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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html>
<head>
<title>HamFax</title>
</head>
<body>
<h1>HamFax help</h1>
<h2>about HamFax</h2>
<p>HamFax is an application for sending and receiving facsimilies in
amateur radio. You can either use a sound card as interface to the
transceiver or a SCS-PTC-II. Receiving of weather facsimile broadcasts
is also possible.</p>
<p>The program is licensed under the terms of the GNU General Public
License. See http://hamfax.sourceforge.net/ for further information
and new releases.</p>
<h2>about facsimiles</h2>
<h3>general</h3>
<p>Facsimiles are pictures which are transmitted line by line. The sending
and receiving station have to agree on the transmission speed (LPM
stands for lines per minute) and the IOC (index of cooperation) which
corresponds the line width. The information transmitted is the
brightness of the current position.</p>
<p>The beginning of a transmission is marked with a APT start signal (APT
stands for automatic picture transmission). Usually this is a black/white
pattern which changes between black and white at 300Hz.</p>
<h3>short wave facsimiles</h3>
<p>Facsimiles on short wave are frequency modulated, that means the
frequency of the carrier is changing with the transmitted information
(the current brightness). Usually the deviation is 400Hz, so the
frequency for white is 800Hz higher than the one for black.</p>
<p>For information about stations broadcasting weather maps, see the
program's homepage.</p>
<h3>weather satellites</h3>
<p>For receiving facsimiles from a weather satellite a suitable FM
receiver is needed. The output of this receiver is a amplitude modulated
signal where the maximum amplitude corresponds to white and no amplitude
means black.</p>
<h2>using HamFax</h2>
<h3>interface setup</h3>
<p>You can either use a SCS PTC-II as modulator and demodulator or
connect a sound card to your transceiver. For the PTC refer to the
manual, especially the chapter about interfacing transceiver, PTC and
computer. When using a sound card you need to connect line-out to the
microphone input (or something similar) of the transceiver and line-in to
some output of the transceiver. The RTS signal of a serial port can be
used to key the PTT as it is often use for PSK31. A simple transistor is
often enough to do the job.</p>
<p>For both interfaces you have to switch your transceiver to USB (upper
side band). In HamFax set carrier to 1900kHz and tune your transceiver
1900kHz below the desired frequency.</p>
<h3>receiving facsimiles</h3>
<p>Set deviation, modulation apt start and stop frequencies, lpm, the type
of phasing lines (normal or inverted) and the mono/color switch to the
appropriate values. Then choose the desired interface in the receive menu
and see what happens. :)</p>
<p>If the apt start tone is not detected properly or you missed it you can
skip it by clicking the skip button. If you missed the phasing lines you
can skip the phasing detection and the value from the lpm checkbox is
used.</p>
<p>While receiving the raw data is stored in memory. So it is possible to
correct the received image with the menu items in the Image menu. The
image can be saved in any format supported by Qt.</p>
<h3>sending facsimiles</h3>
<p>Load the image from somewhere. Then set the control items to the desired
values and scale the image to the desired IOC. Just select the right item
from the transmit menu and you are on the way.</p>
<hr>
<address>Author: Christof Schmitt, DH1CS
<cschmitt@users.sourceforge.net></address>
</body>
</html>
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