Checking The Noise Limiter - Codan NGT 2010 RF Technical & Service Manual

Checking the noise limiter

To check the operation of the noise limiter:
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NGT Transceiver System Technical Service Manual
Connect the signal generator to the RF connector ( ) via a T-piece.
Set the frequency of the signal generator 1 kHz above the SCF of the selected
channel (1 kHz below for LSB).
Set the output of the signal generator to –115 dBm (0.4 µV PD).
Connect the output of a square-wave generator to the other input on the T-piece via a
100 pF capacitor (a BNC to 2-terminal adaptor may be useful).
Set the frequency of the square-wave generator to 100 Hz and the output to 5 V p–p.
When the noise limiter is on, the signal produced by the signal generator should be
heard clearly over the interfering signal from the square-wave generator.
If the signal produced by the signal generator is not heard clearly over the interfering
signal from the square-wave generator, further analysis is required.
Switch the noise limiter off by shorting OFF/ON on the 4-pin plug of the noise
limiter located on the RF/IF PCB in the RF unit (drawing
Figure 28 on page 160, or drawing
The noise from the square-wave generator should obliterate the wanted signal
produced by the signal generator, thereby verifying that the noise limiter is
functioning correctly.
08-05889 (sheet 1) and
NGT—Checks and adjustments
08-05261 (sheet 1) and
Figure 29 on page 161).
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