CAVITY &
DUPLEXER
TUNING
BANDP
ASS
WITH
REJECT
NOTCH
C. Adjustment
of
Reject Notch
on
Transmit Leg
1.
Connect the Analyzer's RF
In/Out
to the in-service duplexer as shown in figure 4-23. Disconnect the cable at the
duplexer transmitter
port
that comes from the transmitter. Move the Analyzer's RF
In/Out
cable from the du-
plexer receiver
port
to the duplexer transmission port. Reconnect the cable coming from the receiver to the du-
plexer receiver port. Disable the receiver
PL.
2. Set DISPLAY to
Gen/Mon
Mtr, FUNCTION switch to Generate FM.
and
enter the receiver frequency.
3.
Set the attenuator to -30 dB and the Variable control to mid-range, to allow adequate signal to get through the
duplexer and quiet the receiver. Reduce the signal generator output, as necessary, to keep the receiver limiter
meter below saturation.
4. Adjust the reject notch adjustments on the duplexer transmit leg cavities for minimum signal level
on
the receiver
limiter meter. Change the signal generator
output,
as necessary, to keep the received signal up
out
of
the noise
and
below saturation.
5. Loosen the cavity reject adjustment nut and slide it within its slot while watching the meter. Tighten the adjust-
ment nut.
Be
careful not to mistune the rejection adjustment. Fine-tune the reject notch adjustment by turning the
bandpass knob a maximum
of
+/-15°.
6. Remove the test equipment and connect the duplexer back to the repeater. Check the duplexer for insertion loss
according to its specifications.
4-42
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