M17 (amateur radio)

From Wikipedia, the free encyclopedia
RF spectrum of the M17 protocol

M17 is a digital radio modulation mode developed by Wojciech Kaczmarski SP5WWP et al.[1][2][3][4][5][6][7] M17 is primarily designed for voice communications on VHF amateur radio band and above.

Overview[]

Spectrogram of the M17 protocol. Time is on vertical axis, advancing from bottom to top. There's a 40 milliseconds preamble visible at the beginning of the transmission.

M17 utilizes 4800 symbols per second 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 9600 bits per second, with the actual data transfer at 3200. Protocol allows for low-speed data transfer (along with voice), e.g. GNSS position data. The mode has been successfully transmitted through EchoStar XXI[8] and QO-100[9] geostationary satellites. M17 has received the 2021 ARRL Technical Innovation Award.[10] It has also received a grant from the Amateur Radio Digital Communications.[11] The protocol's specification is released under GNU General Public License.

Voice encoding[]

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. The 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, bits of data are XORed with a predefined decorrelating pseudorandom stream before transmission. This ensures that there are as many symbol transitions in the baseband as possible.

Hardware support[]

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.

Bridging with other modes[]

Links to DMR and System Fusion exist.[13]

M17 over IP[]

Access nodes and repeaters[14] can be linked using reflectors. Over 100 M17 reflectors exist worldwide (Jan 2022).[15]

See also[]

References[]

  1. ^ Dan Romanchik's (KB6NU) blog entry on M17 Project (Nov 2019)
  2. ^ "Świat Radio" magazine, issue 11/2020, p. 50: "Transceiver TR-9", an article covering M17 (Polish)
  3. ^ Ham Radio 2.0 podcast, "M17 Project - New Ham Radio Digital Mode" episode (Sep 2021)
  4. ^ Linux in the Ham Shack podcast, episode 396: "M17 Deep Dive" (Mar 2021)
  5. ^ David Rowe's (VK5DGR) "M17 Open Source Radio" blog entry (Aug 2020)
  6. ^ "M17 Open Source Digital Radio System", Ham Radio Workbench podcast (Dec 2019)
  7. ^ Open Research Institute website, projects listing subpage
  8. ^ Testing M17 on Echostar XXI at 10° East
  9. ^ AMSAT-DL Twitter entry on QO-100 wideband transponder M17 experiment (Apr 2021)
  10. ^ ARRL Board of Directors Bestows Awards
  11. ^ ARDC grants 250,000 USD to M17 Project (Apr 2021)
  12. ^ OpenRTX - free and open source firmware for ham radios
  13. ^ Douglas McLain's (AD8DP) GitHub page
  14. ^ RepeaterBook list of M17 repeaters
  15. ^ M17 reflectors list

Related links[]

Retrieved from ""