Table of Contents
Advertisement
Make sure the RX amplitude really is -50 dBm over Z205 pin 5 using a spectrum analyser.
Raise or lower the amplitude on the GSM- test set if necessary.
We propose the following settings on the spectrum analyser when measuring the transmitter:
CF- 1842.6 MHz, SPAN- 1 MHz, RBW- 10 kHz, VBW- 10 kHz and Sweep- 30 ms.
15.2.1 Fault in the LO
For GSM 900:
Change CF on the spectrum analyser to 772.4 MHz and raise the SPAN to 200 MHz.
Measure frequency and amplitude on the local oscillator at N303 pin 1, 772.4 MHz ~ - 3 dBm.
If the LO signal is correct as in Fig. 31 are there either too large losses in the signal path, a
phase error or a logical fault. Go to section 15.2.2.
If the frequency is correct, but the amplitude is too low, check the feed voltage on N303 pin 6
+3.7 V
DC
If the voltage is correct, replace N303.
If the voltage is incorrect, check VVCO +3.8 V
components that belong to it.
If the amplitude is correct, but the frequency is incorrect, is it often due to N301. It can also be
due to N303 or D600.
If the signal is several MHz wide, replace C318.
If the amplitude and the frequency are correct, lower SPAN to 1 MHz and measure the LO
signal again. If there is noise on the signal, replace N301.
For GSM 1800:
Change CF on the spectrum analyser to 1667.6 MHz and raise the SPAN to 200 MHz.
Measure frequency and amplitude on the local oscillator at N302 pin 1 1667.6 MHz ~ - 2 dBm.
If the frequency is correct, but the amplitude is too low, check the feed voltage on N302 pin 6
+3.7 V
DC
If the voltage is correct, replace N302.
If the voltage is incorrect, check VVCO +3.8 V
component that is belonging to it.
If the amplitude is correct, but the frequency is incorrect, is it often due to N301.
It can also be due to N302 or D600.
If the signal is several MHz wide, replace C318.
If the amplitude and the frequency are correct, lower SPAN to 1 MHz and measure the LO
signal again.
If there is noise on the signal, replace N301.
4/00021-3/FEA 209 544/18 B
.
.
Trouble Shooting Guide, Advanced
, SYNTON_GSM +3.7 V
DC
, SYNTON_DCS +3.7 V
DC
and V305 with the
DC
and V301 with the
DC
64(121)
Advertisement
Table of Contents
