For fun I've been using an AirSPy SDR (Software Defined Radio) to receive and decode ADS-B packets, primarily DF-11 and DF-17 messages.
The code is written in C++ and works reasonably well. It performs IQ processing / demodulation, packet extraction, CRC checking etc. As its output it generates AVR formatted message strings that are then served via a Listen Socket / Socket based interface. I then use Virtual Radar as a client to decode and display the data.
With regard to the DF-17 and DF-11 packets, I'm currently only forwarding the ones that have an Interrogator ID of zero, the so called "unsolicited squitters". i.e. Complete packets that have a zero remainder after CRCing.
I also receive / decode plenty of packets that have non-zero Interrogator IDs.
Can I use these for anything useful?
In other words, could I extract any useful information, positions, velocities etc. If so I could then re-write them as unsolicited DF-17 messages and pass them to Virtual Radar.
I am researching this to the best of my ability, but currently drowning in specs and documentation as there appears to be so much of it!
Apologies if I've miss used any of the jargon, I'm only a week into my project.