NGT—Checks and adjustments
192 NGT Transceiver System Technical Service Manual
Checking the selectivity
To check the selectivity (USB operation):
1 Set up the equipment as described on page 190, Checking the sensitivity and
(signal+noise)/noise ratio.
1 Set the output of the signal generator to –121 dBm (0.20 µVPD).
1 Measure and record the reference level of the audio output using the AC voltmeter.
1 Monitor the signal generator using a frequency counter.
1 Adjust the frequency to –1 kHz and then to +4 kHz from the SCF (USB operation).
1 Increase the output of the signal generator to –55 dBm (0.4 mV) and check that the
audio output is less than the reference level.
1 Repeat at +4 kHz from the SCF (USB operation) and check that the audio output is
less than the reference level.
If the audio output is not less than the reference level at both frequencies, further
analysis is required.
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