High power—Fault finding and adjustments
NGT Transceiver System Technical Service Manual 243
Adjusting the external high-power amplifier
To adjust the external high-power amplifier:
1 Connect setup as per page 180, Adjusting high output power, ensuring the NGT is
set to 100 W output (Links X2 and X3 open on drawing 08-05416 or, if the power
output is greater than 100 W PEP on a frequency below 10 MHz, solder Link X2 as
per drawing 08-05910 (sheet 1)).
1 Select test channel 25.
1 Set the ALC ADJUST control on the High-power ALC Adaptor PCB fully
counterclockwise (minimum power).
1 Hold down PTT and note the output power.
1 Turn the ALC ADJUST control slowly in a clockwise direction until the required
output power is reached (see Table 17 on page 240).
The indicated PEP level with two-tone modulation depends on the type of
measuring instrument, as shown in Table 17 on page 240.
1 Check that the two-tone waveform is clean and undistorted.
If it is not clean and undistorted, further analysis is required.
1 Release PTT.
NOTE
Ensure the dummy load and power meter are rated to 1 kW PEP (500 W
CW).
NOTE
The transceiver must be in Service mode to perform this adjustment (see
page 154, Accessing Service mode).
NOTE
The output power is factory-set, so it is not likely to be outside the
specified limits. Check that there are no faults with the transmitter circuits
before attempting to adjust the power output.
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