ADSB Tracker

Some time in 2022 I found out it's trivial to track aircraft that have ADSB equipment. A year or so later I got around to building an antenna and buying an SDR, this is how it went.

After the litter box project I was determined to spend as little as possible on this. Luckily I had a fair amount of parts laying around, so all I ended up buying was the radio specific parts.

I'm not convinced buying FlightAware's Pro Stick was worth it. Around the same time I was doing this project, I purchased an RTL-SDR.com SDR and it performed the same as the Pro Stick and was cheaper. The Pro Stick works fine, but if I decide to repurpose these parts the Pro Stick will be useless for anything besides 1090MHz without modifications due to the built in filter.

This project almost ended before it started. I used M0UKD's calculator to get the dimensions for the antenna, then ordered the SMA flange connectors and stopped at Airgas to pickup some aluminum TIG rod. After cutting the rod to length, all there was to do was solder them to the flange connector. Boy what a trainwreck that was. Turns out soldering aluminum is an ordeal. Despite many 'easy' tricks, it aint easy. After several hours of trying every method I could find I went back to Airgas and got carbon steel TIG rod. The neat thing about carbon steel TIG rod is it's copper plated, which is trivial to solder to. After spending roughly 5 hours screwing with the aluminum and getting nowhere, I had a fully assembled steel antenna in 20 minutes.

I don't have a VNA to figure out how well the antenna is tuned, but it receives ADSB signals, so good enough.

After the antenna was built, and everything was plugged together, it was just a matter of following the PiAware Tutorial and adsb.fi Tutorial. More notes about this part below.

Now that I had a nice pile of sensitive electronics laying on my desk, it was time to make them invulnerable to the cat. First thing to improve was the antenna mount...

A few minutes in Solidworks and a while on the 3d printer, I had a satisfactory antenna wall mount.

With the antenna safely out of harms way, next was the pi and SDR. About two hours of CAD and 10 hours of printing, I had a pretty decent enclosure base and enclosure lid.

With the housing complete, it was time to make a more rhobust power supply. Up till now, the system's been running off an Asus USB power brick, which is fine, except I'd like my brick and USB cord back. Since this project is destined to live in the attic, I don't want to mess with voltage sag (truth be told, I tried a cheap USB cable I had and the pi was in a continuous state of brownout). I had a real old 9v Radio Shack wall wart and a fist full of MINI-360 buck converters. Soldering the wall wart to the buck converter and adjusting the converter to 5.15v proved to be a very easy and reliable solution. Now any voltage sag from the wall wart will still give the buck plenty of headroom to keep the pi above 5v. Turns out the 9v wall wart has little to no regulation, open circuit voltage sat around 12v; this psu would be difficult to work with if I needed 9v but for this application it works a treat.

After tapping the holes in the 3d parts, it all went together smoothly. I think the spacing of the pi's mounting holes is a couple mm wider than the pi's holes, but some sketchy manuvers with the allen key got it all to fit.

The lid has mounting points for a 50x10 fan. I didn't put the fan in, mostly because I didn't want to build a fan control circuit at the time and didn't want to listen to the fan run full speed all the time. With the generous ventilation holes, a fan is only borderline necessary in the attic during summer. The pi runs roughly 23°C above ambient, with a peak attic temperature of 54°C (from a quick web search) that puts the CPU temp at 76°C, allegedly the limit is 80°C so a fan might help, but it might also just end up blowing more dust into the hardware.

Last step was mounting the enclosure and powering it up. Uneventful, yet exciting, everything worked without a hitch.

After a week or so of tinkering, it works!

This wasn't too bad, but mostly for my own notes this is how it went:

						sudo apt update && sudo apt upgrade -y && sudo apt autoremove -y
						wget https://flightaware.com/adsb/piaware/files/packages/pool/piaware/f/flightaware-apt-repository/flightaware-apt-repository_1.1_all.deb
						sudo dpkg -i flightaware-apt-repository_1.1_all.deb
						sudo apt install dump1090
						sudo apt install piaware
						sudo piaware-config allow-auto-updates yes
						sudo piaware-config allow-manual-updates yes
						curl -L -o /tmp/feed.sh https://adsb.fi/feed.sh
						sudo bash /tmp/feed.sh
						sudo bash -c "$(wget -O - https://github.com/wiedehopf/adsb-scripts/raw/master/readsb-install.sh)"
						sudo reboot
						nano /etc/default/adsbfi 
					

As for what changed in /etc/default/adsbfi, USER LATITUDE LONGITUDE ALTITUDE were all that were changed from the defaults.

The settings for flight aware's portion were all set via the web ui.

Here are the CAD files, in case you want to duplicate the parts.

• Housing Top [STL] [SLDPRT]
• Housing Bottom [STL] [SLDPRT]
• Antenna Mount [STL] [SLDPRT]
• Antenna Cap [STL] [SLDPRT]
• Antenna Brace [STL] [SLDPRT]

A while after I did this project I nearly poked my eye out with a radial of another 1/4 wave antenna. I printed some caps to blunt the end of the radials to fix that hazard. There wasn't really a better place to put the files, so I added them to this list even though they wern't used for this project.

A while after that I noticed another one of my 1/4 wave antennas was missing a vertical, with the only evidence of what happened being a single strand of cat hair. I presume the cat was trying to rub his face on it and cracked the tiny solder joint between the vertical and the coax bulkhead. Hence the Antenna Brace was born. It has the added benefit of making the antenna trivial to solder together, since all the radials and vertical are held in place by the brace during soldering.