Cecil Moore schreef:
Al Lorona wrote:
I can't find any references anywhere that discuss this, taking into account
all of the variables: height of ionosphere, frequency, etc.

The ARRL Antenna Book has charts and graphs of such.

And, for as far as I know, recent versions of the ARRL antenna book
include the HFTA program, to analyze the effect of sloping/unregular
terrain.

Arie.