User's Manual

2650 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures
435B, Rev. 0 5-12
interface panel. Switch the
transmitter to the Operate position.
3. Adjust the manual gain pot R5 on the
AGC control board for:
• Sync + black 0 IRE setup;
wattmeter=360 watts
• Sync + black 7.5 IRE setup;
wattmeter=325 watts
NOTE: The transmitter must have 40 IRE
units of sync.
4. Obtain a zero span reference of the
visual-only carrier on a spectrum
analyzer. Replace the J16 connector
on the sync tip clamp/modulator
board in the exciter tray. Adjust R5
on the AGC control board until the
same visual reference is obtained.
Adjust R44 on the AGC control board
for 100% Forward Power.
5. Lower the forward power reading to
80% on the front panel meter using
R5, the manual gain adjust on the
AGC control board. Adjust R65, the
AGC fault adjust on the AGC control
board, until the green Module LED
DS3 on the front panel just begins to
light. Use R5 to readjust the forward
power to 100%.
6. Switch Off the tray and reverse the J6
and J7 cables on the 3 way combiner
board. Switch On the tray and adjust
the front panel meter, in the
Reflected Output Power position, to a
100% reading using R53, the
reflected power meter adjust on the
AGC control board. Adjust the
reflected output power to a 20%
reading using R5 on the AGC control
board. Adjust R59, the VSWR
cutback adjust on the AGC control
board, until the red VSWR Cutback
LED DS4 on the front panel lights.
This sets up the VSWR cutback
circuitry.
7. Readjust R5 for 100% on the meter
to achieve a 750 watts peak of sync
+ aural output. However, if the
system requires less output power
per amplifier tray, adjust each tray by
the same amount to give the desired
total output power.
Switch Off the tray and return the J6 and
J7 cables on the 3 way combiner board
back to their original positions. If the
tray was originally operating below 100%
output power, the AGC fault adjust was
set for 20% below the operational %
Output Power of the tray. See the Test
Data Sheet for the transmitter for the
actual readings for the tray.
Place S1 on the AGC control board in the
AGC position. This is the normal
operating position after the setup is
completed.
There is a spare 1 amp and 10 amp fuse
on the top, right-hand side of the tray.
These are replacements for fuses on the
current metering board.
The VHF high band amplifier tray is
aligned, calibrated, and ready for normal
operation. Repeat as needed for the
other amplifier tray.
5.3 Phase and Gain Adjustment of
the VHF Amplifier Trays
The following procedure was completed
at the factory and should only be
followed if one of the VHF amplifier trays
is replaced.
Preset the phase and gain potentiometer
on each VHF amplifier tray fully CCW.
Switch the transmitter to Operate and
adjust the gain pot on each tray for 25%
Output Power. Adjust the phase control
CW on the left VHF amplifier tray. If the
% Visual Output Power goes up, continue
to adjust the phase control until either
the peak is reached or the end-of-travel
is reached. If the % Output Power goes
down, reset the phase control on the VHF
amplifier tray fully CCW and repeat the
above procedure with the phase control
of the other amplifier tray.