OnAirAviation · Experimental
Decode HFDL with an SDR
OnAir receives HFDL. HFDL: the HF aircraft data link (ARINC 635), 3 to 22 MHz, every channel in the band at once.
What HFDL is
HFDL is the HF data link that gives aircraft on oceanic and polar routes a data connection to ground stations when VHF is out of range.
Frequencies and where it is used
Aircraft data link on HF, 3 - 22 MHz.
In OnAir the tuning shortcut is Data link, 8.9 MHz; you can enter any frequency your radio reaches.
What OnAir shows for HFDL
Squitters and ground stations, ACARS, positions on a map; every channel in the band at once.
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 HFDL
Can I decode HFDL 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 HFDL?
Receiving aircraft broadcasts is legal in many countries, but some restrict listening to or using what you hear. OnAir is a receiver. Check the rules where you live.
Can I try HFDL 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.