OnAirAmateur: voice & packet · Experimental
Decode M17 with an SDR
OnAir receives M17. M17 open digital voice and data (4FSK, 9 kHz), 2 m and 70 cm.
What M17 is
M17 is an open digital voice and data protocol for VHF and UHF amateur radio (4FSK, 9 kHz).
Frequencies and where it is used
Open digital voice, 2 m / 70 cm.
In OnAir the tuning shortcut is Digital voice, 433.475 MHz; you can enter any frequency your radio reaches.
What OnAir shows for M17
Callsigns, voice through your libcodec2, text messages, positions on a map.
This receiver is built from the published specification and checked end to end on simulated signals. It has had little or no testing on real transmissions yet, so reports and recordings on Discord are welcome.
Which radio you need
This is a shortwave mode, so the radio has to tune HF. An SDRplay, Airspy HF+ or an RTL-SDR in direct-sampling mode do that directly; with a HackRF an HF upconverter or a direct-sampling receiver is the usual route. A long wire or loop antenna matters more than the radio.
Questions about M17
Can I decode M17 with an RTL-SDR?
An RTL-SDR can receive HF only in direct-sampling mode, which OnAir offers in its radio settings; results depend on the antenna. SDRplay and Airspy HF+ radios are better suited.
Is it legal to receive M17?
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.
Can I try M17 in OnAir without a radio?
Yes. Most modes include a built-in synthetic test signal, so you can open the screen and try the controls before you own a radio.
Try it without a radio
OnAir includes built-in synthetic test signals for most modes, so you can open this screen, see the layout and try the controls before you own a radio. The Tour button walks you through the app.