Garmin AT
Rev --
7-30
GX Service Manual
© 2004 Garmin AT
Headset Output Response
1. Inject a 1000 µV RF signal with 85% AM modulation at 1 kHz into the Comm antenna port.
2. Channel the Comm to the same frequency as the signal generator.
3. Connect a 100 ohm resistor and AC power meter (or voltmeter) across the speaker output.
4. Turn up the volume control on the Comm radio to make sure the output power can be greater
than 280 milliwatts (5.92 Vrms across 100 ohms). Record this level.
5. Change the modulation frequency to 350 Hz and record the output power at the headset.
6. Change the modulation frequency to 2.5 kHz and record the output power at the headset.
7. The audio power at 350 Hz or 2.5 kHz should not be down greater than 6 dB with respect to
the power at 1 kHz.
Audio response: 350 Hz = ___ NMT 6 dB 1 kHz = ___ 0 dB 2.5 kHz = ___ NMT 6 dB
Headset Distortion
1. Inject a 1000 µV RF signal with 85% AM modulation at 1 kHz into the Comm antenna port.
2. Channel the Comm to the same frequency as the signal generator.
3. Connect a 100 ohm resistor and AC power meter (or voltmeter) across the headset output.
4. Turn up the volume control on the Comm radio to make sure the output power can be greater
than 280 milliwatts (5.92 Vrms across 100 ohms).
5. Measure across the headset output using an audio distortion analyzer.
6. Repeat for 350 Hz and 2.5 kHz.
Audio distortion: 350 Hz = ___ NMT 12% 1 kHz = ___ 5% 2.5 kHz = ___ NMT 5%
Speaker Distortion
1. Inject a 1000 µV RF signal with 85% AM modulation at 1 kHz into the Comm antenna port.
2. Channel the Comm to the same frequency as the signal generator.
3. Connect a 4 ohm resistor and AC power meter (or voltmeter) across the speaker output.
4. Turn up the volume control on the Comm radio to make sure the output power can be greater
than 12 watts (6.93 Vrms volts across 4 ohms).
5. Measure across the speaker output using an audio distortion analyzer.
6. Repeat for 350 Hz and 2.5 kHz
Audio distortion: 350 Hz = ___ NMT 12% 1 kHz = ___ 5% 2.5 kHz = ___ NMT 5%
Summary of Contents for APOLLO GX SERIES
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