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Appendix A: RF Troubleshooting
Procedure is explained in section "GSM RX chain activation for manual measurements".
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Measurements can be done with a spectrum analyser and an RF probe. Spectrum analyser centre
frequency should be set according the used RX channel (see section "Frequency mappings").
•
Spectrum analyser RBW and VBW = 1 MHz, Span = 0, sweep time 1 ms. Notice that GSM
transmission has pulsed nature and VCO output power should be measured during RX is active
(triggering needed). Another possibility is to use following settings: RBW = VBW = 1 MHz, Span
200 kHz and sweep time at least 2.5 seconds.
Connect the RF probe to the T7501 input.
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•
Check if the frequency of the RX VCO is as expected. If the VCO signal is not found try to use wider
span setting. The output level of the VCO should be about -20...-30 dBm.
3.2.2.9.1 RX VCO control voltage VC ok?
GSM receiver has to be active before RX VCO control voltage VC can be measured. Procedure is
•
explained in section "GSM RX chain activation for manual measurements".
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Measurement can be done with an oscilloscope and a probe.
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Connect the probe to R7501.
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Typical RX VCO control voltage VC should look somehow similar to figure
voltage should be between 0.7 - 3.8 V. DC voltage level should change if RX channel is changed. VC
is lower on lower channels and higher if higher channel numbers are used.
3.2.2.9.1.1 VCP1-voltage ok?
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GSM receiver has to be active before VCP1 voltage can be measured. Procedure is explained in
section "GSM RX chain activation for manual measurements".
Measurement can be done with an oscilloscope and a probe.
•
•
Connect the probe to C7507.
•
VCP1 voltage should be about 4.75 V.
3.2.2.9.1.1.1 C7507 and C2222 working properly?
•
Check that the components are in place and solder joints are ok
•
Disconnect the power supply from the phone and use an ohmmeter to check that C507 and C2222
are not short-circuited.
3.2.2.9.1.1.2 Retu ok?
3.2.2.9.1.1.3 Hinku (N7500) ok?
3.2.2.9.1.2 Hinku (N7500) RB_EXT voltage ok?
•
GSM receiver has to be active before Hinku's RB_EXT voltage can be measured. Procedure is
explained in section "GSM RX chain activation for manual measurements".
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6.5.7
(GSM mode). VC
A-57
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