TAPR T-238+ Assembly Manual

Tucson Amateur Packet Radio
Internet: tapr@tapr.org www.tapr.org
Non-Profit Research and Development
Corporation
T-238+ Modem Assembly Manual
This document was originally written June 2005. © 2005 Tucson Amateur Packet Radio Corp.
Reproduction or translation of any part of this work beyond that
permitted by sections 107 or 108 of the 1976 United States
Copyright Act (or its legal successor) without the express written
permission of Tucson Amateur Packet Radio Corporation is
unlawful except as noted below. Requests for permission to
copy or for further information should be addressed to Tucson
Amateur Packet Radio Corporation. Except as noted above,
permission is hereby granted to any non-profit group or
individual to reproduce any portion of this document provided
The information contained in this document has been carefully checked and is believed to be entirely reliable. However, no
responsibility is assumed for inaccuracies. Tucson Amateur Packet Radio Corporation (TAPR) reserves the right to make
changes in any products to improve reliability, function or design without obligation to purchasers of previous equipment.
TAPR does not assume any liability arising out of the application or use of any product or circuit described herein; neither
does it convey license under its patent rights or the rights of others.
Introduction ......................................................................1
Acknowledgments ............................................................1
Parts list...........................................................................2
Construction notes ...........................................................3
Construction.....................................................................3
Power-up and initial testing ..............................................5
Board layout.....................................................................7
Schematic diagram ..........................................................8
Introduction
The T238+ modem board prov ides the hardware
necessary for the T238 or T238+ to transmit APRS
packets directly to a radio instead of requiring an external
TNC. The board and the software on the T238 do not
prov ide a full-featured TNC, just the basic functions
needed to get your APRS packets on the air. While wired
up to support data reception as well, no reception
functions exist at this time.
Support for this board requires software rev ision 1.15 or
later.
The modem board plugs into the 16-pin header on either
T238. All power and control signals come from the main
board. Connection to the radio is by means of a DE-9
connector.
The modem board has two LEDs to indicate the radio
status, a red LED to indicate an activ e transmission, and a
yellow LED to indicate incoming signal.
T-238+ Assembly Manual
that: the reproduction is not sold for profit, the intent of the
reproduction is to further disseminate information on Amateur
Packet Radio, the reproduction is not used for advertising or
otherwise promoting any specific commercial product, full credit
is given to Tucson Amateur Packet Radio Corporation (including
address) as the original source of information, and Tucson
Amateur Packet Radio Corporation is notified in writing of the
reproduction.
The modem assumes an activ e low transmit enable that
can be a separate signal or combined with the transmit
audio in the DE-9 connector.
possible using a potentiometer.
While mechanically designed to mate with the T238+ as
well as T238, this board can be used for any project
wanting to add an MX-614 based modem to a project.
Acknowledgments
The Tucson Amateur Packet Radio T238+ Modem Kit was
made possible by the efforts of (in alphabetical order):
William Beals, N0XGA - Conceptual Designer
Russ Chadwick, KB0TVJ - Conceptual Designer
John Koster, W9DDD – Project Manager
If you got this board as part of the T238+ kit, assemble the
main board and button board and complete the checkout
process for those boards first. Once v erified, then build
and v erify this board.
Rev. 8 March 2006
T- 238+
Modem
Audio lev el control is
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