Latest project is receiving ADSB (Automatic Dependent Surveillance–Broadcast) data on my Pi4. The same Pi that is my DMR Hotspot. I'm really getting my monies worth out of my Pi4 😀. This data is being fed into FlightRadar24 and FlightAware
The 1090Mhz pre-amp and SAW filter is available from AliExpress for ~£6. It is quoted as having 21db gain and I found that it gave me ~30% more range and aircraft detected went from ~90 to ~120. I changed the SDR gain from Auto to 18 which decreased the noise figures without affecting range or aircraft count.
The AirSpy R2 might seem like overkill for this application but I'm lucky enough to have 2 of them and it gave vastly superior performance than the next best alternative I had, a RTL SDR V4. You will really need a Pi4 for this to work. A Pi Zero or Pi Zero 2 W just doesn't have the capabilities for this stack, especially if installing on an existing Pi-Star hotspot. If you have an old unused desktop/laptop then install Ubuntu on it and you'll be good to go (replace Pi4 in the prompt below with "Ubuntu").
For the software, I asked ChatGPT with the prompt "I want to receive ADSB data on my Pi4 using tar1090 and readsb. The SDR is a AirSpy R2 and feed the data into FlightAware and FlightRadar24". Change the "AirSpy R2" to whatever SDR you are using. If you are installing this on your existing Pi-Star hot spot, then add to the prompt "I am installing on an existing Pi-Star installation so change the ports of lighttpd as required".
The important numbers:
{
"gain": 18,
"lost_buffers": 0,
"max_aircraft_count": 126,
"snr_median": 13,
"noise_median": 33.5,
"preamble_filter": 19.9
}