Mode ACARS

ACARS: short messages between aircraft and the ground.

Group	Aviation
Default frequency	131.5 MHz
Default sample rate	2 Msps
In the mode list	Aircraft messages, VHF

Step-by-step: Tutorial-ACARS

What ACARS is

ACARS is the VHF data link between aircraft and ground stations: position reports, weather requests, maintenance messages and short operational text, on 25 kHz channels around 131 MHz.

Frequencies and settings

Aircraft data link, VHF.

Setting	Value
Start frequency	131.5 MHz
Tuning range of the mode table	118 to 137 MHz
Sample rate asked	2 Msps
Lowest working rate	1 Msps
Channel width	2 MHz

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 Aircraft messages, VHF.

What OnAir shows

Messages, and positions on a map.

The mode's own tab has these screens: Messages, Aircraft map, Aircraft, 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, VDL2, VDL4, HFDL, Airband, VOR, ILS, NDB, Drone Remote ID, UAT, FLARM, DJI drones