On Nov 29, 9:21*pm, Roy Lewallen wrote:
Richard Fry wrote:
The radiation/reception characteristics at low elevation angles of
such an antenna can be useful in establishing contacts with the most
distant possible single-hop DX sites, can they not?

They can not. I see you're still a bit confused about what happens to
that ground wave signal. Beyond a few miles at HF, that low angle
radiation decays to essentially zero. The pattern of the field beyond
that distance resembles the one reported by EZNEC and other programs
giving distant far field data. And they correctly show that unless the
ground has very high conductivity at the reflection point, there will be
very little field remaining at very low angles beyond that ground wave
decay distance.
_______

I'm not considering that the ground wave signal _provides_ any of that
low-angle DX coverage. It is the direct radiation existing in the
radiation pattern of the monopole at low elevation angles that can do
so. No ground reflection is necessary to create that field - it is
launched by the monopole itself.

Below is a link to a clip from Terman's Radio Engineers Handbook, 1st
edition, showing that the greatest single-hop range for skywave
signals occurs from the radiation of the monopole at elevation angles
of less than ten degrees. But looking at a NEC far-field analysis
this would seem impossible, due to the greatly reduced fields in this
sector that NEC shows for a vertical monopole over real earth.

This clip was done for MW frequencies, but the concept would apply
equally at HF, would it not?

http://i62.photobucket.com/albums/h8...ermanFig55.jpg

RF