Roger Hayter wrote:

snip

I suspect that the sort of precision with which one can measure signal
strength. plus very local variations of surface wave intensity due to
varying ground conditions, mean that it would be hard to know if the
signal level resulted from, say, one, five or fifty percent of the
transmitted power. So I suspect your question has never been answered.
An opportunity for some collaborative research between local amateurs?

The answer would apply only to one specific antenna at one specfic
frequency at one specific location at one specific point in time.

The biggest variable in all this is at one point in time.

The general approximate answer is:

To maximize skywave propagation the antenna main lobe should have an
elevation angle of around 20 to 30 degrees and the frequency has to
be less than the maximum frequency the ionosphere is currently capable
of reflecting.

To maximize line of site propagation the antenna main lobe should have an
elevation angle as close to zero as possible assuming both ends of the
communication are on the Earth.

To maximize surface wave propagation the antenna main lobe should have an
elevation angle as close to zero as possible and the frequency should be
less than 3 MHz.



--
Jim Pennino