System Description Chapter 2

10-kW UHF Transmitter with Chapter 2, System Description
Feedforward Driver
840A, Rev. 0 2-2
load/coupler board; this board supplies
the reflected sample to the dual peak
detector board, single supply. This signal
is then sent to the amplifier control board
for metering purposes. The output of the
250-watt visual amplifier trays is
combined in a UHF tee combiner, and fed
through (A14) a bandpass filter and
(A11) a directional coupler, before being
connected with1/2" heliax to the RF input
jack (A2-A1-J1) of the tube cavity
assembly in the 10-kW amplifier
assembly cabinet. The combined output
of the 250-watt visual amplifier trays
(350 watts) is the level needed to drive
the 10-kW amplifier to 10,000 watts
peak sync visual output.
The main AC input to the
exciter/amplifier assembly is (A2) the AC
distribution panel assembly (1265-1600).
The AC distribution panel assembly
contains a terminal block (TB1) that
connects to the main AC input (208/240
VAC). The terminal block has four metal-
oxide varistors (MOVs) connected across
the input lines for surge and transient
protection. The AC distribution panel
contains CB1, the 40-amp main AC
circuit breaker that distributes the AC
through the circuit breakers CB2 to CB7
to the exciter and amplifier trays.
2.1.2 (A2) 10-kW Diacrode Amplifier
(1299-1100; Appendix A)
The (A11) metering control panel (1293-
1308) on the amplifier assembly provides
the operator with front panel metering
for all voltage (M1 using S1) and current
(M2 using S3) readings that apply to the
tube. The metering control panel also
provides the aural, visual, and reflected
output power readings for the transmitter
using meter M3 with switch S4. The front
panel assembly contains the switches
that control the Operate/Standby (S5)
and Automatic/Manual (S6) operation of
the 10-kW amplifier. When switched to
Operate, the panel supplies the driver
enable (Operate command) to the
exciter/amplifier assembly. The
Automatic/Manual switch selects either
the automatic operation of the
transmitter, which uses the video input
to control the on/off state of the
transmitter, or the Normal front panel
control, manual operation, of the
transmitter. The metering control panel
also provides front panel control, through
switch S8, of the Visual Output Power
level. High-Voltage Enable/Disable switch
S7 controls the high-voltage power
supply from the front panel of the 10-kW
diacrode amplifier. Normal/Exciter Test
switch S10, when in the Exciter Test
position, gives the operator the ability to
operate the exciter/amplifier assembly
without operating the 10-kW amplifier.
Note: The exciter/amplifier assembly
output must be terminated into a
dummy load prior to using this
function
.
The metering control panel also has LEDs
on the front panel for a visual indication
of the operating status of the
transmitter: Operate/Standby,
Auto/Manual, High Voltage
Enable/Disable, Driver Mode
Normal/Test, 3-Fault with Fault Reset
Switch (S9), Fault Status Overtemp, and
VSWR Cutback. The front panel has
command status LEDs that indicate,
when they are lit, that the command has
been given. In addition, the front panel
has Operate status LEDs that indicate,
when they are lit, that the command has
been carried out.
The metering control panel of the (A10)
remote control and cabinet interface
assembly provides intercabinet control
and monitoring for the exciter and high-
voltage cabinets. The remote control and
cabinet interface assembly also provides
remote access to the transmitter for
monitoring and control purposes.
The (A6) screen power supply assembly,
60 Hz (1293-1321), in the rear
compartment of the amplifier cabinet,
produces the 500 VDC at 60 mA for the
tube. The (A5) control and bias power
supply assembly (1181-1402) contains