The ADS-B decoding software has some idiot checking in it to prune out undetected multi-bit errors. One of the checks the code makes is a distance check. I think it’s set at around 350km? Configurable if you know where to look. A couple of years ago as parts of this were still being developed, I remember seeing reports on my screen of a commercial aircraft a few thousand km away doing 250 or 300 knots at an altitude of something like 26 feet. Would have been one hell of a ride, but I suspected bit flips instead.
As a ham radio operator, I’ve worked from the California coast to Hawaii on 6 and 2 meters (54 and 144 MHz) SSB. Ducted signals sound weird!
ADS-B packets are pretty short; not sure if ducting would alter them significantly.