User Guide

PAMS
Technical Documentation
WinTesla User Guide
NHD–4
Page 31
Original 11/97
Deaf Channel Frequency Tuning
This tuning is done to calibrate the VCTCXO oscillator frequency to adjust
for “deaf” or “blocked” AMPS channels.
This tuning is needed if the VCTCXO (G300), any component of AFC–line
or the CDRFI (N700) is changed.
Description of Tuning
This is a secondary tuning done on the VCTCXO for a special case
involving AMPS channels 184, 440 and 696, known as the Deaf channels.
This tuning is performed exactly as it was in the AFC Tuning above, but
now channel 440 is used rather than channel 384. In this case the
RX_SLOPE PDM is low at approximately 0.0 V. Again the AFC PDM is
adjusted to tune the transmit carrier to within 200 Hz of the center
frequency, this time 838.20 MHz. Consult the HD881 Synthesizer
Functional Description for more information on the Deaf Channel
functionality of the synthesizer.
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 – Deaf Channel Frequency”
– Connect the modulation (or spectrum) analyzer to antenna connector
and measure transmitter frequency. Adjust frequency to 838.20 MHz +
– 200Hz with arrow or PgUp/PgDn –keys.
– Press <save & exit> to store value to EEPROM or <Close> to exit
without saving.