User Guide

PAMS
Technical Documentation
NME–3
Service Software Instructions
Page 11
Issue 1 10/99
If the RSSI reading seems to be within 5 - 10 dB the same as the RF input
level check that the VCTCXO (G650) frequency is close enough the
wanted frequency. This is most easiest done 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 1018
MHz. If the deviation is bigger than about +/–20 kHz it is probable that the
VCTCXO is not operating correctly.
If both of these (RSSI reading and the frequency) seem to be correct and
calibration still fails the most probable reason is that there is a little lack of
gain somewhere or the AGC gain control slope in N600 is out of the limits.
This can be verified by changing the generator reference levels from the
demanded ones in the calibration procedure in 1 dB steps up and down. If
the calibration goes through with some reference levels the corrective
action is most probably changing N500 or N600.
2. Alignment of Transmitter Power Levels
Equipment:
– Pulsed power meter or spectrum analyzer and 10 dB attenuator.
– MSJ–13 voltage source within 9–15VDCV.
The following settings for the spectrum analyzer are recommended when
aligning the power levels: zero span, resolution and video bandwidths 1
MHz, input attenuation 40 dB, sweep time 1 ms, video triggering.
Procedure:
Follow the instructions given in chapter ”Service Software Instructions”
section ”TX power... command”.
For GSM the alignment channel is 60 (902 MHz)