OnAirAmateur: digital · Experimental
Decode CW with an SDR
OnAir receives CW. CW (Morse) skimmer: every signal in a 14 kHz window, 5 to 50 WPM, on the HF CW segments.
What CW is
CW is Morse code sent by keying a carrier on and off. A skimmer reads many CW signals at once.
Frequencies and where it is used
Morse code on the HF bands.
In OnAir the tuning shortcut is Morse, 14.020 MHz; you can enter any frequency your radio reaches.
What OnAir shows for CW
Every CW signal in a 14 kHz window at once: speed, SNR and text, callsigns highlighted.
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 CW
Can I decode CW 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 CW?
Amateur radio signals are meant to be received. Receiving needs no licence in most countries; OnAir does not transmit.
Can I try CW 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.