User Guide

2115i/2116/2116i (RH-66)

RF Description and Troubleshooting

Synthesizer Troubleshooting

Faulty synthesizers can cause both Rx and Tx failures during tuning, in addition to the

VCTCXO tuning. However, first check for the presence of various LO signals and their

proper levels. The 19.2 MHz reference clock is needed for the mobile terminal to power

up. Therefore, if everything fails, check for the presence of 19.2 MHz. The level of

19.2 MHz is also important because the UPP is very sensitive and can still pick up a very

weak 19.2 MHz clock, which can result in the mobile terminal constantly resetting. See

"19.2 MHZ VCTCXO Reference Clock" on page 30 for more information.

The following synthesizers are used:

• Dual-band UHF with separate PLL IC and VCO

• 1009.62 MHz for channel 384 in Cell/AMPS

• 2088.1 MHz for channel 600 in PCS

• Tx UHF with PLL inside N7000 IC

• 3296.16 ~ 3395.88 MHz for Cell and AMPS

• 3700 ~ 3819.9 MHz for PCS

• Rx VHF with PLL inside N7100 IC

• 256.2 MHz for Cell, AMPS, and PCS

Incorrect PLL Frequencies

Following are possible causes for incorrect PLL frequencies:

• Incorrect power supplies to the PLL portion

• Control line to the VCO

• Loop filter or resonator components missing or incorrectly installed

• 19.2 MHz reference clock is missing or low

• Component failure (PLL IC, N7100, N7000, VCO, or VCTCXO)