System Description

835A 4 kW, 5 kW or 6 kW UHF Transmitter System Description
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(A2 & A3) 2-3 kW Amplifier Assemblies (1278-1300) - Continued
The RF Input from the Variable Phase/Gain Tray connects to J1 on (A11) the Interface Panel located in the Amplifier Array
Assembly. The RF is connected to the COM Input of (A9-A1) the 8 Way Splitter which splits it eight ways. The outputs
connected to J1, the RF Input Jack on each of the UHF Amplifier Trays or are terminated with 50Ω. Each of the UHF
Amplifier Trays amplify the RF signals to the power needed to produce a the total output power for the Transmitter , with a
maximum of 600 Watts per Tray. The outputs of the UHF Amplifier Trays are combined in (A7) the 4, 5 or 6 Way Combiner
that provides approximately half of the power needed to generate the desired Peak of Sync Output with a maximum of 3000
Watts per Array Assembly. The Combined RF Output is connected to (A8) the Output Coupler Assembly which supplies a
Forward and a Reflected Power Sample of the output from the Amplifier Assembly to the Metering Panel in the Single Exciter
Assembly. The reject output of the Combiner connects to (A12-A2) the Combiner Reject Load Board which dissipates any
reject due to miss-tuning or a malfunction in any of the Amplifier Trays.
In each UHF Amplifier Tray, a Forward Power Sample and a Reflected Power Sample, from the Combiner Board, are
connected to the Dual Peak Detector Board, Single Supply which provides peak detected forward samples to the Amplifier
Control Board that supplies the samples to the front panel meter of the UHF Amplifier Tray. Before exiting each UHF
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 Combiner Board which supplies the Reflected Sample to the Dual Peak Detector
Board, Single Supply located in the Tray that connects to the front panel meter for monitoring purposes.
Transmitter Output Assemblies
The outputs of the (A2 & A3) Amplifier Assemblies connect through (A5 or A6) 1-5/8” to 3-1/8” Adapters to (A4) a Hybrid
Combiner which combines the output from each Amplifier Assembly into a single output. The Reject Output of the Hybrid
Combiner is connected through (A12) a 1-5/8” to 3-1/8” Adapter to (A7) a Directional Coupler (1016-1043) which provides a
Reject Sample from J3 to the Metering Panel located in the Single UHF Exciter Assembly for monitoring purposes. The
output of the Directional Coupler connects to (A8) a 2500 Watt Reject Load which dissipates any reject due to problems in one
of the Amplifier Arrays. Mounted on the 2500 Watt Load is (A8-A1) a Thermal Switch that connects to the Overtemperature
Fault circuit located on the Transmitter Control Board in the UHF Exciter Tray. If the temperature of the load reaches 155°F.
the switch closes and causes an Overtemperature Fault to occur which shuts down the Tray.
The output of the Hybrid Combiner at J3 is fed to (A9) a Bandpass Filter, (A10) an Output Trap Filter Assembly, then to (A11)
the Output Coupler Assembly and finally to the Antenna for your System. 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 which provides a Combined Forward and a Combined Reflected Power Sample to the Metering Panel
located in the Single UHF Exciter Assembly. The Forward Sample is 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. A Sample of the RF Output, for test purposes can be taken from J5 on the Coupler, but a 20 dB
Attenuator must be connected to J6 for the Sample port to operate. An appropriate attenuator must be connected to J5 to
protect any test equipment connected to it.
Control and Status
The Control and Status of the Transmitter are provided by the Meter indications on the Metering Control Panel and the
Variable Phase/Gain 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 (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 each of the Amplifier Arrays.
The Enable to each Amplifier Array Assembly at J4-15 & 16 is split ways on the terminal block A9-TB2 which are then
applied to each of the UHF Amplifier Trays. The Enable is needed to turn on the Switching Power Supplies located in each of