Garmin GNC 420 Maintenance Manual page 77

5.7.3.3 Voice/Ident Audio Distortion
1. Apply an input level from the RF generator of -79 dBm.
2. Modulate a standard VOR audio test signal at 350 Hz, 1000 Hz, and 2500 Hz (must be in
IDENT mode to pass 1000 Hz tone).
3. Measure 500 VOR/ILS AUDIO HI J6-16 with respect to 500
J6-17.
4. Verify the combined distortion and noise in the receiver VOICE/IDENT audio output is not
greater than 10% at all levels up to 100 mW (7.07 RMS or 20Vpp).
Distortion_________ NGT 10%
5.7.3.4 VOR AGC
1. Apply a standard VOR audio test signal between the limits of -99 dBm and -13 dBm.
2. Measure 500 VOR/ILS AUDIO HI J6-16 with respect to 500
(GND) J6-17 (must be in IDENT mode to pass 1000 Hz tone), set to 7.07 Vrms.
3. Verify the difference between the maximum and the minimum VOICE/IDENT audio output
levels is not greater than 3 dB.
Maximum and Minimum Output Level_________ NGT 3 dB
5.7.3.5 VOR Audio Sensitivity
1. Place unit in IDENT mode.
2. Apply a -103.5 dBm RF level to the RF input.
3. Apply a Standard VOR Audio Test signal at RF frequencies of 108.00 MHz, 112.50 MHz,
112.55, and 117.95 MHz.
4. Measure at the 500
outputs, set to 7.07 Vrms.
5. Verify the Audio SINAD or SNR is greater than 6 dB.
Audio SINAD________> 6 dB
Page 5-26
Rev. C
VOR/ILS AUDIO HI J6-16 and 500
VOR/ILS AUDIO LO
VOR/ILS AUDIO LO
VOR/ILS AUDIO LO J6-17
400 SERIES MAINTENANCE MANUAL
P/N 190-00140-05