Field Guide · protocol

Also known as: M17

M17 is an open-source amateur digital-voice and data protocol created by the M17 Project. Its defining choice is the royalty-free Codec 2 vocoder, making it a fully patent-free alternative to AMBE-based systems like DMR and D-STAR.12

synccallsigns (LICH)Codec 2 voice 4FSK · convolutional + Golay coded
An M17 frame carries sync, callsign metadata, and a royalty-free Codec 2 voice payload over 4FSK.

Overview

M17 uses 4FSK at 9600 bps and protects data with a convolutional code and Golay coding. It carries callsign metadata and supports both voice and packet/stream data, with internet reflectors for linking.

Technical characteristics

Property Value
Access FDMA
Modulation 4FSK, 9600 bps
Vocoder Codec 2
Error correction Convolutional (K=5) + Golay(24,12)

History

Started in 2019 as a community project to build a modern, open amateur protocol free of vocoder licensing constraints.1

Deployment

Growing amateur use via M17-capable firmware, hotspots, and reflectors.

Decoding it with GopherTrunk

GopherTrunk decodes the M17 link layer (callsigns, mode, stream metadata). See M17 link layer and Status.

Sources

  1. M17 Project — the official open-source project site for the M17 protocol, Codec 2 usage, and specifications. ↩ ↩2

  2. M17 (amateur radio) — Wikipedia, for background on the open M17 digital-voice protocol and its 4FSK air interface. ↩

See also

Learn it step by step

From the blog