Definitely too many variables going on to make the calculation easy and
straight forward. Effects of height above ground, the actual ground
parameters, and whether it is in an inverted vee configuration or flat dipole
are all going to confound the calculation. Faster to haul the center up into
place with a pulley then measure and snip, measure and snip, until you hit the
desired resonance.
The modelling will get you close but you are still going to end up doing the
measure and snip on the final product.
Don't snip too far!
GL
Earl
N8SS
Subject: Re: [TowerTalk] Cutting a dipole
Message-ID: <C4FCFBFC-BD65-47FD-BB72-18375560CFC0@pacbell.net>
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FWIW I have never had good results trying to calculate the difference in
resonant freq from low heights vs the desired height on an inverted V.
I finally reached the conclusion it was a waste of time to try and calculate
the difference.
Hoist the center up to its final height and leave a generous amount on the ends
and lower and raise each of the ends and keep pruning till you get nirvana.
Bob
K6UJ
From: David Gilbert <xdavid@cis-broadband.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Cutting a dipole
Message-ID: <5227EBDE.4070203@cis-broadband.com>
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That's probably because none of us have a true idea just where our
effective "ground" is. It's not like there is some high conductivity
zone in the top few inches of soil, or that everyone's soil conductivity
profile is at all similar. I'd bet that in some low conductivity soils
the effective ground is several meters below the surface, and I'll also
bet that it is at least to some extent dependent upon the frequency of
interest. I use and depend upon EZNEC and HFTA all the time, but I
don't pretend they are any more accurate than the data I feed them.
Dave AB7E
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