In March 2015 I wrote briefly about plane spotting with dump1090. In short, many airplanes have ADS-B transponders which squawk out their location, airspeed, and current conditions, and you can pick up those transmissions using an inexpensive RTL-SDR tuner stick and a simple antenna.
I’ve been looking into this again to see if I can get a better understanding of how it works as well as to take advantage of a year plus of software development. Here’s a summary of the state of the art circa July 2016.
Hardware: I’m using a Nooelec NESDR Mini 2 tuner stick plugged into a MacBook Air as a portable plane-finding system. I have a Raspberry Pi 2 which looks like it could be a permanent installation for this, though the recommendation for busy skies is a Pi 3 which is enough faster to make a difference if you have a good antenna.
Antenna: The Mini 2 comes with a small whip antenna with a magnetic base, and I’m borrowing a larger antenna. There are scads of antenna designs out there for inexpensive small antennas tuned to 1090 Mhz, but I’m not there yet. There are also filters and amplifiers that can improve plane-finding capabilities; also not there yet.
Software: Here’s where I’ve made progress. The dump1090 software has been forked several times, each time with just a little bit more sophistication on the visual display as well as refinements of the decoding system. The one I’m using right now is a fork by “mutability”, available at https://github.com/mutability/dump1090 . It’s notable for being designed to run on a Raspberry Pi, as well as a bunch of small changes in the display that make it more pleasant to use than the older software I had been using.
Range: Just like I reported back in 2015, the typical results from my house are a range of 40-50 nautical miles in every direction. I haven’t yet taken the rig to my favorite plane-spotting cafe – the Biggby at Platt and Ellsworth – which has a clear view of the southern sky at a good elevation.
Tweaking the setup: Aside from changing out the hardware and relocating the antenna, the tweakable changes seem to be adjusting the gain control on the SDR. Initial experiments don’t give me strong conclusions as to what’s best. The reviews of a $20 band pass filter are promising for increasing the range.
Feeding the data elsewhere: One of the collective efforts around looking for airplanes is the ability to share the data with commerical and non-commericial systems that aggregate data from around the world. I’m digging http://planefinder.net which has a nifty near-real-time feed of ADS-B and FAA and other international data for tracking flights. Planefinder is fast enough that I can hear an airplane overheard, check the display, and figure out which flight is there.
Satellite plane finding: The GOMX-3 satellite has an SDR with ADS-B reception and has successfully fed data to Flightradar24, another commericial plane tracking system. ADS-B receivers are expected to be installed on the Iridium system over the next couple of years, which should over time provide improved global coverage and visibility into the current status of aircraft over oceans and the poles.
What it looks like: I don’t have a permanent installation running, but if you’re interested in the airspace above San Diego, you can see Phil Karn KA9Q’s system at http://maggie.ka9q.net:8080/dump1090/gmap.html noting that he’s in easy range of picking traffic into LAX.