Hi all there!
I don’t know if this is the right place to ask my question, but i didn’t found a better one.
I try to adapt the afsk1200 example to create a ax.25 receiver with my hackrf. I must admit that i’m new to gnu radio and sdr stuff. So i was successful in creating a audio monitor channel. This works. But now i’m not sure if i included the afsk1200 example correct. I got no output from ax.25 decoder.
I don’t have the ogg file which was used in the example. I am not shure if my input to the costas loop is correct. i use a framerate of 480k.
I hope someone can give me a hint where my problem is. I tried serveral framerates and i tried to use the output of the nbfm demod but all with no success.
It seems that you have some sampling rate issues. Try to use a resampler if the existing sampling rate conversions do not suit you.
For example the source sampling rate from the hachrf is 8e6. At the first filter you decimate by 16, thus the resulting sampling rate is 5e3 not 4.8e3 that the second low pass is configured.
Thanks for your hint! I decided to go one step back and i got so far that i can decode the afsk signal which goes through the audio sink and the speakers with my phone using aprsdroid. So i assume that my sample rate is ok now till demodulation.
I looked at various examples about decoding afsk and ax25 and i decided to use the gr-sattelites example as my base. I also tried the gr-satnogs ax25 decoder but also with no luck.
It seems to me that the use of clock recovery mm is th one thing all examples have in common.
Is it right that i can in put the afsk audio wave signal direct into the clock recovery mm block?
I never tougt that it would be so hard to decode good old ax.25 afsk…
my newest attempt looks like this:
I stiil search for the problem. As far a i got is that the omega of the clock recovery mm is the samples per symbol. My calculatuion was 48k/1200bd = 40 samples per symbol. I am right with that calc or did i miss something? I tried other omega values also but still no luck…
(and sry for my late answer, not much time for the hobby right now…)
