General Instructions For Synthesizer Troubleshooting; 26 Mhz Reference Oscillator ( Vcxo ) - Nokia RH-53 Troubleshooting Instructions

RH-53/54
■

General instructions for Synthesizer troubleshooting

Start the Phoenix-Service-Software and
Select:ProductRH53/54 or scan
Select:Testing
RF Controls
Band XX, se table below
Active UnitRX
Operation ModeContinuous
RX/TX ChannelYY se table below
The signal from the VCO is measured at R640 using a spectrum analysator and a 500ohm pas-
sive probe. The frequency should be as found in the table below and the power should be
around –20dBm.
ZZ
RH-54
RH-53
RH-53
RH-54
■

26 MHz Reference Oscillator ( VCXO )

The 26 MHz oscillator is located in the Mjoelner IC (N600). The coarse frequency for this oscil-
lator is set by an external crystal (B600). The reference oscillator is used as a reference fre-
quency for the PLL synthesizer and as the system clock for BaseBand. The 26MHz signal is
divided by 2 to achieve 13MHz inside the UPP IC (D400). The 26 MHz signal from the VCXO
can be measured by probing R420 at the end towards the UPP, see "Measurement points for
the Synthesizer". The level at this point is approx. 700mVpp. Frequency of this oscillator is ad-
justed by changing the AFC-register inside the Mjoelner IC. This is done via the Mjoelner serial
interface.
ISSUE 1 09/2004
Table 4: Frequency table
XX YY
GSM850 189
GSM900 36
GSM1800 700
GSM1900 661
COMPANY CONFIDENTIAL
Copyright © 2004 Nokia. All Rights Reserved.
Nokia Customer Care
PLL frequency [MHz]
3525.6
3768.8
3685.6
3920
31