Checking The Agc; Checking The Audio Output - Codan NGT 2010 RF Technical & Service Manual

Checking the AGC

To check the AGC:
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Checking the audio output

To check the audio output:
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NGT Transceiver System Technical Service Manual
Set up the equipment as described on
(signal+noise)/noise ratio, but set the output of the signal generator to –13 dBm
(50 mV PD).
Press 5 to select RF Gain On.
Adjust the volume control for a suitable, near full-scale dB reading on the AC
voltmeter.
Record the reading.
Reduce the output of the signal generator until the receiver output drops by 6 dB.
The signal generator level should be less than –99 dBm (2.5 µV PD).
If the signal generator level is greater than –99 dBm (2.5 µV PD), further analysis is
required.
Set up the equipment as described on
(signal+noise)/noise ratio, with a signal generator output level of –67 dBm
(100 mV PD).
Connect an oscilloscope in parallel to the AC voltmeter across the audio output
(loudspeaker).
For this test, it is advisable to replace the loudspeaker with an 8 Ω, 5 W resistor.
Increase the audio level by adjusting the volume control and check that the audio
output exceeds 12 V p–p at the onset of clipping (displayed on the oscilloscope).
If the audio output does not exceed 12 V p–p at the onset of clipping, further
analysis is required.
NGT—Checks and adjustments
page 190, Checking the sensitivity and
page 190, Checking the sensitivity and
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