[TowerTalk] COUNTERPOISE for Dipoles

[Tom Rauch]

> I have often wondered about what would be the optimum counterpoise
> (most improvement for least wire) for dipoles.  I'm thinking of several
> wires parallel to the dipole laid on the ground under the dipole. Where is
> the point of diminishing returns for number and spacing of wires? Would
> parallel wires be more efficinet than a radial system centered under the
> center of the dipole?  How long should the wires be for 80M? Is a
> counterpoise worthwhile for dipoles at 1/2 WL high or higher?
> 
> Tom  N4KG

I first learned of this trick back in 1962 or so, when I saw the 
installation at W8PSX on 160 meters. He had by far the strongest 
160 meter signal of anyone from his are, but ran no more power. 
He had a large counterpoise of parallel wires below his 160 meter 
dipole.

When I did the same thing, people saw a definite improvement.

It amazes me people use horizontal full-wave loops near ground in 
an effort to get NVIS gain, when the difference to a dipole is almost 
zero dB...yet ignore ground losses (which if removed can add a few 
dB to the signal).

This enhancement occurs most profoundly with antennas mounted 
near earth, but also occurs in diminishing amounts as height 
increases to large fractions of a wavelength.

I've never seen real world measurements of the change, but I can 
readily see the change in A-B tests of dipoles 1/4 wl high at any 
distance..not just in close.


 
73, Tom W8JI
w8ji@contesting.com

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