One really needs to evaluate the usefulness of 5 degrees and under in a
case-by-case basis. Most people in populated areas have 5 degrees
completely obliterated by conductive and semi-conductive clutter...houses,
trees, overhead powerlines, buildings, yada yada. And probably 10 and 15
degrees are obliterated as well. And unless you are someplace where they
talk about big sky or on a mountain top, you are most likely NOT in a
completely flat place, so plus 5 degrees (85 degrees below zenith) is
beneath the horizon on at least half your compass.
Not only that, if I'm reading it right, the math of ground wave DEPENDS ON,
REQUIRES monolithic uniform dirt, both over distance and to depth, to
support to the level of those good numbers. Those who have their gold
standard radial fields out in open meadows with vistas low to the horizon
surely WILL reap the rewards of their gold standard labors, no argument,
and you WILL be able to find that small bump up at the low low angles that
the far field plot does not show.
BUT you are talking about gnats on the windshield of Queen Elizabeth's
Rolls Royce. Great, wonderful, if you got that kind of stuff. But Average
Joe Ham in the usual clutter of urbia and suburbia, with dirt over land
fill rubble in his building plot, full of rocks, sand and whatever else,
and with an average conductivity of 0.5 milli-Siemens, if even that, will
never see such a bump up from ground wave. He will be quite fortunate to
have vertical angles of 10 or 15 degrees in play, forget 5, and maybe not
even the ten. For him the ground wave discussion is angels on the head of
a pin.
BL&E gave their study conductivity limits as between 20 and 100
milli-Siemens !!! And the photographs in the IEEE synopsis show black dirt,
and absolutely flat out to well beyond a mile. Just simply do not bother
to extrapolate those circumstances downward to Joe Average Ham in
Levittown. OF COURSE BL&E had a ground wave. They better have. And
again, SO WHAT?
God forbid I wind up a widower and can go anywhere I want, I may go find
500 acres of absolutely flat black dirt with 40 milli-Siemens conductivity.
Then I'll call up Rich Fry and ask him, "remind me about all that ground
wave stuff. I got me this new farm, and I'm only going to grow crops on
the black dirt to keep down the trees." And I'll prove that everything
Rich said was correct. And for the first time in my life I WON'T have to
add the "And so what?"
The thing that will get Joe Average Ham going is how to design a
counterpoise that is NOT LOSSY in just plain awful dirt. Everything else
is so what. How many of you guys out there have uniform outward and to
depth 30 milli-Siemens dirt and can see the low horizon from your back
yard? Forget it. Get rid of loss in your counterpoise. Do that first, do
that before you even THINK about doing anything else.
Will someone please tell me what is noble about starting out your 160 meter
career having been recommended and installed a design with a counterpoise
that even NEC duns at -18 dB. Tell me how worrying about ground wave fixes
that. Why is ground wave even being brought up? Let's worry about the
"No-Wave."
73, Guy.
On Tue, May 8, 2012 at 11:58 AM, DAVID CUTHBERT <telegrapher9@gmail.com>wrote:
> If the radiation at 3 degrees is -8.9 dB relative to the maximum amplitude
> we can still work DX.
>
> Dave WX7G
> On May 8, 2012 9:18 AM, "Richard Fry" <rfry@adams.net> wrote:
>
> > Dave WX7G wrote:
> >
> > >The program W6ELProp gives the take-off-angle needed for any path.
> Looking
> > >at 80 meter paths (it does 801-0 meters) the angles for DX paths are in
> > the
> > >range of 3-15 degrees.
> >
> > Assuming those angles are true for DX paths, note that if the NEC
> far-field
> > elevation pattern for a 1/4-wave monopole was the only radiation leaving
> > the
> > antenna, the field at 3 degrees elevation would be about 8.9 dB below the
> > field at the center of the so called take-off angle (see link below -
> note
> > Photobucket stripped the decimal from the 3.9MHz link).
> >
> > The surface wave really needs to be recognized in such evaluations.
> >
> > http://i62.photobucket.com/albums/h85/rfry-100/39MHz_Elepat_6_mS.jpg
> >
> >
> >
> > _______________________________________________
> > UR RST IS ... ... ..9 QSB QSB - hw? BK
> >
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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