In the fall of 2020 I had a spare Raspberry Pi 3 kicking around and no project for it. Can’t have that! After doing some searching I came upon something that scratched a number of itches for me: signal snooping, freedom of information, and neat party tricks. I built an ADS-B receiver & feeder to ADS-B Exchange.
Honestly it was pretty straightforward: a couple of software-defined radios and tuned antennas from Amazon plus flashing an image to a microSD and I was off and running.
After plugging in some account info and my approximate latitude, longitude, and altitude the web interface came alive with information about all of the airplane and helicopter broadcasts that it was able to pick up. Being that I was living near multiple airports and security routes, it was neat to see them all plotted out.
In order to keep everything neat, tidy, and cool I modified a case that I found online to also allow for a 40mm fan to be mounted on the front. The original didn’t really have the capability which was surprising as those radios run HOT and airflow from convection doesn’t really keep them cool. Forcing air in over the CPU (which also needed temperature taming) and venting out through the top has done the trick.
ADS-B exchange at the time was still under the original owner and the appeal of it over their competitors was that they didn’t censor their information. A feeder is a device like mine that simply uploads all the information about what it hears to a central server. Have enough devices in enough locations and you get a pretty clear map about what’s up in the air at any given time. However, some exchanges will hide .gov and .mil (or other VIP) aircraft from public view. This blog is already long winded so I’ll leave it at “not a fan of that” and I chose to send my data where I did.
(Yes, I also know about the drama that came on later with the original owner. So far it doesn’t seem like data is being hidden or rent-seeked and also Newton’s First Law so it’s staying as-is for now until there’s a really compelling reason to switch / something breaks)
Anyways, now for my favorite party trick: What’s Overhead. It’s a Siri shortcut that once installed you simply ask that question and Siri will tell you all about the nearest aircraft to you: its registration, type, bearing + distance to you, altitude + direction + speed, and who owns it. All powered by feeders, a few more hits on public records databases, and on-device sensors. It’s so neat.