OnAirHF utility · Experimental
Decode HF ALE with an SDR
OnAir receives HF ALE. HF ALE (2G, MIL-STD-188-141 / FED-STD-1045): 8-FSK link establishment calls, soundings, AMD messages and LQA on the HFN channels, 14.109 MHz.
What HF ALE is
Automatic Link Establishment (2G ALE) is the protocol HF stations use to call each other and agree on a working channel.
Frequencies and where it is used
2G automatic link establishment (MIL-STD-188-141 / FED-STD-1045) on HF.
In OnAir the tuning shortcut is Link establishment, 14.109 MHz; you can enter any frequency your radio reaches.
What OnAir shows for HF ALE
Who calls whom: soundings, individual, net and group calls, responses and links, AMD messages, LQA reports, with BER and SNR; the stations heard.
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 HF ALE
Can I decode HF ALE 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 HF ALE?
Some HF utility traffic belongs to governments or the military. Receiving is legal in many countries, but rules differ. Check them where you live.
Can I try HF ALE 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.