User Guide

PAMS
Technical Documentation
WinTesla User Guide
NHD–4
Page 35
Original 11/97
RX Audio Gain
The purpose of this tuning operation is to calibrate the gain of audio path.
This tuning is needed if FM detector (D1) including surrounding
components of FM detector or Audio Codec (N600) is changed
Description of Tuning
This tuning adjusts ratio of output audio gain vs. the level of received FM
frequency deviation. A –80 dBm signal with 2.9 kHz FM, 1 kHz audio is
fed into the phone on channel 384 (881.52 MHz). The received,
demodulated output audio level is read from the ear piece at the output of
the bottom connector. The rxgaina value sets the amount of audio gain.
This value is tuned until the output audio level at the ear piece is 78 mVac
, +/– 2 mV.
Demodulation 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 – RX Audio Gain”
– Apply modulated test signal (ch. 384, RX frequency 881.52 MHz, mod-
ulation 1 kHz with 2.9 kHz deviation and RF level –80 dBm) to antenna
connector.
– Adjust tuning value with arrow keys (fine tuning) or with PgUp and
PgDn–keys (coarse tuning) until measured EAR level is 79 mVrms +/–
1mV.
– Press <Save & Exit> to store values to the phone and exit or <Cancel>
to exit without storing.