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Page 4-24
GNS 400W Series Maintenance Manual
Rev. A
190-00356-05
Audio Output Variation
1.
Set the channel spacing to 25 or 8.33 kHz mode, channel to 127 mHz.
2.
Adjust the test set to 127.000 mHz, 1 kHz audio mod, 30% mod depth and 1000 µV RF
output.
3.
Sweep the audio modulation from 350 Hz to 2500 Hz in 100 steps.
4.
Measure the audio output level from the receiver during each sweep step to locate the
point of highest audio response.
5.
Set the audio modulation to the point of highest response that was found in step 4.
6.
Measure and store the response figure.
7.
Measure the audio response at 350, 1000, and 2500 Hz audio modulation. Verify less
than 6 dB variance from the highest to the lowest measured response.
Audio Frequency Cutoff
1.
Set the channel spacing to 25 or 8.33 kHz mode, the channel to 127 mHz.
2.
Set the test set to 127.000 mHz, 1 kHz audio mod, 30% mod depth and 1000 µV RF
output.
3.
Measure the audio output level from the receiver.
4.
Set the test set to 4 kHz audio modulation frequency.
5.
Measure the audio output level from the receiver. Verify a minimum of 18 dB difference
in the audio response between 1 and 4 kHz.
Signal Pin
Signal Name
Reference Pin
Reference Name
Load
J2-7
COMM AUDIO HI
J2-19
COMM AUDIO LO
500 Ohms
AGC Characteristic Requirements
1.
The audio output should not vary more than 6 dB when the level of the RF input signal,
modulated 30% at 1000 Hz, is varied from 5 µV to 100,000 µV.
2.
The audio output must return to within 3 dB of the normal steady-state output at 10 µV
within 100 msec when the level of an RF input signal, modulated 30% at 1000 Hz, is
rapidly reduced from 200 mV to 10 µV.
3.
The audio output must return to within 3 dB of the normal steady-state output at 10 µV
within 100 msec after transferring from a transmit to a receive state.
