Nokia RM-42 Service Manual page 317

Appendix A: RF Troubleshooting
Connect an RF-generator to the GSM-antenna connector
•
• Set RF-generator frequency as following:
EGSM900: 942.46771 MHz
-
GSM1800: 1842.86771 MHz
-
GSM1900: 1960.06771 MHz
-
• Measurements can be done with a spectrum analyser and an RF probe. Remember to make correct
frequency settings to the spectrum analyser (Centre frequency should be set to the same
frequency as the RF-generator). RBW and VBW = 10 kHz, Span = 0 kHz, sweep time 5 ms.
RF-signals in this measurement are pulsed and video triggering is needed in the spectrum
•
analyser (software dependent issue. With some phone softwares these signals are constant in
"Local" mode and triggering is not needed)
• EGSM900: Connect the probe to C7512 or C7514. The RF level should be roughly -85 dBm during RX
period when input signal in GSM antenna connector is -50 dBm. RF-levels should be about the
same on both capacitors. Remember to select the correct band also in Phoenix.
• GSM1800: Connect the probe to C7581 or C7584. The RF level should be roughly -85...-90 dBm
during RX period when input signal in GSM antenna connector is -50 dBm. RF-levels should be
about the same on both capacitors. Remember to select the correct band also in Phoenix.
GSM1900: Connect the probe to C7523 or C7525. The RF level should be roughly -85...-90 dBm
•
during RX period when input signal in GSM antenna connector is -50 dBm. RF-levels should be
about the same on both capacitors. Remember to select the correct band also in Phoenix.
• NOTE!
receiving RF-power correctly from the GSM antenna connector in all three GSM-bands, typically this
means that Hinku ASIC (N7500) is faulty or the ASIC is badly soldered. For example: RSSI-values are
not realistic in EGSM900-band but are ok in other bands and HINKU is receiving RF-power correctly
in all bands. Then it's quite clear that HINKU (N7500) is faulty or badly soldered and the
component should be replaced.
3.2.1.1 Is Z7503 (antenna switch) working correctly?
GSM receiver has to be active before measurements. Procedure is explained in section "GSM RX
•
chain activation for manual measurements".
• Connect an RF-generator to the GSM-antenna connector
• Set RF-generator frequency as following:
EGSM900: 942.46771 MHz (Channel 37)
-
GSM1800: 1842.86771 MHz (Channel 700)
-
GSM1900: 1960.06771 MHz (Channel 661)
-
Measurements can be done with a spectrum analyser and an RF probe. Remember to make correct
•
If RSSI-values are correct only in one or two GSM-bands but RX ASIC HINKU (N7500) is
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