Data Sheet Chapter 5

500-Watt VHF Transmitter Chapter 5, Detailed Alignment Procedures
425A, Rev. 0 5-6
5.9 (A11) 2-Way Combiner Assembly
(1219-1006; Appendix C)
There are no adjustments to (A11) the
VHF combiner assembly (1219-1006).
Note: The bandpass filter is factory
swept and should not be tuned
without the proper equipment. Do
not attempt to tune the filters
without a sweep generator or,
preferably, a network analyzer. If
tuning is required, consult the ADC
Field Support Department before
attempting to make any
adjustments.
5.10 (A13) Bandpass Filter
Assemblies (1076294 through
1076297; Appendix C)
The input to the (A13) bandpass filter
assemblies (1076294 through 1076297)
is the output of the VHF combiner
assembly, which is the combined output
of the VHF amplifier trays. The filter is
made of aluminum waveguide and has
five resonant cavities. The filter has five
bolts for tuning adjustments. The
bandpass filter also utilizes two integral
traps at -4.5 MHz and +9 MHz from F
V
.
Refer to the bandpass filter drawing for
the location of the adjustments.
To tune the filter, connect a sweep signal
to the input of the filter and adjust the
five tuning bolts for a 6-MHz bandwidth
and a flat-frequency response across the
desired band.
Note: The bandpass ripple should be
≤
≤≤
≤
0.25 dB. The 6-MHz band should
also have a minimum of 20 dB return
loss across the pass band.
Table 5-1 contains typical values for the
bandpass filter.
Table 5-1. Bandpass Filter Typical Values
FREQUENCY INSERTION LOSS (DB) RETURN LOSS (DB)
F
V
-4.5
≥ 35
F
V
-0.5
≥ 20
F
V
≤ 0.8 ≥ 20
F
a
≤ 0.8 ≥ 20
F
V
+8.08
≥ 15
F
V
-9
≥ 30
2F
V
≥ 30
5.11 (A6 and A7) 600-Watt High-
Band VHF Amplifier Tray (1219-
1100; Appendix C)
The (A6 and A7) 600-watt high-band VHF
amplifier tray (1219-1100) has been
adjusted at the factory to meet all
specifications, including phase
adjustment to match the multiple trays in
an amplifier array when they are
combined. The tray should not need to
be adjusted to attain normal operation.
Any adjustments to the boards in this
tray should be performed in the Manual
Gain position, with S1 on (A13) the AGC
control board (1142-1601) in Manual.
The idling current for the amplifier boards
are adjusted with no RF drive applied. S1
should be in the Auto AGC position for
the normal operation of the transmitter.
Connect a dummy load with a rating of a
least 300 watts to J2, the RF output jack
of the tray.
5.11.1 (A13) AGC Control Board
(1142-1601; Appendix D)
Using a calibrated wattmeter, check that
the tray is operating at the rated power.
Remove the sample forward power
connection J4 from the (A13) AGC control