The Busy Skies

Several weeks ago I purchased a device called a SDR Dongle to try and catch the signals coming from my wireless temperature transmitters and import them into a computer application    . I quickly found an easier means of doing that job, but by that point I was hooked on the possibilities opened by having the device. SDR stands for “Software Defined Radio” and it essentially functions as a broadband receiver that decodes / encodes radio signals into something a computer can work with. Combined with some impressive (and free) software it can be a very powerful device for identifying and understanding what is happening in the airwaves around you.

Well and good, but it probably would have ended up as an occasionally used tool had I not discovered that the frequency on which ADS-B messages from aircraft are transmitted also happens to be in the SDR reception band. Beyond that, several of the popular flight tracking services are actively looking for ADS-B receiver stations in order to increase their coverage and accuracy, so finding the necessary information and software was very easy. I signed up with flightradar24 and, since I didn’t want to leave my desktop on all the time to run it and I already have a Raspberry Pi running continuously for the swamp cooler control, I used their setup package for the Pi. A handful of mouse clicks and copy and paste lines later I was streaming ADS-B reports to the flightradar24 servers, as well as had the data available for my own use.

Based on some recommendations I opted to install the Virtual Radar Server on my desktop and link it to the datastream coming out of the Pi. This software takes the decoded ADS-B messages and portrays it in a much more easily understood format – a table of the message content as well as a real-time updated map for the aircraft which are sending position reports. It also uses the airplane registration to automatically go out and obtain public record information such as the year it was built, ownership information, and pictures of the airplane. In addition to this, it can also be configured to create a database of the recorded information.

ADS-B is a line of sight transmission system, and being in a valley with mountains around me in nearly all directions I wasn’t expecting to see much of the traffic around me since mountains are in the way. That generally is the case, but I also happen to be under the main eastbound departure track from LAX so there actually is a fair bit of commercial traffic overhead, and depending on timing I sometimes get messages from westbound departures as they transit through a window between mountain peaks. I’ve set up the virtual radar server to launch when I power up the desktop, so even though it’s generally only recording for a few hours each evening, in roughly a month of operation of the receiver I now have a reasonably large database of what’s gone by overhead and decided to take a look at it today.

I was fairly surprised by the results. There were 5,576 unique airplanes which operated 17,980 distinct flights. Of those, 2,165 airplanes were only recorded for one flight, meaning 3,411 airplanes were picked up multiple times. 3 of the top 5 repeat aircraft were helicopters, which isn’t overly surprising given that the local airport is the base for 2 law enforcement helicopters and there is a forest service firefighting helicopter also based in the area, and it’s been a busy season for them so far. What I found most surprising was that the second most frequent airplane was a Spirit A321, which had racked up 41 distinct flights on the database. In terms of commercial aircraft, there were 1,101 unique Airbus aircraft vs. 2,236 unique Boeing aircraft

Some charts..

Leading manufacturers, airframe count:

Leading types, airframe count:

Leading foreign registrations, airframe count:

Leading types, by flights:

Leading operators, by flights:

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