Transmit Deviation Balance (Compensation); Deviation Limit; Transmit Deviation Limit; Squelch - Motorola GTX/LCS 2000 Service Manual

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Transmit Deviation
Balance (Compensation)
& Deviation Limit

Transmit Deviation Limit

Squelch

Ending the Tuning
Procedure
6-4
Radio Tuning Procedure
Compensation alignment balances the modulation sensitivity of the VCO and
reference modulation (synthesizer low frequency port) lines. Compensation
algorithm is critical to the operation of signaling schemes that have very low
frequency components (e.g. DPL) and could result in distorted waveforms if
improperly adjusted.
1.
Press F6 to select TX DEVIATION CALIBRATION. The screen will
indicate the transmit test frequencies to be used.
2.
Begin with the lowest test frequency shown on the screen.
3.
Press F6 to key the radio. Record this measurement.
4.
Press F4 to select 2.5 kHz.
5.
Use the UP/DOWN arrow keys to adjust the deviation to within 0.5 dB of
the value recorded in step 3.
6.
Press ENTER to move to next softpot value.
7.
Repeat steps 5 and 6 for the remaining frequencies.
8.
Press F8 to program the softpot value.
The transmit deviation limit softpot sets the maximum deviation of the carrier.
Tuning is performed for 25 kHz channel spacing.
1.
Begin with the lowest test frequency shown on the screen.
2.
Press F6 to key the radio.
3.
With Test Box 4460A: inject a 1 kHz tone, 2000 mVrms.
4.
Use the UP/DOWN arrow keys to adjust the deviation to between 4.4 kHz
and 4.8 kHz.
5.
Press ENTER to move to the next softpot value.
6.
Repeat steps 4 and 5 for the remaining frequencies shown on the screen.
7.
Press F6 to dekey the radio.
8.
Press F8 to program the softpot value.
The squelch softpots set the signal to noise ratio at which the squelch opens.
1.
Press F9 to select SQUELCH Adjustment.
2.
Adjust the UP/DOWN arrow key to the minimum squelch value.
3.
Set the RF test generator to the test frequency plus +500 Hz offset.
4.
Adjust the UP/DOWN arrow key until the squelch just closes.
5.
Monitor for squelch chatter; if chatter is present, continue to adjust the UP/
DOWN arrow. Wait 500 msec and repeat step 4.
6.
When no chatter is detected, press F8 to program this value.
1.
Press F2 to continue.
2.
Press F10, F10 to return to the Service menu.

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