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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