Checking Intermodulation - Codan NGT 2010 RF Technical & Service Manual

Checking intermodulation

Drawing
ALTERNATIVE TEXT
NOTE
NOTE
NOTE
The test channels 9 to 30 can be used to check for IMD. To facilitate checking each band,
there is a test channel allocated near the bottom, top and centre of each band.
To check the IMD:
1
1
Figure 44: Setup for checking intermodulation distortion
generator
1
NGT Transceiver System Technical Service Manual
08-05416 or 08-05910 (sheet 1)
If the PCB issue status is -04 or earlier, see drawing
The bias gain or active bias must be set before any intermodulation tests
are performed (see
Adjusting the active
The transceiver must be in Service mode to perform this check (see
page 154, Accessing Service
Connect a 50 Ω dummy load to the RF connector ( ).
Connect a spectrum analyser via a 47 kΩ resistor to the RF connector (see
Figure 44).
This provides a low-level output for the spectrum analyser.
Signal
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
page 182, Adjusting the bias gain
bias).
mode).
Test
equipment
Spectrum
analyser
170), or
NGT—Checks and adjustments
08-05910 (sheet
or page 184,
50 W load
Transceiver
47 kW
Figure 41 on page
1).
170)
187