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Re: [TowerTalk] Radial length

To: "Towertalk" <>
Subject: Re: [TowerTalk] Radial length
From: "Jim Brown" <>
Date: Sun, 16 Mar 2008 09:12:21 -0800
List-post: <">>
Certainly a circularly symmetrical radial system is best, but few of us are 
able to realize it. Mine deviates significantly from that ideal, but the 
antenna works well.  The best and most readable description I've seen for the 
function of a radial system is by W2DU, as a chapter of his book 
"Reflections." It's on his website. Google on w2du to find it. N6LF has 
written a rather detailed version that's in the Antenna Book, but there are 
typos in the associated graphics that make it difficult to follow. 

The short answer is that the radial system functions as a return for the 
currents and the fields associated with the antenna. The lower the resistance 
of whatever conductors serve this function (including the earth), the closer 
the antenna comes to full theoretical efficiency. The radial system does NOT 
function as a reflector for the signal. The earth at significantly greater 
distance from the antenna serves that function. 

I have seen many references in the literature to the effect that NEC is not 
very good at modeling ground losses and the effect of radial systems. Count 
me among those who 1) consider real measurement of one radial system compared 
to a reference antenna as the only meaningful predictor; 2) consider soil 
conditions at any given location to be an influence on how many radials it 
takes to get there; and 3) consider Tom's advice, and the advice in the 
Antenna Book to be solid as a rock. 


Jim Brown K9YC

On Sat, 15 Mar 2008 14:23:26 -0400, Robert Carroll wrote:

>On the other hand if I were
>only trying to provide a low loss ground return, I might route the radials
>for convenience in avoid things like a garden, a pool, or some other object.
>Which view is the correct one?


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