UBS Axcera 835-3 UHF television transmitter User Manual Chapter 2
UBS-Axcera UHF television transmitter Chapter 2
Contents
Chapter 2
3-kW UHF Transmitter Chapter 2, System Description
835-3, Rev. 0 2-4
Chapter 2
System Description
The 834-3 is a complete 3-kW UHF solid-state, internally diplexed television transmitter
that operates at a nominal visual output power of 3000 watts peak of sync and average
aural output power of 300 watts, at an A/V ratio of 10 dB.
2.1 System Overview
The 835-3 is made up of two cabinets: a UHF exciter cabinet (the left cabinet) and an
amplifier 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) an
output 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-kW
transmitter, mounted at the top of the cabinet.
The (A2) 3-kW amplifier array assembly (1176-1528) 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), (A10) an AC distribution panel (1245-1300), and (A11) an
interface panel.
Switch S2 is an Automatic/Manual switch that controls the operation of the transmitter
by the presence of the video input signal. When the switch is in Automatic, the green
LED DS3 is lit and, if the video input signal to the transmitter is lost, the transmitter will
automatically switch to Standby. When the video input signal returns, the transmitter
will automatically switch back to Operate. In Manual, the amber LED DS4 is lit and the
operation of the transmitter is controlled by the front panel switches. During normal
operation of the transmitter, switch S2 should be in the Automatic position. The front
panel of the UHF exciter also has LEDs that indicate an overtemperature fault, (red LED
DS6), an ALC fault, (red LED DS8), a video fault (loss) (red LED DS9), and a VSWR
cutback (amber LED DS7).
The (A1) UHF exciter (1227-1200) takes the baseband audio and video inputs and
produces 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 amplifier
assembly (1245-1700), where it is split six ways in (A9-A1) the 8-way power splitter
assembly (ZFSC-8-43). The outputs of the splitter feed the six (A1, A2, A3, A4, A5, and
A6) 600-watt amplifier trays (1227-1300) that amplify the RF signals to approximately
600 watts each.
A forward power sample from the 4-way combiner board inside the 600-watt amplifier
tray is connected to the dual peak detector board. This board provides a peak-detected
forward sample to the amplifier control board that supplies the sample 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 protection of the tray from high VSWR conditions. The
reject port of the circulator provides a reject sample to the 4-way combiner board that
supplies the reflected sample to the dual peak detector board. The peak-detected
reflected sample connects to the amplifier control board that provides the sample to the
front panel meter of the tray. The outputs of the six 600-watt amplifier trays are then
3-kW UHF Transmitter Chapter 2, System Description
835-3, Rev. 0 2-4
combined in (A7) a 6-way combiner that provides approximately 3400 watts peak of
sync output. The combined output of the amplifier assembly is connected to (A9) a
bandpass filter, (A10) an output trap filter, and then to (A11) the output coupler
assembly (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 samples
to the visual/aural metering board in the UHF exciter. The two forward samples are
processed to provide peak-detected Visual and aural power output samples to the
transmitter control board. The reflected power sample is also peak detected and wired to
the 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 Operation
The 835-3 transmitter needs two AC inputs of 220 VAC: one to the exciter cabinet at 80
amps and one to the amplifier assembly cabinet at 100 amps. In the exciter cabinet, the
220-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 is
wired 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 UHF
exciter trays, one for the 3-kW transmitter and one for the 1-kW transmitter. The input
AC is connected to CB1, the main AC circuit breaker (80 amps) that distributes the 220
VAC to TB2. TB2 has three metal-oxide varistors (MOVs), mounted to the terminal
block: one connected from each leg of the input AC to ground and one across the two
legs.
The input AC is wired from TB2 through five circuit breakers (CB2, CB3, CB4, CB5, and
CB6) to the exciters and the rest of the 1-kW transmitter. CB2 (10 amps) supplies the
AC voltage to the IEC outlet strip (A2-A1) into which the UHF exciter for the 3-kW
transmitter and the UHF exciter for the 1-kW transmitter are connected. A circuit
breaker mounted on the rear of each UHF exciter tray can be switched on and off to
control the AC to that individual UHF exciter Tray. CB3 (20 amps) supplies AC through
J5 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, +12
VDC from the bottom UHF exciter tray is supplied to the two 600-watt amplifier trays in
the 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 J1
and the baseband audio input connects to jack J5, balanced audio, or to J3, for
composite, stereo, audio. The back of the UHF exciter also provides connections for
remote monitoring and operation of the transmitter at jack J11. Jack J11 should have a
dummy plug connected to it which has a jumper between pins 23 and 24 that provides
the interlock needed to operate the 3-kW transmitter. If remote connections are made
to 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 Description
835-3, Rev. 0 2-4
The RF input from the UHF exciter tray connects to J1 on (A11) the interface panel in
the amplifier assembly. The RF is connected to the COM input of (A9-A1) the 8-way
splitter which splits it eight ways; six of the outputs are connected to J1, the RF input on
each of the 600-watt amplifier trays (1227-1300), and the other two outputs are
terminated with 50-Ω loads. Each of the 600-watt amplifier trays amplify the RF signals
to the power needed to produce a total of 3000 watts peak of sync, with a maximum of
600 watts.
In each 600-watt amplifier tray, a forward power sample and a reflected power sample
from the 4-way combiner board are connected to the dual peak detector board, single
supply. This board provides peak-detected forward samples to the amplifier control
board 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 the
protection of the tray from high VSWR conditions. The reject port of the circulator
provides a reject sample to the 4-way combiner board. The 4-way combiner board
supplies the reflected sample to the dual peak detector board, single supply, in the tray
that connects to the front panel meter.
The outputs of the six 600-watt amplifier trays are combined in (A7) the 6-way
combiner that provides the 3000 watts peak of sync output with a maximum of 3600
watts. The 6-way combiner has six reject outputs that connect to (A12) a reject load
assembly (1278-1312). The reject load assembly provides loads for any reject power
generated 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 is
mounted on the heatsink for the reject load assembly and connects to the
overtemperature fault circuit on the transmitter control board in the UHF exciter tray;
this shuts down the transmitter if an overtemperature fault occurs. The combined RF
output for the transmitter is at the 1-5/8” hardline connector from the 6-way combiner.
2.2.2 3-kW Transmitter Output Assemblies
The output of (A2) the amplifier assembly connects through a 1-5/8” to 3-1/8” adapter
to (A9) a bandpass filter, (A10) an output trap filter assembly, and then to (A11) the
output coupler assembly (1020-1002). The bandpass filter and trap filter are tuned to
provide high out-of-band rejection of unwanted generated products. The filtered signal
is connected to (A11) an output coupler assembly that provides two combined forward
and a combined reflected power sample to the metering panel in the UHF exciter
assembly.
2.3 Control and Status
The forward samples are processed to provide peak-detected visual and aural power
output samples to the front panel meter of the metering panel. The reflected power
sample 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 on
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 (1265-1311). On the UHF exciter tray, switch S1 is
an Operate/Standby switch that provides the Operate command (enable), when in
Operate, to the amplifier array at J4-15 and J4-16, where it is split six ways and
connected to each 600-watt amplifier tray. The enable is needed to turn on the
switching power supplies in the 600-watt amplifier trays. When the UHF exciter is in
Operate, the green LED DS2 is on and, when in Standby, the amber LED DS1 is on.
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835-3, Rev. 0 2-4
Note: If the transmitter does not switch to Operate when S1 is switched to
Operate, check that a dummy jumper plug, with a jumper between pins 23 and
24, is connected to jack J11 on the rear of the UHF exciter tray. This jumper
provides the interlock needed for the operation of the transmitter. If the
interlock is present, the green LED DS5 on the transmitter control board should
be lit.
The operation of the transmitter is controlled by the front panel switches on the UHF
exciter tray. During the normal operation of the transmitter, switch S2 should be in the
Auto position. The front panel of the UHF exciter also has LEDs that indicate a video
fault (loss) (red LED DS9) and a VSWR cutback (amber LED DS7).
2.4 Baseband Input and Remote Connections
The baseband video and audio inputs to the transmitter connect to the rear of the UHF
exciter assembly. The baseband video input connects to jack J1. The baseband audio
input 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 and
J11 on the rear of the UHF exciter tray. Jack J11 should have a dummy plug connected
to it, with a jumper connected between pins 23 and 24, that provides the interlock to
the exciter which is needed to operate the transmitter. If this jumper is missing, the
transmitter will not switch to Operate. If remote connections are made to the
transmitter, they should be made through the plug provided in the installation material
to jack J11 or J10 on the rear of the UHF exciter tray as shown in the transmitter
interconnect drawing.
2.5 Main AC Input
The transmitter needs an AC input of 220 VAC at 100 amps for the amplifier assembly
and 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 distribution
assembly, amplifier array (1245-1300), on the right side, center rear of the cabinet. The
assembly contains TB1, which is connected to the 220 VAC (line 1 to TB1-1, ground to
TB1-2, and line 2 to TB1-3).
The AC distribution panel contains seven circuit breakers that supply the AC to the rest
of the exciter assembly. The input AC from TB1 is connected to CB1, the main AC circuit
breaker (100 amps), that distributes the 220 VAC to the other six circuit breakers. The
output of CB1 has three MOVs (VR1, VR2, and VR3) mounted to it, one connected from
each leg of the input AC to ground and one across the two legs. The switched input AC is
wired through the six circuit breakers, CB2 to CB7, to the six 600-watt amplifier trays in
the 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 AC
voltage to (A2) the 600-watt amplifier tray. CB4 is a 20-amp circuit breaker that
supplies the AC voltage to (A3) the 600-watt amplifier tray. CB5 is a 20-amp circuit
breaker 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-watt
amplifier tray.
The 220 VAC input to the UHF exciter assembly and 1-kW transmitter connects to (A8)
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835-3, Rev. 0 2-4
the AC distribution assembly (1247-1100) in the right, center rear of the cabinet. The
assembly 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 that
supplies the AC to the rest of the cabinet. The input AC is connected to CB1, the main
AC circuit breaker (80 amps).
The output of CB1 has two neon glow tubes, connected in series, that will light when the
circuit 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 ground
and one across the two legs. The AC output of TB2 connects to five circuit breakers (CB2
through CB6). CB2 is a 10-amp circuit breaker that supplies the AC voltage to (A1) the
IEC outlet strip. The (A1) UHF exciter tray and the UHF exciter tray for the 1-kW
transmitter should connect to the IEC outlet strip. CB3 is a 20-amp circuit breaker that
supplies the AC voltage to (A6) the 600-watt amplifier tray. CB4 is a 20-amp circuit
breaker that supplies the AC voltage to (A7) the 600-watt amplifier tray. The CB5 and
CB6 circuit breakers are not used in the 1-kW transmitter.
When the circuit breaker for the exciters on the exciter cabinet AC distribution panel is
switched on, and the AC circuit breakers on the rear of the trays are on, +12 VDC from
the UHF exciters is supplied to the amplifier array cabinet and the two amplifier trays in
the 1-kW transmitter. The +12 VDC is split six ways in the amplifier array cabinet and
then connected to each of the 600-watt amplifier trays for the operation of the LED
status indicators in the tray.