System Description Chapter 2

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).