Rx 1800 Troubleshooting; Fig 10 Rx 1800 Troubleshooting - Nokia RM-14 Rf Troubleshooting And Manual Tuning

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Rx 1800 troubleshooting

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14
Figure 10:RX 1800 troubleshooting
RX 1800 Troubleshooting
GSM1800 ch. 700. Continuous Rx.
Use AGC "gain step" 14
Apply a signal of 1842,86771 MHz (+67.71 kHz offset)
at -90 dBm to the antenna pad J124
Spectrum analyzer: RBW = 500 kHz, VBW = 500 kHz,
center = 1840 MHz and span = 20 MHz
Measure voltage of a) RXI (J512) b) RXQ (J513).
RXI and RXQ = 500 mVpp and 1.35 VDC.
Note: DC level drops after a while.
Change the signal level to -30 dBm
Measure RF level = -30 dBm at Z802 SAW filter input.
(Z800 antenna switch pin11)
Measure Z809 antenna switch control signal voltages
a) VANT_1 = 0V (C811)
b) VANT_2 = 0V (C809)
c) VANT_3 = 0V (C810).
Measure RF level at Helgo input
(C807, not assembled, both terminals).
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RF Troubleshooting and Manual Tuning
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"Helgo/Synthesizer
troubleshooting"
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ISSUE 1 11/04