I don't introduce another variable in trying to understand why a
particular ham gets equal performance out of a lazy V 4 square and a
shorty forty. The variables are all there, in action. All that varies
is whether we are perceptive enough to know that they are all in play.
Consider a vertical and a horizontal antenna, for talking purposes
both 5 dbi direct, the vertical getting no reflection gain, the
horizontal getting the 6 db.
Knife edge effects, outright blocks, and that sort of thing will
affect the 5dbi direct of both the V and H antenna, as you say. Those
are decidedly terrain effects, but not the only ones.
If the slope of the land out there at a low angle bounce distance is
upward enough then the horizontal energy that would have been
reflected out at some low angle will now be reflected out at some
higher angle.
The 6db reflection "advantage" still exists, just aimed too high to
make the horizontal antenna play better than the vertical at some low
angle.
It is possible to get the same effect with complex irregular terrain.
Family definition of an expert: anyone other than someone that lives
in the same house.
73
----- Original Message -----
From: "Pete Smith" <n4zr@contesting.com>
To: <towertalk@contesting.com>
Sent: Saturday, October 12, 2002 5:10 PM
Subject: Re: [Towertalk] Vertical vs. Horizontal was: 40M 4 Sq vs. 2
el Yagi at 70 ft
> At 04:07 PM 10/12/02 -0400, Guy Olinger, K2AV wrote:
> >There are many terrain configurations that would effectively
nullify
> >ground reflection at angles useful for DX, the bulk of reflection
> >being too high a takeoff angle to be of much use.
> >
> >If one was in such a situation (taking away the ground reflection
> >advantage) and the centers of the vertical dipoles were high enough
to
> >avoid heavy e-plane ground penetration loss, the two would play
pretty
> >much alike.
>
> You are introducing another variable, and I don't think correctly.
I just
> re-read the ARRL Antenna Book's section on vertical and horizontal
antennas
> over real ground, as well as the section on the effects of irregular
local
> terrain in the far field. From what I can understand of the
discussion, it
> appears that, over real ground:
>
> -- ground reflection gain basically benefits the horizontal but not
the
> vertical antenna.
> -- ground losses in the far field affect vertically-polarized waves
far
> more than horizontally-polarized ones, particularly reducing
low-angle
> radiation.
> -- refraction and diffraction due to irregular far-field terrain
affect
> both horizontally and vertically-polarized radiation.
>
> Or to put it another way, the horizontal antenna starts out with an
> advantage, pulls further ahead in the far field due to ground losses
for
> vertically-polarized radiation, and the effects of irregular
far-field
> terrain are basically the same for each.
>
> Am I wrong? Any experts reading this discussion?
>
> 73, Pete N4ZR
>
>
>
>
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