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acarsdec

VHF ACARS decoder for aircraft datalink messages

What it does

Decodes ACARS — the VHF datalink airliners use for short operational messages — from an SDR, and prints each message with its aircraft registration, flight number, label and text. With libacars present it also decodes the application layer inside those messages: CPDLC clearances and ADS-C position reports rather than raw payloads.

Why you would want it

It is the entry point to aeronautical monitoring and it works with the cheapest dongle you own. ACARS sits around 131 MHz in most regions, needs no special antenna beyond something resonant at VHF, and produces readable traffic within minutes. Nothing in Debian does this: apt-cache search finds no acars* package in stable or unstable, which makes this and its siblings the largest single coverage gap the Debian Blend leaves.

Before it will work

An SDR (RTL-SDR, Airspy or anything SoapySDR reaches) and a VHF antenna. Install libacars first or the application layer is left undecoded — the catalog sequences that for you.

How it installs

  • git (cmake) — https://github.com/f00b4r0/acarsdec at v4.6
  • build dependencies: build-essential, cmake, pkg-config, librtlsdr-dev, libsoapysdr-dev, libairspy-dev, libsndfile1-dev, libasound2-dev, libcjson-dev
  • Upstream autodetects each optional library and prints a summary of what was enabled. Missing one does not fail the build — it silently removes an input source or an output format, so the summary is the thing to read rather than the exit status (D-031).

Binaries this produces:

  • acarsdec

Known problems

Optional libraries are autodetected and their absence is silent: without libsndfile there is no file input, without libasound no ALSA input, without libcjson no JSON output. The build prints which were enabled. SDRplay support is deliberately not built here because the vendor API cannot be fetched non-interactively and therefore cannot be verified against a checksum.

Keeping it current

  • probe: github tags
  • strategy: rebuild
  • Tagged releases. Last commit on the default branch 2026-06-28 (verified 2026-08-28 from the branch head, not GitHub's updated_at — D-032).

Where to get help with the software itself

GitHub issues at https://github.com/f00b4r0/acarsdec/issues. Note that the older TLeconte/acarsdec repository is archived and read-only; issues opened there will not be seen.

Source: catalog/packages/acarsdec.yaml