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GTR 8000 Base Radio
5.8.2.3.1 Tuning The UHF Preselector
Procedure Steps
Turn the base radio power supply ON (to provide a 50 Ohm termination).
1
2
Adjust the signal generator to the frequency calculated in
For a Single Receive Frequency, page 5-8
Receive Frequencies, page
3
Insert tuning probe into cavity U2 and adjust tuning screw 2 for a PEAK.
Tighten tension nut on tuning screw 2 to at least 12 in-lb and fine tune tuning screw 2 for a PEAK.
4
5
Keep tuning probe in cavity U2 and adjust tuning screw 3 for a DIP.
6
Tighten tension nut on tuning screw 3 to at least 12 in-lb and fine-tune tuning screw 2 for a DIP.
7
Insert tuning probe into cavity U3. Decrease output from signal generator to –5 dBm.
8
Adjust tuning screw 4 for a DIP.
9
Tighten tension nut on tuning screw 4 to at least 12 in-lb and fine-tune tuning screw 4 for a DIP.
5.9 Tuning a Duplexer
Duplexer modules shipped with base radios are tuned at the factory. If a duplexer must be replaced in the field, the
unit must be installed and tuned specifically to the transmit and receive frequency pair for the particular base radio.
5.9.1 Field Tuning Overview
These tuning procedures are valid for channels with a bandwidth of 200 kHz or less. If bandwidth is more
than 200 kHz, the duplexer must be tuned by the service depot.
The duplexer module is comprised of three low-pass/high-notch cavities and three high-pass/low-notch cavities.
Each set of three cavities provides bandpass filtering for either the transmit RF signal or the receive RF signal. In
general, the duplexer must be tuned so that the transmit cavity set passes the transmit signal and rejects the receive
signal; concurrently, the receive cavity set must be tuned to pass the receive signal and reject the transmit signal.
5-12
or
5.8.2.1.2 Calculating The UHF Alignment Frequency For Multi
5-9. Set the level to +5 dBm.
5.8.2.1.1 Calculating The UHF Alignment Frequency
6871022P86-A - November 2012
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Troubleshooting
