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NHM-8NX
Troubleshooting Instructions
PAMS Technical Documentation
Page 26
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Nokia Corporation
Issue 1 05/02
Fault Finding Chart for GSM900 Receiver
Figure 8: EGSM Receiver fault finding chart
By measuring with an oscilloscope at RXIP or RXQP on a working GSM 900 receiver this
picture should be seen.
Signal amplitude peak-peak 588 mV
DC offset 1.33 V
Apply -55 dBm
942.4 MHz, offset
67.71 kHz
from generator to
antenna connector
Oscilloscope at RX
I/Q
signal 588 mVpp
DC offset 1.35 V
freq. 67.71 kHz
EGSM chain
functional
Check RX/TX
switch at RX 900
Z700
-56 dBm
Oscilloscop
check Vc1 and Vc2
at Z700 signal 0V
Spectrum analyzer
EGSM SAW filter
Z602
output -65 dBm
Spectrum analyzer
Check signal after
inductors L603 and
L602
-65 dBm
Check SAW filter
Z602
Oscilloscope
VRX 2.7 V
check Mjoelner
serial interface
Check inductors
L603, L602
Check Base band
Check RX/TX
switch
Check Mjoelner
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
YES
YES
YES
1
2
3
4
1
2
3
4
5
6