Herb:
The poor performance over salt water is no surprise. The pattern of an
antenna over salt water isn't even recognizable as a Beverage to me.
Assuming 5 and 80 for conductivity and dielectric constant, a NEC simulation
will yield sidelobes and a rear lobe that have more gain than the forward
lobe (and a very strange overall shape). This is purely a result of
conductivity under the antenna; the high dielectric constant of salt water
has virtually no effect.
Even allowing for the fact that simulations might be off some, there's
clearly a large degradation in performance over highly conductive surfaces.
Chuck
-----Original Message-----
From: topband-bounces@contesting.com
[mailto:topband-bounces@contesting.com]On Behalf Of Herb Schoenbohm
Sent: Tuesday, January 06, 2004 9:29 AM
To: gm3poi@btinternet.com
Cc: topband@contesting.com
Subject: Re: Topband: Beverages over Radials
Clive, I ran a long beverage over a salt pond (brackish water with high
salt content) near my QTH and its performance was not good until I ran
the same wire over earth. Another attempt was to use the top strand of
an electric fence no longer in use. I also ran for 1500 feet straight
west and the other two barbed wires were spaced below and grounded to
the metal fence posts very 20 feet. I expected a winner and was very
disappointed. Again the performance was lackluster. A 500 foot 3 foot
high Beverage over the hay field next to my house running in the same
direction beat it hands down. All systems were terminated with a 500
ohm resistor and a ground rod with a few short radials.
I tired to chime in recently on the two wire vertical spaced Beverage
thread but the experts said I was wrong when I suggested it would be
better ot space two wire Beverages apart horizontally, based on
experience with a good conductor beneath a Beverage. But then again the
bottom wire of the suggested two wire antenna was part of the system and
presumably not grounded except at the termination or through the
matching transformer. That may make a big difference. But as I
mentioned in an earlier post that everything I have ever read about the
classic Beverage is that in order to develop a wave tilt and significant
pattern shaping with nulls, the conductivity beneath the Beverage wire
"must" be inferior to the wire above itself. By traveling faster in the
wire than the earth below the signal is enhanced according to Mr.
Beverage himself.
I will probably get flamed for saying this but I just look at the cards
that are dealt to me and this is what I see.
73
Herb Schoenbohm, KV4FZ
Clive GM3POI wrote:
>I'm not sure whether this subject has been aired before, but given that a
>Beverage needs ideally to run over lossy ground. Is it the collective
wisdom
>that a Beverage running for a large percentage of it's length over a radial
>field won't work as well. That is for the moment Ignoring coupling to the
>Tx antenna. Has anyone proved this to be the case. 73 Clive GM3POI
>
>
>
>
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