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Page 4-40
GNS 400W Series Maintenance Manual
Rev. A
190-00356-05
2.
Generate and apply a standard microphone audio signal.
3.
Key the microphone.
4.
Measure the frequency error.
5.
Unkey the microphone.
6.
Verify frequency error is 0 (±5 PPM).
Demodulated Audio Distortion
The combined total of distortion and noise in the demodulated output must not exceed 10% of the
total demodulated output at modulation frequencies of 350, 1000, and 2500 Hz when the
transmitter is modulated with a standard microphone input signal.
1.
Set the RF carrier frequency to 118.500 mHz.
2.
Generate and apply a standard microphone test signal except set the frequency to 350 Hz.
3.
Key the transmitter.
4.
Measure the distortion of the signal after the AM demodulator.
5.
Unkey the transmitter.
6.
Repeat steps 2-5, setting the audio frequency to 1,000 Hz and 2,500 Hz.
7.
Repeat steps 1-6, setting the RF carrier frequency to 127.500 mHz and 136.500 mHz.
8.
Verify demodulated audio distortion
≤
10% for all tests.
Channel ID
Modulation Freq (Hz)
118.500 350
118.500 1000
118.500 2500
127.500 350
127.500 1000
127.500 2500
136.500 350
136.500 1000
136.500 2500
Sidetone Audio Response
•
The sidetone audio frequency response must not vary more than 6 dB over the frequency
range of 350 to 2500 Hz, when the audio input is held constant at the value which
produces 70% modulation at the frequency of maximum response. Measure at channel
127.500.