What is M17?
M17 is a truly open, free to use digital radio system. The M17 standard and everything related, such as schematics, PCB layouts, and source code is available to use for free at the GitHub pages.
How long has M17 been in development? Where did M17 start?
M17 started development in 2019, near Warsaw, Poland by SP5WWP Wojciech Kaczmarski.
Why is M17 being developed?
Mainly because there is no open platform for developing digital radio. By example, the DMR system while an ETSI open standard, is not amateur radio friendly. It cannot be experimented with. M17 aims to address this issue along with others, and provide better voice quality.
What is the main difference of M17 to existing digital standards, like DMR?
M17 is a digital voice and data protocol that is fully open source, and utilizes an open source voice codec, Codec 2. M17 has a channel bandwidth of 9kHz, efficiently using a 12.5kHz channel spacing.
Can M17 be used on HF? What is the difference between M17 and FreeDV?
M17 is optimized and designed for use on VHF and up. M17's bandwidth is 9kHz, which is much too wide to be used on HF while being a considerate Amateur Radio operator.
FreeDV is optimised for weak signal work in a very digital hostile HF channel. FreeDV's modems have a bandwidth in the order of 1 kHz (as opposed to 9kHz for M17), and doesn't have a constant envelope (since linear PAs are more common on HF). However, FreeDV has poorer audio quality (due to having to use more extreme compression) in most modes, and very limited data support, again, because of the severe bitrate limits.
What is the encoded speech bitrate?
M17 encodes speech with the Codec 2 voice codec at 3200 bits per second.
Why not just implement Codec 2 on top of an existing standard?
There are currently no open platforms to experiment with regarding digital voice. Currently available platforms were designed and developed to be a commercial success, instead of a social and hobbyist success. It’s not the best idea to have many voice codecs within one standard, that would cause incompatibility issues within the mode.
Does M17 support encryption?
Encryption is disabled by default
Yes, support for the Advanced Encryption System (AES) will be added with keys of different length. Encryption may be enabled where it is legal, or disabled completely.
How are users identified?
User IDs are generated based on their callsigns. Base40 is used to encode the callsign into a 48-bit value. The user’s ID can also be translated to a DMR Radio ID equivalent using a lookup table.
Can I send data using M17?
Yes, it is possible to send data packets exclusively, or alongside digital voice streams.
Can I send APRS frames with it?
Yes. Using basic/raw packet support in M17 KISS, any packet data can be sent over M17.
Can I put M17 on my repeater? Can M17 run along with my DMR repeater?
Yes. Through efforts by Jonathan G4KLX, the M17 protocol is available on MMDVM hardware, both on modems and hotspots.
Is M17 compatible with other digital voice modes, like DMR?
M17 by itself is not compatible with other commercially available modes, due to M17 using the Codec 2 voice codec. Cross-mode tools do exist, however to run these legally, an AMBE codec license or vocoder chip needs to be owned and used solely by the purchasing individual or organization stated on the purchase order or other purchase documentation.