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fldigi

Multi-mode digital modem for PSK31, RTTY, Olivia, MT63 and more

What it does

Turns a sound card and a transceiver into a modem for around twenty digital modes, including PSK31, RTTY, Olivia, Contestia and MT63, with a waterfall display for tuning them.

Why you would want it

It is the reference implementation for HF digital modes on Linux and the foundation of the NBEMS emergency-messaging stack alongside flmsg and flamp.

Before it will work

Sound-card audio routed to and from the radio, and PTT via hamlib, flrig, CAT, or a serial line. docs/guides/digital-modes.md covers rig control and the first PSK31 and RTTY contacts; docs/guides/audio-routing.md covers the audio path and choosing between fldigi's PulseAudio and PortAudio options.

How it installs

  • source (autotools) from https://downloads.sourceforge.net/project/fldigi/fldigi/fldigi-4.2.13.tar.gz
  • build dependencies: libfltk1.3-dev, libpng-dev, portaudio19-dev, libsamplerate0-dev, libsndfile1-dev, libudev-dev
  • AHRL also installs libportaudio-ocaml-dev here. That is an OCaml binding fldigi does not use; it is a copy-paste error that never surfaced because AHRL checks no exit status. Deliberately omitted — see D-016.

Binaries this produces:

  • src/fldigi
  • src/flarq

This displaces the distribution's own fldigi (D-022: coexist, disclose, never remove silently).

Known problems

The repository package is purged before installing, because the source build installs to the same prefix. The build also produces flarq, which is why this manifest declares it under provides — without that, a parity check reports flarq as a false gap.

Toolkit risk

  • wx3.2: unknown, checked 2026-08-25 — Not fldigi itself, but AHRL resolves libwxgtk*-dev by apt-cache grep for several units; fldigi uses FLTK and is unaffected. Recorded to keep the register honest about what was checked.

Keeping it current

  • probe: binary version
  • strategy: rebuild

Where to get help with the software itself

linuxham groups.io list

Source: catalog/packages/fldigi.yaml