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Re: [TowerTalk] trees verticals modeling results

Subject: Re: [TowerTalk] trees verticals modeling results
From: Jim Lux <>
Date: Thu, 29 Dec 2011 10:46:00 -0800
List-post: <">>
On 12/29/11 10:33 AM, David Jordan wrote:
> Bravo Jim... finally the answer... it don't make enough difference to type
> two sentences about it.  Move that wire away from the tree trunk and hang it
> from a limb and BINGO... you got an antenna that works good enough for most
> folks; sure beats no antenna doesn't it;(?)!
> 73,
> Dave
> wa3gin

Well.. it *is* nice to know that at least the trunk isn't going to cause 
huge problems.  And it's nice that the back of the envelope intuitive 
analysis seems to match the simple finite element model.
(and it's also nice to know that the 6BTV that I put up a few weeks ago 
in amongst the trees will probably work fine, when I put it back up.. 
blown down in the wind)

There's still an issue of "antennas in a forest", which is intriguing, 
because it seems to say that a lowish horizontal dipole among the trees 
might be better than hanging a vertical.  Again, useful to think about 
when talking about stealth antennas.

and the question of leaves.  I'll have to hunt down some info on leaves 
(particularly wet leaves)..

But I'd think, if you're clear of most of the foliage (and the antenna 
isn't touching the leaves at the high voltage end... yep, been there, 
lit the tree on fire with 100W)

An interesting modeling question is "what effect does modern house 
construction have"... I've got my dipole laying on top of my concrete 
tile roof.  Works fine most of the time, but when it's wet, it's 
noticeably worse.  But if I were to go to the trouble of suspending the 
wire, say, 6" above the roof, would that help? Or do I need to go to 1 
foot.  (That's not an antenna, that's a wire to keep the pigeons from 
roosting up there...)

Or the perpetual question you see:  I have a vertical (x-BTV, R7000, 
GAP, 43 foot untuned, whathaveyou) and I want to put it 3 feet from the 
house in the side yard.  Good, bad, indifferent?  Just how bad?

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