Now, 4 DGSN stations receiving APRS from orbit by the @Space_Station! Stations are now in Settrup (a lovely small village in Lower Saxony!), @shackspace in Stuttgart, @ToolboxBodensee near Lake Constance and @eah_satcom in Jena. Where should we put one next? If you have a suggestion, please tell me here >> https://twitter.com/andreashornig/status/897434397925937152
My task is now that I still want to know the content of APRS the @Space_Station sent here! Would anyone please help me decode? :) I uploaded a Python Numpy NPY file here/goo.gl/5zLkwr .. It incuded the Signal Peak you see in the graph above from those 4 stations.
What I know is that APRS uses Bell202 coding with two frequencies of 1200 Hz and of 2200 Hz. Each represent either a 1 or 0. I just started to play with an FFT Kernel of 8K samples and I already found phases of those frequencies but so far I couldn't find the starting flag of the AX.25 frae 01111110.
As far as I know, Bell202 was also used in old internet modems. So I guess that there are people on Hackaday who play around with old modems and solve those problems while sleeping. If so, please comment below.
Until then, I will keep on playing with the 4 stations and trying to decode APRS signals.... :)