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Bell 202 Audio Frequency Shift Keying encoder and APRS packet audio tools

Project description

Library to generate Bell 202 AFSK audio samples and AFSK encoded APRS/AX.25 packets.

The aprs command line program encodes APRS packets as AFSK audio data.


$ aprs -c <your callsign> ":EMAIL Test email"


Install with pip:

$ pip install afsk
$ pip install --allow-external PyAudio --allow-unverified PyAudio PyAudio

PyAudio is optional, so must be installed separately.

If you want to use the CLI program to play APRS packets via your soundcard, install PyAudio. Otherwise, if you just want to generate Wave files of AFSK data, you can skip it.

Note that installing PyAudio will require a C compiler and PyAudio’s various C dependencies, in addition to the --allow-external and --allow-unverified pip flags.

For development, change to the afsk directory and install with:

$ pip install -r requirements.txt
$ python develop

Requires Python 2.6 or 2.7.

Command Line Interface

Generate APRS messages with the aprs CLI program:

$ aprs --callsign <your callsign> ":EMAIL Test email"

Specify your message body with INFO command line argument. Be sure to wrap the message in quotes so it’s passed as one argument, spaces includd.

At the moment, no message formats are implemented in the aprs program; you must construct the body string yourself. For instance, in the example above, the string passed as an argument to aprs follows the email messsage format specified for APRS.

You must specify your amateur radio callsign with the --callsign or -c flags.

Use the --output option to write audio to a Wave file (use ‘-’ for STDOUT) rather than play over the soundcard.

Get a listing of other options with aprs --help.


Playback with PyAudio and short options:

$ aprs --callsign <your callsign> ":EMAIL Test email"

Playback with sox:

$ aprs --callsign <your callsign> --output - ":EMAIL Test email" |\
      play -t wav -

Save to a wave file with using short options:

$ aprs -c <your callsign> -o packet.wav ":EMAIL Test email"


Get the source and report any bugs on Github:

Version History

  • 0.0.3 – Pin dependency versions, fix bug with STDOUT playback, verbosity CLI option.

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