Data Sheet Chapter 5

10-kW UHF Transmitter with Chapter 5, Detailed Alignment Procedures
Feedforward Drive
840A, Rev. 0 5-17
line, one quarter of a wavelength long, to
transform the output impedance of the
tee to 50Ω. The output of the UHF tee is
then sent to (A9) a bandpass waveguide
filter.
Note: The bandpass filter and the
(optional) trap filter are 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 with the
ADC Field Support Department
before attempting to tune the filters.
5.7 (A13) Bandpass Filter
The input to the bandpass filter is the
output of the hybrid combiner, which is
the combined output of the UHF amplifier
trays. The filter is made of aluminum
waveguide and has five resonant cavities.
The filter has five bolts for tuning
adjustments, three located in the middle
on the left and two on the right, and four
or six rods on the front of the bandpass
filter, depending upon the channel, for
coupling adjustments between the
sections. The bandpass filter also utilizes
two integral traps at -4.5 MHz and +9
MHz from F
V
at the top and bottom,
respectively, of the left-hand side of the
bandpass filter, looking from the rear of
the cabinet. Figure 5-2 shows the
location of the bolts used for making
tuning 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.
See Table 5-1 for typical bandpass
values.
Table 5-1. Typical Bandpass Values
FREQUENCY INSERTION LOSS (dB) RETURN LOSS (dB)
F
V
-4.5 ≥ 35
F
V
-0.5 ≥ 20
F
V
≤ 0.6 ≥ 20
F
a
≤ 0.6 ≥ 20
F
V
+8.08 ≥ 15
F
V
-9 ≥ 30
2F
V
≥ 30