UBS Axcera 835-3 UHF television transmitter User Manual Chapter 2

UBS-Axcera UHF television transmitter Chapter 2

Chapter 2

3-kW UHF Transmitter Chapter 2, System Description835-3, Rev. 0 2-4Chapter 2System DescriptionThe 834-3 is a complete 3-kW UHF solid-state, internally diplexed television transmitterthat operates at a nominal visual output power of 3000 watts peak of sync and averageaural output power of 300 watts, at an A/V ratio of 10 dB. 2.1 System OverviewThe 835-3 is made up of two cabinets: a UHF exciter cabinet (the left cabinet) and anamplifier array cabinet (the right cabinet).This 835-3 (1176-1527) is comprised of (A1) a UHF exciter assembly (1227-1200), (A2)an amplifier array assembly (1245-1700), (A9) a bandpass filter (2005-1064), (A10) anoutput trap filter assembly, and (A11) an output coupler assembly (1020-1002).The left cabinet contains (A1) the UHF exciter assembly (1227-1200) for the 3-kWtransmitter, mounted at the top of the cabinet.The (A2) 3-kW amplifier array assembly (1176-1528) contains (A9-A1) an 8-waysplitter (ZFSC-8-43), (A9-A2) an ALC splitter board (1181-1002), six (A1 through A6)600-watt amplifier trays (1227-1300), (A7) a 6-way combiner, (A12) a reject loadassembly (1278-1312), (A10) an AC distribution panel (1245-1300), and (A11) aninterface panel.Switch S2 is an Automatic/Manual switch that controls the operation of the transmitterby the presence of the video input signal. When the switch is in Automatic, the greenLED DS3 is lit and, if the video input signal to the transmitter is lost, the transmitter willautomatically switch to Standby. When the video input signal returns, the transmitterwill automatically switch back to Operate. In Manual, the amber LED DS4 is lit and theoperation of the transmitter is controlled by the front panel switches. During normaloperation of the transmitter, switch S2 should be in the Automatic position. The frontpanel of the UHF exciter also has LEDs that indicate an overtemperature fault, (red LEDDS6), an ALC fault, (red LED DS8), a video fault (loss) (red LED DS9), and a VSWRcutback (amber LED DS7).The (A1) UHF exciter (1227-1200) takes the baseband audio and video inputs andproduces a diplexed, modulated, and on-channel frequency visual + aural RF output.The RF output of the UHF exciter at J15 is connected to (A2) the 3-kW amplifierassembly (1245-1700), where it is split six ways in (A9-A1) the 8-way power splitterassembly (ZFSC-8-43). The outputs of the splitter feed the six (A1, A2, A3, A4, A5, andA6) 600-watt amplifier trays (1227-1300) that amplify the RF signals to approximately600 watts each. A forward power sample from the 4-way combiner board inside the 600-watt amplifiertray is connected to the dual peak detector board. This board provides a peak-detectedforward sample to the amplifier control board that supplies the sample to the front panelmeter of the 600-watt amplifier tray. Before exiting each 600-watt amplifier tray, theRF is fed through a circulator for protection of the tray from high VSWR conditions. Thereject port of the circulator provides a reject sample to the 4-way combiner board thatsupplies the reflected sample to the dual peak detector board. The peak-detectedreflected sample connects to the amplifier control board that provides the sample to thefront panel meter of the tray. The outputs of the six 600-watt amplifier trays are then
3-kW UHF Transmitter Chapter 2, System Description835-3, Rev. 0 2-4combined in (A7) a 6-way combiner that provides approximately 3400 watts peak ofsync output. The combined output of the amplifier assembly is connected to (A9) abandpass filter, (A10) an output trap filter, and then to (A11) the output couplerassembly (1020-1002). The bandpass filter and trap filter are tuned to provide high out-of-band rejection of unwanted products. The output of the trap filter is cabled to (A11)an output coupler assembly that provides two forward and one reflected power samplesto the visual/aural metering board in the UHF exciter. The two forward samples areprocessed to provide peak-detected Visual and aural power output samples to thetransmitter control board. The reflected power sample is also peak detected and wired tothe transmitter control board. The transmitter control board connects the visual, aural,and reflected power output samples to the front panel meter for monitoring.2.2 Transmitter OperationThe 835-3 transmitter needs two AC inputs of 220 VAC: one to the exciter cabinet at 80amps and one to the amplifier assembly cabinet at 100 amps. In the exciter cabinet, the220-VAC input connects to the AC input assembly in the upper, right rear of the cabinet.The assembly contains terminal block TB1 that connects to the 220 VAC. The 220 VAC iswired from the AC input assembly to the TB1 in the AC distribution panel (1247-1100).The AC distribution panel contains six circuit breakers that supply the AC to the two UHFexciter trays, one for the 3-kW transmitter and one for the 1-kW transmitter. The inputAC is connected to CB1, the main AC circuit breaker (80 amps) that distributes the 220VAC to TB2. TB2 has three metal-oxide varistors (MOVs), mounted to the terminalblock: one connected from each leg of the input AC to ground and one across the twolegs.The input AC is wired from TB2 through five circuit breakers (CB2, CB3, CB4, CB5, andCB6) to the exciters and the rest of the 1-kW transmitter. CB2 (10 amps) supplies theAC voltage to the IEC outlet strip (A2-A1) into which the UHF exciter for the 3-kWtransmitter and the UHF exciter for the 1-kW transmitter are connected. A circuitbreaker mounted on the rear of each UHF exciter tray can be switched on and off tocontrol the AC to that individual UHF exciter Tray. CB3 (20 amps) supplies AC throughJ5 to (A6) the 600-watt amplifier tray. CB4 (20 amps) supplies AC through J6 to (A7)the 600-watt amplifier tray. When the UHF exciter circuit breaker is switched on, +12VDC from the bottom UHF exciter tray is supplied to the two 600-watt amplifier trays inthe 1-kW transmitter and +12 VDC from the top UHF exciter tray is supplied to the 3-kW amplifier array assembly for the operation of the LED status indicators in the tray.The baseband video and audio inputs to the 3-kW transmitter connect to the rear of(A1) the UHF exciter tray, the top exciter. The baseband video input connects to jack J1and the baseband audio input connects to jack J5, balanced audio, or to J3, forcomposite, stereo, audio. The back of the UHF exciter also provides connections forremote monitoring and operation of the transmitter at jack J11. Jack J11 should have adummy plug connected to it which has a jumper between pins 23 and 24 that providesthe interlock needed to operate the 3-kW transmitter. If remote connections are madeto the transmitter, they should be made through the plug in J11.2.2.1 (A2) 3-kW Amplifier Assembly (1245-1700)The (A2) 3-kW amplifier assembly contains (A9-A1) an 8-way splitter (ZFSC-8-43), (A9-A2) an ALC splitter board (1181-1002), six (A1 through A6) 600-watt amplifier trays(1227-1300), (A7) a 6-way combiner, (A12) a reject load assembly (1278-1312), and(A10) an AC distribution assembly, amplifier array (1245-1300).
3-kW UHF Transmitter Chapter 2, System Description835-3, Rev. 0 2-4The RF input from the UHF exciter tray connects to J1 on (A11) the interface panel inthe amplifier assembly. The RF is connected to the COM input of (A9-A1) the 8-waysplitter which splits it eight ways; six of the outputs are connected to J1, the RF input oneach of the 600-watt amplifier trays (1227-1300), and the other two outputs areterminated with 50-Ω loads. Each of the 600-watt amplifier trays amplify the RF signalsto the power needed to produce a total of 3000 watts peak of sync, with a maximum of600 watts.In each 600-watt amplifier tray, a forward power sample and a reflected power samplefrom the 4-way combiner board are connected to the dual peak detector board, singlesupply. This board provides peak-detected forward samples to the amplifier controlboard that supplies the samples to the front panel meter of the 600-watt amplifier tray.Before exiting each 600-watt amplifier tray, the RF is fed through a circulator for theprotection of the tray from high VSWR conditions. The reject port of the circulatorprovides a reject sample to the 4-way combiner board. The 4-way combiner boardsupplies the reflected sample to the dual peak detector board, single supply, in the traythat connects to the front panel meter.The outputs of the six 600-watt amplifier trays are combined in (A7) the 6-waycombiner that provides the 3000 watts peak of sync output with a maximum of 3600watts. The 6-way combiner has six reject outputs that connect to (A12) a reject loadassembly (1278-1312). The reject load assembly provides loads for any reject powergenerated due to mismatch in the combing process. The assembly provides a heatsink,(A12-A3 and A12-A5), two fans, and (A12-A4) a thermal switch. The thermal switch ismounted on the heatsink for the reject load assembly and connects to theovertemperature fault circuit on the transmitter control board in the UHF exciter tray;this shuts down the transmitter if an overtemperature fault occurs. The combined RFoutput for the transmitter is at the 1-5/8” hardline connector from the 6-way combiner.2.2.2 3-kW Transmitter Output AssembliesThe output of (A2) the amplifier assembly connects through a 1-5/8” to 3-1/8” adapterto (A9) a bandpass filter, (A10) an output trap filter assembly, and then to (A11) theoutput coupler assembly (1020-1002). The bandpass filter and trap filter are tuned toprovide high out-of-band rejection of unwanted generated products. The filtered signalis connected to (A11) an output coupler assembly that provides two combined forwardand a combined reflected power sample to the metering panel in the UHF exciterassembly.2.3 Control and StatusThe forward samples are processed to provide peak-detected visual and aural poweroutput samples to the front panel meter of the metering panel. The reflected powersample is also peak detected and wired to the front panel meter.The control and status of the 3-kW transmitter is provided by the meter indications onthe UHF exciter tray. The switches and LED indicators, which are mounted so that theswitches and LEDs are operated or viewed from the front panel of the UHF exciter, arepart of the transmitter control board (1265-1311). On the UHF exciter tray, switch S1 isan Operate/Standby switch that provides the Operate command (enable), when inOperate, to the amplifier array at J4-15 and J4-16, where it is split six ways andconnected to each 600-watt amplifier tray. The enable is needed to turn on theswitching power supplies in the 600-watt amplifier trays. When the UHF exciter is inOperate, the green LED DS2 is on and, when in Standby, the amber LED DS1 is on.
3-kW UHF Transmitter Chapter 2, System Description835-3, Rev. 0 2-4Note: If the transmitter does not switch to Operate when S1 is switched toOperate, check that a dummy jumper plug, with a jumper between pins 23 and24, is connected to jack J11 on the rear of the UHF exciter tray. This jumperprovides the interlock needed for the operation of the transmitter. If theinterlock is present, the green LED DS5 on the transmitter control board shouldbe lit.The operation of the transmitter is controlled by the front panel switches on the UHFexciter tray. During the normal operation of the transmitter, switch S2 should be in theAuto position. The front panel of the UHF exciter also has LEDs that indicate a videofault (loss) (red LED DS9) and a VSWR cutback (amber LED DS7).2.4 Baseband Input and Remote ConnectionsThe baseband video and audio inputs to the transmitter connect to the rear of the UHFexciter assembly. The baseband video input connects to jack J1. The baseband audioinput connects to J5 for balanced audio or to jack J3 for composite, stereo, audio.Remote monitoring and operation of the transmitter is provided through jacks J10 andJ11 on the rear of the UHF exciter tray. Jack J11 should have a dummy plug connectedto it, with a jumper connected between pins 23 and 24, that provides the interlock tothe exciter which is needed to operate the transmitter. If this jumper is missing, thetransmitter will not switch to Operate. If remote connections are made to thetransmitter, they should be made through the plug provided in the installation materialto jack J11 or J10 on the rear of the UHF exciter tray as shown in the transmitterinterconnect drawing.2.5 Main AC InputThe transmitter needs an AC input of 220 VAC at 100 amps for the amplifier assemblyand 80 amps for the UHF exciter and the 1-kW transmitter assembly.The 220-VAC input to the amplifier assembly connects to (A10) the AC distributionassembly, amplifier array (1245-1300), on the right side, center rear of the cabinet. Theassembly contains TB1, which is connected to the 220 VAC (line 1 to TB1-1, ground toTB1-2, and line 2 to TB1-3). The AC distribution panel contains seven circuit breakers that supply the AC to the restof the exciter assembly. The input AC from TB1 is connected to CB1, the main AC circuitbreaker (100 amps), that distributes the 220 VAC to the other six circuit breakers. Theoutput of CB1 has three MOVs (VR1, VR2, and VR3) mounted to it, one connected fromeach leg of the input AC to ground and one across the two legs. The switched input AC iswired through the six circuit breakers, CB2 to CB7, to the six 600-watt amplifier trays inthe amplifier cabinets. CB2 is a 20-amp circuit breaker that supplies the AC voltage to(A1) the 600-watt amplifier tray. CB3 is a 20-amp circuit breaker that supplies the ACvoltage to (A2) the 600-watt amplifier tray. CB4 is a 20-amp circuit breaker thatsupplies the AC voltage to (A3) the 600-watt amplifier tray. CB5 is a 20-amp circuitbreaker that supplies the AC voltage to (A4) the 600-watt amplifier tray. CB6 is a 20-amp circuit breaker that supplies the AC voltage to (A5) the 600-watt amplifier tray.CB7 is a 20-amp circuit breaker that supplies the AC voltage to (A6) the 600-wattamplifier tray.The 220 VAC input to the UHF exciter assembly and 1-kW transmitter connects to (A8)
3-kW UHF Transmitter Chapter 2, System Description835-3, Rev. 0 2-4the AC distribution assembly (1247-1100) in the right, center rear of the cabinet. Theassembly contains TB1, which connects to the 220 VAC (line 1 to TB1-1, line 2 to TB1-2,and ground to TB1-3). The AC distribution panel contains one circuit breaker thatsupplies the AC to the rest of the cabinet. The input AC is connected to CB1, the mainAC circuit breaker (80 amps).The output of CB1 has two neon glow tubes, connected in series, that will light when thecircuit breaker is switched on. The AC connects to TB2, which has three MOVs (VR1,VR2, and VR3) connected to it, one connected from each leg of the input AC to groundand one across the two legs. The AC output of TB2 connects to five circuit breakers (CB2through CB6). CB2 is a 10-amp circuit breaker that supplies the AC voltage to (A1) theIEC outlet strip. The (A1) UHF exciter tray and the UHF exciter tray for the 1-kWtransmitter should connect to the IEC outlet strip. CB3 is a 20-amp circuit breaker thatsupplies the AC voltage to (A6) the 600-watt amplifier tray. CB4 is a 20-amp circuitbreaker that supplies the AC voltage to (A7) the 600-watt amplifier tray. The CB5 andCB6 circuit breakers are not used in the 1-kW transmitter.When the circuit breaker for the exciters on the exciter cabinet AC distribution panel isswitched on, and the AC circuit breakers on the rear of the trays are on, +12 VDC fromthe UHF exciters is supplied to the amplifier array cabinet and the two amplifier trays inthe 1-kW transmitter. The +12 VDC is split six ways in the amplifier array cabinet andthen connected to each of the 600-watt amplifier trays for the operation of the LEDstatus indicators in the tray.

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