Enclosure, which contains three (A3-A1,
A3-A2 & A3-A3) VHF Low Band Amplifier
Pallets (P400-VHF-LB) made by Delta RF
Technology. The RF Signals connect to
J1 on each of the Low Band Output
Amplifier Pallets. Each amplifier pallet
provides approximately 18 dB gain.
The RF signal inputs to the Output
Amplifier Boards, +33.3 dBm, are
amplified to +51.3 dBm outputs at J2,
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-8
which are connected to J1, J2 and J3 on
(A4-A1) a 3 Way Combiner Board (1198-
1626).
4.2.7 (A5-A1) 3 Way Combiner
Board (1198-1626; Appendix D)
The 3 Way Combiner takes the three
+51.3 dBm combined inputs and
combines them to form the
approximately 375 Watt (+55.8 dBm) RF
Output at J4 of the Combiner which
connects to J2, the RF Output Jack of the
Tray.
The 3 Way Combiner Board provides a
Forward Power Sample at J5 and a
Reflected Output Power Sample at J8.
The Forward Output Power Sample
connects through the (A4-A2) low pass
filter board to J4 on (A5) the AGC Control
Board. The Reflected Output Power
Sample connects through the (A4-A3)
low pass filter board to J5 on (A5) the
AGC Control Board.
4.2.8 (A5) AGC Control Board
(1306482; Appendix D)
The AGC Control Board contains two
peak detector networks one for forward
and one for reflected power samples.
The forward power sample connects
through J4 to a detector circuit consisting
of CR11 and U3C. The detected forward
level is connected through R44 the
Forward Power metering level
adjustment which controls the gain of the
amplifier U3D. The forward peak
detected sample output of U3D is split
with one output connected to J7-4 which
is wired to the front panel meter for
monitoring purposes. Another output of
U3D connects to the IC U6 and related
components which comprise the module
fault circuit. The front panel mounted
module fault LED DS3, connected to J9-4
& 6, will light if the forward output power
drops below a preset level. The final of
the split outputs of U3D connects to the
IC U3A and related components which
comprise the AGC circuit. This level is
combined with the AGC reference inputs
at J2 and J6-2 which produces the AGC
output at J1 which connects to the
automatic level control circuit on the
Filter/Amplifier Board for the output
power of the tray.
The reflected power sample connects
through J5 to a detector circuit consisting
of CR13 and U5B. The detected reflected
level is connected through R53 the
Reflected Power metering level
adjustment which controls the gain of the
amplifier U5D. The reflected peak
detected sample output of U5D is split
with one output connected to J12-8
which is wired to the front panel meter
for monitoring purposes. The other
output of U5D connects to the IC U5C
and related components which comprise
the VSWR Cutback circuit. The front
panel mounted VSWR Cutback fault LED
DS4, connected to J12-2 & 1, will light if
the reflected output power increases
above the preset level set by R59.
Another output of U5C is detected by
CR15 and connected to the IC U3A and
related components which comprise the
AGC circuit. This level is combined with
the AGC reference inputs from the
forward power sample and at J2 and J6-2
which produces the AGC output at J1.
This output connects to the automatic
level control circuit on the Filter/Amplifier
Board that controls the output power
level of the tray.
Two voltages are applied to the rest of
the VHF amplifier tray when the enable is
connected to the tray. The voltages are
+28 VDC from the internal switching
power supply and +12 VDC from the
current metering board that connects to
J8-2 on the board where it is regulated
by U7 and connected to the rest of the
board.
The +12 VDC from the Driver/Amplifier is
connected to J3-7 & 8 on the rear of the
Tray that is wired to J8 Pin 4 & 1 on (A5)
the AGC Control Board. The +12 VDC is
connected to U8 a +5 VDC Regulator IC,
which supplies the +5 VDC needed for
operation of the front panel mounted
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-9
LEDs. This +12 VDC is supplied to the
tray when the Driver/Amplifier is turned
on.
4.2.9 (A10) +28 VDC Switching
Power Supply Assembly
(A10) The +28 VDC Switching Power
Supply uses the 220VAC input through
the 15A circuit breaker CB1 and
provides the +28 VDC needed for
operation of the tray. Two varistors,
VR3 and VR4, connect to each leg of the
220 VAC input for overvoltage and surge
protection.
The +28 VDC output of the switching
power supply assembly connects to (A8)
the Current Metering Board at TB1-1 thru
TB1-4.
4.2.10 (A8) Current Metering Board
(1304362; Appendix D)
The Current Metering Board distributes
the voltages through fuses to the
Amplifier Devices on the Filter/Amplifier
Board, the VHF Low Band Amplifier
Board, and the three Final High Band
Amplifier Boards. The Fuses F1, F2 & F3
are 20 Amp, F4 is 5 Amp, F6 is 2 Amp
and F7 is a 1 Amp Fuse. The F5 fuse is
not used in this configuration. There are
two Spare Fuses, one 1 Amp and one 20
Amp, located on the top, right rear of the
Tray.
Fuse F1 protects (A3-A1) the Low Band
Output Amplifier Pallet, Fuse F2 protects
(A3-A2) the Low Band Output Amplifier
Pallet, Fuse F3 protects (A3-A3) the Low
Band Output Amplifier Pallet, Fuse F4
protects (A2-A1) the VHF Low Band
Amplifier Board, and Fuse F6 protects
(A1-A12 the Filter/Amplifier Board. Fuse
F7 supplies +28 VDC to J8 Pin 2 on the
AGC Control Board, where it is connected
to the Regulator IC U7 that takes the
+28 VDC and provides a +12 VDC
output. The +12 VDC is used for
operation of the AGC Control Board and
also the +12 VDC is connected through
the Current Metering Board, by the
jumper from TB1-5 to TB1-6, to the
Phase Shifter Board, the Filter/Amplifier
Board and the Overdrive Protection
Board. The Current Metering Board also
supplies sample outputs of the operating
currents of the amplifier devices in the
Tray to the front panel Current Meter.
The Meter in the (I1) position reads the
current for the (A3-A1) P400 Low Band
Output Amplifier Board, (I2) for the (A3-
A2) P400 Low Band Output Amplifier
Board and (I3) for the (A3-A3) P400 Low
Band Output Amplifier Board. The (ID)
position reads the current for the (A2-A1)
VHF Low Band Amplifier Board. To read
the desired current, Switch S2 to the
proper position while checking that S1 is
in the Current position. These current
readings can be used when setting up the
Idling Currents, no RF Drive applied, for
the devices. Refer to the final Test Data
Sheet for your transmitter for the
operational and Idling current readings.
(NOTE: All front panel current readings
must be multiplied by 2 to give the actual
value.)
4.2.11 Operation of the VHF Low
Band Amplifier Tray
220 VAC is applied through Jack J4 to
Terminal Block TB1 in the Tray. When
(CB1) the 15 Amp rear panel mounted
AC Circuit Breaker is switched On, the
220 VAC is distributed from TB1 to (A11
& A12) two cooling Fans, which will
operate, and to (A10) the Switching
Power Supply. There are two Surge
Suppressors, VR1 and VR2, mounted on
TB1 that provide protection from
transients or surges on the input AC Line.
There are two other Surge Suppressors,
VR3 and VR4, mounted at the input to
the switching power supply from each AC
Line to ground, which provide protection
from transients or surges on the AC Line.
The switching power Supply only
operates when the Power Supply Enable
Control Line, Jack (J3 Pins 9 & 10),
located on the rear of the Tray, are
shorted. The Enable is generated by the
exciter/driver chassis assembly when the
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-10
transmitter is switched to Operate. The
Enable is applied to (A5) the AGC Control
Board (1306482), which, if there is no
Thermal Fault, connects the Enable from
J10 Pins 6 & 7 to J1-18 & 14 on the
Switching Power Supply Assembly. The
Green Enable Front Panel LED (DS2) will
light, indicating an Enable is present. If
the Amplifier Array is in Standby or if a
Thermal Fault occurs, the AGC Control
Board will not Enable the Switching
Power Supply, therefore the +28 VDC will
be removed from the Amplifier Modules
and the Front Panel Enable LED and
Module Status LEDs will be out.
The front panel Meter (A9), by switching
(S1) the Front Panel Selector Switch,
monitors the AGC Voltage, % Output
Reflected Power, % Forward Power and
the Switching Power Supply Voltage (+28
VDC). The Meter in the AGC position will
typically read anywhere from 1 to 2
Volts. The Meter is calibrated in the
Power Supply position using R86, the %
Output Power is calibrated using R44 and
the % Reflected Power is calibrated using
R53, all of the pots located on the AGC
Control Board. With S1 in the Current
Position, S2 is switched to read the
operating currents or the Idling currents,
no RF Drive applied, of the High Band
Output Amplifier Boards. The idling
currents are monitored for the set up of
the devices. Refer to the final Test Data
Sheet for your Transmitter for the
operational and Idling current readings.
The Reflected Power Sample, from the 3
Way Combiner Board, is fed back to the
AGC Control Board at J5. On the board
the Reflected Sample is connected thru
the detector circuit to a VSWR Cutback
circuit (U13C). If the Reflected power
increases above 20%, the output power
of the Tray, as set by R60 (VSWR
Cutback) on the AGC Control Board, is
cutback to maintain a 20 % Reflected
Output level. The Red LED (DS4) VSWR
Cutback, located on the front panel,
remains lit until the Reflected level drops
below 20%.
There are three Thermal Switches
mounted in the Tray for
overtemperature protection. Two of the
Thermal Switches (A13 & A14) are
mounted on (A3) the heatsink for the
Low Band Amplifier Pallets and the third
Thermal Switch (A15) is mounted on the
heatsink for the 3 Way Combiner Board.
The Thermal Switches close when the
heatsink on which it is mounted reaches
a temperature of 175° F. The closed
Thermal Switch causes the AGC Control
Board, to remove the Enable to the
Switching Power Supply, eliminating the
+28 VDC, and also to light the Red LED
Indicator, Overtemperature (DS5),
mounted on the front panel. The AGC
Control Board also extinguishes the
Module Status LED (DS3).
4.3 External Boards
4.3.1 (A4) Triple Peak Detector Board
(1159713; Appendix A)
The Triple Peak Detector Board is
mounted on the Bottom, Right Side of
the Cabinet accessed through the back.
The function of the triple peak detector
board is to detect three power samples
and generate output voltages that are
proportional to the power levels of the
sampled signals for use by the control
monitoring assembly in the transmitter.
There are three signal paths on the
board: one for RF I/P 1, one for RF I/P 2
and one for RF I/P3. The circuits function
as described in the following paragraphs.
The RF sample input enters the board at
the RF I/P 1 SMA jack J1. Resistors R9,
R4 and R10 form a 3dB pad. The RF
sample is amplified by U3 and connected
to a detector circuit made up of R11, R3,
CR1, R8, C7, R41, and C6. For digital
operation the jumpers, W1 on J4 and W4
on J8, are both between pins 1 & 2. The
detected output is buffered by the
operational amplifier U1D and then
connected to RF I/P 1 power adjust pot
R14, which adjusts the gain of U2D. The
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-11
output of U2D is connected to J5-1, DC
O/P 1.
The second RF sample input enters the
board at the RF I/P 2 SMA jack J2.
Resistors R22, R17 and R23 form a 50O
input impedance matching circuit. The
sample is connected to a detector circuit
made up of CR3, R24 C8, R42, and C9.
For digital operation the jumpers, W2 on
J6 and W5 on J9, are both between pins
1 & 2. The detected output is buffered
by the operational amplifier U1B and
then connected to RF I/P 2 power adjust
pot R26, which adjusts the gain of U2B.
The output of U2B is split and connected
to J5-2 and J5-3, DC O/P 2.
The third RF sample input enters the
board at the RF I/P 3 SMA jack J3.
Resistors R34, R29 and R35 form a 50O
input impedance matching circuit. The
sample is connected to a detector circuit
made up of CR5, R36, C11, R43, and
C13. For digital operation the jumpers,
W3 on J7 and W6 on J10, are both
between pins 1 & 2. The detected output
is buffered by the operational amplifier
U1C and then connected to RF I/P 3
power adjust pot R38, which adjusts the
gain of U2C. The output of U2C is split
and connected to J5-6 and J5-5, DC O/P
3.
The +12 VDC needed for the operation of
Op Amps U1 and U2 enters the board at
J5-10. The voltage is connected through
a filter and isolation circuit consisting of
L2, C10, and C15 before it is distributed
to the rest of the board.
4.3.2 (K1) Isolation Relay Board
(1002-1108; Appendix A)
The Isolation Relay Board is located on
the inside right side panel of the cabinet.
The Isolation Relay Board when
energized supplies the enable to the VHF
amplifier tray.
The +12 VDC from the Driver/
Amplifier Chassis Assembly is connected
to the board at J1-1, one side of the
energizing coil. -12 VDC from the
Driver/Amplifier is connected to J2-1
which is the NC contacts of the relay. J2-
4 which is the other contact of the NC
connection is not used in this
configuration.
When the Driver/Amplifier Chassis
Assembly is switched to Operate, an
Enable, ground, is applied to J1-2, which
energizes the relay. The contacts of the
relay close which connects J2-2 to J2-1
that applies the -12 VDC, Enable, to the
VHF Amplifier Tray. The opposite occurs
when the On Air Driver/Amplifier Chassis
Assembly is switched to Standby.
This completes the circuit description of
the boards that make up the DT325B.
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures
DT325B, Rev. 0 5-1
Chapter 5
Detailed Alignment Procedures
5.1 System Preparation
This transmitter was aligned at the
factory and should not require additional
adjustments to achieve normal operation.
The Axciter takes the SMPTE 310 digital
stream input and converts it to the digital
IF output that connects to the
driver/amplifier chassis assembly. The
driver/amplifier converts it to the desired
VHF On Channel RF Output that is
amplified by the amplifier tray to produce
the systems output power level.
The Driver/Amplifier Chassis Assembly of
the transmitter is of a Modular design
and when a Module fails that module
needs to be changed out with a
replacement module. The failed module
can then be sent back to Axcera for
repair. Contact Axcera Customer Service
Department at 724-873-8100 or fax to
724-873-8105, before sending in any
module.
5.2 Module Replacement
Module replacement in the
Driver/Amplifier Chassis Assembly is a
relatively simple process. In the
Exciter/Driver assembly, the
Downconverter, Upconverter and
Control/Power Supply Module plug into
blind mating connectors located on the
Backplane board in the chassis. To
replace a module, refer to the following
procedure.
Loosen the two grip lock connectors,
located on the front panel, at the top
and bottom of the module,
counterclockwise until the module
releases. The Downconverter,
Upconverter, and Controller/Power
Supply can then be gently pulled from
the unit. After removal of the failed
module, slide the replacement module in
place and make certain it connects to
the backplane board. If the replacement
module does not slide in easily, verify it
is properly aligned in the nylon tracks,
located on both the top and bottom of
the module. After positioning, tighten
the two grip lock connectors.
Each Module has an assigned slot and
will not fit properly or operate in the
incorrect slot. Do not try to place a
Module in the wrong slot as this may
damage the slot or the connectors on
the backplane board. Each module has
the name of the module on the front,
bottom for identification and correct
placement. The Modules are placed in
the unit from left to right; (1) Axciter
Downconverter, (2) Blank panel, (3)
Blank Panel, (4) Axciter Upconverter, (5)
Controller/Power Supply and (6) Blank
panel.
5.3 (A3) VHF LB Amplifier Tray
(134363; Appendix D)
The Tray has been adjusted at the
factory to meet all specifications,
including Phase Adjustment to match the
multiple Trays in an Amplifier Array when
combined, and should not need adjusted
to attain normal operation. Any
adjustment of the Boards should be
accomplished in Manual Gain, S1 on (A5)
AGC Control Board (1306482) in Manual.
The Idling Currents for the amplifier
boards are adjusted with no RF Drive
applied. For Normal Operation, S1
should be in the Auto AGC position.
Connect a Dummy Load rated of at least
350 Watts to J2 the RF Output Jack of
the Tray.
5.3.1 (A13) AGC Control Board
(1306482; Appendix C)
Using a calibrated Wattmeter, check that
the Tray is operating at rated power.
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures
DT325B, Rev. 0 5-2
Remove the Sample Forward Power
connection J4 from the board. The
Output Power Level should drop to 20 %
because of the VSWR Cutback and DS4
should light. The front panel Module
Status LED should not be illuminated.
Reconnect J4 and adjust R59 to begin
cutting back the Output Power Level
when the Reflected Level increases above
20 %. The front panel Meter in the
Power Supply Voltage position is
calibrated to +32 VDC using R86 located
on the AGC Control Board.
5.3.2 (A1-A1) Phase Shifter Board
(1198-1602; Appendix D)
This board has no adjustments on it. The
Front Panel has adjustments for Phase
that are adjusted during the Amplifier
Array Set Up Procedure. With +4 dBm
input typical output is +4 dBm.
5.3.3 (A1-A2) Filter/Amplifier Board
(1198-1606; Appendix D)
This board has a maximum of 15 dB
gain. Typically with +4 dBm input an
output of +16.5dBm is expected. Tune
the channel filter capacitors C20 (input
loading) & C29 (output loading), C23 &
C26 (center frequency) and C24
(coupling) for best response at J6 the RF
output jack of the filter portion of the
board. Set the Voltage Adjust Pot R19
for +24 VDC at the Anode of CR5.
The idling current, no RF Drive applied, of
the Device Q1 is set for 250 mA. To set
the current, remove the RF Drive,
measure the voltage across R16, a 1 Ω
resistor on the Filter/Amplifier Board, and
adjust R13 for .25 Volts. Using Ohms
Law: (E = I x R) : (E = 250 mA x 1 Ω) :
E = 250 mV.
5.3.4 (A2-A1) VHF Low Band
Amplifier Board
(1198-1605; Appendix D)
This board has 20 dB of gain and is
biased for 3 Amps of Idling Current, no
RF Drive applied. To set the Bias,
remove RF Drive and switch the front
panel Current Meter to the ID position.
Adjust the Bias Adjustment R4 on the
Amplifier Board for 3 Amps on the meter.
Connect a Spectrum Analyzer to the
Output Jack J2 of the Board and adjust
C1 for peak output. Typical output level
is +38.5 dBm.
5.3.5 (A2-A2) Overdrive Protection
Board (1198-1601; Appendix D)
The RF Input and Output of the board
should be approximately +38.5 dBm
during normal operation.
To set up the Overdrive circuit, check
that the Output Power Level of the
Transmitter is at 100 % and adjust R11,
on the Board, for a reading of .4 VDC at
TP1. Increase the Output power level of
the Transmitter to 120 % and adjust R12
until the Output Power begins to Drop
Off. Return the Output Power Level of
the Transmitter to 100 %.
5.3.6 (A2-A3) 3 Way Splitter Board
(1198-1608; Appendix D)
This board contains no tuning
adjustments. The board takes the +38.3
dBm input and splits it into three equal
+33.3 dBm outputs.
5.3.7 (A3-A1, A2 & A3) VHF LB
Output Amplifier Pallets
(1304348; Appendix D)
These P400-VHF-LB pallets are supplied
by Delta RF Technology, Inc. Refer to
the data sheets in the subassembly
section of this manual for more
information. Each pallet has
approximately 18 dB of gain. With +33.3
dBm input an output of +51.3 dBm is
typical.
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures
DT325B, Rev. 0 5-3
5.3.8 (A4-A1) 3 Way Combiner Board
(1198-1626; Appendix D)
There are no adjustments on this board.
The three +51.3 dBm Inputs are
combined to produce the 375 Watts
(+55.8 dBm) Output at J4 that connects
to the RF output jack J2 located on the
rear panel of the tray.
5.4 Calibration of the Output Power
of the VHF Amplifier Tray
Check that a Dummy Load of at least 400
Watts is connected to the Output of the
Tray that is to be calibrated. Switch S1
located on the AGC Control Board to the
Manual position before beginning the set
up. Adjust the front panel Meter for
100% Forward Output Power with R5,
Manual Gain Adjust, located on the AGC
Control Board.
Readjust the Manual Gain Pot for same
Spectrum Analyzer Reference Level.
Adjust R44 for 100% Forward Power
Reading. Calibrate the Front Panel
Output Power Meter to 100 % with R44,
Forward Power Meter Adjust, located on
the AGC Control Board. Lower the
Forward Power reading to 80% on the
front panel meter using R5, Manual Gain
Adjust, located on the AGC Control
Board. Adjust R65, AGC Fault Adjust,
located on the AGC Control Board until
DS3 the Green Module LED mounted on
the front panel just lights. Readjust the
Forward Power to 100 % using R5.
Switch the Tray Off and reverse the J6
and J7 cables located on the 3 Way
Combiner Board. Switch the Tray On and
adjust the front panel meter in the
Reflected Output Power Position to a 100
% reading using R53, Reflected Power
Meter Adjust, located on the AGC Control
Board. Adjust the Reflected Output
Power to a 20 % reading using R5
located on the AGC Control Board. Then
adjust R59, VSWR Cutback Adjust,
located on the AGC Control Board until
DS4 the Red VSWR Cutback LED
mounted on the front panel lights. This
sets up the VSWR Cutback Circuitry.
Readjust R5 for 100 % on the Meter for
250 Watts Output. Switch the Tray Off
and return the J6 and J7 Cables located
on the 3 Way Combiner Board back to
their original positions. Switch S1
located on the AGC Control Board to the
AGC position, which is the normal
operating position, after the set up is
completed.
There is a spare 1 Amp and 20 Amp
Fuse, located on the top, right rear of the
Tray, for replacement of the Fuses on the
Current Metering Board.
The VHF Low Band Amplifier Tray is
aligned and calibrated and ready for
normal operation.
5.5 Setting Up the Output Power of
the Transmitter
The following adjustments are
completed using the LCD screen located
on the front panel of the Axciter
Modulator Tray. On the Axciter Main
Screen, push the button next to the
Up/Downconverter tab on the right side
of the screen. This will open the
Upconverter/Downconverter Main
Screen. Set the AGC to Manual by
selecting 3 on the key board entry. The
screen will now indicate AGC Manual.
Set the transmitter to full power using
the Driver/Amplifier LCD display while
viewing the Power Control Screen in the
Set Up Menu and adjusting the level as
needed to attain 100% output power.
5.5.1 Setting up of AGC 1
To set up the AGC, first the AGC must
be activated. Locate the 8 position DIP
switch SW1 mounted on the Control
Board in the Axciter Upconverter Sled,
mounted in the Driver/Amplifier
Assembly. The Upconverter DIP Switch
Position 6 must be switched ON which
allows the user to modify the AGC 1 gain
through the Axciter Modulator.
See Figure 5-1 for an example of the
Axciter Upconverter/Downconverter
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures
DT325B, Rev. 0 5-4
Main Screen. On the Axciter
Upconverter Screen set AGC 1 to 1.5
Volts, by selecting 4 on the key board
entry. This will cause a detail screen to
appear prompting you to enter a
number value. Monitor the AGC 1 Gain
Value on the screen and increase or
decrease the value of the number
entered until the monitored reading is
1.5 Volts.
5.5.2 Setting up of the Overdrive
Threshold
On the Axciter Upconverter/
Downconverter Screen set the Overdrive
Threshold to 1.7 Volts, by selecting 7 on
the key board entry. This will cause a
detail screen to appear. Increase or
decrease the voltage as needed until the
monitored reading is 1.7 Volts.
Place the Transmitter into AGC by
pushing the 3 of the key board entry on
the Axciter Upconverter Screen. This
will place the Transmitter AGC into Auto.
Figure 5-1: Axciter Upconverter/Downconverter Main Screen
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures
DT325B, Rev. 0 5-5
5.5.3 Axciter Relay K2 Sample
Values
The K2 Relay is mounted on the Lower,
Right Side of the Cabinet, accessed
through the back. The RF Sample levels
must be measured with a power meter
before connecting them. Your
installation may require RF attenuators
to be placed in line with the samples to
get them within the desired range.
J1 Pre Filter connection to the FWD
power sample of the coupler before the
mask filter (Non-Linear Distortion).
Level into Relay at J1 should be 0 dBm
to –10 dBm. –5 dBm typical
J2 Post Filter connection to the forward
power sample after the mask filter
(Linear Distortion). The level into the K1
Relay at J2 should be 0 dBm to –10
dBm. –5 dBm typical, but must be
within .5 dB of the J1 sample.
5.5.4 Upconverter Down Converter
Adjustment
On the Axciter Modulator, activate the
Up/Downconverter Main screen by
selecting Up/Downconverter using the
button next to it on the right side of the
Axciter Main Screen. Activate the
Downconverter Output Gain by pushing
2 on the key board entry. Monitor the
DTVision Linear Display by pushing the
button next to the DTVision Linear
display on the right side of the Axciter
Main Screen. At the bottom of the
DTVision linear screen, locate the
reading next to RMS. If this reading is
between –10 dBm & 0 dBm no
adjustment is needed. If it is not, adjust
the “Downconverter Gain”, then view
the RMS value until it is within the –10
dBm to 0 dBm range.
5.6 System Calibration of Forward
and Reflected Powers Using the
Driver/AmplifierChassis
NOTE: Do not adjust R38 on (A4) the
Triple Peak Detector Board (1159713).
It is factory set for .7 to .8 VDC typical
AGC Reference to the VHF Amplifier Tray
and any readjustment may damage the
tray.
5.6.1 Forward Power Calibration
Check that transmitter is at 100%
output power, as shown on the LCD
display on the (A2) Driver/Amplifier in
the Set Up menus.
Measure with a VOM, TP31-14, Red, and
TP31-12, Black, at the terminal block
TP31 located on the rear chassis of the
(A2) Driver/Amplifier Chassis Assembly.
Adjust R14, Forward Calibration
Adjustment, on the (A4) Triple Peak
Detector Board, mounted on the lower
right side of the cabinet accessed
through the rear cabinet door, for a
reading of .8VDC on the VOM. Locate
the Forward Power Adjust screen on the
Driver/Amplifier LCD display in the Set
Up menus and adjust the up or down
arrow as needed to achieve 100%
output power. This completes the
forward power calibration.
5.6.2 Reflected Power Calibration
Switch the transmitter to Standby.
Remove the connector that is on Jack
J2, on the (A4) Triple Peak Detector
Board (1159713), and replace with the
connector now on J1, also inserting a 10
dB pad in series. Switch the transmitter
to operate. Monitor the LCD display on
the (A2) Driver/Amplifier in the Set Up
menus, reflected power screen. Adjust
R26, Reflected Calibration Adjustment,
on the (A4) Triple Peak Detector Board
for a reading of 10% on the display.
Switch the transmitter to Standby.
Move the connector back to J1 while
removing the 10 dB pad. Replace the
original connector onto J2. This
completes the reflected power
calibration.
This completes the set up and
adjustment of the DT325B transmitter.
If a problem occurred during alignment,
contact Axcera field service at 1-724-
873-8100.
APPENDIX A
DT325B
SYSTEM SPECIFICATIONS
DT334B/DT434B Pictured
DT300B/DT400B Series
Low Power VHF DTV Transmitters/Translators 350W - 2.1kW
These low power VHF DTV transmitters and translators deliver high quality and per-
formance in a compact and economical package - perfect for broadcasters wishing
to get a DTV signal on the air quickly. The time-proven Axcera DT1C modulator or
optional DT2B adaptive modulator, generates the ATSC-compliant 8VSB IF signal,
which feeds the companion upconverter. The upconverter provides a pre-correct-
ed output directly to the high-gain final power amplifier modules (three PAs in the
1000W unit). The entire package is housed in a single 19 inch rack-mount cabinet.
Designed for high reliability and unattended operation, each power amplifier
utilizes a parallel amplifier design with a high level of protection circuitry. Features
such as VSWR cutback, overdrive protection and over-temperature protection ensure
on-air reliability. Convenient system monitoring is achieved through front panel
samples, status indicators and metering, most of which are remote controllable.
Specifications published here are current as of the date of publication of this document. Because we are continuously improving our products, Axcera reserves the right to change specifications without prior notice. At any time, you
may verify product specifications by contacting our office. Axcera views it’s patent portfolio as an important corporate asset and vigorously enforces its patents. Products or features contained herein may be covered by one or more
U.S. or foreign patents.
0601R5 © 2006 AXCERA All Rights Reserved An Equal Opportunity Employer
103 Freedom Drive, PO Box 525, Lawrence, PA 15055 t: 724-873-8100 f: 724-873-8105
General
Model Number DT325B DT330B DT334B DT335B-1.4 DT335B-1.7 DT335B-2.1
DT425B DT430B DT434B DT435B-1.4 DT435B-1.7 DT435B-2.1
Power Output (Watts) 350 500/7002 1050 1400 1750 2100
Output Connector N N/15/8
” EA 15/8
” EIA 31/8” EIA 31/8” EIA 31/8” EIA
Power Consumption (Watts) 2250 4250 6250 8250 10,250 12,250
Number of PAs 1 2 3 4 5 6
Input Power
Line Voltage (Volts)1 208 or 240 ± 10%
Power Requirements Single Phase, 50 or 60 Hz
Size (H x W x D) 69”x22”x34” 69”x44”x34”
Operational Temperature Range 0 to +50°, derate 2°C/1000 ft.
Maximum Altitude1 8500 feet (2600m) AMSL
Operational Humidity Range 0% to 95% non-condensing
RF Load Impedance 50 Ω
1 Consult factory for other frequencies, altitudes and line voltages
2 Available with 700 W Filter Option
DT300B/DT400B Series
Low Power VHF DTV Transmitters/Translators 350W - 2.1kW
Performance
Frequency Range1
Low Band 54 to 88 MHz
High Band 174 to 216 MHz
Output Impedance 50 Ω
Frequency Stability ±250Hz (Max 30 Day Variation)
Regulation of RF Output Power 3%
Out of Band -Compliant with FCC Mask2
Channel Edge ±500kHz -47 dB or better
6MHz from Channel Edge -110 dB or better
Signal to Noise (SNR) 27 dB or better
Data Interface
Input Rate 19.39 Mbps. 6MHz channel
Input Interface SMPTE 310M, Serial Differential
ECL and TTL
Test Signals Staircase, VSB Pilot, Zero Pilot,
Average Power Pilot,
Nyquist Waveform
Options
Dual Exciter with Automatic Switcher
Adaptive Exciter
AC Surge Protector
Precise Frequency Kit
Spare Parts Kit
APPENDIX B
SYSTEM DRAWINGS
350-Watt Digital VHF LB Transmitter Appendix B, System Drawings
DT325B, Rev. 0 B-1
DT325B
DT325B Transmitter w/Axciter Interconnect...........................................1311143
Triple Peak Detector Board
Schematic..........................................................................................1160522
APPENDIX C
EXCITER/DRIVER CHASSIS ASSEMBLY
DRAWINGS
350-Watt Digital VHF LB Transmitter Appendix C, Exciter/Driver Chassis
Assembly Drawings
DT325B, Rev. 0 C-1
Chassis Assembly, Exciter/Driver, LXB, 220 VAC
Block Diagram....................................................................................1302139
Interconnect.......................................................................................1310215
Backplane Board, Innovator LX
Schematic..........................................................................................1310081
NOTE: Information and drawings on the Axciter Modulator Tray (1305842) and the
Upconverter Module (1310226) and Downconverter Module (1311157) are
found in the separate Axciter Manual.
Exciter Control/Power Supply Assembly, LXB, 220 VAC
Block Diagram....................................................................................1310189
Interconnect.......................................................................................1310190
Power Protection Board
Schematic..........................................................................................1302839
LCD w/Switches Board
Schematic..........................................................................................1307978
System Controller Board, LXB
Schematic..........................................................................................1310090
APPENDIX D
VHF LOW BAND AMPLIFIER TRAY
DRAWINGS
350-Watt Digital VHF LB Transmitter Appendix D, VHF LB Amplifier Tray
Drawings
DT325B, Rev. 0 D-1
VHF Low Band Amplifier Tray
Block Diagram....................................................................................1304364
Interconnect.......................................................................................1304365
Overdrive Protection Board
Schematic.......................................................................................1198-3601
Phase Shifter Board
Schematic.......................................................................................1198-3602
VHF Low Band Amplifier Board
Schematic.......................................................................................1198-3605
VHF Filter/Amplifier Board
Schematic.......................................................................................1198-3606
3 Way Splitter Board
Schematic.......................................................................................1198-3608
3 Way Combiner Board, CH
Schematic.......................................................................................1198-3626
VHF Low Band Low Pass Filter Board
Schematic.......................................................................................1198-3628
Current Metering Board
Schematic..........................................................................................1304366
350-Watt Digital VHF LB Transmitter Appendix D, VHF LB Amplifier Tray
Drawings
DT325B, Rev. 0 D-2
AGC Control Board
Schematic..........................................................................................1306481
400 Watt VHF Amplifier Assembly (1304348)
Delta RF Data Sheet........................................................................P400-VHF-L