hello, thanks to your suggestions I have been able to obtain a quite working demodulation, what I am actually trying to demodulate is AFSK 1200baud ax25 packet; the steps I am doing are
1) channeling from USRP stream - complex stream 2) fm demodulation - real stream at this point I have an audio signal with 1200 and 2200 tones 3) mix the signal with a complex sine @ 1700hertz this is an half complex mixer and it shifts my real spectrum 1700 hertx down the frequency axis, with the result I have now: a) one spectral line @ 500 (former 2200 tone) b) one spectral line @ -500 (former 1200 tone) c) one spectral line @ -2900 d) one spectral line @ -3900 4) 500Hz lowpass the complex signal to discard the negative unwanted frequencies 5) fm demodulation to restore the -1,1 symbol stream actually I am getting some ringing, but I guess it depends on the paramters of the lowpass filter that are not correctly choosen. Is there any better way to demodulate this? Do you think that the result would be better with the use of matched filters for mark and space frequencies? Would it get better if I use a particular shaping of the lowpass filter previous to final fm demod? thanks Matteo _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
