In the last post, a video introduced the topic of ADS-B. This post will cover the topic in more detail. Automatic dependent surveillance broadcast is a technology used by aircraft to broadcast location, heading, and velocity. It’s part of the FAA’s NextGen system that was first deployed in 2007 and should be completed by 2030. The standard will likely be used internationally with the purpose of providing ground controllers and pilots situational awareness.

This video provides insight into the FAA requirements around ADS-B.

Using a RTL SDR to receive and decode 1090 MHz ADS-B radio transmissions is possible using numerous repos available online. One of which is available here, https://github.com/MalcolmRobb/dump1090. This particular repo provides formatted text output as well as a web front end. After downloading the repo, these commands were run on a Linux host.

apt install librtlsdr-dev
make

Running these commands offered different outputs.

./dump1090 > /home/local/ADS-B-Dump1090.log	### Raw text output
./dump1090 --interactive			### Formatted table output
./dump1090 --interactive --net			### Web UI http://localhost:8080/, similar to ADS-B Exchange
./dump1090 --help                               ### Detailed help

The program can also decode SDR IQ files. This command will format the IQ output file properly so it can be decoded.

rtl_sdr -f 1090000000 -s 2000000 -g 50 /path/to/binfile.bin
./dump1090 --ifile /path/to/binfile.bin		### Decodes a sampled IQ file

There was mention of ADS-B Exchange, this is a website that is an aggregate of ADS-B data gathered by partners that share their data. This link provides details on how to contribute, https://www.adsbexchange.com/how-to-feed/. This blog gives the perspective of the contributor, https://blog.facha.dev/playing-with-sdr-adsb/.

This video demonstrates another contributor’s setup.

The ADS-B Exchange site provides a simple way to search for callsign, HEX ID, registration, or other filtered details to find a specific aircraft. Searches can be partial entries to show a wider range of aircraft, such as callsigns containing certain characters. It also offers a historical view of past flights.

This video provides a different decoding process for HF ACARS data. This will not be covered here but was worth mentioning since it has some relation.

This site provides more information about ADS-B and some back story on the topic, https://flightradar.live/en/flight-tracker/adsbexchange/

The technical details about ADS-B can be found at these links,  https://wiki.analog.com/resources/eval/user-guides/picozed_sdr/tutorials/adsb and https://www.mathworks.com/help/supportpkg/rtlsdrradio/ug/airplane-tracking-using-ads-b-signals.html.  This site provides information about ADS-B collinear antenna design to help improve reception of signals, https://martybugs.net/wireless/collinear.cgi