Vctcxo Manual Tuning - Nokia 6275 Rf Description And Troubleshooting

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Figure 34
2. Measure the DC voltage at R7201. The following typical voltages are observed.
• AFC PDM[0]=1.3V
• AFC PDM[-1024]=0.8V
• AFC PDM[1023]=2.5V

VCTCXO Manual Tuning

You can manually tune the VCTCXO to verify when a mobile terminal is tuned incorrectly
or if mobile terminal cannot make a call. Monitor the RF signal at the mobile terminal's
output.
1. On the Phone Control dialog box, click the LOCAL button in the Phone State
area to put the mobile terminal into Local Mode. (See
example of the Phone Control dialog box.)
2. Click the Execute button.
3. On the AMPS Control dialog box, set the Set Channel field to 384, the Power
Level field to 5, and select the Transmitter ON check box. (See
page 13
4. Click the Rx RFI tab, make sure the AFC Control check box is cleared, and click
Execute.
5. The frequency accuracy of the VCTCXO can be measured using an HP8960
callbox in AMPS mode or a spectrum analyzer at the output of the transmit
chain.
• If using a spectrum analyzer, set the center frequency to 836.52MHz and the
span to 2MHz initially. Establish a marker at 836.52Mhz.
• If using an HP8960, set the callbox System Type to AMPS, and set the ACC
channel to 384. Use the Frequency Stability measurement to center the
VCTCXO (minimum Frequency Error).
Issue 1 - September 2006
shows a partial schematic of the R7201.
R7201
Figure 34: Partial schematic showing the R7201
for an example of the AMPS Control dialog box.)
Company Confidential
6275/6275i (RM-154)
RF Description and Troubleshooting
Figure 6 on page 12 for an
Figure 7 on
Page 39