The fixed low level audio output from your radio
is on Pin 5 of the ACC1 socket at the back of the radio
(but double check in the manual, it should be described as "AF Detector Output"). The "Ground" side is pin 2 (again double check in the manual).
Connect these with appropriate plugs and cable to your computer microphone input socket - this is easy to make up if adept at soldering else get someone who is to make one up (the ACC1 plug
will be the hard one to solder). If your computer microphone socket takes a stereo plug
then make the output from the radio to the tip connection on the plug. It is best to use a shielded cable.
I use a very old program called WXSat available at WXSat
which is free for non commercial
use - it is the only fully functional one that I know is free. It is a very competent program but is a little trickier to understand as it has much flexibility. Many use JVFax as mentioned by GordMay - as far as I know the only difference between the trial and full versions of that is a nag on the charts
(maybe the printed only charts
??) so is also a good choice (but I have not looked at the current
version) and is probably easiest to start with.
Once cabled up and running, and tuned into a fax station, adjust the level into the computer's mic socket using the computer's mic volume control to the level the program help file describes - if using MSWindows, and depending on your soundcard you may need to select the "Microphone 20db Boost" option under the advanced tab of the mic volume control to get enough input.
If tempted to use WXSat, be aware that it does satellite
weather pictures as well so for ssb
so you have to select the "FM120" option under "Parameters" and set up the width you desire for the received chart - for that one needs to read carefully the section in the help file on setting the "y compression" to get the desired chart width in pixels.