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Open source amateur radio mode From Wikipedia, the free encyclopedia
M17 is a digital radio modulation mode developed by Wojciech Kaczmarski (amateur radio call sign SP5WWP) et al.[1][2][3][4][5][6] M17 is primarily designed for voice communications on the VHF amateur radio bands, and above. The project received a grant from the Amateur Radio Digital Communications in 2021[7] and 2022.[8] The protocol has been integrated into several hardware and software projects.[citation needed] In 2021, Kaczmarski received the ARRL Technical Innovation Award for developing an open-source digital radio communication protocol, leading to further advancements in amateur radio.[9]
M17 uses Frequency-Division Multiple Access (FDMA) technology in which different communication streams are separated by frequency and run concurrently. It utilizes 4,800 symbols per second, 4-level frequency-shift keying (4FSK) with a root Nyquist filter applied to the bitstream. Radio channels are 9 kHz wide, with channel spacing of 12.5 kHz. The gross data rate is 9,600 bits per second, with the actual data transfer at 3,200. The transmission, called stream, is divided into 40-millisecond long frames, each prepended with a 16-bit long synchronization word. A group of 6 frames form a superframe and is needed to decode the link information data. Protocol allows for low-speed data transfer (along with voice), e.g. GNSS position data. The mode has been successfully transmitted through EchoStar XXI[10] and QO-100[11] geostationary satellites. The protocol's specification is released under GNU General Public License.
M17 uses Codec 2, a low bitrate voice codec developed by David Rowe VK5DGR et al. Codec 2 was designed to be used for amateur radio and other high compression voice applications. It is based on linear predictive coding with mixed-harmonic sinusoidal excitation. The protocol supports both 3200 (full-rate) and 1600 bits per second (half-rate) modes.
Three methods are used for error control: binary Golay code, punctured convolutional code and bit interleaving. Additionally, exclusive OR operation is performed between data bits and a predefined decorrelating pseudorandom stream before transmission. This ensures that there are as many symbol transitions in the baseband as possible. A 16-bit cyclic redundancy check (CRC) code is used for data integrity assurance.
The M17 protocol was primarily designed for amateur radio use.
With a small hardware modification, TYT MD-380, MD-390 and MD-UV380 handheld transceivers can be flashed with a custom, free, open source firmware[12] to enable M17 support.
In July 2024, a US-based company Connect Systems, Inc. released the CS7000-M17, being the first commercial off-the-shelf handheld transceiver with native M17 support.[13]
Links between M17 and other digital voice modes and Internet linked networks exist, with several networks providing M17 access. Modes bridged include DMR, P25, System Fusion, D-STAR, NXDN, AllStarLink, EchoLink and IRLP.[14][15][16][17][18][19]
| M17 | Digital Mobile Radio (DMR) | D-STAR | System Fusion (YSF) | |
|---|---|---|---|---|
| Type | Open | Open | Partially open | Closed (proprietary) |
| Developer | Amateur radio community (decentralized) | European Telecommunications Standards Institute (ETSI) | Japan Amateur Radio League (JARL), ICOM Inc., Kenwood Corporation, and others | Yaesu |
| Modulation | 4FSK | 4FSK | GMSK | 4FSK |
| Channel (medium) access | FDMA | FDMA (Tier I), 2-slot TDMA (Tier II/III) | FDMA | FDMA |
| Voice codec | Codec 2 (open-source) | AMBE+2 (proprietary) | AMBE (proprietary) | AMBE+2 (proprietary) |
| Arbitrary data transfer support | Full | Limited (text messaging, geolocation) | Limited (text messaging, geolocation, images) | Limited (text messaging, geolocation, images) |
| Extensibility | Full | Fixed | Fixed | Fixed |
Access nodes and repeaters[20] can be linked using reflectors. Over 190 M17 reflectors exist worldwide (August 2024).[21]
The project was started in 2019 by Wojciech Kaczmarski in Warsaw, Poland. A local amateur radio club he was a member of, was involved in digital voice communications. Kaczmarski, having experimented with TETRA and DMR, decided to create a completely non-proprietary protocol and named it after the club's street address - Mokotowska 17. As every part of the protocol was intended to be open source, Codec 2 released under the GNU GPL 2 license, has been chosen as the speech encoder.
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