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dumpvdl2

VDL Mode 2 decoder for aircraft datalink

What it does

Decodes VDL Mode 2, the higher-rate digital successor to plain ACARS that airliners use over land. It recovers the link layer and, through libacars, the applications riding on it — CPDLC controller-pilot messages, ADS-C position contracts, and ACARS-over-AVLC traffic.

Why you would want it

VDL2 carries most of the datalink traffic that plain ACARS used to, so in much of Europe and North America it is where the interesting messages have moved. It runs on the same dongle and the same VHF antenna as acarsdec, on adjacent frequencies around 136 MHz, and the two are usually run together.

Before it will work

An SDR and a VHF antenna. libacars must be installed first for application decoding, which the catalog sequences. The aircraft-registration lookup needs a Basestation-format database file you supply yourself; upstream documents where to get one.

How it installs

  • git (cmake) — https://github.com/szpajder/dumpvdl2 at v2.7.0
  • build dependencies: build-essential, cmake, git, pkg-config, libglib2.0-dev, librtlsdr-dev, libsoapysdr-dev, libsqlite3-dev, libprotobuf-c-dev
  • Upstream lists librtlsdr, SoapySDR, sqlite3 and protobuf-c as optional and autodetects each. As with the rest of this cluster, a missing one removes a capability without failing the build, so the cmake summary is the thing to check.

Binaries this produces:

  • src/dumpvdl2

Known problems

Skywave ships the archived vdlm2dec instead of this, and its published decoders.sh carries an update_dumpvdl2 function with a missing leading slash in a cd path, so that build runs in whatever directory the previous job left. Neither affects us — we carry the maintained decoder and have no cd to get wrong — but it is why the version Skywave documents and the one it ships differ.

Keeping it current

  • probe: github tags
  • strategy: rebuild
  • Tagged releases. Last commit on the default branch 2026-08-01 (verified 2026-08-28 from the branch head — D-032). The most actively developed of the three szpajder decoders.

Where to get help with the software itself

GitHub issues at https://github.com/szpajder/dumpvdl2/issues. Same author as libacars and dumphfdl.

Source: catalog/packages/dumpvdl2.yaml