Rated Volume - Motorola GM1200E Service Manual

4. Select the first test frequency shown, and set the corresponding value to the start value shown
in table 4-4.
5. Set the RF test generator to the receive test frequency, and set the RF level to 10µV modulated
with a 1 kHz tone at the normal test deviation shown in table 4-3.
6. Measure the RSSI voltage at accessory connector pin 15 with a dc voltmeter capable of 1 mV
resolution.
7. Change the softpot value by the stepsize shown in table 4-4 and note the RSSI voltage.The
target softpot value is achieved when the measured RSSI voltage change between step 6 and
step 7 is lower than the tuning target for the first time. The tuning target, shown in table 4-4, is
expressed as the percentage of the measured RSSI voltage and must be recalculated for every
tuning step. If the measured RSSI voltage decreases before the target value has been
achieved, approximation should be stopped and the current softpot value should be used as
target value. Set test box (GTF180) audio switch to the "SPKR" position. The 1 kHz tone must
be audible at the target value to make sure the radio is receiving.
8. Repeat steps 4 - 7 for all test frequencies shown in the window.
9. Click the Program button to store the softpot values.
1.7

Rated Volume

The rated volume softpot sets the volume at normal test modulation.
1. Set test box (GTF180) meter selection switch to the "AUDIO PA" position and the speaker load
switch to the "MAXAR" position. Connect an AC voltmeter to the test box meter port.
2. From the Service menu, select Receiver Alignment.
3. Select Rated Volume to open the rated volume tuning window. The screen will indicate the
receive test frequency to be used.
4. Set the RF test generator to the receive test frequency, and set the RF level to 1mVolt
modulated with a 1 kHz tone at the normal test deviation shown in table 4-3. Set test box
(GTF180) audio switch to the "SPKR" position. The 1 kHz tone must be audible to make sure
the radio is receiving.
5. Adjust the value of the softpot to obtain rated audio volume (as close to 3.87 Vrms).
Note: The voltage at the meter port of the testbox GTF180 is only half the voltage at the speaker.
6. Click the Program button to store the softpot value.
Radio Tuning Procedure
Table 4-3 Normal Test Deviation.
Channel Spacing
12.5 kHz
20 kHz
25 kHz
Table 4-4 Start Value for Front-End Pre-selector Tuning.
RF-Band Target
UHF 0.42%
VHF
300-350MHz 0.84%
336-390MHz 0.31%
Deviation
1.5 kHz
2.4 kHz
3 kHz
Stepsize
-2
0.5% +2
-2
-2
GM1200E Tuning Procedure
Start Value
Maximum
Minimum
Maximum
Maximum
4-5