Uhf Synthesizer - Nokia 3155 Rf Description And Troubleshooting

3155/3155i (RM-41), 3152 (RM-61)
RF Description and Troubleshooting

UHF Synthesizer

The UHF LO frequency varies with the channel and can be calculated using the Frequency
Calculator dialog box in the Phoenix RF component. Use the following steps to
troubleshoot the UHF LO frequency.
1. Ensure that the LO is locked. Set a channel and check the output of the UHF LO
at L7200 within a very narrow span of 100KHz. The LO must be virtually
immobile.
2. Measure the nominal UHF LO signal levels (see
Points" on page 53).
3. If you do not see the presence of any LOs, check the DC voltages at the following:
• R7209, VR4, supply line for VCO IC and PLL IC = 2.76VDC
4. If the frequency of the LO is not correct, check the DC voltages at the following:
• R7208, VR1A, supply line for PLL charge pump = 4.76VDC
5. Ensure that the lock voltage at C7220 is between 1V and 3V.
6. Check the RF return at R7210.
TX UHF LO (Cell/AMPS) = Tx frequency x 4
•
TX UHF LO (PCS) = Tx frequency x 2
•
Page 52
Figure 44: Tx Output for AMPS channel 384, power level 5
©2005 Nokia Corporation
"UHF Synthesizer Test
Company Confidential ISSUE 1 07/2005