Codan NGT 2010 RF Technical & Service Manual page 217

Figure 43: Setup for adjusting the bias gain
generator
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NGT Transceiver System Technical Service Manual
Signal
Select test channel 28.
Connect the signal generator to provide two-tone audio (700 Hz and 2300 Hz) via
the test unit to:
• the audio input on the 15-way GPIO connector on the junction box or 2012 RF
Unit (see Figure 40 on page
• the 2011 RF Unit via the NGT test handset (see
Set up the spectrum analyser as follows:
Centre frequency
Frequency span
Vertical level
Video bandwidth
Sensitivity
Hold down PTT, then adjust the level of the two tones for compression.
Adjust the two tones displayed on the spectrum analyser for equal amplitude by
adjusting the balance control on the two-tone signal generator.
Adjust the sensitivity control on the spectrum analyser to set the two tones at the top
of the screen.
Adjust the GAIN potentiometer (R244) for a minimum intermodulation distortion
level (see Figure 30 on page
Measure the intermodulation distortion levels relative to each tone.
Add 6 dB to the reading if referenced to PEP (see
specifications for limits).
Release PTT.
Test
equipment
Spectrum
analyser
170), or
24.9 MHz
20 kHz (2 kHz per division)
10 dB per division
300 Hz
Depends on the signal level applied to the spectrum
analyser and requires adjustment when transmitting
161).
NGT—Checks and adjustments
50 W load
Transceiver
47 kW
Figure 41 on page
page 39, Transmitter
170)
183