Data Sheet Chapter 5

10-kW UHF Transmitter with Chapter 5, Detailed Alignment Procedures
Feedforward Drive
840A, Rev. 0 5-21
(1265-1302). Connect a sync and black
test signal to the video input jack of the
UHF exciter tray. Switch the transmitter
to Operate.
Next, set up the transmitter for the
appropriate average output power level
(sync + black 0 IRE setup/wattmeter
=5950 watts; sync + black 7.5 IRE
setup/wattmeter=5400 watts).
Note: The transmitter must have 40
IRE units of sync.
Adjust R28, visual and audio calibration,
on (A19-A2) the visual/aural metering
board (1161-1103) for 2 volts on FL5 on
the visual/aural metering assembly.
Adjust R29 on the same board for 100%
on the front panel meter in the % Visual
Output position.
With the spectrum analyzer set to zero
span mode, obtain a peak reference on
the screen with the following readings:
• Resolution bandwidth – maximum
• Span – 0 MHz
• Scale – linear
Reconnect jumper cable W1 to J16 on
(A5) the sync tip clamp on the modulator
board. Turn the power adjust pot on the
3-watt amplifier tray front panel until the
original peak reference level is attained.
Peak C5 for a maximum aural power
reading and then also adjust R11 for a
100% aural power reading. Switch to the
Visual Output Power position and adjust
R39 for 100% Visual Power. Turn the 3-
watt amplifier tray front panel gain pot
fully CCW and switch the exciter to
standby. Re-terminate the drive output
into the diacrode cavity.
5.11 Calibration of Reflected
Metering
Adjust the 3-watt amplifier tray front
panel gain pot for 15% Visual Power on
the metering control panel. Switch S4,
the power meter, to the Reflected
position. Reverse the J6 cable and the J4
termination on (A18) the final output
coupler. Adjust R6 on (A19-A1) the single
peak detector board (1164-1403) in the
visual/audio metering assembly for a
15% Reflected Power reading. Return J4
and J6 to their original positions.
5.12 Board Level Adjustments
5.12.1 (A1) Control Logic Board
(1137-1402; Appendix B)
The rear of the metering control panel is
shown in Figure 5-4. The control logic
board is in the metering control panel
and provides the circuitry needed for the
control of the automatic on/off sequence
of the transmitter and the monitoring of
the operation of the transmitter for fault
conditions. An Operate command and the
interlocks for the transmitter are also
connected to the board.
The control logic board monitors the air-
on sense, the filament-on sense, the
bias-on sense, the high voltage-on sense,
and the screen-on sense commands
during each step of the automatic turn-
on procedure. The board also provides
the on-command outputs in the proper
sequence and enables to the Command
Status and Operating Status LEDs on the
front panel. The fault circuits monitor the
operation of the power supplies and the
tube, the air flow to the tube, and the
temperature of the transmitter; the
board will shut down the transmitter if
any of these faults occur.
The board supplies the air-on, filament-
on, bias-on, screen-on, high voltage-on,
and RF-on commands to the transmitter.
In addition, the board is connected to the
High-Voltage Enable/Disable switch to
provide commands to magnetic latching
relay K1.