I see other comments that bring up the 'RF pollution' from aircraft travel..all of those airplanes spewing RF, and harmonics all over.
How about normal pollution? All those tons of burned hydro carbon absent from the atmosphere (10K to 40K feet).
Is it possible the non-normal chemical composition of the air is impacting the observed ducting? (de WB0VIX/5)
Interesting observation. Lots of radio traffic by aircraft might substantially raise the noise floor, even though they do not operate near that particular frequency one or more of their harmonics might interfere with signals that quiet. 432 is suspiciously close to 4 times 108 so you may be on to something there.
For local communication, e.g., state to state, a common mode of attempts involve bouncing signals off of airplanes. But transatlantic using this method would be quite unlikely.
I would not be so categorical about that. 108 MHz is the low end of the VHF airband and 432 just so happens to be 4 times 108. So it may very well be that this connection would under normal circumstances be impossible due to interference.
