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Trouble Shooting Guide, Advanced
Fig. 19.3
Set RX-amplitude from GSM-test set to 1842.6 MHz and -50 dBm. Use a non-modulated signal,
GMSK off.
Make sure the RX-amplitude really is -50 dBm at Z205 pin 5 with a spectrum analyser.
Raise or lower the amplitude on the GSM test set if necessary.
We propose the following settings on the spectrum analyser while measuring:
CF- 1842.6MHz, SPAN- 1MHz, RBW- 10 kHz, VBW- 10 kHz and Sweep- 30ms Fig. 19.4.
Fig. 19.4
Measure the signal 175 MHz (the frequency at the first mix) going in to the filter Z250 ~ -29
dBm.
The filter attenuates the signal 5-12 dBm in the pass band.
Do not forget to change CF to 175 MHz.
If the signal going in to the filter is to low, either one of the mixers input signals, 1842.6 MHz
RX-in or 1667.6 MHz LO, or the mixers amplifying is to low.
4/00021-3/FEA 209 544/18 B
83(121)
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