Mode M17

M17: open digital voice, text messages and positions on VHF / UHF.

Group	Amateur: voice & packet
Default frequency	433.475 MHz
Default sample rate	2 Msps
In the mode list	Digital voice, 433.475 MHz

Step-by-step: Tutorial-M17

What M17 is

M17 is an open digital voice and data protocol for VHF and UHF amateur radio (4FSK, 9 kHz).

Frequencies and settings

Open digital voice, 2 m / 70 cm.

Setting	Value
Start frequency	433.475 MHz
Tuning range of the mode table	28 to 1300 MHz
Sample rate asked	2 Msps
Lowest working rate	250 ksps
Channel width	12.5 kHz

OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is Digital voice, 433.475 MHz.

What OnAir shows

Callsigns, voice (codec2 comes with OnAir), text messages, positions on a map.

The mode's own tab has these screens: Now, Activity, Messages, Map. The other tabs (Overview, Receiver, Scan, History) are described on the Main window page.

Tips and caveats

• Checked with generated signals and impairments; recordings of real signals welcome.
• Voice uses codec2, which comes with OnAir; nothing to install.
• Which radio: Usually yes for narrowband signals: an RTL-SDR tunes roughly 24 MHz to 1.7 GHz at up to about 2.4 Msps. Wide signals such as TV channels need a faster radio, and OnAir says next to the source what the selected radio can do.
• Try it without a radio: most modes include a built-in synthetic test signal, so you can open the screen and try the controls first.
• Receiving and the law: Amateur radio signals are meant to be received. Receiving needs no licence in most countries; OnAir does not transmit. Voice needs a codec library you install yourself. See Legal.

Related pages

• Digital voice: DMR, D-STAR, P25
• Voice codecs
• All modes, Amateur: voice & packet
• Supported radios, Troubleshooting, FAQ
• More in Amateur: voice & packet: FreeDV, D-STAR, APRS (AFSK), LoRa APRS, MeshCom