Checking Power Output And Intermodulation - Codan NGT 2010 RF Technical & Service Manual

Checking power output and intermodulation

NOTE
Table 49: Power output PEP vs measuring instrument (12/100/125 W)
Power output PEP
Peak reading meter
RMS reading meter
Average reading meter
Oscilloscope
To check the power output and intermodulation:
1
1
1
1
1
NGT Transceiver System Technical Service Manual
The indicated PEP level with two-tone modulation depends upon the type
of measuring instrument used, as shown in
Connect a 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
Hold down PTT.
Do one of the following:
• If links X2 and X3 on the Filter and Control PCB in the RF unit (drawing
08-05416) are open, check that the power output is 100 W PEP at 1.6 MHz to
30 MHz.
• If links X2 and X3 on the Filter and Control PCB in the RF unit (drawing
08-05416) are closed, check that the power output is 125 W PEP at 1.6 MHz to
100 W PEP at 30 MHz.
Use a spectrum analyser to check that the IMD is better than –32 dB below PEP
(–26 dB below each tone) (see
Release PTT.
12 W
12 W
6 W
5 W
69 V p–p 200 V p–p
170), or
page 187, Checking
NGT—Checks and adjustments
Table 49.
100 W 125 W
100 W 125 W
50 W 62.5 W
40.5 W 50.6 W
224 V p–p
Figure 41 on page
intermodulation).
170)
195