[. . .]
Propagation to the mainland *is* possible (believe it or not!) but I
doubt it could be strong enough to interfere with the powerful local
Honolulu stations, especially those whose transmitters are in the city.
I think receiver overload is a far more likely problem.

Thanks, Doug. I think that explains one observation. Before this
problem started, the reception of the station (fairly good) had even
improved when I touched the antenna. I suppose that my body acts
as an extention of the antenna. But, recently, the sound (already
very noisy) becomes thunderstorm-like noise when I come near the radio!
Perhaps I'll test this hypothesis by moving the radio away from the
window to, say, the bathroom. (But, the second station remains
a mystery.)

Cheers,
Ryo