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RH-42
Troubleshooting Instructions
Note: TXPWRDET is the difference between TX on burst and off burst.
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Synthesizer Troubleshooting
There are four oscillators generating the needed frequencies for RF section: 19.44 MHz
VCTCXO is used as a reference signal oscillator reference oscillator, 2 GHz UHF VCO with
loop filter circuit is used for RX and TX channel selection, TX VHF and RF VHF are for TX
modulator, and 2nd RX mixer locals generation.
The VHF synthesizers are integrated in Taco, but have external VCO coils and loop filters.
RX VHF frequency is fixed 271.08 MHz and TX VHF is fixed to 271.08 MHz . All locals are
locked to stable 19.44 MHz reference oscillator.
The frequency range for 2 GHz UHF VCO is: 2009.1 MHz ... 2125.53 MHz. The output fre-
quency range for the lower band is from 2009.16 MHz to 2059.02 MHz.
A practical way to check out synthesizer status is by measuring control voltage of the
VCO from the Integrator capacitor. If voltage is stable and reasonable, local oscillators
are running correctly.
19.44 MHz reference oscillator
The VCTCXO oscillator frequency (G790) is controlled by UEM. This output 19.44 MHz
signal is connected to Taco. It is used as a reference signal in Taco and also fed out as
buffered clock signal to UPP. All synthesizers use divided 19.44 MHz signal as a reference
signal for Phase locked loop to provide correct LO frequency.
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Power Level
Figure 13: Detected voltage limits
Nokia Corporation
CCS Technical Documentation
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Confidential
A800
D800
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Issue 2 09/2003
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Troubleshooting
