User's Manual

3300-Watt VHF Low Band Transmitter Chapter 5, Detailed Alignment Procedures
335B, Rev. 0 5-6
to 110%, sync only, and adjust R12 until
the output power begins to drop off.
Return the output power level of the
transmitter to 100%.
5.6.6 (A3-A3) 3-Way Splitter Board
(1198-1608; Appendix D)
There are no tuning adjustments for (A3-
A3) the 3-way splitter board. The board
takes the +41.3 dBm input and splits it
into three equal +36.3 dBm outputs.
5.6.7 (A4-A1, A4-A2, and A4-A3)
VHF Low-Band Amplifier Pallet
(1304348; Appendix D)
These pallets, P400-VHF-L, are supplied
by Delta RF Technology, Inc. Refer to
the data sheets in the subassembly
section of this manual for more
information. Each board has
approximately 18 dB of gain and with an
input of +36.3 dBm the output is
typically +54.3 dBm.
5.6.8 (A5-A1) 3-Way Combiner
Board (1198-1626; Appendix D)
There are no adjustments to the (A5-A1)
3-way combiner board. The three +54.3
dBm inputs are combined to produce the
750 watts, +58.8 dBm, peak of sync
output at J2 of the combiner assembly.
5.6.9 Calibration of the Visual Plus
Aural Output Power and VSWR
Cutback of the Tray
Check that a dummy load of at least 750
watts is connected to the output of the
tray that is to be calibrated. Place switch
S1 on the AGC control board in the
Manual position before beginning the
setup.
To adjust the visual output power levels:
1. Remove the J16 cable from (A5) the
sync tip clamp/modulator board
(1265-1302) in the VHF exciter tray.
Set the Manual AGC switch S1, on the
(A13) AGC control board (1142-1601)
in the VHF L.B. amplifier tray, 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 the manual gain pot R5 on the
AGC control board for:
• Sync + black 0 IRE setup;
wattmeter=450 watts
• Sync + black 7.5 IRE setup;
wattmeter=405 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 VHF 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 J6
and J7 cables on the 3-way combiner
enclosure.
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