----- Original Message -----
From: Tom Rauch
> > New to beverage antennas, I've been reading your posts
> > with interest. It
> > seems all agree that lower is better. My problem is that I
> > have to have
> > a 10-12 ft high beverage (people and Elk). I was wondering
> > if anyone has
> > tried to put a grounded wire 2-3 ft below their entire
> > beverage. As Milt
> > did over his arroyo runs. Would this change the apparent
> > height above
> > ground?
Appears that Milt's "fix" helped to maintain the Beverage properties better
than the arroyo's "destructive behavior" by providing bridge for the
discontinuity in the ground surface under the portion of the antenna. Very
interesting and perhaps continuation of "open wire" line that Beverage forms
with the ground surface.
>
> Pete,
>
> A conductor below an antenna will always oppose the
> radiation (and reception) of a wire above it. It does not
> really establish "height" in a Beverage, because a single
> wire or a few wires would be tightly coupled to earth and
> very lossy. A Beverage depends on high earth losses to work,
> and it depends on a reasonably wide lossy area to establish
> effective height and performance. It just isn't what is
> immediately under the wire, but what is also off to the
> sides a good distance.
>
There is some self-contradiction going on here. On one hand, and previously
noted that ground conductivity could range from very poor (bad for Beverage),
through good, to bad (high conductivity). "Beverage depends on high earth
losses to work" - assuming really poor earth, with "wire laying on it tightly
coupled to earth and very lossy" doesn't that bring it up to "good ground" for
Beverage performance? We know that wire laying on the ground or burried shrinks
its electrical length to about 60%, which compared to wire in the air is
"lossy" and when installed with few parallel "sisters" could very well provide
necessary improvement in situations, where really poor ground would give
problems.
Generaly it is known that Beverages over good ground, salty marshes do not
work, but ask W2GD and their station installation using Beverages over salty
marshes, how is that working. They keep coming on the top in the contests.
> That's actually what started this whole thread. The Beverage
> Handbook incorrectly suggests installing a "return wire"
> below a Beverage. That clearly is a terrible idea. If the
> wire worked with low loss and really "returned signals" from
> the far end (which is also a false concept) the wire would
> cancel all Beverage-mode reception.
>
If one reads "The Beverage Antenna Handbook" by V. Misek, W1WCR, one would
realize that Vic IS mentioning Beverage antenna as relying on poor ground
conductivity and wave tilt because of it.
What he is describing in his whole book is the SWA - Stearable Wave Antenna
which is setup over "perfectly conducting ground plane" with tilt provided by
the signal arrival angle and is using half wave minimum, with appropriate
terminations, two wire system, phasing devices and ground wire system
consisting of three wires prallel to the antenna wire.
So the reference to "terrible antenna" is way off the target. Misek should have
not used that title for the book, or should have added SWA more prominently for
those who have problem reading what is inside.
> The only reason it doesn't stop the antenna from working is
> because a wire closer to earth has significantly more loss
> than the wire placed higher. We all know (or should know) a
> Beverage stops working over very good ground, so why would
> someone go out of their way to make the ground below the
> antenna move in that direction?
>
We know that Beverage (wire) on the ground works, so generalizing and making
"gospel" statements doesn't serve the technical discussions. Using some
qualifiers and description of particular situations would be much better.
> Unfortunately when something bad makes it into print it just
> never dies.
>
Nothing bad about it, unless one would build it and find out that it doesn't
work, which is hardly the case as Misek describes the construction, use and
nulling properties of his Wave Antenna.
> 73 Tom
73 Yuri, K3BU
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|