User's Manual

08RE398 TDFM-136B Installation Instructions
2.8 Transmitter Side Tone Level Adjustment
The side tone level is set at the factory and there is no hardware adjustment. However, this
level can be altered, via the radio software, to suit local conditions as follows:
1. Set the transceiver operating frequency to 155.0000 MHz and connect an appropriate test
receiver to the RF output connector. Ensure that the output of the transceiver is terminated
into a proper dummy load.
2. Key the transmitter and input a 1 kHz audio signal @ -10 dBm (0.25 VRMS) into the
microphone input.
3. Select the Side-Tone Adjust command, and then adjust the side-tone level using the
up/down arrows (keys 2 & 8) to produce a +3.0 dBm (1.0 VRMS) at the 600 ohm audio
output (headset output).
2.9 Main and Guard Noise Squelch Adjustment
The squelch on both the main and guard receivers is factory set to open at approximately
0.5 microvolts, there is no hardware adjustment. However, this value can be altered, via
the radio software, to suit local conditions as follows:
1. Set the main receiver of the transceiver to 155.000 MHz. Connect a signal generator to the
antenna input of the transceiver.
2. Set the signal generator to produce a ± 3 deviation with a 1 kHz tone on 156.0000 MHz.
Increase the signal generator RF level from 0.1 uV until the squelch indicator LED is on.
Verify the receiver SINAD ratio is between 12 and 14 dB.
3. If not, re-adjust main receiver squelch via the Edit Squelch software command.
4. Repeat the above procedure to adjust the guard receiver squelch setting using guard
receiver squelch adjustment software command.
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