From: "Laurence KL1X" <hellozerohellozero@hotmail.com>
To: rsgb_lf_group@blacksheep.org
Date: Thu, 11 Nov 2004 12:35:13 -0900
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Subject: RE: LF: Re: Re: Wood formers
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....well Cottonwood/Pine trees were certainly an affect that reduced my 
effectiveness in producing a strong into USA/world signal from Alaska - ok 
the distance was more to the nearest receivers but I was using a pretty 
large vertical and good top loading, and extensive earth radial system 
probably close to "commercial" standards - I just was in a small cut out the 
middle of a deep dark dense damp dank forest  - and used trees to suspend 
additional top loading wires but didnt get the insulators closer than 20ft 
from the support braches. As you say it was always difficult to ascertain 
the loss/gains on additional top loading versus loss C due to proximity.

Working on what we have here in OK with this 380ft circum lazy tx loop, the 
same tx power as was etc and from extensive local field meaurements,  Im up 
about 12dB (or more) compared with my poorer 110 ft vertical and extensive 
top loading! - Its got to be these high Z verticals, trees and the 
associated lossy C, compared with the Low Z loop, that doesnt seem to mind 
rubbing up and down tree trunks, slung without insultors over branches, and 
which birds sit and "cheep" on with close to 35A of aerial current running 
thru it (and no connections to earth per se!)

However if I lived on a farm, with say 20 acres and a 110 ft tower and a few 
trees Id probably go for a vertical....then perhaps not!

ps I used dry cedar to support the vaccum cap which has a few Kv across it 
and now cooking/burning smells as of yet...

Cheers

Laurence KL1X/5

ps conditions are %&^$#!!, but daytime enhancement over a 1500Kms are up 
quite a few dBs at the momemt.

>From: "Vernall" <vernall@xtra.co.nz>
>Reply-To: rsgb_lf_group@blacksheep.org
>To: <rsgb_lf_group@blacksheep.org>
>Subject: LF: Re: Re: Wood formers
>Date: Fri, 12 Nov 2004 09:26:37 +1300
>
>Hi all,
>
>Some interesting comments on wood and plunging Q of LF coils.  It also made
>me think about "live wood" and that definitely does have sap.  It strongly
>suggests that a transmitting antenna should be well clear of trees.  For a
>vertical, the up-wire is where the current is maximum, and that situation 
>is
>similar to a one turn inductor as far as magnetic induction is concerned.
>If the wood is also a lossy dielectric, then the top loading wires and
>electric fields could also be contributing to losses with trees in the
>antenna environment.
>
>In terms of efforts made to maximise radiated power on LF, it would be
>unbalanced to focus only on loading coil loss, even if that is more 
>directly
>under the control of those making the coil.  It would be interesting to 
>find
>out for top loading that is tied off to a tree (with suitable insulation,
>and in a situation where there are no other practical choices for 
>suspending
>the top loading) if there is an optimum spacing of the insulator from the
>tree.  It may be better to accept moderately lower capacitance for top
>loading if the net losses are lower.
>
>73, Bob ZL2CA
>
>
>