Message-ID: <4193FC7F.1040308@genesiswireless.us>
Date: Thu, 11 Nov 2004 17:57:51 -0600
From: WE0H Mike <we0h@genesiswireless.us>
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Subject: Re: LF: Re: Re: Wood formers
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I tried a 45' tall flattop vertical with a 72' long by 5' wide flattop 
all hung in oak trees. It worked OK when it was below freezing temps 
outside and decent when the temperature went below zero degrees in the 
winter. At any temps above freezing, it made a good dummy load. The 
trees have no effect on my TX loops like Laurence found out =-O

Later,

-- 
Mike
WE0H
WD2XGI


Laurence KL1X wrote:

> ....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" <z>
>> 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
>>
>>
>>
>
>
>
>