Discovery and First Attempt
I first learned of software-defined radio attending a Devoxx UK session where the presenter showed how a consumer SDR dongle could receive digital messages from airplanes and canal boats and subsequently plot them on Google Maps. I regularly visited his site after returning home, essentially plane watching planes arrive and depart from Schiphol airport. He eventually took down the site, ending my enjoyment. Unfortunately, I haven’t found the session’s video on Devoxx’s YouTube channel.
Fast-forward a few year and I’ve applied to receive FlightRadar24‘s free ADS-B receiver package. I never was chosen, not surprising for a major metropolitan area with good coverage. I hadn’t decided how the antenna would be mounted to the chimney; routing cables also presented a challenge. To alleviate boredom during COVID, I purchased an RTL-SDR V3 dongle, but shunted it aside after limited experimentation. [If I remember correctly, SDR software for MacOS was limited.]
Reawakening
I occasionally – very occasionally – made new attempts to see what I listen to with the SDR dongle without much success. Despite living close to Minneapolis/St. Paul airport, I was not finding much air traffic broadcasts. Very frustrating without knowing anyone who could help the newbie. And then it changed.
I met Guy Royse at BuildStuff 2024 where we discussed one of his personal hobbies: amateur radio. [Guy holds at least a General class license and perhaps the Amateur Extra license] When continued the discussion At NDC Oslo 2025 where he pulled up a satellite view of my rooftop to propose antenna placement. And, finally, at DevUp St. Louis, his presentation was his personal ADS-B tracking project using a hand-held 1090 antenna. He constantly encouraged me to pursue amateur radio and is very persuasive.
So now I’m convinced, what’s next? I purchased a V4 RTL-SDR – upgraded tuner, improved filtering, improved passive cooling, USB-C – and discovered improved SDR software for MacOS. Great. Now this is getting fun.
Raspberry Pi ADS-B Receiver
Raspberry Pi’s have often been configured as cheap ADS-B receivers when using an SDR dongle attached via USB. I have an unused Raspberry Pi 4 Model B with an 8GB MicroSD card. I have an unused RTL-SDR V3. I have an unused, appropriately-sized power supply. Let’s do it!
FlightRadar24 provides step-by-step instructions plus a pre-configured custom image requires minimal configuration: copy the image to the MicroSD card, boot the Pi, and use a browser (not necessarily the RPis) to log into FlightRadar24 and associate with your account.
[NOTE: account association happens using L2 network discovery, requiring your browser and receiver to be on the same subnet. My home network segregates my personal machines from IoT devices (Tivo, Sonos, etc.) which caused some minor inconveniences.]
Next, I need to install the antennas and connect their cable to the RTL-SDR dongle.
Version 1: Front Deck
As an initial, non-permanent test, I “installed” the antenna on my second-floor deck by clamping the mast to the railing, snaking the cable into my wife’s office. The supplied cable is relatively short (3m/10 ft), minimizing signal loss for the smaller antenna. WiFI proved unreliable, the RPi4 losing its connection every few days without reconnecting, so I connected a network cable. I am unsure whether this is an issue with the operating system or the service receiving the messages.
Our three-story house impeded reception from the north and west, most messages and farther-away message received from planes south and east of our house. The most distant planes received are 77 nautical miles (88.6 miles) away. The number of aircraft received daily varied between 750 to over 900, with an average in the low 800s.
Version 1a: Front Deck, Improved Antenna
I replaced the first antenna with a (supposed) higher-quality one – longer, higher gain, lower VSWR – but observed no real change in quantity or distance.
Version 2: Roof
Since higher antennas typically result in better reception, I decided to install the antenna on our roof: above the third floor, fewer building obstructions, fewer trees and more clear sky. I considered installing the RPi4 adjacent to the antenna, using PoE to minimize signal loss, but desired easier access than climbing out a third-floor window. The second antenna was bundled with a 10m/32.8 ft cable that I hoped would reach my second-floor office without significant signal loss. I purchased a non-penetrating flat roof mount and started planning its installation.
Tools required: socket set, crescent wrench, flat-head screw driver, zip ties, scissors.
The installation was fairly straight-forward, only slight problems aligning the tripod collar correctly before tightening the bolts. One practice run-through followed by actual assemble, done. The instructions are not clear, but, I believe after installing the bolt you should insert the washers and hand-tighten the nut. Once all pieces are positioned, you tightened the nuts. I then attached the antenna to the mast and used zip ties to secure the cable to the mast before throwing the cable in the general direction of my office.
Time required to drag everything onto the roof, assemble the roof mount, attach the antenna, secure the cable: 60 minutes. Add 15 minutes to carry the eight cement blocks (17 lbs/each) to the roof to place on the base to stabilize the mount. Total time: 75 minutes!
Fortunately, the cable was long enough to be brought through my office window. I attached it to the RTL-SDR dongle and booted everything.
Version 2a: Changed Dongle
Surprisingly, I quickly noticed that messages from fewer planes at shorter distances were being received. The underlying dump1090-mutability software supports automatic and manual gain control, but configuration changes to manually define gain resulted in no messages received.
Out of desperation and frustration, I changed to the V4 RTL-SDR dongle and immediately starting receiving messages from more planes from farther away.
The roof antenna with the improved dongle receives messages from planes 100 nautical miles (115 miles) away. The lack of planes northwest and software surprises me: I tracked one plane received for almost 150 nautical miles, yet it different get reflected here. More research to do.
Next Steps
More purchases:
- A 1090 filter that removes all radio transmissions except for ADS-B messages transmitted on 1090Mhz.
- A FlightAware all-in-one SDR/filter/pre-amp. I believe the pre-amp boosts weak signals from planes farther away, perhaps impacted by the long cable.
Final Thoughts
Technical difficulty: low. Overall cost: approximately $325, of which $200 is the flat-root antenna mount. Joy: High. FlightRadar24 filters can filter for your personal receiver, and I’m obsessively following to see what planes are within reach.
Image Credits
- Polar Plot generated by FlightRadar24.
- Mount assembly instructions received from Antenna Parts Outlet.
- All other images © 2025 Scott C Sosna, all rights reserved.
