Another try at an HF FAX decoder…

About two years ago, I spent an evening and hacked together a simple program for taking recordings of HF-FAX transmissions and converting them into image files. The other day, I thought I’d dust that code off, but I couldn’t find it. So, instead, I reimplemented it from scratch. There is an interesting bit of math that I finally understood when I reimplemented it, which actually worked out rather well. I took a recording that I made of the New Orleans Coast Guard’s station broadcast, and it turned into this picture:


I’ll have to work a bit on the sync detection and scaling, as well as rectification, but it’s looking pretty good for the small amount of effort I’ve placed in it.

One thought on “Another try at an HF FAX decoder…”

  1. Mark.

    I enjoy reading you adventures with WX FAX displays.

    Several years ago (maybe 20 or so) I was playing with some code that I wrote to display HF-FAX, I wanted to to see what I could do with the data – I tried displacing (and smear) the pixels “up” within the display image, dependant on it cloud brightness and then merge it back with a base map – the results was very interesting fake 3D like display. My code processed the image from top-to-bottom and therefore it was done in place on a small machine, It was most interesting for viewing circular storm patterns. For a long time I kept several of the most interesting images, but alas, now they are lost.

    As fast as you write code, I am sure you could do something similar in few minutes.

    Eldon – WA0UWH

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