Ron Hardin wrote:
Why, like clockwork, does WFAN 660 NYC, received 500 miles west in
Central Ohio, fade away at (nowadays) 6am and later come back
strong for another hour? They're strong again like a local at
almost 7am now, for instance.

Not just a random once-in-a-while thing, but regularly.

My guess is that it must be a switch in the height of the reflecting
layer somehow, but I can't construct a really consistent picture.

MW always reflects, but the attenuation varies at lower levels with
solar angle, sun killing off the reflected signal.

It's not ``grey line'' because that path is nowhere near the
direction
involved.

ONe thought is that the station goes to full power, allowing a bit
of extra reception even if propagation has declined?

I think I've noticed something like this myself, though on other
stations, but I haven't been up that late recently to have it
fresh in my mind.

Michael