Garmin APOLLO GX SERIES, Service Manual

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Garmin AT Rev --
7-28 GX Service Manual © 2004 Garmin AT
Receiver Sensitivity and Squelch Threshold
1. Inject a 2 µV (-104 dBm) standard (1 k tone 30% modulated) test signal into the Comm
antenna port.
2. Open the Comm squelch by pulling the squelch knob out.
3. Measure SINAD on the speaker output with a 4 ohm load resistor.
4. SINAD should be greater than 6 dB.
SINAD: 118.000 MHz __________ NLT 6 dB
126.500 MHz __________ NLT 6 dB
135.950 MHz __________ NLT 6 dB
5. Vary the signal generator output power until 6 dB SINAD is obtained. Record this value below
(reference sensitivity).
Reference sensitivity: 118.000 MHz __________
126.500 MHz __________
135.950 MHz __________
6. Close squelch by pushing the squelch knob in.
7. Increase the signal generator signal level until the squelch opens.
Squelch sensitivity: 118.000 MHz __________ NLT 2µV (-104 dBm)
126.500 MHz __________ NLT 2µV (-104 dBm)
135.950 MHz __________ NLT 2µV (-104 dBm)