- Direwolf - https://github.com/wb2osz/direwolf
- sox
- wget
Create a file called ax25_9600.conf with the following contents
# Cut-down Direwolf config for 9600 baud FSK decoding
ADEVICE - null
ACHANNELS 1
CHANNEL 0
MODEM 9600
MYCALL N0CALL
Create demod_ax25_9k6.sh with the following contents:
#!/bin/bash
# Demodulate 9600 baud FSK (FM demodulator) using direwolf
# Thanks to cshields and csete :-)
sox -t ogg $1 -esigned-integer -b 16 -r 48000 -t raw - | direwolf -B 9600 -b 16 -n 1 -r 48000 -q hd -t 0 -q h -q d -d p -d t -a 0 -c ax25_9600.conf -
Set this file to be executable using:
$ chmod +x demod_ax25_9k6.sh
Download the OGG file from the observation page using wget or otherwise. For example, for observation https://network.satnogs.org/observations/781981/ the ogg file can be downloaded using the link at the bottom of the sidebar (look for the download section)
$ wget https://network.satnogs.org/media/data_obs/781981/satnogs_781981_2019-06-29T07-37-48.ogg
The file can then be decoded by running:
$ ./demod_ax25_9k6.sh satnogs_781981_2019-06-29T07-37-48.ogg
Which produces the output:
Dire Wolf version 1.3
Includes optional support for: gpsd
Setting such a small audio statistics interval will produce inaccurate sample rate display.
Reading config file ax25_9600.conf
Audio input device for receive: stdin (channel 0)
Audio out device for transmit: null (channel 0)
Channel 0: 9600 baud, K9NG/G3RUH, , 48000 sample rate x 2.
Note: PTT not configured for channel 0. (Ignore this if using VOX.)
Ready to accept AGW client application 0 on port 8000 ...
Ready to accept KISS client application on port 8001 ...
Use -p command line option to enable KISS pseudo terminal.
Audio input level is too high. Reduce so most stations are around 50.
[0] CQCQCQ>ACRUX1:<0x05>
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U frame UI: p/f=0, No layer 3 protocol implemented., length = 271
dest ACRUX1 0 c/r=0 res=3 last=0
source CQCQCQ 0 c/r=1 res=3 last=1
000: 82 86 a4 aa b0 62 60 86 a2 86 a2 86 a2 e1 03 f0 .....b`.........
010: 05 00 00 05 1e 00 e5 33 03 00 a5 33 50 0c 00 80 .......3...3P...
020: 00 80 00 80 00 80 00 80 00 80 00 80 00 80 00 80 ................
030: 00 80 00 80 00 80 00 80 00 80 00 80 00 80 00 80 ................
040: 00 80 00 80 00 80 00 80 00 80 00 80 00 80 00 80 ................
050: 00 80 90 5f 7e 00 00 00 00 00 e9 1e 00 00 00 00 ..._~...........
060: 00 00 00 00 54 4f 44 4f 3a 20 50 6c 65 61 73 65 ....TODO: Please
070: 20 74 65 6c 6c 20 4d 53 50 20 74 68 61 74 20 74 tell MSP that t
080: 68 65 69 72 20 73 61 74 65 6c 6c 69 74 65 20 77 heir satellite w
090: 6f 72 6b 73 00 00 00 00 00 00 00 00 00 00 00 00 orks............
0a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 15 ................
0f0: 0e f0 f8 18 10 f3 1a 23 c5 86 10 44 19 81 6e 94 .......#...D..n.
100: ff e5 f2 ed e5 0f c3 df 58 d3 b0 ba 66 85 7e ........X...f.~
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