250 Receiver Fault Finding TM8100/TM8200 Service Manual
© Tait Electronics Limited June 2006
10.4 Incorrect RSSI Readings
Introduction If the RSSI readings are incorrect, the receiver calibration is suspect.
There are four tasks, which cover the four types of settings concerned:
■ Task 10: AGC voltage calibration
■ Task 11: FE tune BPF settings
■ Task 12: RSSI delta gain
■ Task 13: AGC delta gain
If the receiver is properly calibrated but the fault persists, then the receiver
sensitivity is suspect.
Task 1 0 —
AGC Voltage
Calibration
The first settings to check concern the AGC voltage calibration.
1. In the calibration application open the “Raw Data” page and click the
“Receiver” tab.
2. Note the settings listed in the “AGC Voltage Cal Pts” field. The nominal
settings should be as listed in Table 10.3. The AGC values depend
on which demod IC is fitted (IC400). The IC is either an RF9667 or
an RF2667.
3. If the settings are correct, go to Tas k 11
. If they are not, go to Step 4.
4. Recalibrate the receiver and check the settings again.
5. If the settings are now correct, go to Step 6. If they are not, go to
Tas k 1
and check the receiver sensitivity.
6. Check if the RSSI fault has been removed. If it has, go to “Final
Tasks” on page 157. If it has not, go to Tas k 1 1
.
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