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LF: Re: earth losses

To: [email protected]
Subject: LF: Re: earth losses
From: "g3ldo" <[email protected]>
Date: Wed, 9 Jul 2003 09:48:38 +0100
References: <[email protected]>
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Bryan

 Of the earth return loss resistance, how much of the resistance is the
actual earth rod(s)-to-soil contact and how much is the earth path ?
With an  inverted L antenna ,  is not a counterpoise of the same length as
the horizontal section and directly underneath but a few feet off the
ground
a good way of avoiding the earth rod to soil contact losses ??
Because the radiation resistance of the normally electrically short
(suburban) LF antenna is so low earth resistance consumes much of the
transmitted power. Appendix 1 'The Earthing Resistance of Antennae' (written
in 1922!) of the LF Handbook illustrates the considerable effort and expense
that went into trying to reduce earth resistance. Because of the effect of
trees and other electromagnetic obstacles we now tend to think of the losses
as environmental rather than just earth losses.
It is said that,  at HF, a few radials four feet off the ground are better
by far than an earth rod for a L/4 vertical "ground plane" . Does LF need
far more than four feet??
You need a lot of wire and some wide open spaces for a few quarter wave
radials!
I did some experiments at Amberley museum with a wire radial because the
ground there is made of chalk and is a poor earth. I found that I could get
the radial to work provided it was resonated with a separate variable
inductor but the loading of such an arrangement proved tricky.
In a suburban environment earth rods have proved to be the most reliable.
Experiment with any other earth systems you have around the place such as
water pipes (not gas). Every QTH seems to be different in this respect.

Regards,
Peter, G3LDO


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