Table of Contents
Portable ADSB Receiver with GPS
I have been running an ADSB receiver for a couple of years now, feeding FlightAware and Flight Radar 24 before I discovered the OARC ADSB map. I also have a camper van, and I got to thinking it might be quite fun to track planes when I'm parked up somewhere, just to fill in the gaps on the OARC map even if only for a few days. This should be straightforward; the only catch is you need to set the location of the receiver each time for the MLAT feed to work properly. The obvious solution to that is a USB GPS dongle and some startup scripts that set the location before the feeders start - easy, right?
The basics really were easy, but getting it all to work together, and in a case, took a number of false starts and a box full of adapters I ended up not using 
The 'design'
Other people are using Pi Zeros successfully for ADSB so I figured that would be a good starting point (they were also fairly easy to get hold of, unlike any other Pi variants at the time!). I wanted everything inside a box, rather than having the dongle sticking out the back, and I know from other builds that the USB SDRs run hot, so it should be a metal box to help with heat dissipation. I'd had good experience with the NooElec dongles on other projects so these 'Nano' RTL Dongles looked a good bet - small, come with a heat sink, and with fly lead to connect to a bulkhead socket for the antenna. The USB GPS was a bit of a punt but works perfectly. The problem now becoming apparent was I needed to run power, GPS and SDR through just two micro USB ports on the Pi Zero. This 4-port hub connects to the Pi board through pogo pins, and has the option to supply power for the USB ports directly rather than further loading the Pi's power circuits. I used a panel mount Micro-USB extension to a breakout board to feed power to the Pi and the Hub - if you were feeling clever with brackets you should be able to directly mount the breakout board and skip this cable. Finally I found a metal case that was just the right size.
The Software
I planned to use Mark, 2M0IIG's excellent feeder setup instructions for the basics, but I wanted to be able to just plug in the power and have the whole system start up, without any need to connect through SSH or a browser to configure anything. Similarly, I wanted to be able to cleanly shut the Pi down without SSH. So the startup scripts need to
- wait for the GPS to initialise
- get a location and updates the feeder configuration
- start the feeder.
And then I needed a way to initiate a clean shutdown. Fortunately I found a way to do this with just a pushbutton.
Bill of Materials
- Raspberry Pi Zero W
- From the junk box
- connecting wire
- latching and non latching push switches
- rubber feet