NGT—Checks and adjustments
NGT Transceiver System Technical Service Manual 193
Checking the noise limiter
To check the operation of the noise limiter:
1 Connect the signal generator to the RF connector ( ) via a T-piece.
1 Set the frequency of the signal generator 1 kHz above the SCF of the selected
channel (1 kHz below for LSB).
1 Set the output of the signal generator to –115 dBm (0.4 µVPD).
1 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).
1 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.
1 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 08-05261 (sheet 1) and
Figure 28 on page 160, or drawing 08-05889 (sheet 1) and Figure 29 on page 161).
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.
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