I've managed to recover a few more FCAL packets from the audio that SatScape is automagically recording for me. I have a number of good candidate audio files that AGWPE doesn't decode, in spite of the audio being pretty strong. I don't see a "pass all" setting on AGWPE, so I presume there are bit errors causing the packets to be discarded. Any suggestions for post-processing the audio with the intent of pulling AX.25 packets out of the muck?
Jim3 KB3MPL
2007feb08 03:31 EST 1:Fm KD4HBO To TELEM Via TELEM <UI pid=F0 Len=57 >[xx:xx:xx] Analog 00040004000000DB00A5000C00DE000B N 0000001E
2007feb09 03:47 EST 1:Fm KD4HBO To TELEM Via TELEM <UI pid=F0 Len=55 >[xx:xx:xx] 004194EFFE0128FFFE0210FFFE01D8FFFE0278FFFE01D0FFFE01B0
2007feb10 02:27 EST 1:Fm KD4HBO To TELEM Via TELEM <UI pid=F0 Len=56 >[xx:xx:xx] Analog 001200FA00FE00DB00A600FC00DD0010 N 0000001E
mcguire@stensat.org wrote:
Any suggestions for post-processing the audio with the intent of pulling AX.25 packets out of the muck?
Jim3 KB3MPL
Get an audio processing program like CoolEdit, Audition, or Audacity and FIR filter the audio to remove as much of the "noise" as you can. You probably want to start by filtering out everything below about 1000 Hertz or above about 2500 Hertz. The exact cutoff numbers you choose depend on the characteristics of the particular DSP filter you are using and its rolloff, but the idea is to throw away as much of the noise as you can and just leave the packet tones.
Sometimes this is all you need...
Of course, if one or more bits in the packet really ARE corrupted with in-band noise, then the packet still won't decode.
If you want, email me a copy of the recording and I'll take a look too.
Douglas KA2UPW/5
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mcguire＠stensat.org