User Guide

RM-11

Troubleshooting - RF (Part 2) CC Technical Documentation

UHF Synthesizer Troubleshooting

Figure 5: UHF Synthesizer dialog box for Cell (left) and PCS (right) bands

UHF LO frequency varies with channel and can be quickly calculated using the

UHF Synthesizer dialog box on the RF menu. Check to see if the LO is actually locked.

Set a channel and check the status of the UHF LO within a very narrow span of 100KHz.

You should see the LO virtually immobile. Nominal UHF LO signal levels are measured

with an RF probe (see the following figures). If you do not see the presence of any LOs,

check DC voltages at the following locations:

• R513, VR1A, supply line for UHF PLL IC. Should be 4.76VDC

• R515, VR4, supply line for VCO IC. Should be 2.76VDC

UHF Synthesizer Schematic

Figure 6: UHF synthesizer schematic

Dual Band VCO

Lock voltage

Loop filter components

UHF PLL IC