MULTIMON-NG(1)

📦
version 1.6.2 · 3 versions
, in arch rolling, nixpkgs unstable

💅 multimon-ng(1) — General Commands Manual

ok so bestie, welcome to the multimon-ng era 🎀

✨ NAME ✨

multimon-ng — the program that literally decodes radio transmissions 📻💖

🌸 SYNOPSIS 🌸

multimon-ng [options] [input_file]

🦋 DESCRIPTION 🦋

okay so this manual page is a short lil intro to the multimon-ng command, and here's the tea: it was written for Debian because the original program straight up does not have a manual page 💀 so we made one. you're welcome.

The multimon-ng software decodes a whole variety of digital transmission modes that are commonly found on VHF/UHF radio ✨. It uses a standard PC soundcard to grab the signal from a transceiver, and the decoding is done completely in software — no extra hardware brain needed 🧠💅. Currently these are the modes it supports:

  • AX.25
    • 1200 Baud AFSK
    • 2400 Baud AFSK (2 variants)
    • 4800 Baud HAPN
    • 9600 Baud FSK (G3RUH)
  • POCSAG
    • 512 Baud
    • 1200 Baud
    • 2400 Baud
  • Selective call
    • CCIR
    • EEA
    • EIA
  • Frequency Shift Keying
    • 1200 Baud FSK (2200/1200 Hz)
    • 1200 Baud FSK (2300/1100 Hz)
    • 1200 baud FMS FSK
  • Miscellaneous
    • DTMF
    • CW/Morse
    • EAS
    • FLEX
    • SCOPE
    • X10
    • ZVEI

An arbitrary set of the above modes may run concurrently on the same input signal (provided the CPU power is sufficient 🔥), so you genuinely do not have to know in advance which mode is being used — it's giving mind-reading, honestly. But heads up: some modes might require modifications to the radio (especially the 9600 baud FSK and the POCSAG modes) to work properly 😭 so don't come for the program if your rig isn't set up.

here's the little glossary moment, iykyk:

  • AX.25 — Amateur Packet Radio protocol datagram format.
  • DTMF — Dual Tone Multi Frequency. Commonly used in in-band telephone dialing.
  • EAS — Emergency Alert System.
  • FLEX — a paging format.
  • GSC (Golay Sequential Code) — a 600 baud paging format using Golay and BCH error correction.
  • POCSAG (Post Office Code Standards Advisory Group) — a common paging transmission format.
  • SCOPE — show samples in a rudimentary oscilloscope display on an X server.
  • SDL_SCOPE — digital phosphor oscilloscope display using SDL3. Features green/amber phosphor emulation with intensity grading. Press Space to toggle color, Q/Esc to quit. (the phosphor emulation is so aesthetic, ngl 🟢🟡)
  • X10 — a home automation protocol.
  • ZVEI — The German Electrical and Electronic Manufacturers' Association — paging tone format.

⭐ OPTIONS ⭐

  • -t <type> — Input file type. Auto-detected from file extension if not specified. Use "hw" for hardware audio input (default when no file specified). Types other than raw require sox. Allowed types: hw raw aiff au hcom sf voc cdr dat smp wav maud vwe mp3 mp4 ogg flac.
  • -a <demod> — Add demodulator (see below).
  • -s <demod> — Subtract demodulator.
  • -c — Remove all demodulators (must be added with -a <demod>).
  • -q — Quiet output messages. 🤫
  • -v <num> — Verbosity level (0-10). For POCSAG and MORSE_CW '-v1' prints decoding statistics.
  • -h — Print the help.
  • -A — APRS mode (TNC2 text output).
  • -m — Mute SoX warnings.
  • -r — (Deprecated) Repeatable mode is now always enabled. This flag is kept for backwards compatibility but has no effect. 🫠 it's giving legacy support.
  • -n — Don't flush stdout, increases performance.
  • -j — FMS: Just output hex data and CRC, no parsing.
  • -e — POCSAG: Hide empty messages.
  • -u — POCSAG: Heuristically prune unlikely decodes.
  • -i — POCSAG: (Deprecated) Signal polarity is now auto-detected. This flag is kept for backwards compatibility but has no effect. 💀 another one that just sits there.
  • -p — POCSAG: Show partially received messages.
  • -P <mode> — POCSAG: Set signal polarity detection mode. <mode> can be 'auto' (default), 'normal' (only try normal polarity), or 'inverted' (only try inverted polarity). Use 'normal' to reduce false positives when signal polarity is known.
  • -f <mode> — POCSAG: Disables auto-detection and forces decoding of data as <mode> (<mode> can be 'numeric', 'alpha', 'skyper' and 'auto').
  • -b <level> — POCSAG: BCH bit error correction level. Set 0 to disable, default is 2. Lower levels increase performance and lower false positives.
  • -C <cs> — POCSAG: Set charset (default: US), where <cs> is one of: US, FR, DE, SE, SI.
  • -o <time> — CW: Set threshold for dit detection (default: 500).
  • -d <time> — CW: Dit length in ms (default: 50).
  • -g <time> — CW: Gap length in ms (default: 50).
  • -x — CW: Disable auto threshold detection.
  • -y — CW: Disable auto timing detection.
  • --timestamp — Add a time stamp in front of every printed line. ⏰
  • --iso8601 — Use UTC timestamp in ISO 8601 format that includes microseconds.
  • --label <label> — Add a label to the front of every printed line.
  • --flex-no-ts — FLEX: Do not add a timestamp to the FLEX demodulator output.
  • --json — Format output as JSON. Supported by the following demodulators: DTMF, EAS, FLEX, POCSAG. (Other demodulators will silently ignore this flag. 🙈)

and where <demod> is one of: POCSAG512 POCSAG1200 POCSAG2400 FLEX FLEX_NEXT GSC EAS UFSK1200 CLIPFSK FMSFSK AFSK1200 AFSK2400 AFSK2400_2 AFSK2400_3 HAPN4800 FSK9600 DTMF ZVEI1 ZVEI2 ZVEI3 DZVEI PZVEI EEA EIA CCIR MORSE_CW DUMPCSV X10 SCOPE SDL_SCOPE

The -a and -s options may be given multiple times to specify the desired list of demodulators 👑 stack 'em, customise 'em, it's your world.

🍓 EXAMPLE 🍓

Decode signal modulations from a sound file /tmp/message.wav without using a SCOPE display:

multimon-ng -s SCOPE -t wav /tmp/message.wav

With no input file specified, the program listens directly to the sound card using PulseAudio 🎧. So to decode (only) DTMF tones on the sound card input:

multimon-ng -a DTMF

🌈 NOTICE 🌈

Please note that monitoring commercial services may be prohibited in some countries ⚠️ — this software should therefore only be used to monitor the amateur radio service. fr fr, check your local laws bestie, we are not trying to get you in trouble 💖

💀 BUGS 💀

The DTMF and ZVEI decoders have more frequent spurious detection reports. 😭 they're a little dramatic, they see ghosts. love them anyway.

🫶 AUTHOR 🫶

This manual page was written by A. Maitland Bottoms <bottoms@debian.org>, Göran Weinholt <weinholt@debian.org> and Elias Oenal <multimon-ng@eliasoenal.com> for the Debian GNU/Linux system (but may be used by others). This is free software. You can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or any later version. 📜✨

and that's the whole vibe check diva 💅 this edition dropped April 18, 2026 — General Commands Manual, MULTIMON-NG(1), mwah 🎀💖 go decode something iconic 🔥

📦 where this page comes from