Garmin GNC 420 Maintenance Manual page 69

5.7.2.8 Sidetone
1. Apply a standard mic input signal. Measure com audio out and while transmitting, verify
sidetone level is 1.4 Vrms 0.2 Vrms.
118.50 MHz ______ Vrms
127.50 MHz ______ Vrms
136.50 MHz ______ Vrms
5.7.2.9 MIC Intercom Test
1. Remove RF input from the unit.
2. Squelch the receive audio (enable compressor).
3. Apply a 125 mVrms, 1 kHz audio signal to the intercom mic audio input.
Audio Level ________ > 7.07 Vrms
4. Remove intercom audio input signal.
5.7.2.10 Receiver Sensitivity
1. Disable the compressor.
2. Apply a 2 V (hard), 30% modulated, 1000 Hz RF signal to the unit and set volume to rated
audio ( 7.07 Vrms).
3. Measure the sensitivity in the 25 kHz channel mode (signal + noise to noise ratio).
118.025 MHz ______ > 6 dB
127.000 MHz ______ > 6 dB
136.975 MHz ______ > 6 dB
4. Measure in the 8.33 kHz channel mode.
118.030 MHz ______ > 6 dB
127.005 MHz ______ > 6 dB
136.980 MHz ______ > 6 dB
Page 5-18
Rev. C
400 SERIES MAINTENANCE MANUAL
P/N 190-00140-05