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1995-04-22
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73 lines
WEFAX
Weather Satellite Facsimile
by CHARLES JACKSON
Antic Program Editor
Tune in a weather satellite and downlink a few pictures
from space! A standard shortwave radio plus this issue's
WEFAX Decoder software and WEFAX Interface board are all that
your Atari needs for receiving and displaying Weather
Facsimile pictures from the satellites of the US and other
nations, as well as facsimile photos from newswire services.
This Weather Facsimile system is the most ambitious
project ever published by Antic. It required more than six
months of intensive research, programming and hardware
tinkering. But the result is the most versatile and
friendliest weather satellite software available for the
Atari 8-bit and ST computers.
The reason this project turned out to be so demanding is
that its success depends on many factors -- including
software, hardware and the forces of nature Especially
important are what type of radio and antenna you use, and the
area you live in.
You need a shortwave radio capable of receiving SSB
(single side-band) signals. Inexpensive "all-band" portables
with telescoping antennas will not suit our purposes. We
developed these programs using a Radio Shack DX-302 attached
to a 25-foot longwire antenna. But for good results, you
should use the best receiver and outdoor shortwave antenna
you can afford.
Also, even if you type in the program perfectly and
build the interface circuit without a hitch, you could be out
of luck if you live in an area with poor shortwave reception.
WEFAX signals are clearest in suburban and rural areas. If
you live in the center of a large city, you may have trouble
receiving a clean WEFAX picture.
PROJECT ELEMENTS
Before you can use the Decoder programs, you'll have to
build the WEFAX Interface described in this issue. The
interface is a simple circuit that can be built for under
$20.
WEFAX.EXE is for 8-bit machines, WEFAX.TOS is for the
ST. Copy WEFAX.EXE to another
disk and rename it AUTORUN.SYS, then follow the instructions
in the accompanying articles.
Listings 2 and 3, FAX.M65 and FAXA.M65, contain the
MAC/65 source code for WEFAX.EXE. You do not need to type in
these listings to use the WEFAX program.
Listing 4, WESIM.BAS, is a BASIC program that simulates
a WEFAX signal. If you've never heard a WEFAX signal, this
program will create one for you. Listing 5, WETST.BAS, is a
BASIC program that helps you test your WEFAX Interface
circuit.
The ST version of WEFAX Decoder is WEFAX.TOS and you'll
find the article explaining it in this issue's ST Resource
section.
THANK YOU!
Finally, Antic would like to thank all the people who
helped us with this project, including: Dr. Ralph Taggart,
Dr. Marty Goodman, CompuServe Vice-President Sandy Trevor,
Vic Moore, Jim Grubs, Chris Elmquist and Wayne Day. Special
thanks to the staff of the San Francisco Area Office of the
National Oceanic and Atmospheric Administration, including
William Pettyplace and Jan Null.
SUGGESTED READING
If you want to learn more about Weather Satellite
transmissions, here are some of the best sources to get you
started:
The New Weather Satellite Handbook, by Dr. Ralph
Taggart. This is the definitive text on WEFAX. Formerly out
of print, an updated edition of this popular book is
available from the author for $12.50.