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Re: [TowerTalk] 'WWV halfwave vertical", was Vertical vs Beam

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 'WWV halfwave vertical", was Vertical vs Beam
From: jim Jarvis <jimjarvis@optonline.net>
Date: Mon, 06 Apr 2009 11:28:12 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
The WWV "halfwave" vertical is actually a quarter wave vertical with  
sloping, elevated radials.
It can also be seen as a center fed half wave vertical dipole.    No  
magic.

I have personally used one of these on 40m for many years, with good  
effect.
Held regular skeds with VS6DO from the east coast on 40, for several  
years.

The idea is to get the high current portion of the antenna as high as  
you can.

 From what I've read about vertical performance, the use of on-ground  
radials
not connected to the antenna, is of marginal value.   Possibly of  
zero value.
What is most important is the first reflection zone, which lies  
outside the quarter
wave circle.  This impacts the 'pseudo-Brewster Angle',  below which  
a reflected
wave is refracted into the earth.  It's a function of the index of  
refraction of the
medium (earth), and the better it is (like salt water), the lower the  
radiation angle
of the antenna.

Radials would have to be quite long and dense, to significantly  
improve ground conductivity
in that first reflection zone.    For most amateurs, that would be  
outside our property, outside our control,
and outside most rational budgets.

The WWV website indicates that they took care to keep feedlines from  
crossing.
I can see no purpose for this, other than convenience of installation.

AS TO THE ORGINAL QUESTION:   Vertical vs. Beam... there are so many  
variables
that are site and antenna dependent that this question can only be  
answered by trying it.

It is true that modelling software will answer the question about  
gain in a particular direction
and elevation.   But in order to understand what the models tell you,  
you need to define what
you're trying to accomplish.   Others have said this quite well.

My 40m elevated GP was compared with a 2 el CC @ 70',  with two  
identical stations about
15 miles apart, working guys in EU,  stateside, and into Asia.   The  
GP was always 2 s units louder
than the beam in Hong Kong.   In EU, it was a tossup, and stateside,  
the beam always won.
The one exception to the asian path was during a greyline when  
skewpath down the south pacific
was open.   The beam was much much louder, and the vertical suffered  
from severe multipathing
requiring that code speeds be slowed, to copy.

In general, I would prefer to have a 2 el 40 @ 90' than the vertical  
dipole, if I could only have one.
But if the choice were to put that beam @ 50'... I'd go vertical,  
with an elevated feedpoint.
You don't need a model for that.   If the choice were a tribander @  
50' vs. a vertical for 20... I'd
pick the beam, and go vertical for 40, 80, 160.

N2EA
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