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PAMS Technical Documentation
Yellow trace :
Pink trace :
** TXIQ signals look the same in PCN and GSM
Synthesizer
There is only one PLL synthesizer generating Local Oscillator frequencies for both RX and
TX in both bands ( PCN and EGSM). The VCO frequency is divided by 2 for PCN operation
or by 4 for EGSM operation inside the Mjoelner IC.
General instructions for Synthesizer troubleshooting
Start the Phoenix-Service-Software and
Select: Product: NHM-8NX
Select: Maintenance, Testing and then RF Controls.
Band
Active Unit
Operation Mode
RX/TX Channel
It is not possible to measure the output of the VCO (G600) directly as this component is
placed underneath a shielding can without detachable lid. However with spectrum ana-
lyzer and 500 ohm passive probe it is possible to get an indication if the VCO outputs the
correct frequency. To do this probe R656 – the frequency should be 3685.6MHz and the
power should be around –50 dBm.
26 MHz Reference Oscillator ( VCXO )
The 26 MHz oscillator is located in the Mjoelner IC (N600). The coarse frequency for this
oscillator is set by an external crystal (B600). The reference oscillator is used as a refer-
ence frequency for the PLL synthesizer and as the system clock for BaseBand. The
Issue 1 05/02
Figure 19: VPCTRL_P & TXC
Vpctrl_P @ power level 0, ch700
TXC
PCN1800 band
GSM1800
RX
Continuous
700
ãNokia Corporation
NHM-8NX
Troubleshooting Instructions
Page 39
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Troubleshooting
