68P81083C20-D December 6, 2004
Radio Tuning Procedure: Tuning Procedure 6-3
Adjusting the softpot value sends information to the radio to increase (or decrease) a DC voltage in
the corresponding circuit. For example, pressing the UP arrow key at the Reference Oscillator
screen instructs the radio microprocessor to decrease the voltage across a varactor in the reference
oscillator, which decreases the frequency.
Figure 6-3. Softpot Concept
In ALL cases, the softpot value is just a relative number corresponding to a D/A (Digital-to-Analog)
generated voltage in the radio.
Tuning Procedure
NOTE: Perform the following procedures in the sequence indicated
Reference Oscillator Alignment
Adjustment of the reference oscillator is critical for proper radio operation. Improper adjustment will
not only result in poor operation, but also a misaligned radio that will interfere with other users
operating on adjacent channels. For this reason, the reference oscillator should be checked every
time the radio is serviced. The frequency counter used for this procedure must have a stability of 0.1
ppm (or better).
1. From the SERVICE menu, press F2 to select TRANSMITTER alignment.
2. Press F2 again to select the REFERENCE OSCILLATOR softpot.
3. Press F6 to key the radio. The screen will indicate that the radio is transmitting.
4. Measure the transmit frequency on your frequency counter.
5. Use the UP/DOWN arrow keys to adjust the reference oscillator per the targets shown in Fig-
ure 6-1.
6. Press F6 again to dekey the radio and then press F8 to program the softpot value.
7. Press F10, F10 to return to SERVICE menu.
Transmitter Power
The radio requires two power level adjustments, a high power or rated power adjustment, and a low
power adjustment.
Band Target
VHF ±150 Hz
UHF ±150 Hz
800 MHz / 900 MHz 0.3 ppm
Table 6-1. Reference Oscillator Alignment
Min.
Value
Max.
Value
015
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