EMCEE Broadcast TU1000F UHF LPTV Translator User Manual TTU1000F Mnl Cover Pg 1

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FAX: (570) 443-9257
Phone: (570) 443-9575
P.O. Box 68, White Haven, PA 18661
Broadcast Products
TU1000F V/U
SOLID STATE
1000W UHF TRANSLATOR
MDS  MMDS  ITFS  LPTV
North America  South America  Europe  Asia  Australia  Africa
Since 1960
TU1000F V/U
SOLID STATE
1000W UHF TRANSLATOR
02/00
TABLE OF CONTENTS
I.
THE TU1000F V/U TRANSLATOR
1.1
1.2
1.3
1.4
1.5
II.
CIRCUIT DESCRIPTION
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
III.
Introduction
Specifications
Installation
Operation
Warranty and Parts Ordering
Receiver Drawer
Exciter/Upconverter Drawer
Power Splitter
Dual 300W Power Amplifier Drawer
Power Combiner
Metering Coupler
Front Panel
Output Filter
MAINTENANCE
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
Periodic Maintenance Schedule
Recommended Test Equipment
Troubleshooting
Translator Alignment
Output Power Calibration
Precorrection Adjustment
Control Board Setup
Remote Monitor Signal Levels
Spare Modules and Components Lists
IV.
DATA PAK
V.
SCHEMATIC DIAGRAMS
SECTION I
THE TU1000F V/U TRANSLATOR
1.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
1.2
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
1.3
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
1.4
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
1.5
Warranty and Parts Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
SECTION I
THE TU1000F V/U TRANSLATOR
1.1
Introduction:
The EMCEE TU1000F V/U Translator is rated to provide 1000 watts peak visual and 50 watts
average aural power on any FCC specified channel extending from 470 to 806MHz. The TU1000F
is completely solid-state providing maximum performance and reliability. It is comprised of a
Receiver Drawer, a 20 Watt UHF Exciter/Upconverter, two Dual 300W Power Amplifier assemblies
and a panel for power distribution and metering. The TU1000F is easy to service and maintain while
RF alignment is practically nonexistent. A number of front panel indicators are included which
display the results of the translator's diagnostic/control circuitry.
The TU1000F Translator is designed for the express purpose of broadcasting as authorized by the
U.S. Federal Communications Commission under Part 74, Subpart G, of the FCC Rules and
Regulations.
1.2
Specifications:
Output Power
1000W peak visual
50W average aural
Emissions
5M75C3F visual
250KF3E aural
Color Transmission
NTSC, PAL, or SECAM
Output Frequency Range
470-806MHz
Input Frequency Range
54-88MHz
174-216MHz
470-806MHz
Frequency Stability
±1kHz
Visual Output Power Stability
±0.5dB
Spurious Products
60dB below peak sync
Harmonics
60dB below peak sync
In-band Intermodulation (IM3)
52dB below peak sync
Differential Gain
5%
Differential Phase
±3(
Frequency Response
±1.0dB
161
(FCC Ch. 2-60)
(FCC Ch. 7-13)
(FCC Ch. 14-69)
1.3
Envelope Delay
±50nsec
Output Impedance
50 ohms (7/8" EIA flange connector)
RF Input Level
70dBm to 30dBm
RF Input Impedance
50 ohms unbalanced (N connector)
Video Signal to Noise
50dB @ 47dBm in
Audio Distortion
<1%
Aural FM Noise
<55dB
Ambient Temperature
30(C to +50(C
Power Requirements
230Vac ± 15% @ 50/60Hz, 3.8kW
Mechanical Dimensions
69"H x 23"W x 29"D
Weight
350 lb.
Installation:
Except where otherwise noted, the connectors mentioned in the following instructions are located
on the rear of the translator.
1.
After unpacking the translator, a thorough inspection should be conducted to reveal any
damage which may have occurred during shipment. If damage is found, immediately notify
the shipping agency and advise EMCEE Broadcast Products Customer Service or its field
representative. Also check to see that any connectors, cables or miscellaneous equipment,
which may have been ordered separately, are included.
2.
Place the translator in a clean, weatherproof environment providing adequate ventilation for
the exhaust fans at the top of the cabinet. It is important to maintain the translator's ambient
temperature within the 30(C and +50(C limits. Cooler ambient temperatures will provide
increased reliability.
3.
Place the translator in its permanent location near a single-phase receptacle that supplies
230Vac at 50/60Hz. The ac source should have a minimum power capacity of 5kW.
IMPORTANT
Do not apply ac power to the translator at this time since its RF output must be properly
terminated before being placed in operation.
162
1.4
4.
Set all circuit breakers and switches, including the customer's incoming ac line breaker, to
the OFF position. Place an appropriate ac power line protector (surge suppressor) across the
ac line that supplies the translator.
5.
With the appropriate cables (customer supplied), connect the receiving antenna to the RF IN
“N” connector located on the top rear panel of the translator cabinet.
6.
Connect the transmitting antenna cable to the 7/8" EIA flange connector marked RF OUTPUT
located at the top, rear, right-hand corner of the cabinet (as seen from the front).
7.
Verify that the power cords of the Receiver and Exciter drawers are plugged into the
receptacle at the bottom of the cabinet inside the rear door. Check all other factory installed
RF cables and DC wire harnesses for tight connections.
8.
Using the 4-prong, twist lock, female plug supplied with the translator, fabricate an ac power
cord and plug it into the translator's AC MAINS connector at the top left rear (as seen facing
the front of the cabinet) of the translator's cabinet. Connect the other end of the power cord
into an appropriate electrical outlet.
Operation:
Assuming the installation instructions of Section 1.3 have been completed and the translator is
receiving a signal of appropriate frequency and amplitude, proceed with the following steps to place
the translator in operation. Except where otherwise noted, the controls, switches, and indicators
mentioned in these steps are located on the front of the translator.
1.
Close the transmission site’s ac mains breaker. Place the Receiver front panel OPERATE/
ALIGN switch to OPERATE and its AC POWER circuit breaker to ON. Verify that the
CARRIER PRESENT indicator is illuminated green.
2.
Turn the Exciter/Upconverter POWER ADJUST control fully counterclockwise and place its
OPERATE/STANDBY switch to STANDBY, its OPERATE/ALIGN switch to OPERATE.
Place the Control/Metering Panel’s AC POWER circuit breaker and the Exciter POWER ON
breaker both to the on/up position. Then verify the following responses of the translator:
a.
The fans of the translator should be operating. The Exciter exhausts air out the rear of
the drawer while the Power Amplifier drawer exhausts air through the cabinet top with
the aid of cabinet-mounted exhaust fans.
b.
The Exciter's OPERATE, SYNTH LOCK, and DRIVER AMP indicators should be
illuminated green.
c.
The Exciter’s TEMP EXCITER, ON, FINAL BIAS and VSWR OVLD indicators should
be extinguished.
d.
The TEMPERATURE, VSWR OVLD and COLLECTOR BIAS indicators of each Power
Amplifier should be extinguished.
e.
The Control/Metering Panel’s four Amplifier Status indicators should be illuminated
green.
163
3.
Place the Exciter’s OPERATE/STANDBY switch to OPERATE. Then verify the following
responses of the translator:
a.
The Exciter's OPERATE, SYNTH LOCK and DRIVER AMP indicators should remain
illuminated green.
b.
The Exciter's ON and FINAL BIAS indicators should be illuminated green while the
VSWR OVLD and TEMP indicators remain extinguished.
c.
The TEMPERATURE indicator of each Power Amplifier drawer should remain
extinguished while the COLLECTOR BIAS indicators are illuminated green.
d.
The Control/Metering Panel’s AMPL 1 through AMPL 4 indicators should remain
illuminated green.
4.
Place the Control/Metering Panel's meter switch to FWD and turn the Exciter's POWER
ADJUST control clockwise until a 100% indication appears on the Control/Metering Panel's
RF POWER meter. Set the Exciter’s % meter to display FWD power. Note that the meter
may show a reading less than 100%. This is appropriate.
5.
Place the Control/Metering Panel's meter switch to REFLD and verify that the meter indicates
no more than 10% returned power. If the reflected power is more than 10%, shut down the
translator and check the VSWR of the transmitting antenna and its associated cable.
6.
Place the Control/Metering Panel's meter switch to FWD for constant monitoring of the
translator's final output power.
The translator is now in operation. Check its coverage area for clean, sharp television reception.
If the reception or picture quality is unsatisfactory, examine the amount of power delivered to the
transmitting antenna (see Section 3.5) and, if necessary, examine the antenna orientation, antenna
VSWR, and transmission line VSWR to insure maximum radiation in the proper direction.
1.5
Warranty and Parts Ordering:
Warranty – EMCEE warrants its equipment to be free from defects in material and workmanship for
a period of one year after delivery to the customer. Equipment or components returned as defective
(prepaid) will be, at our option, repaired or replaced at no charge as long as the equipment or
component part in question has not been improperly used or damaged by external causes
(e.g., water, ac line transients or lightning). Semiconductors are excepted from this warranty and
shall be warranted for a period of not more than ninety (90) days from date of shipment. Equipment
or component parts sold or used by EMCEE, but manufactured by others, shall carry the same
warranty as extended to EMCEE by the original manufacturer.
Equipment Returns – If the customer desires to return a unit, drawer, or module to EMCEE for
repair, follow the procedure described below:
1.
Contact EMCEE Customer Service Department by phone or fax for a Return Authorization
Number.
164
2.
Provide Customer Service with the following information:
Equipment model and serial numbers.
Date of purchase.
Unit input and output frequencies.
Part number (PN) and Schematic Diagram designator if a module is being sent.
Detailed information concerning the nature of the malfunction.
The customer shall designate the mode of shipping desired (e.g., Air Freight, UPS, Fed Ex, etc.).
EMCEE will not be responsible for damage to the material while in transit. Therefore, it is of utmost
importance that the customer insure the returned item is properly packed.
Parts Ordering – If the customer desires to purchase parts or modules, utilize the following
procedure:
1.
Contact EMCEE Customer Service by phone or fax indicating the customer's purchase order
number. If the purchase order number is provided by phone, written confirmation of the order
is required.
2.
Also provide:
The equipment model and serial number.
The unit input and output frequencies.
The quantity, description, vendor, number, and designation of the parts needed as found in
the Parts Lists subsection of this manual.
If a module is required, give the part number (PN) and Schematic Diagram designator
(e.g., 10331209).
Designate the mode of shipping desired (e.g., Air Freight, UPS, Fed Ex, etc.).
Shipping and billing addresses.
Spare and Replacement Parts – The Spare Modules and Components section of this manual
provides a detailed listing of the modules and some discrete components contained within the
translator. The listing contains those modules or components considered to be essential benchstock items and should be available to the technician at all times. The Schematic or Interconnection
Diagram is the governing document of this manual. Should there be a discrepancy between a
modules or components list and a diagram, the diagram takes precedence. Such a discrepancy is
possible since manufacturing changes cannot always be incorporated immediately into the
instruction manual.
Component Referencing – The translator consists of a number of modules and components mounted
in four drawers, a number of components mounted on panels, and several cabinet-mounted
components and modules. Components mounted in a module which is included in a drawer take
the drawer number and the module number in addition to a component number. Thus the reference
designator A2A1Q1 means transistor Q1 in module A1 of drawer A2. Components mounted in a
drawer take only the drawer number and a component number (e.g., A2M1 designates meter M1 of
drawer A2). Components mounted directly to a panel take only the panel number and a component
number. Components and modules mounted directly to the cabinet take only a component or
module number.
165
For EMERGENCY technical assistance, EMCEE offers a toll free, 24-hour, 7-day-a-week
customer service hot line: 1-800-233-6193.
166
SECTION II
CIRCUIT DESCRIPTION
2.1
Receiver Drawer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
2.1a
2.1b
2.1c
2.1d
2.1e
2.1f
2.1g
2.1h
2.1i
2.1j
2.1k
2.1l
2.1m
2.1n
2.1o
2.1p
2.1q
2.1r
2.2
Exciter/Upconverter Drawer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2613
2.2a
2.2b
2.2c
2.2d
2.2e
2.2f
2.2g
2.2h
2.2i
2.2j
2.2k
2.3
2.4
VHF/UHF Remote Preamplifier (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
VHF Bandpass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
UHF Bandpass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
Crystal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
X2 Multiplier and X4 Multiplier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
X16 Multiplier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
10MHz Reference Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
VHF Synthesizer Low Band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
VHF Synthesizer High Band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
UHF Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
Downconverter/Preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
IF SAW Filter/Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
IF AGC Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
Automatic-On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2610
Limiter/Output AGC Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2610
Aural Notch Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2611
Multioutput Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2611
Digital Code ID Unit (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2612
Linearizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IF/Upconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UHF Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reference Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UHF Bandpass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Watt UHF Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20 Watt UHF Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Metering Coupler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Metering Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2614
2614
2616
2617
2617
2617
2618
2619
2619
2620
2622
Power Splitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2622
Dual 300W Power Amplifier Drawer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2622
2.4a
2.4b
2.4c
300W UHF Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2623
Status Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2623
+28V Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2624
2.5
Power Combiner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2624
2.6
Metering Coupler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2624
2.7
Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2624
2.7a
2.7b
2.8
Metering Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2625
Control Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2625
Output Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2628
iia
SECTION II
CIRCUIT DESCRIPTION
2.1
Receiver Drawer:
Interconnection Diagram 30383094/Rev 54 t A1 (Vectron Oscillator with Multiplier)
Interconnection Diagram 30383104/Rev 55 t A1 (Synthesizer)
70dBm to 30dBm peak visual
6dBm
RF IN
IF OUT
LO SAMPLE
0dBm
The Receiver drawer provides highly selective VHF or UHF to IF signal conversion, IF
amplification, and prevention of unauthorized radiation if the proper input signal is not received.
Signal conversion is accomplished via a VHF or UHF Bandpass Filter (FL1), and a Downconverter/
Preamplifier (A1). The LO for downconversion is provided by one of six sources depending upon
the application. A high stability crystal oscillator (G1) with a X2, X4 or X16 Multiplier (A4) is used
when a frequency offset is required when receiving VHF Low Band (Ch.2-6), VHF High Band
(Ch.7-13) or UHF (Ch.14-69) respectively. If no frequency offset is required, the corresponding
Synthesizer (A4) and 10MHz Reference Oscillator (A5) are used. IF amplification and filtering are
furnished through the IF Amplifier w/SAW Filter (A2) and the IF AGC Amplifier (A3). The Aural
Notch Filter (FL2) allows for attenuation of the aural carrier to facilitate a reduction of in-band third
order intermodulation products or to maintain the minimum visual to aural carrier ratio. Finally, a
6dB attenuator reduces the IF signal to a level that is within the input range of the Exciter/
Upconverter (A2).
The Receiver drawer also insures that the translator does not exceed or deviate from its rated
output power while receiving signal variations of up to 40dB (70dBm to 30dBm). This function
is accomplished through a complex gain control system employing the IF AGC Amplifier's variable
pin diode attenuator and a Limiter/Output AGC (PC1). The IF AGC Amplifier's variable pin diode
attenuator is controlled by the input AGC circuit of the IF AGC Amplifier and the output AGC circuit
of the Limiter/Output AGC. As the received signal increases, the input AGC circuit of the IF AGC
Amplifier provides an increase in the AGC voltage applied to the variable pin diode attenuator.
This condition causes an increase in the attenuation provided by the variable pin diode attenuator.
As a result, the IF output of the Receiver drawer is held constant at approximately 6dBm (±1dB)
throughout the 40dB variation in the received signal.
The input AGC circuit alone does not provide for controlling changes in amplifier gain occurring
after the IF section of the Receiver. (An amplifier's gain may change during warm-up, over long
periods of time, and under varying temperatures.) The output gain control circuit of the Limiter/
Output AGC is incorporated to monitor and correct any changes in the translator's output power.
The output AGC circuit controls the gain of the IF AGC Amplifier by monitoring the dc voltage that
drives the translator's % Power meter. Any deviation from the translator's correct output power will
shift the metering voltage, causing the output AGC circuit to vary the biasing on the IF AGC
Amplifier's variable pin diode attenuator. The attenuation will vary in such a way that any power
fluctuations at the output of the translator will be counteracted.
Should the Receiver drawer experience a temporary loss of signal (fading, etc.), the limiter circuit
of the Limiter/Output AGC serves to prevent overdriving the translator's power amplifier modules.
(A decrease in the received signal reduces the AGC voltage and consequently increases the gain
261
of the IF AGC Amplifier.) When the received signal regains its strength, the limiter circuit will
momentarily attenuate (20dB) the IF output of the Receiver drawer until adequate AGC voltage
is developed to control the Receiver's overall gain.
In the event of a significant reduction or loss of the Receiver's input signal for more than
30 seconds, an Automatic-On circuit (PC2) will prevent the radiation of noise by shutting down the
Receiver. Should the VHF or UHF input signal to the Receiver fall below the minimum acceptable
level of 70dBm, the accompanying AGC voltage will fall below a preset Auto-On Threshold
voltage. This in turn causes Auto-On relay K1 to de-energize which opens the interlock loop and
shuts down the translator.
2.1a
VHF/UHF Remote Preamplifier: (OPTIONAL)
Scala Model 8000
Specifications
2.1b
See Data Pak
VHF Bandpass Filter:
Schematic A280-92/Rev 1 (Ch.2-6) t A1FL1
Schematic A280-89/Rev 1 (Ch.7-13) t A1FL1
Frequency Response (J1-J2)
Insertion Loss (J1-J2)
7MHz @ 1dB
2dB Max.
The high band VHF bandpass filter is a two-section overcoupled circuit that rejects all frequencies
other than the single VHF channel to which it is tuned. The bandpass filter is adjusted to provide
a 7MHz @ 1dB frequency response with an insertion loss of approximately 2dB or less. In the
filter, inductors L3 and L4, in conjunction with stagger-tuned capacitors C1 through C4, provide the
required bandpass response. Capacitor C5 also effects the response by changing the effective
coupling between the two circuits. Impedance matching is accomplished by inductors L1 and L2
along with variable capacitors C1 and C2.
2.1c
UHF Bandpass Filter:
Schematic 10331209/Rev 52 (Ch.14-83) t A1FL1
Frequency Response
Insertion Loss
7MHz @ 1dB
3dB Max.
The filter is composed of three overcoupled, 1/4 wave coaxial cavities that reject all frequencies
other than the single UHF channel to which it is tuned. The UHF Filter provides a 7MHz bandwidth
at 1dB and has an insertion loss of 3dB or less. In the filter, components L2, L3 and L4 are solid
brass rods acting as 1/4 wave shorted transmission lines. The length of these lines, controlled by
variable capacitors C1, C2 and C3, dictates the resonant frequency of the filter. Inductors L1 and
L5 link couple the UHF signal into and out of the filter. The position of these two inductors in
relation to the 1/4 wave brass rods determines the filter's input and output impedance, as well as
262
skirt selectivity and insertion loss. The Variable Coupling Barriers regulate the amount of signal
passed between the coaxial cavities and therefore control the bandwidth of the filter.
2.1d
Crystal Oscillator:
Vectron CO-254D57 t A1G1
Supply Voltage
Output Power
Operating Temperature
Stability
28V
+7dBm
30(C to +70(C
±5 x 10-7
The CO-254D57 is a high stability, temperature-compensated crystal oscillator (TCXO)
manufactured by Vectron Laboratories, Inc. This oscillator, in conjunction with a X2, X4 or X16
Multiplier, is used in place of the EMCEE Synthesizer when ±10kHz precision offset is required.
See the Data Pak for further information.
2.1e
X2 Multiplier and X4 Multiplier:
Schematic B280-35/Rev E (Ch.2-6) t A1A4 (X2 Multiplier)
Schematic C331-24/Rev D (Ch.7-13) t A1A4 (X4 Multiplier)
Multiplier
Collector V
Output Power
Output Frequency
Q1
Q2
Q3
25
15
15
10-40mW
Osc. 2nd/4th Harmonic
The VHF Multiplier consists of an amplifier and two doubler stages fed by the fundamental
frequency of the crystal oscillator. Transistor Q1 is an untuned class A VHF amplifier coupled to
a resonated idler loop tuned to the fundamental frequency (series circuit L3 and C7). Transistor
Q2 is a class AB X2 frequency multiplier that feeds an LC series circuit (L5, C12) tuned to the
second harmonic. Capacitors C13 through C17 and inductors L6 through L8 make up a
three-section bandpass filter which passes only the second harmonic frequency. If the multiplier
is a X4 type, transistor Q3 is a class C frequency doubler with both input and output tuning. Tuning
consists of a second harmonic idler circuit (L9 and C19) at the input and an output network (L12,
C22 and C23) that is tuned to the oscillator's 4th harmonic. C26 through C29 and inductors L13
and L14 make up a two-section bandpass filter tuned to pass the oscillator's fourth harmonic. An
LO sample (1mW) port (J3) is provided on the front panel of the translator drawer for convenient
monitoring or mixing.
263
2.1f
X16 Multiplier:
Schematic Diagram 30367226/Rev A t A1A4
INPUT power
0 to +10dBm
Typical +7dBm
LO OUT (J2)
Output power
Output frequency
+15dBm Min.
16th harmonic of input
The X16 Multiplier provides three sections of frequency multiplication to generate the LO necessary
for downconverting UHF channels to IF.
Section 1 consists of a frequency multiplier (A1), a bandpass filter (FL1), and an amplifier (U1).
A1 produces harmonics from the input signal of the crystal oscillator. The desired harmonic from
A1 is the fourth, whose level should typically be 30dB below the oscillator level. FL1 is a narrow
bandpass filter, which also employs two tunable notch filters. When properly tuned, FL1 has a
typical insertion loss of 2 to 2.5dB. The notch filters are tuned to the 3rd and 5th harmonics
providing an additional minimum attenuation of 15dB to these harmonics. Output level from FL1
is approximately 28 to 32dBm. U1 is a monolithic amplifier with a typical gain of 33dB at these
frequencies. U1 provides the nominal level of 0dBm for the next section of frequency
multiplication.
Section 2 consists of a frequency multiplier (A2), a filter FL2, and a two-stage amplifier (U2, U3).
A2 produces harmonics of the signal taken from the previous section. The desired frequency from
this section is the 2nd harmonic of the input (8th harmonic of OSC.). The output level of A2 at the
2nd harmonic is typically 15dBm. FL2 is a tunable microstrip bandpass filter. The filter has a
frequency range of 250-470MHz, an insertion loss of 2dB and is tuned to pass the 2nd harmonic
of A2. The output level from FL2 is a nominal 17dBm. U2 and U3 are monolithic amplifiers with
a combined typical gain of 25dB. These are used to produce an input level of +8dBm to the third
section.
Section 3 consists of a frequency multiplier (A3), two different stages of amplification (U4 and U5,
U6), and two filters (FL3, FL4). A3 is used to produce harmonics of the frequency from Section 2.
The desired frequency from A3 is the second harmonic of its input (16th of OSC.). Output level
of the second harmonic from A3 is typically 6dBm. U4 is used to amplify the output of A3 before
filtering by FL3. The output level of U4 at the 2nd harmonic of A3 is at a nominal 2dBm level. FL3
is a tunable microstrip bandpass filter with a frequency range of 500-940MHz and an insertion loss
of 2dB. The filter is tuned to the 2nd harmonic of A3. The output level of FL3 is 0dBm. U5 is a
monolithic amplifier with a 12dB gain. U5 is run into compression allowing the oscillator level to
vary while the output of U5 remains constant. The output of U5 drives U6, another monolithic
amplifier with a gain of 11.5dB. This amplifier is also operated in compression for the same reason
as U5. The output of U6 is +18 to +20dBm. FL4 is tuned for the second harmonic from A3 and
provides additional filtering to suppress the undesired harmonics from previous frequency
multiplication. Secondly, the filter removes any additional undesired signals caused by
compressing amplifiers U5 and U6. The output level from FL4 is typically +16dBm to +18dBm.
264
2.1g
10MHz Reference Oscillator:
Schematic Diagram 10368037/Rev B t A1A4A2
10MHz REF. OUT (J1, J2)
3.5V P/P square wave
The Reference Oscillator provides a 10MHz reference signal for the Synthesizer (A4A1). This
module is centered around a 10MHz temperature-compensated crystal oscillator (G1). The output
from G1 is applied to two exclusive-OR gates used as inverting buffers. The output signal from
each gate is a 10MHz low-level square wave with a frequency stability of 0.3 parts per million
(PPM).
2.1h
VHF Synthesizer Low Band:
Schematic Diagram 30362427/Rev C t A1A4A1
10MHz REF. IN (J1)
LO OUT (J2)
SYNTH. LOCK (Pin A of J4)
3.5V P/P square wave
+15.25dBm min.
logic high (locked)
logic low (unlocked)
The VHF Synthesizer is a phase-lock loop type and uses one of the 10MHz reference signals from
the Reference Oscillator (A4A2) and develops a programmable LO signal for the Mixer (MX1) in
the Downconverter/Preamplifier (A1). The frequency of the LO signal is calculated as the sum of
the visual IF carrier and the visual VHF carrier of the specified input channel. The LO signal's
frequency is programmed by the setting of switches S1 through S4 which are accessible through
the module's cover. The relationship between the setting of these switches and the resulting LO
frequency is provided in Table 263 for each VHF channel.
A 10MHz reference signal is brought in from the Reference Oscillator (A4A2) through J1, 10MHz
IN. Both sections of U4 perform binary divide-by-5 counting to provide a 400kHz signal to the
OSCin input of U1, pin 27. To create U1's internal 50kHz reference signal, U1 performs a binary
divide-by-8 operation on the OSCin signal.
Controlling the VCO, G1, is the output of op-amp U3. U3 compares and integrates the 0
/ V and 0/R
phase detector outputs of U1. The output of U3 is filtered to create the dc control voltage for the
VCO. The output of G1, RF OUT, is amplified by U5 and available as the Receiver's LO at J2,
OUT.
The output of G1 is also amplified by U6 and then fed to a ÷32/÷33 prescaler, U2. After prescaling,
the signal is connected to U1 pin 1, Fin, from U2 pin 4, OUT, completing the loop. The prescaling
factor of U2 is selected by the MOD CONTROL, pin 9, of U1. Switches S1 to S4 set two
divide-by-ratios, counters A and N, within U1. When divide-by-A is being performed on the signal
at Fin, MOD CONTROL is set high, selecting ÷32 in the prescaler, U2. MOD CONTROL goes low
for divide-by-N selecting ÷33 in U2.
The A and N counters form a binary number from A0 to N9 with A0 being the LSB and N9 being
the MSB. The decimal equivalent of this number, when multiplied by the internal reference
frequency 50kHz, gives the synthesizer's output frequency. Hence, for NTSC operation, A0 and
A1, pins 21 and 23 on U1, are grounded. For PAL operation, A0 and A1 are made high by cutting
265
the traces from pins 21 and 23 to ground thereby adding the 150kHz to the LO that is characteristic
of the PAL system.
When the synthesizer is locked onto a frequency, LD is high. This saturates Q1 and puts a low on
SYNTH LOCK. C28 provides a time delay to ensure that the synthesizer has successfully locked
before indicating so on the SYNTH LOCK line. For an unlocked condition, LD pulses low
preventing C28 from charging and saturating Q1. +5V is therefore present on the SYNTH LOCK
line for the unlocked condition.
2.1i
VHF Synthesizer High Band:
Schematic Diagram 30362003/Rev D t A1A4A1
10MHz REF. IN (J1)
LO OUT (J2)
SYNTH. LOCK (Pin A of J4)
3.5V P/P square wave
+15.25dBm min.
logic high (locked)
logic low (unlocked)
The VHF Synthesizer is a phase-lock loop type and uses one of the 10MHz reference signals from
the Reference Oscillator (A4A2) and develops a programmable LO signal for the Mixer (MX1) in
the Downconverter/Preamplifier (A1). The frequency of the LO signal is calculated as the sum of
the visual IF carrier and the visual VHF carrier of the specified output channel. The LO signal's
frequency is programmed by the setting of switches S1 through S4 which are accessible through
the module's cover via access holes. The relationship between the setting of these switches and
the resulting LO frequency is provided in Table 262 for each VHF channel.
A 10MHz reference signal is brought in from the Reference Oscillator (A4A2) through J1, 10MHz
IN. Both sections of U4 perform binary divide-by-5 counting to provide a 400kHz signal to the
OSCin input of U1, pin 27. To create U1's internal 50kHz reference signal, U1 performs a binary
divide-by-8 operation on the OSCin signal.
Controlling the VCO, G1, is the output of op-amp U3. U3 compares and integrates the 0
/ V and 0/R
phase detector outputs of U1. The output of U3 is filtered to create the dc control voltage for the
VCO. The output of G1, RF OUT, is amplified by U5 and available as the Receiver's LO at J2,
OUT.
The output of G1 is also amplified by U6 and then fed to a ÷64/÷65 prescaler, U2. After prescaling,
the signal is connected to U1 pin 1, Fin, from U2 pin 4, OUT, completing the loop. The prescaling
factor of U2 is selected by the MOD CONTROL, pin 9, of U1. Switches S1 to S4 set two
divide-by-ratios, counters A and N, within U1. When divide-by-A is being performed on the signal
at Fin, MOD CONTROL is set high, selecting ÷64 in the prescaler, U2. MOD CONTROL goes low
for divide-by-N selecting ÷65 in U2.
The A and N counters form a binary number from A0 to N9 with A0 being the LSB and N9 being
the MSB. The decimal equivalent of this number, when multiplied by the internal reference
frequency 50kHz, gives the synthesizer's output frequency. Hence, for NTSC operation, A0 and
A1, pins 21 and 23 on U1, are grounded. For PAL operation, A0 and A1 are made high by cutting
the traces from pins 21 and 23 to ground thereby adding the 150kHz to the LO that is characteristic
of the PAL system.
266
When the synthesizer is locked onto a frequency, LD is high. This saturates Q1 and puts a low on
SYNTH LOCK. C28 provides a time delay to ensure that the synthesizer has successfully locked
before indicating so on the SYNTH LOCK line. For an unlocked condition, LD pulses low
preventing C28 from charging and saturating Q1. +5V is therefore present on the SYNTH LOCK
line for the unlocked condition.
2.1j
UHF Synthesizer:
Schematic Diagram 30367094/Rev B t A1A4A1
10MHz REF. IN (J1)
LO OUT (J2)
SYNTH. LOCK (Pin A of J4)
3.5V P/P square wave
+15.25dBm min.
logic high (locked)
logic low (unlocked)
The UHF Synthesizer is a phase-lock loop type and uses one of the 10MHz reference signals from
the Reference Oscillator (A4A2) and develops a programmable LO signal for the Mixer in the
Downconverter/Preamplifier (A1). The frequency of the LO signal is calculated as the sum of the
visual IF carrier and the visual UHF carrier of the specified output channel. The LO signal's
frequency is programmed by the setting of switches S1 through S4 which are accessible through
the module's cover via access holes. The relationship between the setting of these switches and
the resulting LO frequency is provided in Table 261 for each UHF channel.
A 10MHz reference signal is brought in from the Reference Oscillator (A4A2) through J1, 10MHz
IN. Both sections of U4 perform binary divide-by-5 counting to provide a 400kHz signal to the
OSCin input of U1, pin 27. To create U1's internal 50kHz reference signal, U1 performs a binary
divide-by-8 operation on the OSCin signal.
Controlling the VCO, G1, is the output of op-amp U3. U3 compares and integrates the 0
/ V and 0/R
phase detector outputs of U1. The output of U3 is filtered to create the dc control voltage for the
VCO. The output of G1, RF OUT, is amplified by U5 and available as the Receiver's LO at J2,
OUT.
The output of G1 is also amplified by U6 and then fed to a ÷64/÷65 prescaler, U2. After prescaling,
the signal is connected to U1 pin 1, Fin, from U2 pin 4, OUT, completing the loop. The prescaling
factor of U2 is selected by the MOD CONTROL, pin 9, of U1. Switches S1 to S4 set two
divide-by-ratios, counters A and N, within U1. When divide-by-A is being performed on the signal
at Fin, MOD CONTROL is set high, selecting ÷64 in the prescaler, U2. MOD CONTROL goes low
for divide-by-N selecting ÷65 in U2.
The A and N counters form a binary number from A0 to N9 with A0 being the LSB and N9 being
the MSB. The decimal equivalent of this number, when multiplied by the internal reference
frequency 50kHz, gives the synthesizer's output frequency. Hence, for NTSC operation, A0 and
A1, pins 21 and 23 on U1, are grounded. For PAL operation, A0 and A1 are made high by cutting
the traces from pins 21 and 23 to ground thereby adding the 150kHz to the LO that is characteristic
of the PAL system.
When the synthesizer is locked onto a frequency, LD is high. This saturates Q1 and puts a low on
SYNTH LOCK. C28 provides a time delay to ensure that the synthesizer has successfully locked
before indicating so on the SYNTH LOCK line. For an unlocked condition, LD pulses low
267
preventing C28 from charging and saturating Q1. +5V is therefore present on the SYNTH LOCK
line for the unlocked condition.
2.1k
Downconverter/Preamplifier:
Schematic A331-29/Rev B t A1A1
Gain with Conversion (J1-J2)
Collector V (Q1)
LO Input (Min.) (J3)
3.0dB
7.9V
+7dBm
The Downconverter preamplifier (A1) consists of a single stage, low noise, broadband amplifier
with a double balanced mixer. The VHF or UHF input signal is coupled to Q1 where it is amplified
before driving the mixer. The mixer combines the composite VHF or UHF television signal from
Q1 with a constant amplitude unmodulated RF signal (LO) from the reference oscillator/synthesizer
pair or the crystal oscillator/multiplier pair. Both signals are heterodyned in the mixer where their
sum and difference frequencies are developed. Capacitors C10 through C13 along with inductors
L4 through L7 comprise a low-pass filter network allowing only the modulated difference frequency
(IF) to pass.
2.1l
IF SAW Filter/Amplifier:
Schematic B331-21/Rev D t A1A2
Q1
Q2
Q3
Gain
J1-J2
21dB
Collector V
15V
18V
11V
Collector I
16mA
56mA
16mA
The IF Surface Acoustic Wave (SAW) Filter/Amplifier is a three-stage amplifier. Transistors
Q1/Q2 amplify the IF input signal while their associated feedback networks maintain a flat
passband response. The SAW filter provides high selectivity with no need for tuning or alignment.
Transistor amplifier Q3 overcomes the loss associated with the SAW filter. Its feedback circuitry
is also designed to compensate for nonlinear gain characteristics (i.e., lower gain at the higher
frequencies).
268
2.1m
IF AGC Amplifier:
Schematic C331-37/Rev G t A1A3
Q2
Q1
Q3
Gain
J1-J2
10-50dB
Collector V
+20.5Vdc
+25Vdc
+23.4Vdc
Collector I
4.5mAdc
27mAdc
60mAdc
0dBm
Power Output
The IF AGC Amplifier is a variable gain amplifier with its own automatic gain control and limiter
sections. The IF AGC Amplifier is calibrated to provide a constant IF output of approximately
0dBm with a range of 70dBm to 30dBm received signal. The amplifier section consists of three
common-emitter RF transistor stages (Q1, Q2, Q3) that produce a combined gain of 50dB.
Overall gain is adjustable by varying the amount of Q1's emitter bypass via potentiometer R15
(GAIN ADJ). Q2 and Q3 are fixed bias amplifiers separated by a 9dB, 50 ohm-to-50 ohm matching
pad (R22, 23, 24). Q3's feedback network, consisting of TILT ADJ potentiometer R31, inductor L2,
and capacitor C12, is designed to compensate for the overall frequency characteristics of the
module (lower gain at higher frequencies). TILT ADJ potentiometer R31 controls the amplifier's
frequency response by varying the amount of Q3's negative feedback.
The automatic gain control section consists of an input AGC circuit (L3, C14, CR8, U1, and
surrounding components) and a variable pin diode attenuator (CR1, 2, 4, and surrounding
components). The input AGC circuit is centered around operational amplifier U1. A portion of the
IF signal is coupled off of Q3 to a tank circuit (C14, L3) tuned to the visual IF carrier frequency
(45.75MHz). The tank energy forward biases detector diode CR8 and then becomes filtered by an
RC network (C13, R29) which results in a negative dc voltage proportional to the peak value of the
visual IF signal. This negative dc voltage is buffered by operational amplifier U1B and then
supplied to the Limiter/Output AGC Control (PC1) as the LIMITER REFERENCE OUT voltage.
The buffered negative dc voltage is also supplied to operational amplifier U1A where it is inverted
and summed with the negative OUTPUT AGC IN reference voltage from PC1, resulting in a
positive dc voltage (AGC) proportional to the visual IF signal level. This AGC voltage is used to
control the biasing (thus attenuation) of the variable pin diode attenuator and to activate the
Automatic-On circuit (PC2).
NOTE:
When the front panel OPERATE/ALIGN switch of the Receiver drawer is in the ALIGN
position, the IF AGC Amplifier's PRIMARY AGC OUT voltage is replaced by a +5Vdc
reference voltage at pin J3-1.
The main function of the limiter circuit is to prevent overdriving the amplifier modules in the
translator's Upconverter and Power Amplifier drawers when the input signal to the Receiver returns
after periods of reception fading. For example, following a temporary reduction (fading, etc.) in the
received signal, the AGC voltage decreases which reduces the attenuation provided by the IF AGC
Amplifier's variable pin diode attenuator. However, once the received signal regains its strength,
the variable pin diode attenuator cannot attenuate this signal fast enough. The limiter circuit is
used to overcome this characteristic of the variable pin diode attenuator. Notice that with an
increase in the received signal, the AGC voltage increases while the limiter reference voltage
decreases. The variable pin diode attenuator will eventually respond to the increase in the AGC
voltage by increasing its attenuation. The limiter control circuit on PC1 quickly responds to a 3dB
or greater instantaneous increase in the IF AGC Amplifier's LIMITER REFERENCE OUT voltage
J3-3 by pulling the LIMITER ENABLE IN J3-4 low, turning off transistor Q4 of the IF AGC Amplifier.
269
With Q4 turned off, the dc forward bias is removed from pin diode CR9, thus reducing momentarily
the IF output of the IF AGC Amplifier by approximately 20dB. The momentary attenuation in the
IF output by the limiter circuit allows sufficient time for the variable pin diode attenuator to adjust
itself to the change in the AGC voltage. Overdriving can also occur when the translator is first
turned on. To compensate, Q6 is on, turning on Q5. This shuts off Q4, increasing the attenuation
of CR9, as above, until C32 charges. Q6 and Q5 then turn off, allowing LIMITER ENABLE IN,
which is normally high, to turn on Q4. This forward biases CR9 by providing a dc path to ground
through it for the +15V from pin J3-5.
2.1n
Automatic-On:
Schematic B331-44/Rev C t A1PC2
The Automatic-On circuit uses differential amplifier U1A to compare the AGC voltage, developed
by the IF AGC Amplifier, to a preset reference voltage set by THRESHOLD ADJUST potentiometer
R4. An input signal above the minimum acceptable Receiver input level of 60dBm will produce
an AGC voltage above the Auto-On Threshold potential. As the AGC voltage (pin 3 of U1A)
exceeds the Auto-On Threshold reference voltage (pin 2 of U1A), differential amplifier U1A
saturates in the positive mode charging capacitor C1. Once C1 charges above the reference
potential at pin 6 of U18, differential amplifier U1B will also saturate in the positive mode turning
on transistor Q1. With Q1 forward biased, a ground is provided for relay K1 which energizes the
device. The closed contacts of K1 place +5Vdc on the INTLK (VIDEO SENSE) line going to the
Exciter’s Control Board (A2PC1). An Auto-On delay network consisting of R8, R9, and C1 slows
down the turn-on and turn-off activation time. This delay of approximately 30 seconds prevents
on/off cycling from occurring during periods of weak reception lasting for less than 30 seconds.
2.1o
Limiter/Output AGC Control:
Schematic B331-34/Rev C t A1PC1
The Limiter/Output AGC Control board monitors and controls the IF AGC Amplifier (A3) and
controls the CARRIER PRESENT LED (DS1) on the Receiver front panel.
The AGC negative reference voltage is placed on pin 3, OUTPUT AGC, by inverting op-amp U1B.
Potentiometer R9, AGC REF, sets this voltage. Keep the PRE AGC REF ADJ potentiometer fully
clockwise because it and the POWER REFERENCE portion of the AGC circuit, from pin 1 to pin 2,
are not used in this application.
LIMITER REFERENCE IN is brought in from A3 on pin 12 and is compared to an 11.8V reference
by U2B. When a carrier greater than 60dB is received, the output of U2B will saturate by
approximately +15V turning on Q3. This provides a path to ground through current limiting resistor
R23 on pin 10 for the CARRIER PRESENT LED (DS1) on the Receiver drawer front panel,
illuminating it green. If the received carrier level drops below 60dBm, U2B saturates to 15V
turning off Q3. The LIMITER ADJUST potentiometer, R13, voltage divides the LIMITER
REFERENCE INPUT and passes it through unity gain follower U2A and unity gain follower U2C.
U2D takes the difference between the 8.7V reference, from CR2, and the output U2C. For the
nominal level of the carrier being received, the output of U2C is less than 8.7V and U2D puts
approximately +15V on LIMITER ENABLE OUT, pin 9. The LIMITER ADJ is set so that, if
2610
LIMITER REFERENCE IN increases by 3dB, the output of U2C will be greater than 8.7V and U2D
will saturate to approximately 15V pulling down LIMITER ENABLE OUT.
2.1p
Aural Notch Filter:
Schematic Diagram 10383097/Rev 51 t A1FL2
Insertion Loss (J1-J2)
0.4dB Max.
The Aural Notch Filter provides a means of attenuating the aural carrier 3dB which can be useful
for reducing the effects of in-band and out-of-band intermodulation. Variable capacitor C3 tunes
the notch to the aural IF frequency in an NTSC system, 41.25MHz. This capacitor is preset by the
EMCEE Test Department. R1 sets the amount of attenuation; up to 3.5dB of attenuation can be
attained. The filter is a very high Q type and does not have an appreciable effect on the visual
carrier or color subcarrier.
2.1q
Multi-Output Power Supply:
Interconnection Diagram B326-18/Rev C t A1PS1
Voltage
Rated Current
+25Vdc
1Adc
±15Vdc
1Adc
±5Vdc
1Adc
As shown on the Interconnection Diagram, the Multioutput Power Supply consists of surge
suppressor E1, transformer T1, and printed circuit boards PC1 and PC2. PC1 is the +25V Power
Supply, and PC2 is the ±15V/±5V Power Supply. Surge suppressor E1 provides voltage-transient
protection for the step-down transformer T1 and the +25V Power Supply.
+25V Power Supply:
Schematic B326-15/Rev C t A1PS1PC1
The secondary voltage of step-down transformer A1PS1T1 is applied to bridge rectifier CR1. After
filtering, the rectified voltage (36V) is regulated by U1 to the +25Vdc level. The output voltage
of U1 is fixed by resistors R1, R2, and R3. +25Vdc is supplied to various modules in the Receiver
drawer.
2611
±15V/±5V Power Supply:
Schematic B326-12/Rev D t A1PS1PC2
120Vac is placed across the primary of step-down transformer T1. Surge suppressor E1 provides
voltage-transient protection for this supply. Transformer T1 supplies a secondary voltage to bridge
rectifier CR1. The output of CR1 is divided, with the negative voltage applied to 15Vdc regulator
U2 and the positive potential fed to +15Vdc regulator U1. Voltage regulators U3 and U4 tap off of
the 15V lines to provide +5Vdc and 5Vdc, respectively. The capacitors provide filtering for the
different regulators. ±15Vdc is supplied to the IF AGC Amplifier (A3), the Limiter/Output AGC
circuit (PC1), and the Automatic-On circuit (PC2). +5Vdc is supplied to the IF AGC Amplifier (A3).
2.1r
Digital Code ID Unit: (OPTIONAL)
Schematic 20258029/Rev A t A1PC3
According to FCC Rules and Regulations, Section 74.783, each television broadcast transmitter
in the United States of over 1 watt peak visual power must transmit its call sign in International
Morse Code every 60 minutes or arrange for the primary station to visually or aurally identify the
transmitter and its location. The Digital Code Identification Unit is available for the customer who
wishes to identify a transmitter station with Morse Code. The ID unit is a sixteen word by eight bit
sequencer which generates a series of pulses used to shift the frequency of the transmitted carriers
by frequency shift keying (FSK) the transmitter's Upconverter Oscillator.
The Digital Code ID Unit is composed of four integrated circuits: a Dual Timer (U4), a Dual 4 Bit
Counter (U3), a Programmable Read Only Memory (U2) and an 8 to 1 Line Multiplex (U1). The
Dual Timer or master clock contains two sections which control the operation of the ID unit by
dictating when and at what rate pulses will be fed to the Upconverter oscillator. The first section
of the timer is a gated astable oscillator or bit clock which produces square-wave pulses at a rate
of approximately 20Hz. The bit rate is controlled by U4 resistors R11, R12 and capacitor C2. The
second section of U4 is a 20 minute timer controlled by resistors R9, R10 and capacitor C1. When
C1 charges to 63% of its capacity (after 20 minutes), pin 9 of U4 will go low, reverse biasing
transistor Q3 which presents a high (4Vdc) at pin 4. This high gates on the bit generator which
feeds the 20Hz pulses to pin 1 of the Dual 4 Bit Counter (U3).
As each clock pulse reaches pin 1 of U3, the 4 Bit Counter "counts" the number of pulses entering
the chip and displays that count in binary code at its own pins 3, 4 and 5. For example, as the first
pulse is fed to U3, pin 3 goes high representing the decimal number 1 in binary code (001). With
the second clock pulse, U3 pin 4 goes high and pin 3 goes low representing the binary number 2
(010). This counting process will continue up to the number 7 (111) and, as the eighth pulse is fed
to the counter, pins 3, 4, and 5 will all go low (000) to begin the sequence over again. During this
time integrated circuit U2, the Programmable Read Only Memory (PROM), has a series of high and
low voltages present at its pins 1 through 9 (excluding pin 8 which is ground). These voltages are
bits which make up the first word (Morse code letters or numbers) of the transmitter's call sign.
(The transmitter's call sign is programmed into the PROM by the EMCEE test department.) In
order for this information to be delivered to the Upconverter oscillator, it must be converted from
parallel form to serial form by the 8 Line to 1 Line Multiplexer (U1). The binary numbers developed
by the Dual 4 Bit Counter are fed to pins 9, 10, and 11 of the 8 to 1 Line Multiplexer. Each binary
number (or voltage fluctuation) presented to U1 signals the multiplexer circuit to individually read
(take) the parallel bits presented by the PROM and deliver them serially to the oscillator via
transistor Q4. Therefore, as the Dual 4 Bit Counter (U3) feeds the binary numbers 1 (001) to pins
2612
9, 10 and 11 of the Line Multiplexer (bit address), the Multiplexer reads the bit at pin 1 of the
PROM (U2) and delivers it to the base of transistor Q4. With each subsequent binary number
(010, 011, 100, 101, 110, 111, 000) provided by the Dual Counter, the Line Multiplexer will read
each individual PROM bit present at U2 pins 2 through 9 (exclude pin 8) until the Dual Counter
reaches 111. The next pulse then resets the count to 0 (000). The transition from high to low (1
to 0) at pin 5 of the counter is seen by pin 13, causing pin 11 of U3 to go high. This binary
number 1 (0001) seen by pins 10, 11, 12 and 13 (word address) of U2 causes the PROM to present
the second set (word) of eight bits to the Line Multiplexer. The Dual Counter (U3 – pins 3, 4, 5)
presents another binary eight count to the Line Multiplexer (U1 – pins 9, 10, 11) which individually
reads the eight new PROM bits (U2 – pins 1 through 9) and delivers them to transistor Q4. At the
end of the second eight count, pin 13 of U3 again sees a high to low transition which causes pin 10
of U3 to go high while pin 11 goes low (binary number 2 = 0010). With U2 pins 10 through 13
receiving a binary number 2, a third word is presented to the Line Multiplexer by the PROM. This
entire process occurs so that the PROM delivers 16, eight bit words to the Upconverter oscillator
via the Line Multiplexer. After word 16, pins 8 through 10 of U3, which were all high (binary
number 16 = 1111), drop to zero. The negative going transition at pin 8 of U3 is coupled to
transistor Q1 via C3. This action forward biases transistor Q2 which discharges capacitor C1. As
the voltage at pin 12 of the Dual Timer drops, pin 9 goes high causing pin 4 of U4 to go low. The
Dual Timer's bit clock is gated off, disabling the Digital Code Identification Unit for 20 minutes until
capacitor C1 recharges.
2.2
Exciter/Upconverter Drawer:
Interconnection Diagram 40383113/Rev 55 t A2 TTU20F
8dBm peak visual
Composite IF IN (J1)
RF OUT (J2)
+43dBm peak visual
+33dBm average aural
+9dBm ± 2dBm
LO SAMPLE (J3)
The Exciter/Upconverter drawer converts the composite IF signal from the Receiver to the desired
UHF channel, then amplifies the RF signal to the desired output level. This drawer is used to drive
the two Dual 300W Final Amplifier Drawers (A3, A4). The Linearizer provides precorrection to the
composite IF signal. Upconversion is performed by the IF Upconverter (A1) along with the UHF
Synthesizer (A4). The UHF Synthesizer provides a programmable LO to the IF Upconverter
module where the LO and IF signal from the Receiver are mixed to create the desired UHF
frequency. The IF Upconverter also provides AGC and precorrector functions. The UHF signal
from the Upconverter module is passed through a UHF Bandpass Filter (FL1) to remove the
unwanted products from the conversion process while passing the desired signal with a minimal
loss. The RF is then amplified approximately 50dB by a 2W Driver Amplifier (A2) and then
amplified another 12dB by a 20W UHF Amplifier (A3). The output signal is passed through the
Metering Coupler (DC1). The Metering Coupler provides samples for the Metering Detector (A5)
while passing the signal to the output of the drawer.
Metering and control functions are provided by the Metering Detector, the Metering Switch (PC2),
and the Control Board (PC1). The Control Board also has several status and diagnostic LED
indicators. Power is supplied to the drawer by two power supplies, a ±15V/+5V linear supply (PS2)
and a +28V switching supply (PS1).
2613
2.2a
Linearizer:
Schematic Diagram 30367078/Rev 60 t A2A6
Gain with S1 OFF (J1-J2)
Gain with S1 ON (J1-J2)
Emitter of Q1/Q2
Emitter of Q3/Q4
Emitter of Q5
3dB min./6dB max.
6dB min./12dB max.
+4.8Vdc @ 13mAdc/+13Vdc @ 30mAdc
+3.3Vdc @ 11mAdc/+15Vdc @ 45mAdc
+8.7Vdc @ 22mAdc
The Linearizer is a five-stage circuit which compensates for linearity distortions generated by the
translator's Class AB power amplifiers. Transistors Q1 through Q5 are all amplifier stages with the
Q1/Q2 combination providing approximately 20dB of gain. 8dB of gain is provided by transistors
Q3/Q4. Q2, Q4, and Q5 are used as low impedance emitter followers. Variable gain expansion
networks which furnish linearity correction are centered around diodes CR1 through CR8, slope
potentiometers SL1 through SL4 (i.e., R10, R11, R21, R22), unity gain inverting amplifiers U1 and
U2, threshold potentiometers TH1 through TH4 (i.e., R37, R38, R39, R40), and switch S1. When
S1 is in the OFF position, each diode pair is continuously reverse biased throughout the positive
and negative cycles of the visual IF carrier. Due to the high reverse resistance provided by CR1
through CR8, each network essentially represents a resistive L-pad with the composite IF signal
attenuated by a fixed amount. As a result, no linearity correction is provided. However, when S1
is in the ON position and the Linearizer is properly adjusted, the four diode pairs form a nonlinear
circuit where each diode pair is biased to turn on at different points of the positive and negative
cycles of the visual IF carrier envelope. Each diode pair is initially reverse biased by equal but
opposite polarity dc voltages established by U1 and U2. L1 through L8, shunted by R29 through
R36, isolate the visual IF carrier from the diode biasing circuitry. When the positive and negative
peaks of the visual IF carrier are sufficient to forward bias a diode pair, the diode pair turns on
placing the resistance of its respective slope potentiometer either in parallel or in shunt to ground
with its respective series arm resistance. As a result of switching additional resistance in parallel
or shunt with the series arm of the L-pad, the attenuation of the visual IF carrier is reduced.
Threshold potentiometers TH1 through TH4 determine the turn-on point of each diode pair while
slope potentiometers SL1 through SL4 vary the amount of gain expansion achieved during the
turn-on period of each diode pair. Threshold controls TH1, TH2, and TH3 are used to adjust the
differential gain of the white to black region while TH4 adjusts the sync amplitude. When properly
adjusted, the Linearizer provides sync amplitude, differential gain, and intermodulation correction
to the RF output signal.
2.2b
IF/Upconverter:
Schematic Diagram 30383013/Rev 55 t A2A1
8dBm peak visual
13.5dBm minimum
IF INPUT (J1)
RF OUTPUT (J2)
LO SAMPLE (J3)
LO INPUT (J4)
+9dBm ± 2dB
+13dBm minimum
The IF/Upconverter performs three tasks in this translator. It provides signal precorrection, AGC
level control, and it upconverts the IF signal to the desired UHF channel. This module also
provides a sample of the LO signal to the Exciter’s front panel.
2614
The IF input at J1 is attenuated by AT1, an adjustable attenuator which can be tuned to
compensate for different input levels. A monolithic amplifier (U1) provides approximately 12dB
of gain to the signal passed through the attenuator. U1 is biased by R1 with L1 providing
impedance matching and isolation. C2 is an RF bypass capacitor, while C1 and C3 are coupling
capacitors. T1 steps up the signal's voltage to drive the precorrector circuit made up of CR1, C4
to C6, C8 to C12, R2 through R10, L4, L5, U2, and S1. This circuit compensates for linearity
distortions generated by the wideband power amplifiers or created by the Receiver. When switch
S1 is in the off position (open), this circuit reduces to a simple attenuator formed by R2 and R3;
therefore, no precorrection is provided. When S1 is on, the precorrector becomes a nonlinear
circuit that provides less attenuation for the positive and negative peaks of the IF signal, thereby
stretching the waveform. CR1 is biased by U2 A and B, with each op amp biasing one half of CR1.
The amount of bias provided by U2 is determined by R7 through R10. R9 allows the bias level to
be adjusted. This adjustment determines at which point on the waveform precorrection begins.
R5, R6, C8 through C11, L4, and L5 provide isolation between CR1 and U2. C4 to C6 are dc
blocking capacitors. The precorrector operates by placing R4 in parallel with R2 when the IF signal
is positive or negative enough to forward bias half of CR1. Adjusting R4 determines the amount
of precorrection provided. At the output of the precorrector, a second monolithic amplifier provides
+12dB of gain to the IF signal. C7 and C14 are coupling capacitors while C13 acts as an RF
bypass. L2 is an RF choke and R11 provides the correct bias voltage for U3.
The next circuit in the Upconverter is the AGC circuit. Three PIN diodes, CR2, CR3, and CR4,
form a voltage controlled attenuator along with R14 and C17. C14, C16, and C18 serve as dc
blocking capacitors. Bias is provided to this attenuator by R12, VR1, and R13, as well as R15, L3,
and the three operational amplifiers U4(A), U5(A), and U5(B). C15, C32, and C19 are bypasses.
The control voltage for the AGC is generated by U5(B). A dc voltage proportional to the output
power is connected to pin 6 of U5 by R26. A reference voltage from the Control Board's Power
Adjust circuit is supplied to pin 5 of U5 by R22. U5(B) compares these two voltages and provides
a control voltage at pin 7 of U5. R27 sets the gain of U5(B) to unity. U5(A) is an integrator that
provides a smooth transition for the changing control voltage. Input to U5(A) is provided by R20,
with C22 as the integration capacitor. A reference voltage is provided to pin 3 of U5 by R21 and
CR5 through CR7. The output of U5(A) is passed through an attenuator formed by R18 and R19
before driving the unity gain buffer amplifier formed by U4(A) R16 and R17. When the OPERATE/
ALIGN switch is in the ALIGN position, pin 3 of U4A is grounded. This defeats the AGC circuit and
allows minimum attenuation of the IF signal. Q1, R35-R37 and C33 make up a soft start circuit
that retards the spike in output power that normally would occur when the translator is turned ON
and the OPERATE/STANDBY switch is placed in the OPERATE position. The circuit places
approximately +13Vdc on pin 3 of U4A, putting the AGC circuit into a condition of maximum
attenuation. As C33 charges, this imposed voltage on pin 3 decreases giving the AGC circuit time
to stabilize before Q1 turns off and the output of U5A takes control of the AGC. Whenever +28V
switched is removed from the drawer (OFF or STANDBY), CR8 forward biases and C33 discharges
through it and R38 to ground. The output of U4(A) is the AGC control voltage.
The IF output of the AGC circuit connects to mixer MX1 where it is combined with the LO signal
from the synthesizer to produce the desired UHF channel frequency at the RF output port, J2. The
LO is brought to the mixer by R29 and R30 (which provide isolation) and U7, an amplifier that
provides about 12dB of gain to the signal. U7 is biased by R28. A sample of the LO is also
supplied to connector J3 via U6, the input of which is attenuated by R31 to R33. U6, biased by
R34, provides 12dB of gain. C24 to C27 are coupling capacitors, while all remaining capacitors
are RF bypasses.
2615
2.2c
UHF Synthesizer:
Schematic Diagram 30367094/Rev B t A2A4A1
10MHz REF. IN (J1)
LO OUT (J2)
SYNTH. LOCK (Pin A of J4)
3.5V P/P square wave
+15.25dBm min.
logic high (locked)
logic low (unlocked)
The UHF Synthesizer is a phase-lock loop type and uses one of the 10MHz reference signals from
the Reference Oscillator (A4A2) and develops a programmable LO signal for the Mixer (MX1) in
the IF Upconverter (A1). The frequency of the LO signal is calculated as the sum of the visual IF
carrier and the visual UHF carrier of the specified output channel. The LO signal's frequency is
programmed by the setting of switches S1 through S4 which are accessible through the module's
cover via access holes. The relationship between the setting of these switches and the resulting
LO frequency is provided in Table 261 for each UHF channel.
A 10MHz reference signal is brought in from the Reference Oscillator (A4A2) through J1, 10MHz
IN. Both sections of U4 perform binary divide-by-5 counting to provide a 400kHz signal to the
OSCin input of U1, pin 27. To create U1's internal 50kHz reference signal, U1 performs a binary
divide-by-8 operation on the OSCin signal.
Controlling the VCO, G1, is the output of op-amp U3. U3 compares and integrates the 0
/ V and 0/R
phase detector outputs of U1. The output of U3 is filtered to create the dc control voltage for the
VCO. The output of G1, RF OUT, is amplified by U5 and available as the Exciter/Upconverter's
LO at J2, OUT.
The output of G1 is also amplified by U6 and then fed to a ÷64/÷65 prescaler, U2. After prescaling,
the signal is connected to U1 pin 1, Fin, from U2 pin 4, OUT, completing the loop. The prescaling
factor of U2 is selected by the MOD CONTROL, pin 9, of U1. Switches S1 to S4 set two
divide-by-ratios, counters A and N, within U1. When divide-by-A is being performed on the signal
at Fin, MOD CONTROL is set high, selecting ÷64 in the prescaler, U2. MOD CONTROL goes low
for divide-by-N selecting ÷65 in U2.
The A and N counters form a binary number from A0 to N9 with A0 being the LSB and N9 being
the MSB. The decimal equivalent of this number, when multiplied by the internal reference
frequency 50kHz, gives the synthesizer's output frequency. Hence, for NTSC operation, A0 and
A1, pins 21 and 23 on U1, are grounded. For PAL operation, A0 and A1 are made high by cutting
the traces from pins 21 and 23 to ground thereby adding the 150kHz to the LO that is characteristic
of the PAL system.
When the synthesizer is locked onto a frequency, LD is high. This saturates Q1 and puts a low on
SYNTH LOCK. C28 provides a time delay to ensure that the synthesizer has successfully locked
before indicating so on the SYNTH LOCK line. For an unlocked condition, LD pulses low
preventing C28 from charging and saturating Q1. +5V is therefore present on the SYNTH LOCK
line for the unlocked condition.
2616
2.2d
Reference Oscillator:
Schematic Diagram 10368037/Rev B t A2A4A2
10MHz REF. OUT (J1, J2)
3.5V P/P square wave
The Reference Oscillator provides a 10MHz reference signal for the UHF Synthesizer (A4A1). This
module is centered around a 10MHz temperature-compensated crystal oscillator (G1). The output
from G1 is applied to two exclusive-OR gates used as inverting buffers. The output signal from
each gate is a 10MHz low-level square wave with a frequency stability of 0.3 parts per million
(PPM).
2.2e
UHF Bandpass Filter:
Schematic Diagram 10331209/Rev 52 t A2FL1
1dB Bandwidth (J1-J2)
Insertion Loss (J1-J2)
7MHz
3dB Max.
The UHF Bandpass Filter (FL1) consists of three tunable resonant cavities, with the three tuning
capacitors of the filter adjusted to provide the frequency response, shown in Figure 365, selecting
the appropriate UHF channel. FL1 is tuned to select the desired UHF mixer products from the
lower sideband or difference signal found at the RF OUTput (J2) of the IF/Upconverter (A1)
module.
2.2f
2W UHF Amplifier:
Schematic Diagram 30367002/Rev A t A2A2
Gain (J1-J2)
Power Output
50dB
+33dBm peak visual
+23dBm average aural
Flatness (J1-J2)
U1, PIN 3
U2, PIN 3
U3, PIN 4
Q1, Collector
±1dB from 470-860MHz
+3.9Vdc @ 29mA
+5.3Vdc @ 58mA
+20Vdc @ 100mA
+25Vdc @ 600mA
The 2W UHF Amplifier (A2) provides amplification to the selected UHF channel. The Amplifier is
a four-stage, class A, microstrip design. The first three stages are centered around broadband
monolithic amplifiers U1 through U3 which provide a combined gain of 40dB. The fourth stage is
an RF transistor amplifier Q1 which provides a gain of approximately 10dB. Q1 is biased by a dc
current regulator consisting of Q2, R4, R5, R6, R7, and R9. This circuit continuously maintains the
collector voltage and current of Q1 over a wide variation of load and temperature. The required
collector voltage and current of Q1 is established by potentiometer R5. Input matching for Q1 is
provided by C9, C10, C11, C12, and C24 while output matching is accomplished by C13, C14 and
C30. Capacitor C10 is tuned for maximum gain with a flat frequency response from 470 to
860MHz. C1, C3, C5, C8, and C14 provide signal coupling while all other capacitors are used for
2617
bypassing. Coils L1 through L4 function as RF chokes while R1 through R3 are used as biasing
resistors.
2.2g
20W UHF Amplifier:
Schematic Diagram 40383053/Rev 52 t A2A3
Gain (J1-J2)
Power Output
12dB min.
+44.5dBm peak visual/
+34.5dBm average aural
Flatness (J1-J2)
Collector of Q1 & Q2
±1dB from 470-860MHz
+26.8Vdc @ 1.2Adc (each side)
The 20W UHF Amplifier is a class A, broadband, microstrip design consisting of two RF transistor
stages centered around push-pull devices Q1 and Q2. These two stages are connected in parallel
via splitter CP1 and combiner CP2. Q1 and Q2 are biased by separate dc current regulators which
continuously maintain each collector voltage and current, over a wide variation of temperature and
signal level. Each current regulator is made up of PNP transistors Q3 and Q4 working with
potentiometers R4 and R11 to provide the required collector voltage and current for each side of
Q1 and Q2. CP1 and CP2 are Wireline quadrature 3dB,90( hybrid couplers which split and
combine power equally with resistors R5/R12 used to terminate the isolated port of each. The
function of R5/R12 is to absorb any imbalance that develops in either hybrid as well as to establish
a 50 ohm input/output impedance. Baluns Z1/Z3 transform the unbalanced signal into a balanced
input to drive the push-pull transistor pair of Q1/Q2. Baluns Z2/Z4 act in the opposite manner to
transform the balanced output from Q1/Q2 into an unbalanced output. Input matching for
transistors Q1/Q2 is provided by capacitors C1-3, C32, C65, C76/C18-C21, C66, C77, C80 while
output matching is accomplished by capacitors C43, C68-C70, C72, C81/C48, C53-C55, C74, C82.
Variable capacitors C79, C32, C80, and C18 are tuned for maximum gain with a flat frequency
response. Coils L1 through L8 function as RF chokes while capacitors C1, C2, C20, C21, C68,
C69, C54 and C55 are used for signal coupling. All other capacitors are used for bypassing.
Fault Circuit:
The Fault Circuit board (PC3) detects the presence of either an open or shorted RF device in the
20W UHF Amplifier. Under normal operation, the collector voltage on both sides of each push-pull
transistor in the 20W UHF Amplifier is typically +26.8Vdc. Under this condition, Q1 through Q3
of the fault circuit are turned on, the diodes identified by pins 1 and 3 in CR2 and CR3 are turned
on, the diodes identified by pins 2 and 3 are turned off, and the diodes identified by pins 1/14 and
7/8 of CR1 are turned on while those identified by pins 2/13 and 3/12 are turned off. Hence, for
normal operation of each push-pull RF transistor, the FAULT line (pin C of connector J3) is set at
a logic low (approximately 0Vdc) by the pull-down resistor (R10) or the Control Board (A2PC1).
However, if either side of one of the push-pull transistors opens, its collector voltage rises from
+26.8Vdc to about +27.4Vdc. This action results in turning off Q3 and Q2 as well as the diode
identified by pins 7 and 8 of CR1. With these components turned off, the diode identified by pins
3 and 12 of CR1 turns on applying a logic high (approximately +4.7Vdc) to the FAULT line. On the
other hand, if either side of one of the push-pull transistors shorts, the shorted transistor collector
falls from +26.8Vdc to about +0.2Vdc causing the diode identified by pins 2 and 3 of either CR2
or CR3 to turn on. This action results in turning off Q1 and the diode identified by pins 1 and 14
of CR1. With these components turned off, the diode identified by pins 2 and 13 of CR1 turns on
2618
applying a logic high to the FAULT line. The information on the FAULT line is processed by the
fault monitoring/display section of the Control board (A2PC1).
2.2h
Metering Coupler:
Schematic Diagram 10199178/Rev 52 t A2DC1
Insertion Loss (J1-J2)
FWD Coupling (J1-J3)
REFL Coupling (J1-J4)
<0.5dB
30dB
30dB
The Metering Coupler is a four-port device designed to provide forward and reflected RF samples
to the Metering Detector (A5) with minimal loss to the output signal. The RF signal is applied to
the coupler's input port (J1) and exits the coupler with a maximum of 0.5dB of loss at J2. A 30dB
sample of the signal's forward power is provided at J3, and a 30dB sample of the reflected power
is provided at J4. These two signals are connected to the Metering Detector (A5) which then
provides DC signals proportional to the output signal to the Control Board (PC1), the AGC circuits,
and the Metering Switch (PC2).
2.2i
Metering Detector:
Schematic Diagram 30368024/Rev P t A2A5
The Metering Detector contains three circuits for monitoring signal levels. Each of these circuits
can take an RF signal at its input and provide a DC voltage at its output proportional to the input
signal's strength. Only two of the detector circuits are used in this application. A sample of the
output signal is supplied to the VISual port of the detector, and a sample of the reflected power is
provided at the REFLected input of the detector. These signals are provided by the Metering
Coupler (DC1). The front end or detector portion of each circuit is basically the same. Diodes CR2
and CR4, together with their surrounding components, convert the sampled on-channel RF signals
to positive dc voltages proportional to the detected RF power. Detection of the sampled visual
output carrier is accomplished by CR2 in conjunction with R4 and C2 which form a time constant
of 1 second. R4 is the dc load while C1 and C11 form the RF ground of the visual power detector.
Detection of the sampled reflected signal is the same except for a faster time constant. R22/C6
forms a time constant of 1 millisecond. The positive dc voltages from the visual and reflected
power detectors are processed by buffer amplifiers U1 and U2 which provide voltage gains of 1V/V
and 2V/V, respectively. These buffer amplifiers also provide isolation between the % POWER
meter and the detectors. The settings of potentiometers R9 and R27 determine the voltage level
applied to the % POWER meter when the meter switch (PC2) is in its FWD or REFL positions,
respectively. The aural detector circuit is not used in this application.
A dc voltage proportional to the Exciter's output power is available at pin 5 of connector J4,
designated VISUAL POWER REFERENCE.
2619
2.2j
Control Board:
Schematic Diagram 40383016/Rev 62 t A2PC1
The Exciter’s Control Board (PC1) is mounted to the inside of the Exciter/Upconverter's front panel.
It provides various monitoring and control functions for the Exciter while displaying the results on
front panel indicators and the metering display. The circuitry can be divided into three sections:
(1)
(2)
(3)
Interlock Monitoring/Display
Amplifier Fault Monitoring/Display
Miscellaneous Control/Display
The Interlock section monitors the VIDEO SENSE from the modulator (optional), SYNTH LOCK,
the 20W amplifier TEMP SENSOR, VSWR OVLD, the +28V FINAL PS and OPERATE/STANDBY
switch. When these signals are of the appropriate level with the OPERATE/STANDBY switch set
to OPERATE and the POWER circuit breaker ON, the contactor (K1) closes placing the translator
on line. The FINAL BIAS, ON and SYNTH LOCK indicators are now illuminated green and the
TEMP EXCITER and VSWR OVLD indicators are unlit when the interlock is closed.
With baseband video present, the optional VIDEO SENSE line (J1-3) from the modulator is high.
The SYNTH LOCK line at J1-8 is low when the synthesizer is locked on frequency. This forces the
outputs of U1D and U1F high. U1F saturates Q9, illuminating the SYNTH LOCK LED (DS5) green.
If video is lost, the VIDEO SENSE line will go low. An unlocked synthesizer puts a high on the
SYNTH LOCK line causing the outputs of U1D and U1F to go low and Q9 to cut off, extinguishing
DS5. Should either of these situations occur, the output of U3A, which is normally high, will be
driven low. Note that the VIDEO SENSE line can be left unconnected and R30 will hold it high so
that the translator will operate.
The 20 WATT TEMP SENSOR line (J1-7) connects to ground through thermostat S1 mounted to
the heat sink of the 20 Watt UHF Amplifier, A3. When the temperature of the thermostat is below
150(F, the thermostat is closed. This pulls the 20 WATT TEMP SENSOR line low, driving inverter
U1H high and buffer U2H low. Temperatures in excess of 150(F cause the thermostat to open and
the 20 WATT TEMP SENSOR line goes high. This high drives U1H low and U2H high shutting
transistor Q8 off and extinguishing TEMP EXCITER LED DS4. DS4 is illuminated yellow when
U2H is forced high causing Q8 to conduct.
The FINAL AMPL TEMP SENSOR line (J1-24) in the Exciter monitors the momentary (10 second)
VSWR OVLD signal from the main Control Board (A5PC1)mounted behind the Front Panel (A5)
at the top of the translator cabinet. This line is normally low, driving U1B high and reverse biasing
CR1. When a VSWR OVLD occurs at the output of the translator, a high is present at J1-24 driving
U1B low. A low at the output of U1H or U1B forward biases CR1 or CR4, respectively, and places
a low on pin 5 of U3B which is normally high.
The final VSWR OVLD signal from the main Control Board (A5PC1) is applied to pin J1-5. Under
normal operation with the forward and reflected powers correctly set, this line is low. This turns Q1
off and Q2 on. U4A is set to have a high at Q/pin 6, and a low at Q/pin 5. The low at pin 5 turns
off Q5 and the red VSWR OVLD indicator (DS7). If the reflected power exceeds the reference
level set in the translator’s output Metering Detector (A5A7), the VSWR OVLD line goes high,
turning on Q1 and providing a discharge path for C11. C11, R22, and CR2 provide a quick on/
slow off circuit so that a transient does not trigger the VSWR OVLD circuit. When C11 has
discharged sufficiently, Q2 will shut off. This causes the CLK input, pin 3, of U4A to go from low
to high triggering the flip-flop action of U4A. Q is now high turning on Q5 and the red section of
DS7. Q is now low and places a low at pin 4 of U3B. The VSWR OVLD line returns to
2620
approximately 0.6Vdc when this occurs. The Exciter’s momentary VSWR RESET switch (S2)
resets U4A by grounding the CLR input/pin 1 when depressed. The REMOTE VSWR OVLD
RESET (J1-21) allows the VSWR overload circuit to be reset from a remote location through the
REMOTE MONITOR jack J4.
The output of U3B is normally high; however, if a low appears at either input of U3B, its output will
be driven low. The output of U3B connects to one input of U3D while the output of U3A connects
to the other input through the OPERATE/STANDBY switch. Under normal operating conditions,
the output of U3D is also high. If U3A goes low while S1 is in the OPERATE (closed) or STANDBY
(open) position or if U3B goes low, the output of U3D will be pulled low. When U3D is high, Q6 and
the green section of the FINAL BIAS indicator (DS6) are turned on, Q3 is off and the FINAL PS
INHIBIT line at J1-4 is floating. If U3D goes low, Q6 and DS6 turn off while Q3 turns on, grounding
the FINAL PS INHIBIT line which shuts down the power supplies of each 300 Watt UHF Power
Amplifier placing the translator in standby.
The output of U3C is normally high with U3D connected to one input of U3C. RF DRIVE
CONTROL J1-9 will also be high provided that all the +28V Power Supplies (A3PS1, A3PS2,
A4PS1, A4PS2) contained in the Dual 300W UHF Power Amplifier drawers are functioning
properly. If this is not the case or if U3D goes low, U3C will trip low turning off transistors Q7, Q4
and the ON indicator (DS8). With Q4 off, ground is removed from the CONTACTOR CONTROL
line (J1-11) and it is left floating. This deenergizes the contactor and removes +28V from the IF
Upconverter (A1), the 2 Watt UHF Amplifier (A2) and the 20 Watt UHF Amplifier (A3). During
normal operation U3C is high, turning on transistors Q7, Q4 and the green portion of LED DS8.
The CONTACTOR CONTROL line is pulled to ground through Q4. (Note that J1-9 cannot be left
unconnected or U3C will never go high.) Once the output of U3C goes low, it will remain in that
state until the condition which caused the low at either of U3C's inputs is corrected.
The Amplifier Fault Monitoring/Display section monitors the 20W AMPL FAULT line (J1-13) which
is low when the 20 WATT UHF AMPLIFIER module (A3) is functioning properly. A fault is
represented by a high on the line. For normal operation of the 20 WATT UHF AMPLIFIER, U1E
is high illuminating the green section of the DRIVER AMP indicator (DS1). At the same time, U2E
is low bypassing the red section of DS1. For a fault, the opposite occurs. U1E goes low
extinguishing the green section of DS1 and U2E goes high illuminating the red section of DS1.
There are three Miscellaneous Control/Display circuits. The POWER ADJUST potentiometer,
which is accessible through the front panel of the Exciter, sends a DC voltage to the AGC circuit
in the IF Upconverter (A1) to control the final output power of the translator. The OPERATE/
ALIGN switch engages or defeats the AGC circuit. In the ALIGN position, J1-23 is grounded and
the OPERATE indicator (DS9) is unlit. In the OPERATE position DS9 is illuminated green and the
OP/ALIGN line is an open circuit on the Control Board. The voltage on the METER line (J1-15)
is selected by the METERING SWITCH (PC2) mounted below the 30-segment LED bar graph
display on the front panel. Forward power (FWD), reflected power (REFL), +28V or +5V meter
indications can be chosen. The voltage level is decoded by three voltage level-indicator drivers
(U5-U7) and the appropriate number of LEDs are lit on the bar graph display (DS10-DS12).
2621
2.2k
Power Supplies:
Schematic Diagrams N/A t A2PS1, A2PS2
±15V/+5V Power Supply Outputs
±15Vdc @ 400mA maximum
+5Vdc @ 2A maximum
+28Vdc @ 9A maximum
+28V Power Supply Output
Two DC power supplies are used in the Exciter/Upconverter drawer to provide power to the
modules. A +28V supply is used to power the 2 Watt UHF Amplifier (A2) and the 20 Watt UHF
Amplifier (A3) while all other modules are powered by a ±15V/+5V supply. The ±15V/+5V unit is
a fully regulated, multiple output, linear power supply. The +28V supply is a high efficiency, single
output, switching power supply.
2.3
Power Splitter:
Schematic Diagram N/A t CP1
Insertion Loss (INPUT-OUTPUT)
Frequency
6.25dB
450-810MHz
The Power Splitter is a low-loss Wilkinson design which divides the output signal from the Exciter
drawer into four signals of equal magnitude and phase. These four in-phase signals are used to
separately drive the four parallel amplifier modules (A3A1, A3A2, A4A1, A4A2) contained in the
Dual 300W UHF Power Amplifier drawers.
2.4
Dual 300W Power Amplifier Drawer:
Interconnection Diagram 40386003/Rev 56 t A3, A4
+36.7dBm peak visual
+55.0dBm peak visual
VISUAL RF IN (J1, J4)
VISUAL RF OUT (J2, J5)
Visual Gain (J1-J2, J4-J5)
16dB min.
For final amplification this translator is composed of two Dual 300W Power Amplifier drawers (A3,
A4) containing two 300W amplifier assemblies in each drawer. Each amplifier assembly amplifies
an equal portion of the divided signal from the Power Splitter and provides approximately 300 watts
of peak visual power. The individual 300W amplifier unit includes a 60W UHF Amplifier pallet
(A1), a two-way Splitter (CP1), two 200W UHF Amplifier pallets (A2, A3), and a two-way Combiner
(CP2). The Diagnostic/Control circuitry consists of a Current Monitor board (A1PC1) and a 150(F
thermostat (A1S1). Power is supplied to each 300W amplifier assembly by a Single Output +28V,
750W Power Supply (PS1, PS2). Each drawer contains a Status Display board (PC1), which
drives the LED indicators on the drawer’s front panel showing power supply and temperature status.
2622
2.4a
300W UHF Amplifier:
Schematic Diagram 40386003/Rev 56 t A3A1, A3A2, A4A1, A4A2
Gain (J1-J2, J4-J5)
Flatness (J1-J2, J4-J5)
16dB min.
±1dB from 470-860MHz
Each 300W UHF Amplifier consists of a 60W UHF Amplifier (A1), a Splitter (CP1), two 200W UHF
Amplifiers (A2, A3), a Combiner (CP2), a Circulator (HY1), a Current Monitor (PC1), and a 150(F
thermostat (S1). The 60W UHF Amplifier and the two 200W UHF Amplifiers are class AB,
microstrip designs that provide at least 8dB and 7.5dB of gain, respectively. Each amplifier's gain
variation from 470 to 860MHz is typically ±0.75dB. The Splitter and Combiner are both two-section
Wilkinson couplers which separately contribute about 0.1dB of insertion loss. The Splitter divides
the signal from the 60W UHF Amplifier into two signals of equal amplitude and phase. These two
in-phase signals are used to separately drive the two 200W UHF Amplifiers. The Combiner joins
the amplified signals to form the output of the drawer. The Current Monitor is a Hall Effect sensor
which monitors the current drawn by the 60W UHF Amplifier and the two 200W UHF Amplifiers,
while applying a signal to the CURRENT SENSE line at pin 6 of connector J3. The information on
this line is processed by the fault monitoring/display section of the Control Board (PC1) located
behind the Front Panel (A5), which is mounted in the top rack position of the translator cabinet.
The thermostat monitors the temperature of the 300W UHF Amplifier's heat sink by grounding
pin B of A1PC1J2. If the temperature rises above 175(F, the thermostat opens, placing +5V on
pin 10 of CONTROL plug J3 or J6. In turn, the Control Board (A5PC1) responds by placing 5V on
Pin 9 of CONTROL plug J3 or J6 disabling the corresponding 28V power supply (PS1 or PS2). As
a result, +28Vdc is removed from the 60W UHF Amplifier and the two 200W UHF Amplifiers while
the appropriate TEMPERATURE indicator of the Status Display (PC1DS4 or PC1DS8) illuminates
yellow. At the same time the COLLECTOR BIAS indicator for that amplifier will extinguish.
2.4b
Status Display:
Schematic Diagram 30386105/Rev 52 t A3PC1, A4PC1
On each Dual Power Amplifier drawer the Status Display board monitors the +28Vdc voltages from
the corresponding Power Supply (PS1/PS2) as well as the status of each thermostat (A1S1/A2S1).
The results are displayed on the COLLECTOR BIAS (DS1/DS5) and TEMPERATURE (DS4/DS8)
indicators. When the translator's interlock circuit and the thermostats are closed, each power
supply provides +28Vdc to the corresponding 300W UHF Amplifier assemblies while the
corresponding DS1 and DS5 indicators are illuminated green and DS4 and DS8 are extinguished.
When the interlock circuit is opened, each Power Supply is disabled, +28Vdc is removed from each
300W UHF Amplifier, and the corresponding DS1 and DS5 indicators are extinguished while DS4
and DS8 remain out. However, if the circuit breaker on the Front Panel (A5) is in the ON position
and the circuit breaker on the Front Panel of the Exciter drawer (A2) is in the OFF position,
COLLECTOR BIAS indicators DS1 and DS5 will illuminate green. If either thermostat opens due
to high ambient temperature or an amplifier problem, each Power Supply is again disabled. This
is indicated by the corresponding DS1 or DS5 indicators being extinguished, and TEMPERATURE
indicators DS4 or DS8 illuminating yellow as appropriate.
2623
2.4c
+28V Power Supply:
Schematic Diagram N/A t A3PS1, A3PS2, A4PS1, A4PS2
The+28V Power Supply provides +28Vdc at up to 750W or 27A for the three amplifiers when the
translator's interlock circuit is closed. The power supplies are high efficiency, switching types with
power factor correction and remote inhibit lines. These power supplies provide the supply voltage
to the 60W and 200W UHF amplifier pallets within each 300W UHF Amplifier assembly. The
supplies are energized from the Front Panel Control Board (A5PC1) which provides a +5Vdc
enable signal to J1-2 of each supply via CONTROL plugs J3-9 and J6-9 of the amplifier drawers.
This occurs only when the translator’s interlock circuits are closed.
2.5
Power Combiner:
Schematic Diagram N/A t CP2
Insertion Loss (INPUT-OUTPUT)
Frequency
0.25dB
450-810MHz
The 4-way Power Combiner is a Wilkinson design that combines the four 300 watt amplified signals
from each of the Dual 300W UHF Power Amplifier Drawers (A3, A4). The recombined signal is
then applied to the Output Bandpass Filter (FL1) and Metering Coupler (DC1).
2.6
Metering Coupler:
Schematic Diagram N/A t DC1
Insertion Loss (J1-J2)
FWD Coupling (J1-J3)
REFLD Coupling (J2-J4)
<0.5dB
45dB
45dB
The Metering Coupler is a four-port directional coupler that provides samples of the translator’s
forward and reflected output power. These samples are used by the Metering Detector (A7) to
drive the output % POWER meter.
2.7
Front Panel:
Interconnection Diagram N/A t A5
Located in the top rack position, the Front Panel holds the AC POWER circuit breaker, the
Metering Detector (A7) and the Control Board (PC1).
2624
2.7a
Metering Detector:
Schematic Diagram 30368024/Rev P t A5A7
The Metering Detector contains separate but similar circuitry for monitoring the peak forward and
average reflected power at the output of the translator. Samples of these two RF signals are
supplied by the Directional Coupler mentioned above.
The front end or detector portion of each circuit is basically the same. Diodes CR2 and CR4,
together with their surrounding components, convert the sampled on-channel RF signals to positive
dc voltages proportional to the detected RF power. Detection of the sampled output carrier is
accomplished by CR2 in conjunction with R4 and C2 which form a time constant of 1 second. R4
is the dc load while C1 and C11 form the RF ground of the visual power detector. Detection of the
sampled reflected signal is the same except for a faster time constant furnished by R22/C6
(1 millisecond). The positive dc voltages from the visual and reflected power detectors are
processed by buffer amplifiers U1 and U2 which provide voltage gains of 1V/V and 2V/V,
respectively. These buffer amplifiers also provide isolation between the % POWER meter and the
detector. The settings of potentiometers R9 and R27 determine the voltage level applied to the
% POWER meter when the meter switch (PC1S1) is in its VISUAL or REFL positions, respectively.
The aural power detector is not used in this application.
A dc voltage proportional to the translator's forward output power is applied to pin 5 of connector
J4, designated VIS PWR REF. This voltage is fed back to the Exciter drawer's Control Board
(A2PC1). When the OUTPUT AGC switch (A2S2) is in its ON position, this voltage ultimately
controls the attenuation of the visual IF signal so that the translator's forward output power is
automatically maintained at its rated value.
A dc voltage proportional to the translator's reflected output power is fed to pin 10 of comparator
U2. This voltage is compared to a reference voltage at pin 9 whose magnitude is determined by
potentiometer R30. With R30 properly set (see paragraph 3.5b), the voltage on pin 10 will be
greater than the reference voltage whenever the translator's reflected power is more than 10% of
its rated forward power. As a result, the output of the comparator saturates in the positive mode
applying approximately +4Vdc to the VSWR OVLD line. This voltage instructs the Control Board
(PC1) that a VSWR overload condition has been detected. If the translator's reflected power is less
than 10% of its rated forward power, the voltage on pin 10 of comparator U2 will be less than the
reference voltage. As a result, the comparator saturates in the negative mode, diode CR1 is
forward biased, and approximately 0.7Vdc is applied to pin 7 of connector J4. This voltage
instructs the Control Board that no VSWR overload condition exists and, therefore, no action is
taken.
2.7b
Control Board:
Schematic Diagram 40386012/Rev 55 t A5PC1
The Control Board provides various monitoring, control and display functions in conjunction with
an interface for remote monitoring. The circuitry of this board can be divided into four sections:
(1)
(2)
(3)
(4)
VSWR OVLD Monitoring/Interlock Control
300 Watt UHF Power Amplifier Fault Monitoring/Display
300 Watt UHF Power Amplifier Temperature Monitoring/DC Control
Metering Display
2625
The VSWR OVLD Monitoring/Interlock Control section is made up of two separate circuits. One
monitors the VSWR OVLD and the Remote ON/OFF. This circuit is centered around two one-shot
multivibrator circuits, U1A and U1B, and a two-bit binary counter formed by flip-flops U2A and U2B.
The other circuit is comprised of three OR gates U16A, C, D, and monitors the Fault lines for the
four 300 Watt Power Amplifiers.
Under normal operating conditions the VSWR OVLD line (J2-14) is low and Q1 is turned off with
+5V at its collector. The OUTput of U1A (pin 5) is low and becomes inverted by U10D before being
ANDed with the REMOTE ON/OFF (J2-1) signal at U4A. The high output of U4A is inverted by
U10E, placing a low at J1-1 which is fed to the Control Board of the Exciter (A2PC1). The
REMOTE ON/OFF line is high for an ON condition and low for an OFF condition. If the REMOTE
ON/OFF is not connected, R12 holds the line high simulating a REMOTE ON. U4D ANDs together
the normally low Q outputs (pins 5 and 9) of U2A and U2B producing a low at its output. When the
Exciter drawer’s POWER circuit breaker is set to ON, the outputs of U2A and U2B are cleared as
Q2 provides a ground to the CLR pins 1 and 13. Q2 is turned on because the +15V supply rises
to +5Vdc before the +5V supply does producing a negative voltage at the output of U7A. After the
+5V supply reaches +5Vdc, +0.3V higher than the inverting input is clamped by zener diode VR1,
the output of U7A goes high turning off Q2. The low output of U4D is ANDed with the normally low
OUTput of U1B at U4C which delivers a low to the Exciter drawer on pin J1-19, EXCITER VSWR
OVLD.
When REFLected power exceeds 10% of the FWD power (or whatever ratio the trip point was set
at), the VSWR OVLD line (J2-14) from the Metering Detector is pulled high. This action turns on
Q1 grounding the TRIG inputs of U1A and U1B and the CLR input of U2A. The OUTput of U1A
goes high for 10 seconds, placing a high on J1-1 and shutting down the translator. For
4 1/2 minutes the OUTput of U1B will also be high. When the translator is shut down, there is no
output power and the VSWR OVLD line goes low turning off Q1. The resulting low to high
transition at the collector of Q1 triggers the clock input of U2A, flip-flopping its outputs so that Q
is now high. If the reflected power exceeds 10% a second time within four minutes of the first, U1A
will again shut the translator down for 10 seconds and then bring it back up. U1B will continue to
be high and the Q outputs of U2A and U2B will count up one. A third occurrence of a VSWR
overload within approximately four minutes of the first will have the same results as the previous
occurrence except that, when U1A brings the system back on line, the flip-flop counter will reach
binary three; the Q outputs of U2A and U2B will both be high. This causes the output of U4D to
go high which, together with the high OUTput of U1B, drives U4C high placing 5V on J1-19, the
EXCITER VSWR OVLD line.
The AMPL FAULT lines from the four 300 Watt UHF Power Amplifiers are monitored by OR gates
U16A and U16C. These lines are normally high, driving the output of U16D high and holding the
RF DRIVE CONTROL line at +5V which connects back to the interlock section of the Exciter’s
Control Board (A2PC1). Provided the power amplifier’s +28V Power Supply is turned on and
operating correctly, this line will stay high. Otherwise, it will go low and the Interlock circuit will
open placing the translator in standby.
The 300 Watt UHF Power Amplifier Fault Monitoring/Display section gets its input signals from the
four CURRENT SENSE lines (J1-21, J1-3, J1-2, and J1-22) furnished by the Hall Effect CURRENT
MONITORS (A1PC1 and A2PC2) mounted with each amplifier. Each of these signals is passed
through its own unity gain amplifier (U20A through U20D) and is sent out on the REMOTE
CURRENT SENSE lines to an optional REMOTE MONITOR via J1-5, J1-6, J1-23 and J1-24.
The four U6 op-amps, in conjunction with U7C, produce a voltage that is the average of the four
CURRENT SENSE voltages. With the four U6 op-amps wired as unity gain amplifiers, the voltage
at pin 10 of U7C is equal to one half of the average input to U6A, U6B, U6C and U6D. Normally
the voltage at pin 8 of U7C is near 0V and negligible. The U8 op-amps compare each of the
2626
buffered CURRENT SENSE input signals to 86% of the average. When the translator is ON and
the 300 Watt UHF Power Amplifiers are operating normally, the outputs of U6A, U6B, U6C, and
U6D are each greater than 86% of their average causing U8A, U8B, U8C, and U8D to saturate to
+15V. The resistive voltage divider at the output of each U8 op-amp divides the +15V down to
4.2V, a TTL level, for input to the inverters and buffers – U9 and U10. This causes the associated
U9 buffers to be high, illuminating the green section of indicators AMPL 1 (DS1), AMPL 2 (DS2),
AMPL 3 (DS3), and AMPL 4 (DS4). At the same time the U10 inverters are low, forward biasing
diodes CR9, 11, 13 and 15 while extinguishing the red section of the indicators.
If a CURRENT SENSE voltage from one of the 300W Amplifiers drops by more than 14%, the
output of its corresponding U8 comparator will go to 15V and the inputs of the associated inverter
and buffer will go to 0.5V. This extinguishes the green section of the associated AMPL indicator
and illuminates the red section.
Because the four 300W Power Amplifiers (A3A1, A3A2, A4A1, A4A2) may not all draw the same
current, the CURRENT SENSE circuit sometimes can indicate that a fault has occurred when the
amplifiers are actually operating within tolerance. To prevent this, each input has a balance
potentiometer, R20, R25, R29 and R34. These can be adjusted so that the inputs to each of the
four U6 op-amps are the same level. Section 3.7 explains the procedure for adjusting these
potentiometers.
The 300 Watt UHF Power Amplifier Temperature Monitoring/DC Control section takes the
THERMAL MONITOR lines from the Power Amplifiers as its inputs. Normally these lines (J1-15,
J1-34, J1-16, and J1-35) are low. The circuit containing U7D and Q3 is identical to the U7A/Q2
circuit in the VSWR OVLD section. When the translator is turned on, Q3 conducts clearing
flip-flops U12A, U12B, U11A, and U11B. This sets the flip-flop outputs to their normal states where
Q is low and Q is high. The Q outputs drive the THERMAL OVLD INDICATOR lines along with the
U19 buffers which drive the REMOTE THERMAL OVLD INDICATOR lines connector to REMOTE
MONITOR plug J4 (pins 14 thru 17). Each Q output connects to a U14 NAND gate and, being
normally low, the output of each NAND gate holds its connected transistor (Q4 through Q7) in the
on condition so that the DC CONTROL lines are high.
If the translator’s Interlock system opens, the FINAL PS INHIBIT at pin J1-29 will go low, driving
U14A, B, C, and D high. This will turn off their respective transistors (Q4 thru Q7) thereby
grounding the DC CONTROL lines and shutting off each 300 Watt UHF Power Amplifier +28V
Power Supply. With the +28V Power Supply off in each Power Amplifier, the voltage on the
CURRENT SENSE lines will be 0V. This could cause one or more of the AMPLIFIER STATUS
indicators to illuminate red incorrectly indicating a fault in an amplifier. Inverter U10C corrects this.
A low on the FINAL PS INHIBIT line drives U10C high placing a small positive voltage on pin 9 of
U7C. This voltage is approximately 0.1V and is sufficient to keep the outputs of the U8 op-amps
saturated at +15V and the AMPLIFIER STATUS indicator illuminated green. The FINAL PS
INHIBIT line is normally high and originates on the Exciter’s Control Board (A2PC1).
When an amplifier’s heat sink temperature exceeds 150(C, its THERMAL MONITOR line goes
high triggering the associated flip-flop and driving the corresponding THERMAL OVLD INDICATOR
line high. The REMOTE THERMAL OVLD INDICATOR line is also forced high along with NAND
gate U14, which shuts down the PNP transistor supplying +5V to the amplifier’s DC CONTROL line.
0V on one of the DC CONTROL lines shuts off the appropriate +28V Power Supply and its
associated Power Amplifier. The affected amplifier and power supply will remain off until the
MOMENTARY TEMP RESET switch is depressed triggering the CLR inputs on the U11 and U12
flip-flops. (Removing and reapplying AC POWER to the translator will also clear the flip-flops.)
Because this type of fault places an amplifier’s power supply in standby, its CURRENT SENSE
level drops to 0V causing the appropriate AMPL fault indicator to illuminate red.
2627
The RF ENABLE IN line at J2-8 takes the switched +28V from the EXCITER drawer (A2) and
voltage divides it to a high TTL logic level for the RF ENABLE OUT pin at J2-7. This provides a
logic signal to the REMOTE MONITOR plug J4 (pin 23) indicating that RF drive has been enabled
(high) or disabled (low).
The Metering Display section consists of three 10-segment LED bar graphs (DS6, DS7 and DS8)
and their drivers (U13, J17 and U18). Switch S1 selects the FORWARD or REFLected voltage
directly from the Metering Detector at J1-36 or J1-17 and delivers it to the LED drivers. Unity gain
op-amps U21C and U21A provide FORWARD METER and REFLected METER signals to the
REMOTE MONITOR plug (J4) via pins J1-37 and J1-18 respectively.
2.8
Output Filter:
Schematic Diagram N/A t FL1
Insertion Loss (J1-J2)
<0.5dB
The Output Filter, located in the bottom of the translator cabinet, is a multisection bandpass
resonant cavity type. This filter is tuned to channel by the EMCEE test department and is not field
serviceable. If it becomes necessary to have the filter retuned, contact the EMCEE Customer
Service Department for a return authorization.
2628
UHF SYNTHESIZER PROGRAMMING CHART (NTSC)
Channel
Visual Frequency
(MHz)
LO Freq
(MHz)
S4
S3
S2
S1
14
471.25
517
15
477.25
523
16
483.25
529
17
489.25
535
18
495.25
541
19
501.25
547
20
507.25
553
21
513.25
559
22
519.25
565
23
525.25
571
24
531.25
577
25
537.25
583
26
543.25
589
27
549.25
595
28
555.25
601
29
561.25
607
30
567.25
613
31
573.25
619
32
579.25
625
33
585.25
631
34
591.25
637
35
597.25
643
36
603.25
649
Table 261
Page 1 of 3
UHF SYNTHESIZER PROGRAMMING CHART (NTSC)
Channel
Visual Frequency
(MHz)
LO Freq
(MHz)
S4
S3
S2
S1
37
609.25
655
38
615.25
661
39
621.25
667
40
627.25
673
41
633.25
679
42
639.25
685
43
645.25
691
44
651.25
697
45
657.25
703
46
663.25
709
47
669.25
715
48
675.25
721
49
681.25
727
50
687.25
733
51
693.25
739
52
699.25
745
53
705.25
751
54
711.25
757
55
717.25
763
56
723.25
769
57
729.25
775
58
735.25
781
59
741.25
787
Table 261
Page 2 of 3
UHF SYNTHESIZER PROGRAMMING CHART (NTSC)
Channel
Visual Frequency
(MHz)
LO Freq
(MHz)
S4
S3
S2
S1
60
747.25
793
61
753.25
799
62
759.25
805
63
765.25
811
64
771.25
817
65
777.25
823
66
783.25
829
67
789.25
835
68
795.25
841
69
801.25
847
Table 261
Page 3 of 3
UHF SYNTHESIZER PROGRAMMING CHART (PAL)
Channel
Visual Frequency
(MHz)
LO Freq
(MHz)
S4
S3
S2
S1
21
471.25
510.15
22
479.25
518.15
23
487.25
526.15
24
495.25
534.15
25
503.25
542.15
26
511.25
550.15
27
519.25
558.15
28
527.25
566.15
29
535.25
574.15
30
543.25
582.15
31
551.25
590.15
32
559.25
598.15
33
567.25
606.15
34
575.25
614.15
35
583.25
622.15
36
591.25
630.15
37
599.25
638.15
38
607.25
646.15
39
615.25
654.15
40
623.25
662.15
41
631.25
670.15
42
639.25
678.15
43
647.25
686.15
44
655.25
694.15
For PAL operation the grounds to Pins 21 and 23 of U1 (MC145152) must be removed.
Table 261
Page 1 of 2
UHF SYNTHESIZER PROGRAMMING CHART (PAL)
Channel
Visual Frequency
(MHz)
LO Freq
(MHz)
S4
S3
S2
S1
45
663.25
702.15
46
671.25
710.15
47
679.25
718.15
48
687.25
726.15
49
695.25
734.15
50
703.25
742.15
51
711.25
750.15
52
719.25
758.15
53
727.25
766.15
54
735.25
774.15
55
743.25
782.15
56
751.25
790.15
57
759.25
798.15
58
767.25
806.15
59
775.25
814.15
60
783.25
822.15
61
791.25
830.15
62
799.25
838.15
63
807.25
846.15
64
815.25
854.15
65
823.25
862.15
66
831.25
870.15
67
839.25
878.15
68
847.25
886.15
For PAL operation the grounds to Pins 21 and 23 of U1 (MC145152) must be removed.
Table 261
Page 2 of 2
SECTION III
MAINTENANCE
3.1
Periodic Maintenance Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
3.2
Recommended Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
3.3
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
3.3a
3.3b
3.3c
3.3d
3.3e
3.4
3 62
3 62
3 63
3 63
3 64
Translator Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
3.4a
3.4b
3.5
Front Panel Control Board Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dual 300W Power (Final) Amplifier Drawer Indicators . . . . . . . . . . . . . . . . . . . . . . .
UHF Exciter/Upconverter Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Receiver Drawer Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TU1000F V/U Troubleshooting Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Receiver Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
Exciter/Upconverter Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3611
Output Power Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3612
3.5a
3.5b
Forward Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3612
Reflected Power (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3613
3.6
Precorrection Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3614
3.7
Control Board Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3614
3.8
Remote Monitor Signal Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3616
3.9
Spare Modules and Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S61
iii
SECTION III
MAINTENANCE
3.1
Periodic Maintenance Schedule:
CHECK
3.2
RECOMMENDATION
ALIGNMENT
Upon installation and at one-year intervals
thereafter (see section 3.4).
OUTPUT POWER CALIBRATION
SAME AS ABOVE (see section 3.5).
FANS
Inspect as often as possible (at least monthly)
and clean when necessary. No lubrication
needed.
Recommended Test Equipment:
EQUIPMENT
MANUFACTURER
MODEL #
Digital Multimeter
HEWLETT PACKARD
E2378A
Oscilloscope
TEKTRONIX
2232
Sweep Generator
WAVETEK
2001
50 Ohm RF Detector
TELONIC BERKELEY
8553
20dB Attenuator
NARDA
766-20
20dB Directional Coupler
NARDA
3001-20
50 Ohm, 1000W Dummy Load
BIRD
8833
Power Meter
HEWLETT PACKARD
435B
Step Attenuator
KAY
1/432
Frequency Counter
HEWLETT PACKARD
5386A
Spectrum Analyzer
HEWLETT PACKARD
8594E
NTSC Video Generator
TEKTRONIX
TSG100
361
3.3
Troubleshooting:
If the output signals from the translator appear distorted, noisy or nonexistent, consider the
following procedure as a troubleshooting aid. This procedure assumes the translator wiring as well
as the cabling and connectors are trouble free. It also assumes the Receiver drawer is receiving
the appropriate input signal while providing the required visual and aural IF carriers. The general
problem area will be indicated by simply checking the front panel diagnostic lights as well as the
% POWER meters. The diagnostic indicators are located on the front panels of the UHF Exciter/
Upconverter (A2), the Front Panel (A5) and the Dual 300W Power (Final) Amplifier drawers (A3,
A4).
3.3a
3.3b
Front Panel Control Board Indicators:
1.
Under normal operation all indicators will be lit green and the RF POWER meter will furnish
a 100% indication with the meter switch placed to FWD.
2.
Under standby conditions, all indicators will be lit green.
3.
Any AMPLIFIER STATUS/AMPL 1, 2, 3 or 4 indicator which turns red during normal
operation signifies an amplifier module or power supply malfunction within the drawer
specified. Typically the COLLECTOR BIAS LED associated with the failed amplifier or
power supply will extinguish unless the announced amplifier failure is an open. In either
case, replace the malfunctioning Final Amplifier drawer. If the operator has the appropriate
technical experience to locate the malfunction, he may repair the Final Amplifier drawer by
replacing its power supply or its power amplifier heat sink assembly instead of replacing the
entire drawer.
Dual 300W Power (Final) Amplifier Drawer Indicators:
COLLECTOR BIAS indicator monitors the voltage applied to the 60 watt driver and two 200 watt
final amplifier pallets within the 300W amplifier module. If the power supply malfunctions, this
green indicator will turn off. When a COLLECTOR BIAS indicator goes out, the associated Front
Panel Control Board (A5PC1) AMPLIFIER STATUS/AMPL 1, 2, 3 or 4 indicator will turn red.
The TEMPerature indicator monitors the thermostat fixed to the heat sink of the drawer's amplifier
section. If the heat sink temperature exceeds 150(F due to high ambient temperature or because
of an amplifier malfunction, the thermostat will open shutting off the amplifier's power supply and
illuminating the yellow TEMP indicator. Since the 28Vdc power supply is now off, the
COLLECTOR BIAS LED will have turned off and the related Control Board AMPLIFIER STATUS
(1, 2, 3 or 4) indicator will turn red. If any of the above malfunctions occur, the Final Amplifier
drawer should be substituted or, depending on the problem's location, the drawer's power supply
or amplifier section should be replaced.
362
3.3c
UHF Exciter/Upconverter Indicators:
Under normal operating conditions, the OPERATE/ALIGN and STBY/OPERATE switches will be
in the OPERATE position, the FINAL BIAS, ON, OPERATE, SYNTH LOCK and DRIVER AMP
indicators should be illuminated green and the VSWR OVLD and TEMP EXCITER LEDs should
be extinguished.
If the DRIVER AMP LED is lit red, the 20 watt amplifier has failed. Replace the 20 watt amplifier
module.
The green SYNTH LOCK indicator turns off when the Exciter's frequency synthesizer is not
properly locked. Also, the green FINAL BIAS and ON LEDs will turn off. If the problem persists,
the synthesizer should be replaced.
An extinguished ON LED with all other LEDs remaining in their normal states indicates a fault in
the Exciter’s +28V power supply. Replace the power supply.
The TEMP indicator monitors the thermostat fixed to the heat sink of the drawer's 20 Watt
Amplifier. If the heat sink temperature exceeds 150(F due to high ambient temperature or
because of an amplifier malfunction, the thermostat will open, illuminating the Exciter’s yellow
TEMP indicator. This will also cause the FINAL BIAS and ON LEDs to turn off indicating that the
+28V has been removed from the Exciter’s 2 watt and 20 watt amplifiers. Replace any faulty
modules and ensure that fans are operational and have adequate room to ventilate the drawer.
If the FINAL BIAS and ON LEDs are extinguished for 10 seconds and then come back on with all
other LEDs remaining in their normal states, the system was in a state of temporary VSWR
overload. If this occurs two more times within a 4 1/2 minute period, the VSWR OVLD indicator
will illuminate and the translator will be placed in a permanent standby mode. This condition is
accompanied by the FINAL BIAS and ON indicators remaining off, indicating that the +28V has
been removed from the Exciter’s 2 watt and 20 watt amplifiers. Under this condition, the cause of
the VSWR problem at the translator's output must be cleared before lifting the VSWR OVLD
RESET switch to reactivate the unit. If the FINAL BIAS and ON LEDs are extinguished and do not
come back on and all other LEDs remain in their normal states, this indicates that the appropriate
receive signal is not being detected at the input of the Receiver drawer. Check the receive
antenna, preamplifier (if used) and the down lead cabling to ensure that the receive signal is
present. If the receive signal is present, troubleshoot the Receiver.
The OPERATE indicator will be green if the position of the OPERATE/ALIGN switch is up. This
is the appropriate position when the translator is on the air. The OPERATE/ALIGN switch should
only be in the ALIGN position (down) while performing sweep alignment of the Exciter. This switch
position sets the AGC for minimum signal attenuation.
3.3d
Receiver Drawer Indicators:
The CARRIER PRESENT green LED indicates that the Receiver is seeing an input signal of
appropriate frequency and amplitude necessary to develop the IF AGC voltage which places the
translator in operation.
363
3.3e
TU1000F V/U Troubleshooting Chart:
The following chart is meant as an aid for uncovering faults that have developed in this translator.
During normal operation, all indicator LEDs are green, except the VSWR OVLD LED which is
normally extinguished. This chart lists the LEDs that are indicating a fault (i.e., are not in their
normal state). If a problem develops, note the state of the indicator LED and compare it to the
chart.
TU1000F V/U TROUBLESHOOTING CHART
PROBLEM
NO OUTPUT
POWER
INDICATORS
CAUSE
ALL EXCITER
INDICATORS
UNLIT
SYNTH LOCK
ON
FINAL BIAS
FINAL BIAS
ON
ON
DRIVER AMP
TEMP
FINAL BIAS
ON
SOLUTION
+5VDC Power Supply
faulty or shorted
Check Meter reading for
5V. Replace power
supply if necessary.
UNLIT
UNLIT
UNLIT
Defective Synthesizer
Check synthesizer for
correct output level and
frequency. Replace if
faulty.
UNLIT
UNLIT
Operate/Standby switch
on Standby
Place switch to Operate.
Turned off by Remote
Ensure translator has not
been turned off by
remote.
No signal detected at
input of Receiver
Check cabling. Troubleshoot Receiver if faulty.
Temporary VSWR
overload
Will return after
10 seconds.
+28V Exciter Supply
faulty
Replace power supply.
20 Watt Amplifier faulty
Replace module.
High ambient
temperature
Ensure fans are operational and have adequate
room ventilation. If
problem persists, check
for faulty operation of
amplifier and replace if
necessary.
UNLIT
RED
YELLOW
UNLIT
UNLIT
364
TU1000F V/U TROUBLESHOOTING CHART
PROBLEM
NO OUTPUT
POWER
INDICATORS
VSWR OVLD
ON
FINAL BIAS
CAUSE
RED
UNLIT
UNLIT
VSWR overload has
occurred.
SOLUTION
Check the transmission
line and antenna for high
VSWR. Repair or
replace any component
with a high VSWR.
Clear problem at
translator’s output, then
lift the VSWR OVLD
RESET switch.
No fault indicated
LOW OUTPUT
POWER OR
DISTORTED
OUTPUT
No Fault indicated
TEMPERATURE YELLOW
COLLECTOR BIAS UNLIT
AMPL 1,2,3 or 4
UNLIT
COLLECTOR BIAS
AMPL 1,2,3 or 4
UNLIT
RED
365
Receiver failure
Repair Receiver.
Bad cable
Check cabling between
the Receiver and Exciter.
Output Power Calibration
is incorrect
See Section 3.5.
Receiver malfunction
Repair Receiver.
High loss in one of the
modules
Test each module for
correct gain/loss. See
Signal Flow Diagram
(Fig. 362) for gains/
losses.
RF chain misaligned
See Section 3.4.
Precorrector improperly
adjusted or not turned on
See Section 3.6.
Heat sink temperature too
high due to high ambient
temperature
Ensure fans are operational and have adequate
room ventilation.
Heat sink temperature too
high due to amplifier malfunction
Replace faulty amplifier
assembly.
Faulty +28V Power
Supply
Replace power supply.
Power supply exceeded
current limit due to malfunctioning amplifier
module
Replace amplifier
assembly.
TU1000F V/U TROUBLESHOOTING CHART
PROBLEM
INDICATORS
CAUSE
LOW OUTPUT
POWER OR
DISTORTED
OUTPUT
AMPL 1,2,3 or 4
CONTACTOR
CYCLES
28VDC reading on Exciter
% power meter will cycle
HIGH OUTPUT
POWER AND
DISTORTED
RED
Several red bars on % RF
POWER meter lit and
POWER ADJUST does not
reduce output
366
SOLUTION
Faulty 300W Amplifier
Replace amplifier
assembly.
Internal Short on 28V
Unplug each module and
check for a short.
Replace module(s) or
amplifier assembly as
needed.
Power Supply folds back
when under a load
Replace Power Supply.
AGC loop is broken
Ensure OPERATE/ALIGN
set to OPERATE.
Misaligned AGC trap in IF
AGC Amplifier
Readjust visual IF trap
inductor core.
IF AGC Amplifier or
Limiter/Output AGC
circuit failure
Replace IF AGC Amplifier
or Limiter/Output AGC
PC board.
Failure in Exciter IF
Converter
Replace IF Converter
module.
3.4
Translator Alignment:
3.4a
Receiver Alignment:
1.
Remove the four screws on the front panel of the Receiver drawer, carefully pull out the
drawer, and remove the top cover. Set up the test equipment as shown in Figure 364.
Place the Receiver's front panel AC POWER switch (S2) to ON and place the Exciter’s front
panel AC POWER switch (A2CB1) to OFF.
2.
Disconnect the coaxial cable from the output connector of the Vectron Oscillator. Connect
a power meter to the output of the oscillator (point A of Figure 364). An indication of 3mW
to 6mW should be present. (If the oscillator’s output power is low or nonexistent, return the
oscillator to EMCEE for repair or replacement as this is not a field repairable item.)
3.
Connect a frequency counter to the oscillator output and wait approximately fifteen (15)
minutes for the oscillator to heat or until the frequency stabilizes.
4.
If the measured frequency differs by more than 50Hz from the oscillator’s designated
frequency, proceed to step #5. If the measured frequency is within 50Hz of the designated
frequency, then remove the frequency counter from the output of the oscillator, reconnect
this module to the input of the multiplier and proceed to step #7.
5.
Remove the cover screw from the side of the oscillator exposing the access hole and, with
a small tuning tool, slowly vary the frequency adjust potentiometer for the correct frequency.
6.
Remove the frequency counter from the output of the oscillator and reconnect this module
to the input of the multiplier (A3).
7.
Remove the retaining screws and lift the multiplier module off the Receiver's chassis.
Connect a spectrum analyzer to the output connector (J2) of the multiplier (point B of
Figure 364). Tune the spectrum analyzer to either the second, fourth, or sixteenth harmonic
of the oscillator frequency depending on whether a X2, X4, or X16 Multiplier is being used.
(The X2 Multiplier is used for VHF channels 2-6, the X4 Multiplier is used for VHF
channels 7-13, and the X16 Multiplier is used for UHF channels 14-69). Carefully "touch up"
the capacitors accessible through the bottom cover of the module for maximum power
(10 to 30mW) at the proper harmonic of the oscillator frequency. If power is low or
nonexistent, proceed to step #8, #9, or #10 depending on whether a X2, X4, or X16
Multiplier is being used. Otherwise, proceed to step #11.
8.
X2 Multiplier (Ch.2-6)
a.
Remove the module's bottom cover and tune capacitors C7, C12, C13, C14, C15,
C16, C17 and inductors L6, L7, L8 for a minimum of 10mW at the oscillator's second
harmonic (see Schematic B280-35). Insure that the fundamental and other harmonics
are at least 20dB below the second harmonic.
NOTE:
If the X2 Multiplier's output power is low or nonexistent, troubleshoot the
circuit and repeat the tuning procedure given in step #8a.
367
b.
9.
Replace the bottom cover and slightly readjust capacitors C12, C13, C14, C15, C16,
and C17 for the specifications stated in step #8a. When these specifications are
obtained, proceed to step #11.
X4 Multiplier (Ch.7-13)
a.
Remove the bottom cover of the module and disconnect the jumper wire attached to
terminal post D on the X4 Multiplier's PC board (see Schematic C331-24).
b.
Solder an open-ended 50 ohm coaxial cable to terminal posts D (center conductor)
and K (shield) and connect a spectrum analyzer to the opposite end of the coaxial
cable.
c.
Tune the spectrum analyzer to the second harmonic of the oscillator's output
frequency and adjust capacitors C7, C12 through C17 and inductors L6, L7, and L8 for
maximum power (25 to 55mW) at the second harmonic of the oscillator's output
frequency. Insure that the other harmonics are at least 40dB below the second
harmonic by tuning capacitors C14 and C16 near minimum coupling (least capacitance) without sacrificing power.
d.
Remove the coaxial cable from terminal posts D and K. Resolder the jumper wire
which connects terminal posts D and E.
e.
Disconnect the jumper wire attached to terminal post M on the X4 Multiplier's PC
board (see Schematic C331-24).
f.
Solder the open-ended 50 ohm coaxial cable to terminal posts M (center conductor)
and N (shield). Connect a spectrum analyzer to the opposite end of the coaxial cable.
g.
Tune the spectrum analyzer to the frequency of the oscillator's fourth harmonic and
adjust capacitors C19, C22, and C23 for maximum power (75 to 100mW) at that
frequency. Insure that all other harmonics are at least 20dB lower.
h.
Remove the coaxial cable from terminal post M and ground. Resolder the jumper wire
to terminal post M.
i.
Attach the spectrum analyzer to the output connector (J2) of the X4 Multiplier module
(point B of Figure 364).
j.
Tune the spectrum analyzer to the frequency of the oscillator's fourth harmonic and
adjust capacitors C19, C22, C23, C26, C27, and C29 for maximum power (10 to
30mW) at the same frequency. Insure that all other harmonics are at least 20dB down
from the fourth harmonic.
NOTE:
k.
If the output power of any section of the X4 Multiplier is low or nonexistent,
troubleshoot the circuit responsible and repeat the alignment procedure.
Replace the bottom cover and slightly readjust capacitors C19, C22, C23, C26, C27,
and C29 for the specifications stated in step #9j. When the specifications are
obtained, proceed to step #11.
368
10.
X16 Multiplier (Ch.14-69)
a.
For tuning this multiplier fabricate a test cable by soldering a .01)F capacitor to the
center conductor of an open-ended 50 ohm cable. Ensure that there is enough outer
conductor (braid) available for soldering at the open end and attach a good RF
connector (BNC, N, SMA) to the opposite end.
b.
Turn the multiplier module over and solder the open capacitor lead of the test cable
to the output side of coupling capacitor C8 (see Schematic 30367226) and connect the
opposite end of the cable to a spectrum analyzer. Make sure that the test cable outer
conductor is soldered to the PC board’s ground plane.
c.
Adjust the spectrum analyzer to view the fourth harmonic of the oscillator and tune
multiplier capacitors C1, C2, C3, C4, C5 and C33 for maximum power at that
frequency.
d.
Remove the cable from C8 and solder the capacitor lead to the output side of coupling
capacitor C17. Remember to solder the braid to ground.
e.
Adjust the analyzer to observe the eighth harmonic of the oscillator and tune
capacitors C9, C10 and C11for maximum amplitude at that frequency.
f.
Unsolder the test cable from C17 and ground and attach a cable to the multiplier
output connector J2 (SMA) and connect the opposite end to the spectrum analyzer.
g.
Readjust the spectrum analyzer to observe the sixteenth harmonic of the oscillator and
tune multiplier capacitors C21, C22, C23, C30, C31 and C32 for maximum power.
h.
Carefully retune all the multiplier capacitors for maximum power at the sixteenth
harmonic. The multiplier should furnish 20 to 25mW of power.
NOTE:
11.
If the output power of any section of the X16 Multiplier is low or nonexistent,
troubleshoot the circuit responsible and repeat the tuning procedure.
Reconnect the output of the Multiplier to the LO port (J3) of the Downconverter/Preamplifier
and secure the module to the bottom of the Receiver drawer.
RF Amplifier Chain
12.
Place the Receiver's front panel OPERATE/ALIGN switch (S1) to ALIGN and set up the test
equipment as shown in Figure 365 with the 10dB attenuator connected to the output of
either the VHF or UHF Bandpass Filter (point A of Figure 365).
13.
Adjust the sweep and marker generator for an oscilloscope display width of 15MHz at the
input frequency of the Receiver. To prevent overdriving any amplifiers, set the oscilloscope
for maximum sensitivity.
14.
a.
For a VHF input: Adjust capacitors C1 through C5 of the VHF Bandpass Filter (FL1)
to obtain a frequency response as that shown in Figure 366A. There should be less
than 2dB of insertion loss.
369
b.
For a UHF input: Tune capacitors C1, C2, and C3 of the UHF Bandpass Filter (FL1)
for a frequency response as that shown in Figure 366A with less than 3dB of insertion
loss. Only if absolutely necessary, adjust the Variable Coupling Barriers and inductors
L1 and L4 for the correct response (see Schematic 10331209).
15.
Remove the attenuator from the output of either the VHF or UHF Bandpass Filter (FL1) and
connect the attenuator to the output of the Downconverter/Preamplifier module (point B of
Figure 365). Reconnect either the VHF or UHF Bandpass Filter to the input of the
Downconverter/Preamplifier (A1).
16.
Check the output of the Downconverter/Preamplifier for a gain (with conversion) of 3dB and
a frequency response as shown in Figure 366A. Correct any slight frequency response
variations (tilt) with either the VHF or UHF Bandpass Filter as explained in step #14 of this
section. If there are any major frequency response or gain problems (>±1dB), sweep and
troubleshoot the Downconverter/Preamplifier by itself.
17.
Remove the attenuator from the output of the Downconverter/Preamplifier and connect the
attenuator to the output of the IF Amplifier w/SAW Filter (point C of Figure 365). Reconnect
the output of the Downconverter/Preamplifier to the input of the IF Amplifier w/SAW Filter
(A2).
18.
Check for a frequency response as shown in Figure 366B and a minimum gain of 20dB. If
there is a major discrepancy in frequency response or gain (±2dB), sweep and troubleshoot
the IF Amplifier w/SAW Filter by itself.
19.
Disconnect the attenuator from the output of the IF Amplifier w/SAW Filter and connect the
attenuator to the output of the Receiver drawer (point D of Figure 365). Reconnect the
output of the IF Amplifier w/SAW Filter to the input of the IF AGC Amplifier (A3).
20.
With the Receiver's front panel OPERATE/ALIGN switch in the ALIGN position, adjust the
IF AGC Amplifier's TILT ADJ control (R31) to obtain a flat frequency response as shown in
Figure 366B. The TILT ADJ potentiometer is accessible through the top of the IF AGC
Amplifier module. Check the IF AGC Amplifier for a gain of approximately 25dB. (This gain
is dependent on the +5Vdc reference voltage provided to the IF AGC Amplifier's variable
pin diode attenuator when the Receiver's OPERATE/ALIGN switch is in the ALIGN position.)
Limiter/Output AGC Calibration:
21.
Connect an IF modulator to the input of the IF AGC Amplifier (point C of Figure 365).
Adjust the modulator to deliver the visual carrier frequency (45.75MHz) at 39dBm peak
power. Place the Receiver's front panel OPERATE/ALIGN switch (S1) to OPERATE.
22.
Connect a power meter or spectrum analyzer to the output of the Receiver drawer (point D
of Figure 365).
23.
Adjust the AGC REF potentiometer (PC1R8) fully CW and adjust the LIMITER ADJ
potentiometer (PC1R13) fully CCW. These two potentiometers are located on the Limiter/
Output AGC board (see Schematic B331-34).
24.
Adjust the IF AGC Amplifier's GAIN ADJ potentiometer (A3R15) for a +2dBm signal at the
output of the Receiver drawer (see Schematic C331-37). The GAIN ADJ control is
accessible through the top of the IF AGC Amplifier module.
3610
25.
Recalibrate the modulator so that it now delivers a +1dBm peak visual signal at 45.75MHz
to the IF AGC Amplifier module. Slowly adjust IF AGC Amplifier inductor L3 of the visual
tank circuit so that a minimum power indication is seen on the external power meter or
spectrum analyzer. Inductor L3 is accessible through the top of the IF AGC Amplifier
module.
26.
Place the Receiver's front panel AGC ON/OFF switch to OFF. Adjust the AGC REF
potentiometer (PC1R8) for a 6dBm output level from the Receiver drawer.
27.
Slowly adjust the LIMITER ADJ potentiometer (PC1R13) CW until the 6dBm output level
begins to fluctuate (i.e., as the limiter circuit begins to activate).
28.
Readjust the AGC REF potentiometer to bring the output level from 6dBm down to 9dBm.
29.
Short capacitor C2 on the Limiter/Output AGC board.
NOTE:
3.4b
K1 on the Limiter/Output AGC board will deenergize causing the AGC voltage
to be replaced by the PRE AGC REF voltage. This voltage is set by the PRE
AGC REF ADJ potentiometer (PC1R25).
30.
Adjust the PRE AGC REF ADJ potentiometer (PC1R25) for 8dBm at the output of the
Receiver drawer. This potentiometer is located on the Limiter/Output AGC board.
31.
Remove the short from across C2.
32.
Monitor test point TP1 (OUTPUT AGC) on the Limiter/Output AGC board and vary the
Receiver's front panel AGC ADJUST potentiometer (R3) for a 0Vdc reading at TP1.
33.
Place the Receiver's front panel AGC ON/OFF switch to ON.
34.
If necessary, adjust the Receiver's output power level for 6dBm using the front panel AGC
ADJUST potentiometer.
35.
Disconnect the power meter or spectrum analyzer from the output of the Receiver drawer.
Reconnect the Receiver drawer's IF OUTput to the Exciter/Upconverter drawer's IF INput.
Reconnect the IF AGC Amplifier's input to the output of the IF Amplifier w/SAW Filter.
36.
Reinstall the top cover to the translator's Receiver drawer. Carefully slide the drawer back
into the cabinet and secure it properly.
Exciter/Upconverter Alignment:
1.
If the Exciter is operating, place the Exciter’s OPERATE/STANDBY switch to STANDBY
and the OPERATE/ALIGN switch to ALIGN. Remove the four screws on the front panel of
the Exciter/Upconverter drawer, carefully pull out the drawer, and remove its top cover.
Leave the Power Adjust control as it would be for normal operation.
2.
Remove the Receiver cable attached to the IF INPUT connector, J1. Set up the test
equipment as shown in Figure 367. Connect the VHF sweep generator's RF output to the
IF INPUT connector of the Exciter. Set the VHF sweep generator to sweep from 36 to
50MHz. (Use 45.75MHz and 41.25MHz markers if available.) Tune the spectrum analyzer
3611
to the UHF Synthesizer's LO frequency. The frequency corresponds to the translator's
output channel as shown in Table 261.
3.5
3.
Place the OPERATE/STANDBY switch to OPERATE. Adjust C1, C2, and C3 on the UHF
Bandpass Filter to obtain the frequency response shown in Figure 366A.
4.
If the translator's output channel is being changed to one that is 40MHz or more from the
factory preset, connect a spectrum analyzer to the 30dB attenuator in Figure 367 to ensure
that the sweep appears on the low side of the LO. Tune the spectrum analyzer to the UHF
Synthesizer’s LO frequency as shown in Table 261, UHF Synthesizer Programming Chart.
Program the synthesizer for the new channel and look for the LO carrier on the analyzer.
Tune the analyzer 45.75MHz (38.9MHz for PAL B/G) below the LO frequency and tune C1,
C2 and C3 of the UHF Bandpass Filter for maximum amplitude of the sweep generator
signal on the spectrum analyzer. Replace the analyzer with the sweeper diode detector and
adjust the UHF Bandpass Filter for the response of Figure 366A as shown on the
oscilloscope.
5.
Remove the sweep generator cable from the Exciter drawer IF INput connector (J1) and
disconnect the RF detector from the drawer’s RF OUTput (J2). Replace the Exciter’s top
cover and push the drawer into the rack replacing the four front panel screws. Reconnect
the Receiver cable to the IF INput connector (J1) and the Splitter’s RF cable to the IF
OUTput connector (J2).
Output Power Calibration:
To ensure proper transmission, the output power level and % RF Power meter calibration should
be checked once every year. With the meter switch in the FWD position, the % RF Power meter
has been factory calibrated for 100% with the translator providing 1000 watts peak visual and
50 watts average aural. The average power measurements in this calibration procedure assume
that the composite signal from the translator has the aural carrier 13dB down from the visual with
the visual carrier having 87.5% video modulation and 0% (sync only) average picture level (APL).
Average power levels employing 50% APL (stairstep/ramp/flat field) are included in brackets
following the power levels at 0% APL. It is also assumed that the setup in Figure 368 is being used
and the output of the receiver drawer has been currently calibrated. If the received broadcast
channel frequency is in the VHF band (Ch.2-13), the mixer may be removed and the VHF output
of the agile modulator can be connected directly to the RF INput (J1) of the Receiver drawer.
3.5a
Forward Power:
1.
With the Exciter OPERATE/STANDBY switch on STANDBY, set up the test equipment as
shown in Figure 368.
2.
Verify that the modulator is providing 87.5% video modulation and the aural carrier is 13dB
down from the visual carrier. With the Receiver OPERATE/ALIGN switch in the OPERATE
position and the Meter Switch on FWD, place the Exciter OPERATE/STANDBY switch to
OPERATE.
3612
3.5b
3.
To set the output power, adjust the Exciter’s POWER ADJUST control for an external power
meter reading of 645W [430W]. Note that 1000W peak visual at 0% [50%] APL plus
50 watts average aural for a 13:1 peak visual to average aural ratio equals 645W [430W].
4.
To check or adjust visual to aural ratio, replace the power meter in Figure 368 with a
spectrum analyzer. Adjust the aural carrier level on the modulator for the desired ratio.
Remove the spectrum analyzer and return the power meter to the setup to reset the output
power. Set the POWER ADJUST again for an external power meter reading of 595W
[380W] visual plus the average aural carrier level for the set ratio. Modulators are preset
by EMCEE test department.
5.
With the external power meter reading correctly, place the Front Panel (A5) meter switch
to FWD and check the translator's % RF Power meter for a 100% indication. If this reading
is not obtained, adjust potentiometer R9 of the Metering Detector located behind the Front
Panel (A5) and accessible through the METER ADJUST hole marked FWD.
Reflected Power (Optional):
6.
Through the METER ADJUST access hole marked VSWR OVLD, adjust potentiometer R30
of the Metering Detector fully clockwise to disable the VSWR overload detection circuit.
Place the % RF POWER meter switch to REFL.
7.
Place the Exciter’s OPERATE/STANDBY switch to STANDBY and the OPERATE/ALIGN
switch to ALIGN. Disconnect and reverse the FWD (J3) and REFLD (J4) coupling port
cables on the Metering Coupler (DC1). J3 (REFLD) of the Metering Detector (A5A7) should
now be connected to J3 (FWD) of the Metering Coupler (DC1). This simulates an open
circuit at the translator's RF OUTput (J2) delivering maximum returned power to the
reflected power detector. Insert a 1dB step attenuator between the Receiver and the
Exciter’s IF INput connector and set the attenuator for 10dB of attenuation.
8.
Place the OPERATE/STANDBY switch to OPERATE. Remove attenuation from the step
attenuator until an external power meter reading of 645W [430W] is reached. Check the
front panel % RF POWER meter for a 100% [70%] reading. If the meter is incorrect, adjust
it using potentiometer R27 of the Metering Detector found behind the METER ADJUST hole
marked REFL.
9.
Decrease the translator's power to 10% using the step attenuator (an external power meter
reading of 64.5W [43W]). This power level is used for setting the trip point of the VSWR
overload detection circuit. Adjust R30 of the Metering Detector, found through the METER
ADJUST access hole marked VSWR OVLD, slowly counterclockwise until the front panel
VSWR OVLD indicator illuminates red and the translator’s output power drops to zero.
10.
Check the VSWR OVLD trip point by adding an additional 1dB of attenuation in the step
attenuator. Press the momentary VSWR RESET switch to reactivate the translator and
remove an additional 1or 2dB of attenuation from the step attenuator. The VSWR OVLD
circuit should again trip. If it does not, repeat this section beginning at step #6.
11.
Place the Exciter’s OPERATE/STANDBY switch to STANDBY. Return the metering cables
to their original coupler ports. Place the OPERATE/ALIGN switch to OPERATE, remove
the test equipment, properly load the translator output and place the OPERATE/STANDBY
switch to OPERATE.
3613
3.6
Precorrection Adjustment:
Adjustment of the precorrection is accomplished with two potentiometers in the IF Upconverter and
eight potentiometers in the Linearizer which should not be realigned unless absolutely necessary.
(The IF Upconverter and Linearizer can produce unwanted distortion if adjusted incorrectly.) The
test equipment which should be available for readjustment of the precorrector is a spectrum
analyzer which provides demodulated video for measurement of sync and intermodulation or a
waveform monitor and television demodulator for sync and differential gain measurements.
Acquire as much of this test equipment as possible since the precorrection accuracy will depend
on equipment versatility. It is assumed that the translator's overall frequency response is correct,
allowing the unit to operate with maximum efficiency.
3.7
1.
To the output of the translator connect the test equipment available for monitoring
intermodulation, sync amplitude and differential gain.
2.
Remove the four screws on the front panel of the 20W Exciter drawer, pull out the drawer,
and remove its top cover. Insure switch S1 of the IF Upconverter is in the ON (right)
position and S1 of the Linearizer is in the ON position.
3.
Place the translator in operation with the system providing its rated output. After demodulating video, slowly adjust R9 and R4 of the IF Upconverter and/or R37, R38, R39, R40,
R10, R11, R21 and R22 of the Linearizer for 100% horizontal sync.
4.
While looking at the spectral waveform, adjust R4 and R9 of the IF Upconverter and/or R10,
R11, R21, R22, R37, R38, R39, and R40 of the Linearizer for minimum in-band intermodulation products. This can be accomplished using a modulated ramp video signal and
100kHz resolution bandwidth on the spectrum analyzer.
5.
Check and, if necessary, correct the translator's output power with the front panel POWER
ADJUST.
6.
Repeat steps #3 through #5 to find the appropriate trade-off for 100% horizontal sync and
minimum in-band intermodulation products.
7.
Reinstall the top cover to the 20W Exciter drawer, slide the drawer back into the cabinet,
secure it, remove the test equipment, and properly load the translator output before
reactivation.
Control Board Setup:
The TU1000F V/U CONTROL BOARD (A5PC1) circuit allows the fault voltages to be balanced
preventing fault indications due to gain variations in the 300W Amplifier modules. To set up the
CONTROL BOARD the translator must have four 300W amplifier assemblies in good working
condition.
1.
To set CONTROL BOARD, turn off the translator, remove the four screws on the Front
Panel (A5) and pull the panel out.
3614
2.
Make sure the board is properly fastened to the panel and both dc plugs properly connected.
Turn the four potentiometers at the top of the board (R58, R60, R62, and R64) fully
clockwise.
3.
Place the translator into operation. Make sure the translator is providing 1000W peak visual
(100% on the % RF POWER meter) with a 0% APL video signal and proper depth of
modulation.
4.
Using a voltmeter, check the voltages at test points TP1, TP2, TP3, and TP4. (NOTE: TP5
is a ground point.) Note which test point has the lowest voltage.
5.
Place the voltmeter on the test point with the lowest voltage as noted in the previous step.
Adjust the corresponding potentiometer to reduce this voltage by 0.25V to 0.5V. (R58
corresponds to TP1, R60 to TP2, R62 to TP3, and R64 to TP4.)
6.
Adjust the remaining three potentiometers so that the voltage of the corresponding test point
is within ±0.1V of the voltage set in step #5.
7.
Disconnect the voltmeter and replace the Front Panel, securing it properly.
3615
3.8
Remote Monitor Signal Levels:
This table lists the signal type and levels provided on the REMOTE MONITOR 25-pin cabinet
connector (J4).
NAME
I/O
FWD POWER
18
+5
REFL POWER
19
RF ENABLE
23
+5
REMOTE ON/OFF
24
+5
REMOTE VSWR OVLD RESET
20
+5
PS FAULT AMPL 1
+5
PS FAULT AMPL 2
+5
PS FAULT AMPL 3
+5
PS FAULT AMPL 4
+5
I SENSE AMPL 1
10
+4.5
I SENSE AMPL 2
11
+4.5
I SENSE AMPL 3
12
+4.5
I SENSE AMPL 4
13
+4.5
THERM OVLD AMPL 1
15
THERM OVLD AMPL 2
14
THERM OVLD AMPL 3
16
THERM OVLD AMPL 4
17
+5V POWER SUPPLY
+5
+15V POWER SUPPLY
+15
15V POWER SUPPLY
15
+28V POWER SUPPLY
+28
GND
1, 25
3616
TTL
TYPICAL LEVEL
(VOLTS)
PIN
3.9
Spare Modules and Components:
The following contains the description, vendor, part number, and designator of each module found
in the TU1000F V/U Translator which EMCEE considers to be essential bench-stock items. These
modules should be available to the technician at all times.
TU1000F V/U
INTERCONNECTION DIAGRAM 40386002
DESCRIPTION
VENDOR/PART #
DESIGNATOR
Fans 10" 560CFM 220Vac
EMCEE/4C829
B1, B2
Control Board
EMCEE/40386014-1
A5/PC1
Splitter/Combiner
EMCEE/40367291-1
CP1, CP2
Metering Detector
EMCEE/60386050-1
A5/A7
DUAL 300W UHF AMPLIFIER
INTERCONNECTION DIAGRAM 403860003
DESCRIPTION
VENDOR/PART #
DESIGNATOR
Fans 4.5" 106CFM 220Vac
EMCEE/A30135-10
A3B1, A3B2,
A4B1, A4B2
300W UHF Amplifier
EMCEE/40386007-1
A3A1, A3A2,
A4A1, A4A2
Status Display
EMCEE/20386107-1
A3PC1, A4PC1
+28V Power Supply
TODD/SPF-750-28
A3PS1, A3PS2,
A4PS1, A4PS2
S61
TU20F EXCITER
INTERCONNECTION DIAGRAM 40383113
DESCRIPTION
VENDOR/PART #
DESIGNATOR
Linearizer
EMCEE/60367083-1
A2A6
IF Upconverter
EMCEE/70383030-1
A2A1
2 Watt UHF Amplifier
EMCEE/70367080-1
A2A2
20 Watt UHF Amplifier
EMCEE/80383011-1
A2A3
UHF Synthesizer
EMCEE/60367103-1
A2A4A1
Reference Oscillator
EMCEE/60368055-1
A2A4A2
Metering Detector
EMCEE/60368050-1
A2A5
+28V Power Supply
TODD/SC28-9
A2PS1
±15V/+5V Power Supply
Deltron/W300A
A2PS2
Control Board
EMCEE/80383018-1
A2PC1
Contactor
Telemecanique/LP1-EC03
A2K1
Voltage Regulator
Motorola/MC7812CT
A2U1
Fans 4.5" 106CFM 220Vac
EMCEE/A30135-10
A2B1, A2B2
S62
RECEIVER DRAWER (A1) SPARE MODULES LIST
INTERCONNECTION DIAGRAM 30383094 (OSC/MULT)
DESCRIPTION
VENDOR/PART #
DESIGNATOR
Limiter/Output AGC Control
EMCEE/B331-36-1
PC1
Automatic-On
EMCEE/B331-46-1
PC2
IF AGC Amplifier
EMCEE/B331-42-1
A3
IF Amplifier with SAW Filter
EMCEE/B331-27-1
A2
Downconverter/Preamplifier
EMCEE/B331-47-1
A1
+25V Power Supply
EMCEE/B326-17-1
PS1PC1
±15V, ±5V Power Supply
EMCEE/70326117
PS1PC2
Oscillator
Vectron/CD254D57
G1
*** SELECT APPROPRIATE MULTIPLIER AND FILTER ***
VHF Bandpass Filter CH 2-6
EMCEE/A280-90-2
FL1
VHF Bandpass Filter CH 7-13
EMCEE/A280-90-1
FL1
UHF Bandpass Filter CH 14-69
EMCEE/ P/LC331-218-1
FL1
X2 Multiplier
EMCEE/B280-76-1
A4
X4 Multiplier
EMCEE/B331-19-1
A4
X16 Multiplier
EMCEE/70367248
A4
S63
RECEIVER DRAWER (A1) SPARE MODULES LIST
INTERCONNECTION DIAGRAM 30383104 (SYNTH)
DESCRIPTION
VENDOR/PART #
DESIGNATOR
Limiter/Output AGC Control
EMCEE/B331-36-1
PC1
Automatic-On
EMCEE/B331-46-1
PC2
IF AGC Amplifier
EMCEE/B331-42-1
A3
IF Amplifier with SAW Filter
EMCEE/B331-27-1
A2
Downconverter/Preamplifier
EMCEE/B331-47-1
A1
+25V Power Supply
EMCEE/B326-17-1
PS1PC1
±15V, ±5V Power Supply
EMCEE/70326117
PS1PC2
Reference Oscillator
EMCEE/60368055-1
A4A2
*** SELECT APPROPRIATE SYNTHESIZER AND FILTER ***
VHF Bandpass Filter CH 2-6
EMCEE/A280-90-2
FL1
VHF Bandpass Filter CH 7-13
EMCEE/A280-90-1
FL1
UHF Bandpass Filter CH 14-69
EMCEE/ P/LC331-218-1
FL1
VHF Synthesizer High Band
EMCEE/60367103-2
A4A1
VHF Synthesizer Low Band
EMCEE/60367103-3
A4A1
UHF Synthesizer
EMCEE/60367103-1
A4A1
S64

---

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