User's Manual

3300-Watt VHF Low Band Transmitter Chapter 5, Detailed Alignment Procedures
335B, Rev. 0 5-14
2. The combined IF output of the sync
tip clamp modulator board is cabled
to jack J32 of the ALC board.
Remove J32 from the board, and
look to see if DS1, Input Fault, is
illuminated. Reconnect J32 and
make sure that DS1 is
extinguished.
3. Jumper W3 on J6 should be in the
Manual position. Monitor jack J3
with a spectrum analyzer.
4. With a multiburst video signal
present, tune C4 for a flat-
frequency response of ±0.5 dB.
5. Before proceeding with the second
part of the ALC board alignment,
check to see that the IF phase
corrector board (1227-1250) is
functioning properly.
5.12.9 (A9) IF Phase Corrector Board
(1227-1250; Appendix D)
This board is set up during system
alignment. The signal level into the
board should be approximately the same
as the output of the board.
The IF input jack (0 dBm) of the IF phase
corrector board is fed from the J3 IF O/P
jack of (A8) the ALC board.
The IF output jack of the IF phase
corrector board at J4 is fed to J7 IF I/P
jack (0 dBm) of the ALC board (A8).
5.12.10 (A8) ALC Board (1265-1305;
Appendix D) (Part 2 of 2)
To align this board:
1. Input a multiburst video test signal.
Connect a spectrum analyzer to
J11. Tune C63 for a flat-frequency
response of ±0.5 dB.
2. Move the Operate/Standby switch
on the front panel to the Operate
position.
3. Place jumper W3 on jack J6 in the
Manual mode and adjust R87 for
0.5 volts at TP4.
4. Place jumper W3 on J6 in the Auto
mode and adjust the front panel
power adjust control A20 fully CW.
If the (optional) remote power
raise/lower kit is present, then
adjust switch S1 on the board to
maximum voltage at TP4. Adjust
R74, the range adjust, for 1 volt at
TP4.
5. Adjust the front panel power adjust
control A20 for 0.5 VDC at TP4. If
the (optional) remote power
raise/lower kit is present, move
switch S1 on the board to mid-
range and then adjust (A20) the
front panel power adjust control for
0.8 VDC at TP4.
6. Disconnect the plug that is on J12
(IF output) and monitor J12 with a
spectrum analyzer. Verify an output
of approximately 0 dBm. If
necessary, adjust R99 to increase
the output level. If less of an output
level is needed, move jumpers J27
and J28 to pins 2 and 3 and then
adjust R99. Reconnect J12.
7. Move W2 on J5 to the Cutback
Enable position. Remove the input
video signal and verify that the
output of the transmitter drops to
25%. Adjust R71, the cutback level,
if necessary. Restore the input
video.
NOTE: The following step affects the
response of the entire transmitter.
8. Connect a video sweep signal to the
input of the tray. Monitor the
output of the system with a
spectrum analyzer. Adjust C71 with
R103 and C72 with R106, as
needed, to flatten the response.
C71 and C72 adjust for the
frequency of the correction notch
being applied to the visual response