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Page 4-42
GNS 400W Series Maintenance Manual
Rev. A
190-00356-05
VSWR
Across the entire band of operation when a 3:1 mismatch is applied to the transmitter output
terminals at all possible phase angles, the power output must be at minimum 5 watts for a 10 watt
radio, or 8 watts minimum for a 16 watt radio.
The requirements of the demodulated audio distortion and spurious emissions sections must be
met with the following exceptions: the total noise and distortion of the modulated transmitter
must not exceed 25%, and harmonically related spurious emissions must not exceed -16 dBm.
Perform the test at frequencies of 118.500, 127.500 , and 136.500 mHz.
Frequency Modulation
NOTE
FM deviation is to be measured with a detector calibrated to respond according to
the formula [RMS x Sqrt(2)].
When the transmitter is modulated with a standard microphone input signal, the frequency
deviation due to unwanted frequency modulation of the carrier must not exceed
±
1000 Hz.
Measure at channels 118.500, 127.500, and 136.500.
1.
Generate and apply a standard microphone test signal.
2.
Set the carrier frequency to 118.500 mHz.
3.
Key the transmitter.
4.
Measure the FM deviation.
5.
Unkey the transmitter.
6.
Repeat steps 2-5, setting the RF carrier frequency to 127.500 mHz and 136.500 mHz.
7.
Verify FM deviation is
≤
1000Hz.
Demodulated Audio Response
With the transmitter set to 70% modulation at the frequency of maximum response, the frequency
response of the audio output must not vary more than 6 dB when the audio input frequency is
swept from 350 to 2500 Hz. Measure at channel 127.500 while sweeping the modulation from
350 Hz to 2500 Hz in 100 Hz increments.
1.
Set the unit to 127.500 mHz.
2.
Generate and apply a standard microphone audio test signal.
3.
Key the microphone.
4.
Measure the AM modulation depth.
