Sorry, but unless I'm wrong, you are missing the point, Jim.
All of the below has to do with the "amount" of radiation at low angles.
Nobody ever disputed that.
My comment, which triggered this "thread within a thread", was that it does
not affect the "angle" of maximum radiation. The low angle radiation is
reduced, but so is the high angle radiation. When we run verticals, we're
interested in low angle radiation and that's why they talk about what
happens to the strength of the radiated signal as the ground losses vary.
We all agree that the strength of radiated power depends on the ground, but
my point is that the angle does not.
From: firstname.lastname@example.org [mailto:email@example.com]
On Behalf Of Richards
Sent: Wednesday, January 05, 2011 4:45 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] New and Improved Terminology (NVIS origins)
Er... ah... No joke. Do you doubt the proposition that a
good ground plane lowers radiation take off angle? If so,
I would be curious as to your reasons. (Seriously, and with
no intention to flame or cause an argument, as I have
made quite an investment in time and resources in vertical
developing a reasonably decent vertical antenna system
for my small, suburban back yard. Any info would be
greatly appreciated. )
------ Extra Class Exam Questions of interest -----
Question E9A12 - and the answer is that the efficiency
of a quarter wave grounded vertical antenna can be improved by
installing a good radial system.
Question E9A13 - answer is - soil conductivity is the most important
factor in determining ground losses for a ground-mounted vertical
antenna operating in the 3-30 MHz range.
Question E9C13 - answer is - When a vertically polarized antenna
is mounted over seawater versus rocky ground, the far-field
elevation pattern low-angle radiation increases.
Question E9C17 - answer - The main effect of placing a vertical
antenna over an imperfect ground is that it reduces low-angle
Also, on the audio study guide, Gordo makes some stray comments
about using 3 inch copper strap for radials on his roof, and
mentions improving the ground field increases low angle
radiation - he goes on to say it does not increase signal strength,
of course, but only that it increases the amount of signal that
has low take off angle.
This information is consistent with all that I have read on verticals
in the ARRL Antenna Handbook, and I did LOTS of research before
installing a large vertical monopole in the back yard.
A huge ground pane does lower take off angle (as NEC modeling
shows) and also improves antenna efficiency -- I stopped at 65 radials
but I wish had installed even more just to be sure. Also, my back yard
soil is very conductive and remains moist even through the summer, so
the soil, itself, helps me considerably. Rob Sherwood and I exchanged
some nice email at the time I was doing this homework, and I believe
he lives over a more dry, rocky soil, and that is much harder to work
over. I also corresponded with the infamous Rudy Severns N6LF
and his findings are consistent with this conclusion. NEC modeling
produces consistent results.
N'est ce pas? Happy trails OM.
=============== JHR ============================
On 1/5/2011 1:01 PM, Steve Hunt wrote:
> I presume the "wink" indicates that is a joke !
> The only thing that would improve the elevation pattern would be
> improved ground conditions in the Fresnel Zone where the ground
> reflections are taking place. That would take some awfully long radials
> - certainly well beyond my property boundary - and an awful lot of them
> to achieve a copper density that would affect the conductivity so far out.
> Steve G3TXQ
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