science

M17 (amateur radio)

M17 (amateur radio) is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand M17 (amateur radio) rather than just read about it. In short: M17 is a digital voice and data protocol specification developed by Wojciech Kaczmarski (amateur radio call sign SP5WWP) with contributions from the amateur radio community. M17 is primarily designed for voice communications on the VHF amateur radio bands, and above.

Key takeaways

M17 (amateur radio) belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect M17 (amateur radio) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of M17 (amateur radio) from memory before moving on to harder problems.

Reference excerpt

M17 is a digital voice and data protocol specification developed by Wojciech Kaczmarski (amateur radio call sign SP5WWP) with contributions from the amateur radio community. M17 is primarily designed for voice communications on the VHF amateur radio bands, and above. The project received grants from the Amateur Radio Digital Communications in 2021 and 2022. The protocol has been integrated into several hardware and software projects, including commercial handheld radios.

Technical characteristics

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 symbol-mapped 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. The protocol allows for low-speed data transfer (along with voice), e.g. GNSS position data. The mode has been successfully transmitted through EchoStar XXI and QO-100 geostationary satellites. M17 transmissions have also been tested using the OPS-SAT experimental satellite platform.

Voice encoding M17 uses Codec 2, a low bitrate voice codec developed by David Rowe VK5DGR et al. Codec 2 was selected as the voice codec due to its open licensing and suitability for low-bitrate digital voice applications. It is based on linear predictive coding with mixed-harmonic sinusoidal excitation. The M17 protocol supports both 3200 (full-rate) and 1600 bits per second (half-rate) modes.

Error control 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.

Application functions The M17 protocol is designed for use in amateur radio communications.

Callsign encoding: a 48-bit field holding up to 9 alphanumeric characters allows stations to be identified directly by callsign, eliminating the need for a centralized user-ID registration system. Two modes of operation: stream mode for continuous voice or data transmission, and packet mode for discrete data transfer. Stream mode offers one 3200bps net bitrate channel (encoded speech or data) or two 1600bps channels (encoded speech alongside data). Packet mode supports text messaging, APRS, AX.25, 6LoWPAN, Winlink, and raw binary data transfer. Slow-speed side channel for short and repeated data transfers, e.g. GNSS position data or telemetry. Network operation via reflectors and IP links, allowing repeaters and private access points (hotspots) to interconnect and route voice calls and data streams between distant stations.

Security features Bit scrambler encryption: a pseudorandom binary sequence created by combining an exclusive-or bitwise operation on the audio or data stream and a linear-feedback shift register using one of 3 feedback polynomials with 255, 65,535 and 16,777,215-bit repeat periods. AES encryption: symmetric, 128-bit block cipher operating in CTR mode with user-selectable 128, 192 or 256-bit keys. Digital signature authentication using ECDSA: a rolling digest is accumulated over the transmitted stream and signed by the sender using the secp256r1 curve. The signature is transmitted in additional frames at the end of the transmission and can be verified by receivers using the sender public key. This provides stream authentication independently of whether encryption is used.

Hardware support

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 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.

Bridging with other modes 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.

Comparison with other standards

M17 over IP Access nodes and repeaters can be linked using reflectors. Over 130 M17 reflectors exist worldwide (June 2026).

Governance and licensing The protocol's specification is released under GNU General Public License, with reference implementations released as open-source software. Development is coordinated publicly, with protocol documentation, reference code, and discussion available to the amateur radio community.

History 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 LGPL 2.1 license, was chosen as the speech encoder.

Applications and projects with M17 support OpenRTX - free and open-source firmware for ham radios DroidStar - digital voice client for Android SDR++ - multiplatform, open-source software defined radio receiver SDRangel - multiplatform, open-source software defined radio receiver/transmitter OpenWebRX - web-based software defined radio receiver mrefd - M17 reflector rpitx - general radio frequency transmitter for Raspberry Pi dsd-fme - digital speech decoder mvoice - voice client and graphical repeater application (Raspberry and Linux) mspot - hotspot software

See also NXDN D-STAR Speech coding Quadratic permutation polynomials (QPP)

References

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with M17 (amateur radio)

Start with the simplest possible case. Write down what M17 (amateur radio) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to M17 (amateur radio) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about M17 (amateur radio) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of M17 (amateur radio)

In research: M17 (amateur radio) appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses M17 (amateur radio) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: M17 (amateur radio) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amateur radio, Digital amateur radio, Quantized radio modulation modes, so understanding it makes those chapters shorter.
In everyday life: Look for M17 (amateur radio) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “M17 (amateur radio)” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study M17 (amateur radio) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what M17 (amateur radio) means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain M17 (amateur radio) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is M17 (amateur radio) in simple terms?

Why does M17 (amateur radio) matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study M17 (amateur radio)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on M17 (amateur radio).