Garmin APOLLO GX SERIES Service Manual - page 66
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)