You misunderstood what I said.
I said a HALF WAVE vertical fed from the bottom is essentially
the same as a half wave vertical dipole fed in the center.
I wasn't talking about ground mounted quarter wave verticals.
However, now that you brought it up, I have also compared
a quarter wave 20M vertical with 32 radials against a
half wave 20M vertical with no radials. Can't tell the difference
on the air. (Both ground mounted).
Rick N6RK
Jim Brown wrote:
> On Sat, 14 Jun 2008 22:04:53 -0700, Richard (Rick) Karlquist wrote:
>
>> These are essentially the same array, just different feed
>> implementation. There is no fundamental difference.
>
> Yes and no. Remember that one of the most important properties of
> any antenna installation is how it interacts with the earth in the
> far field (that is, what does the first reflection do), which is
> strongly affected by its height.
>
> A quarter-wave vertical typically has its feedpoint on the ground or
> close to it, placing its current maxima close to the ground. The
> CLOSEST a half wave dipole's feedpoint (current maxima) can be to
> the ground is a quarter wave. This has MAJOR impact on the vertical
> pattern. The Power Point pdf I cited earlier in this thread has NEC
> models for a 40M dipole at various heights that I was able to
> achieve here (by hanging it from one of my redwoods). None of these
> was particularly thrilling at low angles, and raising the vertical
> dipole simply improved its vertical pattern at higher angles.
>
> And I DO have this antenna rigged with the top of it at about 100
> ft, I HAVE compared it to horizontal dipoles at that height, and the
> horizontal dipoles kick its butt by 10 dB every day of the week. :)
>
> 73,
>
> Jim Brown K9YC
>
>
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