User Guide

PAMS
Technical Documentation
WinTesla User Guide
NHD–4
Page 33
Original 11/97
TX Modulation Index Calibration
This tuning is done to adjust the FM Modulators and the gain of TX–audio
path.
This tuning is needed if Codec (N600), or components D1, N500 or D704
is changed.
Description of Tuning
This tuning adjusts the level of FM modulation on the AMPS transmitter.
To do this, the Signaling Tone (ST) is turned on and the modulation level
on the transmit signal is monitored. The TX_MOD level in the DSP is
adjusted in software. This value controls the level of the audio frequency
tone leaving the CDRFI pin 25 on route to the VHF synthesizer for
modulation. At the CDRFI, pin 25 this line is called DAFOUT. Into the
VHF synthesizer it named ANATX. For the ST tone the TX_MOD level is
adjusted until the FM modulation is 8 kHz +/– 0.2 kHz
FM Modulation adjustment:
– 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 – TX Modulation Index”
– Connect modulation analyzer to antenna connector. Use 20 kHz low
pass filter.
– Use PgUp/PgDn keys to adjust to 8.0 kHz +/– 100 Hz. (ST signal is
switched ON)
– Press <Save & Exit> to store values to the phone and exit or <Cancel>
to exit without saving.