X-2 Technical Service Manual Adjustments 7-15
Publication No: 15-02047
7.13.2 ALC
Use the Transceiver Test Unit with two tone audio source to modulate the
transmitter. In the transmit mode, slowly increase the audio output until the
output power just ceases to increase (ALC threshold).
Note the PEP output and increase the audio input by 20 dB. The increase in
output should be less than 0.5 dB above the ALC threshold.
7.13.3 Power Output and Intermodulation
For Australian use:
Power output 100 W PEP ± 0.5 dB (solder Link 'X' fitted). Intermodulation
distortion should be better than -32 dB below PEP (-26 dB below each tone)
as measured with a Spectrum Analyser. Use 700 Hz and 2300 Hz tones.
For use outside Australia:
Power output 125 W PEP at 2 MHz reducing to 100 W at 18 MHz (solder
Link 'X' not fitted). Intermodulation distortion should be better than
-32 db below PEP (-26 dB below each tone) as measured with a Spectrum
Analyser.
Note: The indicated PEP level with two tone modulation will depend upon
the type of measuring instrument used. See Table 7.2 in Section 7.11.3.
7.13.4 Emergency Call
The Emergency Call facility is for use with the Australian Royal Flying
Doctor Service.
The two-tone modulation frequencies of 880 Hz and 1320 Hz are determined
by the software in the Microcontroller. Therefore it is only necessary to carry
out a function check as follows:
1 Connect a 50 Ω Dummy Load to the selected Antenna Connector
complete with Power Meter.
2 Connect an Oscilloscope via a 47 kΩ resistor to the Antenna
Connector.
3 Select a channel with Emergency Call enabled.
4 Operate the EMGCY CALL on the front panel and check the
following:
• The output power equals approximately 100 W PEP.
• The two modulating tones are approximately of equal amplitude
(viewed on the Oscilloscope).
• The modulating tones are heard in the loudspeaker.
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