> Date: Sat, 17 Sep 2011 17:38:09 -0500
> From: mikewate@gmail.com
> To: topband@contesting.com
> Subject: Re: Topband: Effect of current max not at base of vertical.
>
> Guy,
>
> I'm not saying that I understand this 100%, but I certainly do find it
> fascinating. I have a question, though.
>
> For quite some time, my understanding has been that by making a bottom-fed
> vertical (or inverted-L) longer than 1/4λ --and thereby raising the max
> current point-- that we simply move the point of maximum current farther out
> on the radials. This makes sense to me, if we consider the thought that the
> ground is an image of the antenna, the "missing" portion (for lack of a
> better expression).
>
> Other well-respected hams used to say that this condition significantly
> added to the requirements for the radial system under such a longer vertical
> in such a way that we now need even longer radials. Later, though, one of
> these hams seems to have reversed his beliefs 180°. I don't pretend to know
> the answer. (And at this point, I'm not sure anyone does. :-)
>
> If I use a 5/16λ or 3/8λ inverted-L, how does this change the requirements
> of:
>
> 1. ~60 radials stapled to the surface of the earth ?
> 2. An elevated counterpoise (which would of course require far fewer
> radials) ?
>
> Thanks,
> Mike
> www.w0btu.com I have the same issue and opinion that Mike describes,
> although my thoughts on how to deal with it are different. The point of
> difference is that I just don't want to put my hand in a bag of snakes
> fussing with the erection and tuning of elevated radials that in my case must
> weave around trees within a wooded area. My inverted L is 85' up and 85' out
> in the belief that its point of maximum current is located half way up the
> vertical leg. There are 55 in-ground radials, most of them 120-160 feet long
> (a dozen are only 75' long). My thought is that instead of adding more
> radials originating at the base feedpoint and extending each of them out
> 120-160 feet, there would be economies of copper and labor to "crow foot"
> those additional radials. By "crow foot", I mean digging up an existing
> radial at, say, 60 feet out from the base feedpoint and splicing in a new
> radial that would fit within the interstice of two existing radials and would
> itself be only 60-100 feet long. And, by extension, repeating this crow
> footing at, say, another 30 feet away, splicing and siting each new radial
> between pairs of then-existing radials. As such, the newest radials would be
> only 30-70 feet long By this means I would avoid what I judge to be an
> unnecessary intensification of radial density close to the feedpoint, and
> instead deploy the copper further away and at areas where the existing
> radials are extremely far apart from one another. Charles, W2SH
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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