"Denny" wrote
But, I bring us back to the topic, no where do I see HF mentioned
in the quotes from Terman... Ground wave transmission becomes
markedly poorer beginning somewhere around a thousand KC -
which is why hams were relegated to the waste land of 200 meters
and down....
_________

Just to point out that, although groundwave _propagation loss_ is greater
when progressing from lower to higher radio frequencies, the radiation
patterns and peak gains in the horizontal plane from ground-mounted vertical
radiators remain the same for corresponding radiator heights in wavelengths
and equal r-f ground resistances, no matter what the frequency.

All ground-mounted, vertical monopoles through 5/8-wavelength in height
develop maximum radiated relative field in the horizontal plane. If the
vertical radiator is 1/4-wave tall, then the _radiated_ elevation pattern is
approximately a function of the cosine of the elevation angle, no matter
what the ground conditions are, at and near the radiator site.

These are the distinctions I am trying to make, because the common belief
seems to be that the relative field of the elevation pattern launched by a
ground-mounted vertical is dependent on ground conditions, and always zero
in the horizontal plane to peak at some greater elevation angle.

The field strengths measured by Brown, Lewis & Epstein in the benchmark 1937
study defining an effective r-f ground were taken at 3 MHz. And for the
best-case radial ground system the groundwave fields at 3/10 of a mile were
within a few percent of the theoretical maximum possible for that radiated
power over a perfectly conducting earth -- even though the tests were done
in NJ over a path of rather poor conductivity -- maybe 4 mS/m. It's clear
from this that even in the low HF spectrum, the field radiated from their
test antenna over a poor earth path was not zero in the horizontal plane!

RF

On Tue, 26 Sep 2006 16:22:15 -0500, "Richard Fry"
wrote:


All ground-mounted, vertical monopoles through 5/8-wavelength in height
develop maximum radiated relative field in the horizontal plane. If the

Richard,is this true in general, or is it restricted to perfect ground
(infinite size, perfect conductor, perfectly flat).

NEC models would suggest that the major lobe of a monopole up to 5/8
wave over "real" ground is dependent on the ground characteristics,
and can be quite high relative to the 0deg to 3deg region that people
are focussing upon.

Owen
--

"Owen Duffy" wrote
On Tue, 26 Sep 2006 16:22:15 -0500, "Richard Fry"
wrote:
All ground-mounted, vertical monopoles through 5/8-wavelength in height
develop maximum radiated relative field in the horizontal plane. If the

Richard,is this true in general, or is it restricted to perfect ground
(infinite size, perfect conductor, perfectly flat).

NEC models would suggest that the major lobe of a monopole up to 5/8
wave over "real" ground is dependent on the ground characteristics,
and can be quite high relative to the 0deg to 3deg region that people
are focussing upon.
__________________

For the shape of the relative field elevation pattern, it is true in
general. A poor r-f ground for the monopole (i.e., a ground of high r-f
resistance) will change the peak gain of that radiated elevation pattern,
but not its shape.

NEC evaluations typically don't show 100% relative field in the horizontal
plane in the elevation pattern radiated by a vertical monopole except over a
perfectly conducting ground plane, which is the root of all this confusion.

Once the radiation is launched, then it becomes subject to the propagation
losses for the path and frequency. But for verticals up to 5/8-wave tall,
peak relative field always lies in the horizontal plane, regardless of the
ground conditions on and near the radiator site. This is the basis used by
the FCC in determining the coverage capabilities of AM broadcast stations,
and has been proven to be a rather accurate approach going back some 60
years.

RF