Assembly Instructions Chapter 4

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4-6 kW UHF Translator Chapter 4, Circuit Descriptions

837B, Rev. 0 4-1

Chapter 4

Circuit Descriptions

4.0 (A1) UHF Exciter Assembly

(1278-1400; Appendix C)

The (A1) UHF Exciter Assembly

contains (A1) a UHF Exciter Tray

(1142458 or 1245-1100), (A4 & A5)

two Variable Gain/Phase Trays (1245-

1200), (A6) a Metering Panel (1136811

or 1245-1400), (A7) a UHF Receiver

Tray (1142479 or 1265-1100), (A8) an

Exciter AC Distribution Assembly

(1245-1500) and (A9) a Remote

Interface Assembly (1245-1801).

The (A7) UHF Receiver Tray, uses the

ON Channel RF input, at J5 for 75 or

J1 for 50, and produces a Combined

IF output at J4 that connects to the

UHF Exciter at J6.

The (A1) UHF Exciter Tray, if the

Optional Modulator Kit is present in the

tray, takes the Baseband Audio and

Video Inputs and mixes them with

internally generated 45.75 MHz and

41.25 MHz Ifs that combines them.

The Combined IF, from the Receiver

Tray or from the Modulator Kit, is

upconverted to the On Channel RF

output frequency by mixing it with a

L.O. signal generated by the Channel

Oscillator Assembly. The RF Output of

the UHF Exciter at J15 connects to (A3)

a Splitter which splits the RF two ways

with the RF Output #1 connected to the

input of the (A5) Variable Gain/Phase

Tray (1245-1200) and the RF Output

#2 connected to the input of the (A4)

Variable Gain/Phase Tray (1245-1200).

The output of the (A4) Variable

Gain/Phase Tray connects to (A2) the

Side A Amplifier Array Assembly. The

output of the (A5) Variable Gain/Phase

Tray connects to (A3) the Side B

Amplifier Array Assembly.

4.0.1 Control and Status

The Control and Status of the

Translator are provided by the Meter

indications on the Metering Panel and

the Variable Gain Phase Trays. There

are also Control, Status and LED

Indications located on the front panel of

the UHF Exciter Tray. The switches and

LED indicators, which are mounted so

that the switches and LEDs are

operated or viewed from the front

Panel of the UHF Exciter, are part of the

Transmitter Control Board (1245-

1101). On the UHF Exciter Tray, switch

(S1) is an Operate/Standby Switch that

provides the Operate Commands

(Enables), when in Operate, to each of

the Amplifier Arrays. The power supply

Enable is needed to turn on the

Switching Power Supplies located in

each of the UHF Amplifier Trays. The

Fan Enable is needed to turn on the

exhaust fan in the (Optional) External

Exhaust Kit. When the UHF Exciter is

in Operate, the Green LED (DS2) is On

and when in Standby the Amber LED

(DS1) is On. NOTE:

If the Translator

does not switch to Operate, when S1 is

switched to Operate, check that a

Dummy Jumper Plug is connected to

Jack J7, with a Jumper between Pins 1

& 2, located on (A9) the Remote

Interface Assembly in the Single UHF

Exciter Assembly. The Jumper provides

the Interlock to the UHF Exciter needed

for the operation of the Translator. If

the Interlock is present, the Green LED

(DS5), located on the Transmitter

Control Board, should be lit.

Operation of the Translator is controlled

by the front panel switches located on

the UHF Exciter Tray. During Normal

operation of the Translator, Switch S2

should be in the Auto position. The

front panel of the UHF Exciter also has

LEDs that indicate a Video Fault (Loss),

Summary of content (47 pages)

PAGE 1
4-6 kW UHF Translator Chapter 4, Circuit Descriptions Chapter 4 Circuit Descriptions 4.0 (A1) UHF Exciter Assembly (1278-1400; Appendix C) The (A1) UHF Exciter Assembly contains (A1) a UHF Exciter Tray (1142458 or 1245-1100), (A4 & A5) two Variable Gain/Phase Trays (12451200), (A6) a Metering Panel (1136811 or 1245-1400), (A7) a UHF Receiver Tray (1142479 or 1265-1100), (A8) an Exciter AC Distribution Assembly (1245-1500) and (A9) a Remote Interface Assembly (1245-1801).
PAGE 2
4-6 kW UHF Translator Chapter 4, Circuit Descriptions Red LED (DS9) and a VSWR Cutback, Amber LED (DS7). 4.0.2 RF, Baseband Remote Connections Input and The RF, Baseband Video and Audio Inputs to the Translator, connect to the (A9) Remote Interface Panel located on the rear of the Single UHF Exciter Assembly. The On Channel RF input connects to the “F” connector J3 for 75Ω or the “N” connector J1 for 50Ω.
PAGE 3
4-6 kW UHF Translator RF Signal Path 4.1.1 (A7) 50Ω Filter, DC Multiplexed, UHF (1035-1204), VHF L.B. (1035-1902) or VHF H.B. (2065-1024) or 75Ω, UHF (10351207), VHF L.B. (1035-1903) or VHF H.B.
PAGE 4
-6 kW UHF Translator VCXO Channel Oscillator Assembly (1145-1206), which contains the VCXO Channel Oscillator Board (1145-1204), is used in place of the standard Channel Oscillator Assembly, and an AFC voltage from the PLL circuit maintains the frequency of the VCXO. 4.1.
PAGE 5
4-6 kW UHF Translator comparator drives the Pin Diode Attenuator Circuit to maintain the desired output level, typically +2 dBm. The other split output connects to J2 the Combined IF Output of the board that is cabled to the IF Output Jack of the Tray at J4 (+2 dBm).
PAGE 6
4-6 kW UHF Translator Voltages for Operation of the Tray The AC input to the Tray is 117 VAC or 230 VAC and is directed thru Jack J2, of the (A1) Power Entry Module (12651104), to the step down Toroid (A2). The Power Entry Module contains an On/Off Switch, a 4 Amp Slo-Blo Fuse and three MOVs which protect the Tray from transients or surges which may occur on the AC Input Lines. When the On/Off Switch is switched On, AC is applied to the (A2) Toroid.
PAGE 7
4-6 kW UHF Translator by jumper W3 on J11. Jumper W3 on jack J11 is positioned according to the input level of the audio signal (0 or +10 dBm). If the input level is approximately 0 dBm, the mini-jumper should be in the high gain position between pins 1 and 2 of jack J11. If the input level is approximately +10 dBm, the mini-jumper should be in low gain position between pins 2 and 3 of jack J11.
PAGE 8
4-6 kW UHF Translator compared in the IC and the fV, and fR is applied to the differential amplifier U3B. The output of U3B is fed back through CR17 to the 4.5-MHz VCO IC U10; this sets up a PLL circuit. The 4.5MHz VCO will maintain the extremely accurate 4.5-MHz separation between the visual and aural IF signals; any change in frequency will be corrected by the AFC error voltage. PLL chip U5 also contains an internal lock detector that indicates the status of the PLL circuit.
PAGE 9
4-6 kW UHF Translator board. If the 4.5-MHz composite input kit is purchased, the 4.5-MHz composite signal at J22 connects to the external composite 4.5-MHz filter board and the 4.5-MHz bandpass filter board. These two boards provide the videoonly signal to J27 and the 4.5-MHz intercarrier signal to J28 from the 4.5MHz composite input. The video through video gain pot R12 (adjusted for 1 Vpk-pk at TP2) connects to amplifier U1B.
PAGE 10
4-6 kW UHF Translator prevent video transients from overmodulating the video carrier. The clamped video is connected to sync clipper circuit Q4 (adjusted by R24); Q4 limits the sync to -40 IRE units. The corrected video connects to emitter follower Q4 whose output is wired to unity gain amplifier U2A and provides a low-impedance, clamped video output at pin 1. 4.2.2.4 Visual Modulator Circuit The clamped video signal from U2A is split.
PAGE 11
4-6 kW UHF Translator MHz is then connected to J7 and, if jumper W3 is between pins 1 and 2, the 4.5-MHz signal from the external source is connected to the mixer. Mixer Z2 heterodynes the aural-modulated, 4.5-MHz signal with the 45.75-MHz CW signal to produce the modulated 41.25MHz aural IF signal. The output of the mixer is fed to a bandpass filter that is tuned to pass only the modulated 41.25-MHz aural IF signal that is fed to jack J16, the 41.25-MHz loop-through out jack of the board.
PAGE 12
4-6 kW UHF Translator sample of the delayed video signal is connected to J2 on the board and can be used for testing purposes. The ±12 VDC needed to operate the board enters the board at J1. The +12 VDC connects to J1-9, which is filtered by L5 and C11 before it is directed to the rest of the board. The -12 VDC connects to J1-6, which is filtered by L6 and C12 before it is directed to the rest of the board. 4.2.
PAGE 13
4-6 kW UHF Translator Chapter 4, Circuit Descriptions The stages U1, U2, Q5, and Q6 are powered by +5.1 VDC, which is obtained by using the +12 VDC line voltage, and voltage-dropping resistor R16 and zener diode VR2. receiver IF input at J1, if present, to the rest of the board. When K3 is energized, it connects to the modulator IF input at J32 to 50 watts; Modulator Enable LED DS5 will not be illuminated.
PAGE 14
4-6 kW UHF Translator the input level detector circuit. The amplified IF is fed to T4; T4 is a stepup transformer that feeds diode detector CR14. The positive-going detected signal is then low-pass filtered by C49, L18, and C50. This allows only the video with positive sync to be applied through emitter follower Q1. The signal is then connected to detector CR15 to produce a peak-sync voltage that is applied to op-amp U9A.
PAGE 15
4-6 kW UHF Translator level pot R71, which is set at the factory to cut back the output to approximately 25%, is applied to U9B, pin 5. The output of U9B at pin 7 goes low and is applied through the power adjust pot to U10A, pin 2, whose output goes low. This low is applied to the pin-diode attenuator to cut back the level of the output to approximately 25%. 4.2.5.5 Pin-Diode Attenuator Circuit The input IF signal is fed to a pin-diode attenuator circuit that consists of CR1 to CR3.
PAGE 16
4-6 kW UHF Translator Chapter 4, Circuit Descriptions the magnitude control determines the amount of gain change that occurs once the breakpoint is reached. Two reference voltages are needed for the operation of the corrector circuits. Zener diode VR1, with R33 and R135, provides a +6.8 VDC reference and the diodes CR11 and CR12 provide a .9 VDC reference that temperature compensates for the two diodes in each corrector stage.
PAGE 17
4-6 kW UHF Translator 2 on J27 and J28. Normally, the pad is out. The IF signal is then applied to a two-stage, frequency-response corrector circuit that is adjusted as needed. Variable resistors R103 and R106 are used to adjust the depth and gain of the notches and variable caps C71 and C72 are used to adjust the frequency position of the notches. The IF signal is amplified by U13 and U14 before it is connected to J12, the IF output jack of the board.
PAGE 18
4-6 kW UHF Translator Chapter 4, Circuit Descriptions the null condition would no longer occur at U10A, pin 2. When the level drops, the output of U10A, pin 1, will go more positive. If jumper W3 on J6 is in the Automatic position, it will cause the ALC pin-diode attenuators CR1, CR2, and CR3 to have less attenuation and increase the IF level; this will compensate for the decrease in the level.
PAGE 19
4-6 kW UHF Translator 4.2.5.12 ±12 VDC Needed to Operate the Board The ±12 VDC connects to the board at J14. The +12 VDC connects to J14-3 and is filtered by L30, L41, and C80 before it is applied to the rest of the board. The -12 VDC connects to J14-5 and is filtered by L31 and C81 before it is applied to the rest of the board. The +12 VDC also connects to U16, a 5-VDC regulator IC, which produces the +5 VDC needed to operate timing IC U17. 4.2.
PAGE 20
4-6 kW UHF Translator adjusted signal is next applied to amplifier U2 to compensate for the loss through the L-pad. U2 is powered through L4 and R10 from the +12 VDC line. After the signal is amplified by U2, it is applied to the second corrector stage through T2 and then to a third corrector stage through T3. The other two corrector stages operate in the same manner as the first; they are independent and do not interact with each other.
PAGE 21
4-6 kW UHF Translator After the signal is amplified by U5, it is applied to a second stage through T5. The transformer doubles the voltage swing by means of a 1:4 impedance transformation. Resistors R39, R57, R58, and R40 form an L-pad that lowers the level of the signal. The signal is applied to amplifier U6 to compensate for the loss in level through the L-pad. After the signal is amplified by U6, it is applied to a third stage through T6.
PAGE 22
4-6 kW UHF Translator The translator is now in the Operate mode. When Operate/Standby switch S1 is moved to Standby, the other coil of relay K1 energizes, causing the contacts to open and a high (+12 VDC) to be applied to U4B-9. The high at the input causes the output at U4B-13 to go high. The high biases on Q1 and applies a low to the amber Standby LED DS1, on the front panel, which turns on and applies a low to Q2. This causes Q2 to turn off and extinguishes the green Operate LED DS2.
PAGE 23
4-6 kW UHF Translator biased off, and causes the drain of Q18 to go high. The high connects to U3D, pin 12, whose output at pin 14 goes high. The high connects to U5C, pins 8 and 9, causing its output at pin 10 to go low, and to U5A, pin 1, causing its output at pin 3 to go low. With S2 set to Automatic, a low is applied to U5A, pin 2, and to U5D, pin 13. When U5A, pin 1, is high and U5A, pin 2, is low, it causes the output at pin 3 to go low.
PAGE 24
4-6 kW UHF Translator on J10, the base of Q16 goes high. The red Video Loss Fault LED DS9 on the front panel will be extinguished. Q16 is biased on, which causes its drain to go low. The low is wired to U5B, pin 5; U5B, pin 6, will be low if no ALC fault occurs. The two lows at the inputs make the output at U5B, pin 4, go high. The high is wired to Q18, which is biased on, causing the drain to go low. The low is connected to U3D, pin 12, which causes its output at U3D, pin 14, to go low.
PAGE 25
4-6 kW UHF Translator has a low that is connected to U5B, pin 5, and produces a high at output pin 4. The high is wired to Q18, which is biased on, and makes its drain low. The low connects to U3D, pin 12, which, because the level is below the preset, causes the output at U3D, pin 14, to go low. A low at this point indicates a nofault condition. The high that is connected to U3A, pin 2, causes its output to go low. The low is connected to Q25, which is biased off.
PAGE 26
4-6 kW UHF Translator U6 is a temperature-sensor IC that gives the operator the ability to measure the temperature inside the tray by measuring the voltage at TP1. The sensor is set up for +10 mV equals 1° F (for example, 750 mV equals 75° F). 4.2.7.6 Operational Voltages The +12 VDC needed for the operation of the transmitter control board enters the board at jack J4, pin 3. C28, L1, and L3 are for the filtering and isolation of the +12 VDC before it is split and applied to the rest of the board.
PAGE 27
4-6 kW UHF Translator 4.2.10 (A13) (Optional) EEPROM FSK Identifier Board (1265-1308; Appendix D) The optional FSK identifier board, with EEPROM, generates a morse code identification call sign by frequencyshift keying the VCXO oscillator in the upconverter or by sending a bias voltage to the IF attenuator board to amplitude modulate the aural carrier. This gives the station a means of automatically repeating its identification call sign, at a given time interval, to meet FCC requirements.
PAGE 28
4-6 kW UHF Translator MHz signal is connected to a foursection, low-pass filter circuit, which is adjusted by C2, L1, C5, L2, C8, L3, L4, C11, L5, C15, L6, and C19, and has a sharp roll-off that eliminates the 4.5MHz signal. The filter is set up at the factory for the desired video-only output and should not be adjusted by the customer. The video low-pass signal is amplified by U2B and applied to the video low-pass output jack of the board at J5, which is connected to the sync tip clamp/modulator board.
PAGE 29
4-6 kW UHF Translator board. The -12 VDC connects to the board at J4-5 and is filtered and isolated by L9 and C21 before it is connected to the rest of the board. 4.2.13 (A3)+12V(4A)/-12V(1A) Power Supply Board (1265-1312; Appendix D) The ±12-volt power supply board consists of three separate power supplies, two of which produce the +12 VDC and one for the -12 VDC needed to power the circuit boards in the exciter tray. 4.2.13.
PAGE 30
4-6 kW UHF Translator 4.2.15 (A15-A1) x8 Multiplier Board (1227-1002; Appendix D) The x8 multiplier board multiplies the frequency of an RF input signal by a factor of eight. The board is made up of three identical x2 broadband frequency doublers. The input signal (+5 dBm) at the fundamental frequency enters through SMA jack J1 and is fed through a 3-dB matching pad, consisting of R1, R2, and R3, to amplifier IC U1.
PAGE 31
4-6 kW UHF Translator The frequency of the LO is the sum of the IF frequency above the required visual carrier. For instance, in system M, the IF visual frequency is at 45.75 MHz and the relative location of the aural would be 4.5 MHz lower, or 41.25 MHz. For digital applications, the LO is the center frequency of the digital channel added to the 44-MHz IF frequency. By picking the local oscillator to be 45.
PAGE 32
4-6 kW UHF Translator DC blocking for the output signals. The RF signals connect to L7, which consists of UT-141 coaxial cable. L7 combines the RF back to a single-RF output at a 50-Ω impedance and sends it to L8, which provides a sample of the RF. The main path through L10 is to J5, the RF output jack of the board (+10 to +20 dBm). The sample of the RF connects to a splitter that provides a sample output (0 dBm) at J6 of the board.
PAGE 33
4-6 kW UHF Translator adjust Pot (A7) connects through the Metering Board to J4 on the Variable Phase/Gain Board which controls the phasing of the RF output. The Phasing adjust is needed to phase the two RF outputs of the Amplifier Arrays, when they are combined, to achieve maximum output. The phase and level controlled RF signal connects to J2 of the Variable Phase/Gain Board which connects to the RF Output Jack J3 located on the rear panel of the Tray.
PAGE 34
4-6 kW UHF Translator B Output Power with (S3) the Meter Control Switch. 4.4.1 (A4, A5, A6 & A11) Splitter Board (1181-1002; Appendix D) The (A4) Splitter Board (1181-1002) takes the ALC reference from the (A4) Variable Phase/Gain Tray at J1-1 and splits it six ways that connect to the UHF Amplifier Trays mounted in the Side A Amplifier Array.
PAGE 35
4-6 kW UHF Translator final path uses a detected Combined Reflected sample. These samples are compared to the threshold settings, 20% Reflected level, and provide an output to cut back the translator if the reflected level of any of the input samples increase above 20%. A Sample of the Side A Reflected level enters the board at J1-1. The level is split and one path connects to J1-2 to be used as a Side A Remote Reflected output.
PAGE 36
4-6 kW UHF Translator by capacitor C4 and bypassed by C5 to prevent oscillations. The filtered -12 VDC is applied to U2 a 7912 IC voltage regulator and current limiter. C6 is a bypass capacitor to prevent oscillations in the output DC lines. C7 is a holding capacitor to maintain -12VDC for an instance even if the supply is lost. This is to allow the positive voltages to be removed from the Amplifier devices to prevent damage to the devices.
PAGE 37
4-6 kW UHF Translator Interface Panel located in the Amplifier Array Assembly. The RF is cabled to the COM Input of (A9-A1) the 8 Way Splitter that splits it eight ways. Four, five or six of the RF outputs (+6 dBm) of the Splitter are connected to J1, the RF Input Jack on each of the four, five or six UHF Amplifier Trays. The outputs of the Splitter that are not used are terminated with 50Ω.
PAGE 38
4-6 kW UHF Translator Chapter 4, Circuit Descriptions Line 2 to Line 3, VR3 from Line 1 to Line 3, VR4 from Line 1 to Ground, VR5 from Line 2 to Ground and VR6 from Line 3 to Ground. of the (Optional) External Exhaust Kits in the Amplifier Array Cabinets for operation of the isolation relays. For single phase, connect Line 1 to TB1-1A, Line 2 to TB1-3A and Ground to TB1-4A. The AC Distribution Panel contains Circuit Breakers that supply the AC to the rest of the Amplifier Assembly.
PAGE 39
4-6 kW UHF Translator 4.7.2 (A2-A1) Variable Gain/Phase Board (1301549; Appendix D) The variable gain/phase board provides the circuits that adjust the phase and the gain of the RF signal for the amplifier tray in which it is mounted. The RF input signal at J1 (+3dBm) is split, with one output connected to a detector circuit consisting of C8, CR4, and U3A.
PAGE 40
4-6 kW UHF Translator VDC needed to operate the ICs on the board. The output of the variable gain/phase board (+19 dBm) at J2 connects through A16 a 6dB pad to J1 (+13 dBm) on the 1 Watt amplifier board assembly. 4.7.
PAGE 41
4-6 kW UHF Translator Chapter 4, Circuit Descriptions amplifier assembly is made up of a (515378-308-00) module, which is a class AB module that is a highly linear broadband amplifier for the frequency range of 470 to 860 MHz. It can deliver an output power of 40 watts (CW) at an amplification of approximately 13 dB. track to SMA output jack J2. A hybridcoupler circuit picks off a forward sample that is connected to SMA type connector jack J3. R1 is a dissipation load for the reject port of the coupler.
PAGE 42
4-6 kW UHF Translator to mismatching in the first splitter will be dissipated. One of the two outputs from the splitter connects to another 2way splitter that contains R2. R2 is a 100 Ω balancing resistor in which any RF due to mismatching in the splitter will be dissipated. The other output of the first splitter connects to the third 2way splitter that contains R3. R3 is a 100 Ω balancing resistor in which any RF due to mismatching in the splitter will be dissipated.
PAGE 43
4-6 kW UHF Translator 4.7.12 (A6) Dual Peak Detector Enclosure (1227-1317; Appendix D) The dual peak detector enclosure provides EMI and RFI protection for the dual peak detector board, single supply (1227-1333), which is mounted inside the enclosure. The enclosure has two inputs: a forward power sample at SMA jack J1 and a reflected power sample at SMA jack J2.
PAGE 44
4-6 kW UHF Translator Chapter 4, Circuit Descriptions control board and is connected to the dual peak detector board. F7 is a 15amp and F8 is a 3-amp spare fuse. The +32 VDC from the switching power supply enters the board at TB1, with the plus (+) connections sent to pins 1 to 4 and the minus (-) connections sent to pins 5 and 6. The +32 VDC is connected across the .
PAGE 45
4-6 kW UHF Translator monitoring the AGC, % Reflected Power, % Output Power, and the power supply voltage. A –12-VDC enable is applied to the board at J4-1 from the transmitter control board in the UHF exciter tray. The enable causes the J-FET Q5 to be biased off, making the drain go high; the high is applied to Q4, which is biased on. The drain of Q4 goes low and lights the green Enable LED DS4 on the front panel.
PAGE 46
4-6 kW UHF Translator Chapter 4, Circuit Descriptions creating a positive feedback loop that could damage the amplifier tray. at position 1 of S2, the Front Panel Meter switch. 4.7.15.4 Metering Circuits 4.7.15.5 Operational Voltages The +32 VDC that is connected to the board from the switching power supply is applied to jack J6, pin 1, of the board and connected through R63, R96, R66, R65, and R76 to the front panel meter for monitoring.
PAGE 47
4-6 kW UHF Translator 4.9 Translator Output Assemblies The outputs of the (A2 & A3) 2-3 kW Amplifier Assemblies (+63.5-+65.2 dBm) connect through 1-5/8” hard-line and (A5 or A6) 1-5/8” to 3-1/8” Adapters to (A4) a Hybrid Combiner. The combiner combines the output from each Amplifier Assembly into a single output.