Ever wondered how sites like FlightAware.com get their aircraft tracking data? Chances are someone contributed the ADS-B (Automatic Dependent Surveillance-Broadcast) data they received from said aircraft as it flew over their home. With the RTL-SDR and some free software you too can listen in on these broadcasts that contain location and altitude information which are used by air traffic control to track and identify aircraft.
Along with the RTL-SDR receiver you will need to construct or purchase an antenna capable of tuning to the 1090 MHz frequency used by ADS-B broadcasts. Some starter kits for RTL-SDR come with a dipole antenna that is tuned to 1090 MHz already which I have but never bothered testing to see if its any good. Personally I got an empty tin can, drilled a hole in the bottom large enough to fit a female to female “F” connector through and connected some RG6 coax to the connector inside the tin. On the outside, a 69mm piece of copper wire was inserted into the center pin connector of the “F” joiner as shown below (69 mm from the tip to the body of the connector. Making it 2 mm or so longer will allow for tuning after construction). The tin in this case acts as a ground plane for the antenna.
Ideally you would use a panel mount connector with the piece of wire soldered to the center pin but this works well enough as a proof of concept thing. After putting the antenna outside somewhere with a good view of the sky, you can then connect the other end of your coax to the RTL-SDR.
To receive and decode the ADS-B signal we will be using a program called RTL1090. This eliminates the need for SDR# or similar and feeds the decoded data via a local network connection to a program called Virtual Radar Server. This is the software that allows you to display aircraft locations and other useful information such as speed and altitude.
Installing RTL1090: Download from http://rtl1090.com for the RTL-SDR it is best to use the RTL1090 IMU installer as it will download and install all needed files for it to run. Once installed its pretty much good to go and if working properly, you will see a stream of hex values appear under the ‘List’ tab. Selecting the ‘Table’ tab will display the decoded data such as ICAO ID, call sign, altitude etc. 127.0.0.1:31001 is the TCP output for RTL1090.
Installing Virtual Radar Server: Download from http://www.virtualradarserver.co.uk/. Follow the installer instructions. Once installed you should see under ‘Feed status’ that the receiver is connected and receiving messages. From here click ‘Take Online’ before opening a web browser and going to http://127.0.0.1/VirtualRadar. Here you should be able to see aircraft as they come into range of you.
With a basic antenna sitting on the roof of my garden shed, I can see aircraft within around 80 km of me depending on direction and altitude. With the antenna mounted up high to clear the roof line of my house, I’d expect the range to be better. Using the above software makes ADS-B reception simple and easy and a basic antenna will allow you to easily track overflying aircraft from home.