Mode VDL2

VDL Mode 2: ACARS and ATN messages between aircraft and ground stations, positions on a map.

Group	Aviation
Default frequency	136.85 MHz
Default sample rate	2 Msps
In the mode list	Data link, 136.9 MHz

Step-by-step: Tutorial-VDL2

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 settings

Aircraft data link, 136.7 - 137 MHz.

Setting	Value
Start frequency	136.85 MHz
Tuning range of the mode table	118 to 140 MHz
Sample rate asked	2 Msps
Lowest working rate	250 ksps
Channel width	400 kHz

OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is Data link, 136.9 MHz.

What OnAir shows

Every VDL2 channel at once: ACARS, X.25 / CLNP, ADS-C, aircraft and ground stations, positions on a map.

The mode's own tab has these screens: Messages, Map, Aircraft, Ground stations, Channels. The other tabs (Overview, Receiver, Scan, History) are described on the Main window page.

Tips and caveats

• Checked with generated signals and impairments; recordings of real signals welcome.
• Which radio: Usually yes for narrowband signals: 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.
• Try it without a radio: most modes include a built-in synthetic test signal, so you can open the screen and try the controls first.
• Receiving and the law: 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. See Legal.

Related pages

• All modes, Aviation
• Supported radios, Troubleshooting, FAQ
• More in Aviation: ADS-B, Mode S uplink, ACARS, VDL4, HFDL, Airband, VOR, ILS, NDB, Drone Remote ID, UAT, FLARM, DJI drones