Data Sheet Chapter 5

500-Watt VHF Transmitter Chapter 5, Detailed Alignment Procedures
425A, Rev. 0 5-9
600-watt amplifier, to the Manual
position. Turn the transmitter to the
Operate position.
2. Connect a sync and black test signal
to the video input jack of the remote
interface panel.
3. Adjust manual gain pot R5 on the
AGC control board for:
• Sync + black 0 IRE setup;
wattmeter=180 watts
• Sync + black 7.5 IRE setup;
wattmeter=163 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.
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%.
Switch off the tray and reverse the J9
and J11 cables on the 4-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.
Readjust R5 for 100% on the meter to
achieve a 300 watts peak of sync and
sound 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 J9 and
J11 cables on the 4-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 600-watt amplifier tray is aligned,
calibrated, and ready for normal
operation.
5.12 Board Level Alignment
Procedures
5.12.1 (Optional) 4.5-MHz
Composite Input Kit
If the (optional) 4.5-MHz composite input
kit is purchased, the tray is capable of
operating by using either the 4.5-MHz
composite input or the baseband audio
and video inputs. The kit adds the (A24)
composite 4.5-MHz filter board (1227-
1244; Appendix D) and the (A25) 4.5-
MHz bandpass filter board (1265-1307;
Appendix D) to the transmitter. When the
4.5-MHz intercarrier signal generated by
the 4.5-MHz composite input has been
selected by the 4.5-MHz composite input
kit, the 4.5-MHz generated by the aural
IF synthesizer board is not used. When
the 4.5-MHz intercarrier signal generated