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GNS 400W Series Maintenance Manual
Page 4-29
190-00356-05
Rev. A
25 kHz Channel
8.33 kHz Channel
118.025 118.030
127.000 127.005
136.975 136.980
The noise squelch must operate in 25 kHz mode only and must open the audio output when the
RF level is between 1.0 and 4.0 µV modulated 30% at 1 kHz. The noise squelch must close the
audio output within 6 dB of opening squelch level. Noise squelch operation must be tested at the
channels shown below in 25 kHz channel mode only.
25 kHz Channel
118.025
127.000
136.975
The 25 kHz noise squelch must open within 60 mSec when the RF signal transitions from no
signal to 4.0 µV modulated 30% at 1 kHz. The 8.33 kHz carrier squelch must open within 60
mSec when the RF signal transitions from no signal to 6.0 µV, modulated 30% at 1 kHz.
The 25 kHz noise squelch and 8.33 kHz carrier squelch must open within 40 mSec when the RF
signal transitions from no signal to 1000 µV modulated 30% at 1 kHz.
Carrier Squelch (25 kHz)
1.
Enable the compressor.
2.
Set the unit to 118.000 mHz, 25 kHz spacing, squelch enabled.
3.
Set the signal generator to 118 mHz, 85% modulation, 8 kHz audio frequency.
4.
Sweep the output level from 5 µV to 25 µV using a step size of 1 µV.
5.
Measure the audio output in Vrms (ac).
6.
Repeat steps 3 and 4 until the squelch opens (the audio is present).
7.
Store the squelch open point.
8.
Reduce the signal generator output by 6 dB.
9.
Measure the unit audio output in Vrms (hysteresis).
10.
Repeat steps 1-8 at 127.000 mHz and 136.975 mHz.
11.
Verify the following:
•
Squelch open point: 6.3 µV
≤
X
≤
25 µV.
•
Hysteresis: Vrms (ac) < 10 mVrms.
