Garmin GNC 420 Maintenance Manual page 74

5.7.2.19 Squelch Test
Note: Opened squelch—Audio
1. Enable compressor (see Section 5.7.2).
2. Set the unit and the RF signal generator to 127.000 MHz, 30% modulated with a 1 kHz tone.
3. Turn the RF level down below 1µV.
4. Turn the power/volume control on the radio fully clockwise.
5. SLOWLY increase the RF level until the squelch just breaks open and audio can be heard.
6. Verify the RF signal generator level is between 1 and 4 µV (1.5-6 µV for 8.33 kHz).
7. SLOWLY decrease the RF level until the squelch closes (no audio).
8. Verify the RF level is less than 6 dB below that level which opened the squelch.
9. Test squelch at the channels shown below in the 25 kHz channel mode.
118.025 MHz ______ < 6 dB
127.000 MHz ______ < 6 dB
136.975 MHz ______ < 6 dB
10. Measure in the 8.33 kHz channel mode:
118.030 MHz ______ < 6 dB
127.005 MHz ______ < 6 dB
136.980 MHz ______ < 6 dB
400 SERIES MAINTENANCE MANUAL
P/N 190-00140-05
Closed Squelch—No Audio
Page 5-23
Rev. C