Transmit Deviation Limit Alignment - Motorola Astro XTS 4000 Service Manual

Radio Alignment Procedures: Transmit Deviation Limit Alignment
10. Adjust the softpot value until the measured deviation/voltage, when using the high tone, is
within +/- 1.5% of the value observed when using the low tone.
11. Repeat the above process for all frequencies.
12. Click the Program All button to save the tuned values in the radio.
13. Click the Close button to return to the Transmitter Alignments menu.
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Transmit Deviation Limit Alignment

This alignment procedure limits the modulation of a baseband signal. It is used for primary
modulation limiting.
This procedure needs to be performed at multiple frequencies to allow for proper alignment across
the entire RF band. The RF band is divided into frequency zones with a calibration point (value) in
each zone.
NOTE: This alignment is required after replacing (or servicing) the main board.
This test can be done with either the R-2670 Communication Analyzer or the 8901_ Series
Modulation Analyzer. The method of choice is the R-2670 analyzer.
1. Initial setup using the R-2670 Communication Analyzer:
– Connect a BNC cable between the "DEMOD OUT" port and the "VERT/SINAD DIST/DMM
COUNTER IN" port on the R-2670.
– Press the SPF key on the R-2670 to display the "SPECIAL FUNCTIONS MENU." Move the
cursor to "High Pass," and select 5 Hz on the soft key menu. Select 20 kHz for the "Low Pass"
setting.
– In the "RF Control" section of the R-2670, enter the frequency displayed on the RSS screen.
Move the cursor to the "B/W" setting and select "WIDE +/- 100 kHz" on the soft key menu.
– Place the R-2670 cursor in the "Display" zone. Select "AC VOLTS" on the soft key menu.
Move the cursor to the "Range" setting and select "AUTO."
2. Initial setup using the 8901_ Series Modulation Analyzer:
– Press the FM MEASUREMENT button. (The "Error 03-input level too low" indication is
normal until an input signal is applied.)
– Simultaneously press the Peak – and Peak + buttons. Both LEDs on the buttons should light.
– Press the 15 kHz LP filter key.
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