Pa Bias Voltage; Battery Threshold - Motorola GM-950 Manual

1.2

PA Bias Voltage

Adjustment of the PA Bias is critical for proper radio operation. Improper adjustment will result in
poor operation and may damage the PA FET device. For this reason, the PA bias must be set before
the transmitter is keyed the first time.
Note: For certain radio models there are two bias voltage settings. For these radios both ' Bias 1
Voltage ' and ' Bias 2 Voltage ' need to be adjusted when aligning the PA Bias. For models
that only have one bias voltage setting, the ' Bias 2 Voltage ' will be shown in grey on the
service menu. After entering the tuning window the bias is switched off and the quiescent
current is 0mA. The status bar will indicate whether the bias is switched on or off.
1. From the Service menu, select Tx Alignments.
2. Select Bias Voltage to open the bias voltage tuning window. If the control voltage is out of
range, an error message will be displayed. In this case the radio hardware has a problem and
tuning must be stopped immediately.
3. Measure the DC current of the radio. Note the measured value and add the specified quiescent
current shown in table 2-1. The result is the tuning target.
4. Click the Toggle Bias button to switch on the quiescent current.
5. Adjust the current per the target calculated in step 3.
6. Click the Toggle Bias button to switch on the quiescent current again.
7. Click the Program button to store the softpot value.
1.3

Battery Threshold

The radio uses 2 battery threshold levels Tx High and Tx Low to determine the battery condition.
The Program buttons must only be activated when the power supply is set to the indicated voltage. If
the RSS detects that the voltage is not within the expected range for the threshold in question then a
message will be displayed to warn that the radio may not be set up correctly for the alignment
operation.
CAUTION:
1. From the Service menu, select Tx Alignments.
2. Select Battery Thresholds to open the battery thresholds tuning window.
3. Set the supply voltage to the value indicated for Tx High.
4. Click the Tx High Program button to store the softpot value for Tx High.
5. Set the supply voltage to the value indicated for Tx Low.
6. Click the Tx Low Program button to store the softpot value for Tx Low.
7. Close the window by pressing Cancel.
Radio Tuning Procedure
Table 2-1 Quiescent Current Alignment.
RF-Band
Midband
Inadvertant Use Of The Program Buttons May Result In Radio Failure.
Midband (66-88MHz) Tuning Procedure
Target
150mA±15%
5C.2-3