120 10503-201 PRELIMINARY
T-96S Technical Manual
14
3.4.4 Opening the Unit
1.
Remove the two retaining nuts from the
data I/O connector, and the nut and
washer from the antenna connector.
2.
Remove the four screws holding the rear
panel heat sink.
3.
Slide the unit out of the case from the
rear.
3.4.5 Location of Adjustments
and Test Points
3.4.5.1
All Models, Logic PCB
Adjustments and test points are shown be-
low.
Figure 7 - Logic Board Adjustments and Test Points
4. Loader/Modem Board
Circuit Description
4.1 GENERAL
The Loader/Modem board, Part No.
03280-xxx, is a plug-in circuit board.
The four main functions of the
Loader/Modem board include, loading
the radio synthesizer, providing the
baseband modulating signal for the
transmitter and demodulating receive
audio signals. The Loader/Modem board
is programmed by a personal computer
and software. The Loader/Modem board
connects to the radio through 14-pin
connector P1/J201. User data, pro-
gramming channels and other operating
parameters are provided through a DE-
15 connector. A block diagram of the
modem is shown at the end of this sec-
tion.
4.2 TRANSMIT
DATA
Transmit Data from the RS-232 port is
level-shifted to TTL by U1, then gated
through U6 and converted from asyn-
chronous to synchronous format by U2.
The CPLD modem, U6 takes the digital
data stream and synthesizes to the con-
stant-amplitude analog baseband signal,
which is filtered by U12, buffered by
U10B then applied to radio module TXA
at P1-6.
The modem IC is a CPLD based on a
Philips eXtended Programmable Logic
Array (XPLA, PZ5128) which, with a
programmable Raise–Cosine filter
Access Hole for TCXO
SW1
L1
TP2
TP4
Y1
U3
U6
U2
U1
U4
TP1
TP3
U5
J1
