User Guide

PAMS
Technical Documentation
NSE–5
Service Software Instructions
Page 37
Issue 1 07/99
During tuning, proceed as follows:
- Take care not to damage sensitive measuring instruments with exces-
sive RF power.
- Carry out all tuning steps in the shortest possible time to avoid exces-
sive heating of RF units.
- Perform all tuning steps in the order presented.
- Never try to mask a fault by tuning it out!
After the tuning has finished the software reports the following:
- AFC init value
- AFC slope
- PSW slope
- AGC DAC values and the corresponding voltages for each gain step (0
– 57dB)
Limits for the reported values
If everything went well the reported values should approximately be the
following:
Parameter Low limit High limit
AFC init value -80 80
AFC slope 135 230
PSW slope 250 350
AGC 0 dB 175 325
AGC 57 dB 440 740
Difference between the two neighbor AGC steps 10 20
Troubleshooting
If the calibration does not succeed the software normally reports ”Unable
to read data from phone” or ”Failed to set high reference” or ”Failed to set
low reference”. In this case check first the basic functionality of the
receiver chain: RF generator frequency set as in the calibration and level
for example to the high reference value.
Then go to the RSSI reading menu (under RF controls). If the reading is
very low there is something broken in the receiver and must be found by
measuring voltages and signal levels at different places (information of
these can be found elsewhere in this manual).
If the RSSI reading seems to be within 5 – 10 dB the same as the RF
in–put level check that the VCTCXO (G650) frequency is close enough
the wanted frequency. The easiest way to check this is by measuring the
UHF VCO (G550) frequency, because the absolute value of the deviation
is biggest there. In the GSM mid channel the UHF-VCO frequency should
be 2040.0 MHz. If the deviation is bigger than about +/-20 kHz it is
probable that the VCTCXO is not operating correctly.