As someone who used to work with Transponders, I'd be interested in hearing more about what kind of analysis you are doing. Im familiar with using an SDR to receive ADS-B data, but hadn't heard of much analysis beyond graphing of current position, altitude, speed, etc. Unless you are near an airport, chances are most broadcasts that are strong enough for you to receive are going to be from passenger jets with high power Transponders, and unfortunately when planes are at cruising altitude, they tend to follow pretty standard flight plans, barring weather conditions, etc. If you could get a receiver near a small airport in an affluent area (where GA aircraft have been fitted with ADS-B OUT already), then I think you would hear much more interesting things :). Are you listening to the 978 MHz band, or just the 1090 Mhz band?