User Guide

PAMS
Technical Documentation
WinTesla User Guide
NHD–4
Page 30
Original 11/97
AFC Tuning
This tuning is done to calibrate the VCTCXO oscillator frequency.
This tuning is needed if the VCTCXO (G300), any component of AFC–line
or the CDRFI (N700) is changed.
Description of Tuning
This procedure tunes the VCTCXO to 15.36 MHz. The unmodulated
AMPS transmitter carrier on channel 384 is used to perform this test. The
output carrier is monitored with a spectrum analyzer with a 10 kHz span.
The VCTCXO is tuned by adjusting the AFC PDM until the carrier is on
frequency at 836.52 MHz within 200 Hz. For standard AFC operation the
RX_SLOPE PDM is high, at approximately 3.15 V.
AFC calibration steps & equipment:
– Using the JBS–7 service jig, replace the standard battery of the phone
with the dummy battery BTS–4.
– Apply +6.0 V to dummy battery.
– Select ” Tuning – AFC ”
– Connect the modulation (or spectrum) analyzer to antenna connector
and measure transmitter frequency. Adjust frequency to 836.52 MHz +
– 200Hz with arrow or PgUp/PgDn –keys.
– Press <save & exit> to store value to EEPROM or <cancel> to exit
without saving.