Roy Lewallen's post of Dec 29, 9:45 pm generally supports the points I
have been writing about.

But two observations are due:

Fortunately for the broadcasters, the surface wave component
doesn't detach itself from the Earth and head for the ionosphere
as the Earth curves away, but follows the curvature of the Earth.
This allows broadcasting beyond the horizon without ionospheric
skip, and prevents fading from the ground wave alone. It doesn't
reach the ionosphere as Richard has claimed.

The last sentence above is incorrect in that I made no such claim. My
post stated only that radiation from elevation angles as small as one
degree will reach the ionosophere. See the paste below.

"But that isn't the case -- the relative field over real ground at low
elevation angles close to the vertical radiator can be very high, and
will continue onward to produce a long-range skywave. Even radiation
at an elevation angle of one degree will reach the ionosphere, due to
earth curvature."

A low elevation angle does not include zero degrees (the horizontal
plane).

The reported field strengths are in dBi for easy comparison; ...

The term "dBi" is not a unit of field strength. Field strength is a
voltage existing between two points in space typically one meter
apart, and is expressed in terms of that voltage with respect to that
distance, as in volts/meter (V/m).

Field strengths can be compared using decibels, but such comparisons
are referenced to the field strength shown in standard form. For
example, a field strength of 1,000 µV/m may be expressed as 60 dBµV/m.

RF