Some of you may remember that I wrote my own APT satellite decoder. I ran across someone else who did the same:
ATPDEC by Thierry Leconte (F4DWV)
It has the same basic philosophy as my own crude efforts: hand it a WAV file, and it will find and produce the APT imagery from inside it. I went outside and recorded some of the NOAA 19 pass over my location today, and came up with the following:
Pretty nifty! I did have some trouble with some of the older recordings though: I suspect that noise may toss off his calibration in some way which isn’t entirely obvious. I’ll have to play with it more.
I got pointed at this rather large collection of shortwave recordings which are archived on the archive.org website:
Shortwave Pirate Radio : Free & Unlicensed Shortwave Radio Stations : Free Download & Streaming : Internet Archive
They have many crazy recordings of radio pirates, some of which are pretty dull, but some of which were pretty interesting. I was interested to find that there was a recording of a “digital” pirate radio station: station “XYZ”. It was easily recognizable to me as being transmitted in Hellscrieber, an old fax-like mode that was developed in the 1920s. The amateur software “fldigi” is capable of decoding these signals, which looks like this:
There is lots of fading in the recording, but it’s still quite legible. I’ve often thought making a small QRP Hellscrieber rig would be an awesome project. Oh well, I just thought it was mildly interesting.