RTL-SDR Tutorial: Receiving Airplane Data with ACARS

What is ACARS?




Examples of the RTL-SDR being used to decode ACARS


ACARS Decoding with RTL SDR (RTL2832), SDR Sharp and ACARSD




Adding ADS-B, ACARS, and ATC Reception to PlanePlotter

Tutorial - Decoding ACARS using SDRSharp and RTL-SDR


We also assume you have some sort of decent antenna set up that is tuned to the air band frequencies (118 MHz - 138 MHz). An air band bandpass filter may help to receive stronger ACARS signals by removing out of band interference.



ACARS Packets

Before decoding ACARS we will try to receive ACARS messages in SDR# first to confirm if we are receiving them.

  1. Open SDRSharp and tune to an appropriate ACARS frequency for your country such as the standard frequency of 131.500 MHz.
  2. Adjust the RTL-SDR RF gain in SDRSharp for best reception.
  3. Adjust the tuned bandwidth of your receiver to around 5-10 kHz, so that the bandwidth just covers the entire ACARS signal.
  4. Set the receiver mode to AM, turn off squelch and turn off any noise reduction filters. If decoding with PlanePlotter or ACARSD (described below) experiment with turning the audio AGC and Filter Audio settings on or off.

There are many software packages that can be used to decode the received ACARS packets. Currently the software that we most recommend using is the free Acarsdeco2PlanePlotter is another good decoding program. It has a trial period of 21 days after which you must purchase a licence for 25 euros. Acarsd is a free decoding program that also works well. AirNav ACARS is another paid decoding program, but is a little pricer than PlanePlotter.

Using Acarsdeco2 to Decode ACARS

Acarsdeco2 is a Windows, Linux, Raspberry Pi and OSX compatible command line based multi channel ACARS decoder that directly interfaces with the RTL-SDR. Here we use the Windows version, but use of the Linux, OSX and Raspberry Pi versions should be very similar. Acarsdeco2 is probably the best decoder for ACARS available as it has good decoding performance, is capable of decoding up to 3 ACARS channels simultaneously. Also, while Acarsdeco2 is a command line program it also has a nice web interface that can be used to browse the received ACARS messages.

  1. First, using SDR# or another program discover your dongles PPM frequency offset and best gain settings appropriate for receiving ACARS signals. Adjust the gain settings until ACARS signals are received strongly without any interference. Record the dongles PPM offset and optimal gain, then close SDR#.
  2. Next, download the latest Windows version of Acarsdeco2 from xdeco.org. Unzip the files into a folder on your PC.
  3. Using Notepad open the file “ad2.bat”
  4. Edit the line by entering your optimal gain and PPM frequency correction settings that you found while viewing the signal in SDR# after the appropriate flags --gain and --freq-correction. (Note there is a bug where --freq-correction cannot be set to zero). Also be sure to set the --freq frequencies to the actual active frequencies used at your location. The default code in ad2.bat is shown below:
    cmd /c acarsdeco2.exe --device-serial 1 --gain 38.6 --freq-correction 1 --vrs-url --db C:\data\basestation.sqb --frdb C:\data\flightroute.sqb --silhouettes C:\data\silhouettes --pictures C:\data\pictures --banners c:\data\logos --outServer sbs:30008 --outServer ad2:31008 --freq 131550000 --freq 131725000 --outConnectUdp pp:
    You should set all the flag values (the words with the double dashes before them) appropriately. Most flags apart from --gain, --freq-correction and --freq can be ignored for simple operation unless you wish to use those features which are explained in the flags description below.
    --gain - the optimal gain setting you found in step 1
    --freq-correction - the PPM offset of your dongle (very important, must be set accurately)
    --freq - you can add up to three ACARS frequencies by specifying more than one --freq flag
    --vrs-url - if you are running the software known as “Virtual Radar Server” at the same time for ADS-B decoding then set this flag to the VRS web interface IP address so that you can get the images of the aircraft to show up in the Acarsdeco web interface (flag not required if not using Virtual Radar Server)
    --db, --frdb, --silhouettes --pictures, --banners - Folders where appropriate plane images are stored.
    --outServer, --outConnectUdp - Output server for SBS/AD2/Plane Plotter interfaces.
  5. Save and close notepad, then run the modified ad2.bat file by double clicking on it.
  6. Now with acarsdeco2 running, open a web browser and open Here you should be able to see your ACARS messages being received in real time.

Using PlanePlotter to Decode ACARS


  1. First open SDR# and tune to an ACARS frequency. Set the receive mode to AM, and turn off any noise reduction filters. Set SDR# to output to your chosen audio piping device such as stereo mix, VB Cable or Virtual Audio Cable.
  2. Open PlanePlotter. Click on the "I/O Settings" icon that looks like a spanner with an 'i' to its left. You can see the icon name by hovering over it with your mouse.
  3. Ensure that the option "ACARS reception from audio input is checked". Push OK.

PlanePlotter Settings

  2. Press the "Start" button which is the green circle icon. This will start the decoding.

Plane Plotter Raw Signal

  1. Now you can look at either the "Message View" or "Aircraft View" which are the two icons next to the Signal icon to see the decoded information.

Plane Plotter Planes Window

Using ACARSD to Decode ACARS



  3. Run acarsd.exe in your acarsd folder to open acarsd.
  5. Decoded ACARS packets should begin to show up.




Some ACARS Tips

  • A bandpass filter for airband frequencies will generally significantly improve ACARS reception if you have strong interfering signals nearby.
  • If you prefer to decode using SDR# and PlanePlotter or Acarsd instead of with Acarsdeco2 then you might want to try out the Multi-VFO plugin, or SDR-Radio V2. This plusing/program let you listen to multiple channels simultaneously. You can then send the audio to multiple audio pipes and decoder instances, or just send the audio all to the same audio pipe with squelch on, and hope two channels don't transmit at the same time.

ACARS Frequencies


131.550 Primary Channel worldwide
129.125 Additional channel for USA & Canada
130.025 Secondary channel for USA and Canada
130.425 Additional channel for USA
130.450 Additional channel for USA & Canada
131.125 Additional channel for USA
131.450 Primary channel for Japan
131.475 Air Canada company channel
131.525 European secondary
131.725 Primary channel in Europe
136.700 Additional channel for USA
136.750 Additional channel for USA
136.800 Additional channel for USA
136.900 European secondary
136.850 SITA North American Frequency
136.750 New European frequency
131.850 New European frequency

Table Source: Acarsd

Other Decoding Software



If you enjoyed this tutorial you may like our available on Amazon. Available in eBook and physical formats.



    • john

      Im having the same problem…route missing from my acars decode…even though im decoding ASCARD 99% of the time…must be missing a file somewhere..any help would be appreciated !!!

  1. Henry Leupp



  2. Jean-Marc


  3. Mark


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