OnAirAviation · Experimental
Decode VDL2 with an SDR
OnAir receives VDL2. VDL Mode 2: the aircraft data link on 136.725 to 136.975 MHz, every channel at once.
What VDL2 is
VDL Mode 2 is the modern VHF data link between aircraft and ground, carrying ACARS over AVLC frames (and ADS-C or CPDLC) on channels near 136.7 to 137 MHz.
Frequencies and where it is used
Aircraft data link, 136.7 - 137 MHz.
In OnAir the tuning shortcut is Data link, 136.9 MHz; you can enter any frequency your radio reaches.
What OnAir shows for VDL2
Every VDL2 channel at once: ACARS, X.25 / CLNP, ADS-C, aircraft and ground stations, 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
Any radio that tunes this range works. An RTL-SDR covers roughly 24 MHz to 1.7 GHz, and every other radio in the radio guide reaches it too. Antenna height and a clear view of the transmitter matter most.
Questions about VDL2
Can I decode VDL2 with an RTL-SDR?
Usually yes for narrowband signals, as 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.
Is it legal to receive VDL2?
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 VDL2 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.