Tait TM8100 mobiles Service Manual page 352

Task 4 —
Check Forward and
Reverse Powers
352 Transmitter Fault Finding (25W)
First check the forward and reverse powers for an indication of which part
of the circuitry is suspect.
Enter the CCTM command 326 4 to set the transmitter power level
1.
high.
2. Enter the CCTM command 33 to place the radio in transmit mode.
Enter the CCTM command 318 to check the forward power.
3.
The value returned is the voltage in millivolts corresponding to the
power level, and should be as shown in
4. Confirm the above result by checking the level at the
point (see Figure
Enter the CCTM command 319 to check the reverse power.
5.
The value returned is the voltage in millivolts corresponding to the
power level, and should be as shown in
6. Confirm the above result by checking the level at the
point (see Figure
If the oscilloscope momentarily indicates a very high reverse power,
then the most likely scenario is that the antenna VSWR threshold has
been exceeded and the PA has shut down to very low power.
Enter the CCTM command 32 to place the radio in receive mode.
7.
8. If the values obtained in
is no indication of a momentary high reverse power, go to
If one or both are incorrect, go to
9. Check the connection from the RF connector on the radio to the test
set.
10. If there is no fault, go to
repeat the above measurements.
11. If the reverse power is momentarily too high, the directional coupler,
PIN switch or LPF is suspect; go to
Table
12.4) using an oscilloscope.
Table
12.4) using an oscilloscope.
Step 3 and Step 5
Step 9.
Step 11. If there is, rectify the fault and
Task 29. Otherwise go to
© Tait Electronics Limited November 2007
12.3.
test
FWD PWR
12.3.
test
REV PWR
are both correct, and there
Task
Task
TM8100/TM8200 Service Manual
5.
5.