[TenTec] New and Improved Terminology

[Walt Amos]

Yogh, Steve:

So, what is improved by the old adage 120 radials are needed? The EFFICIENCY ? Certainly not the radiation angle by your graph!

Walt K8CV Royal Oak, MI.


----- Original Message ----- 
From: "Steve Hunt" <steve at karinya.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Friday, January 07, 2011 9:22 AM
Subject: Re: [TenTec] New and Improved Terminology


> Folk who have been following the discussion may be interested in this chart:
> 
> http://www.karinya.net/g3txq/temp/ground_zones_2.png
> 
> It shows how the optimum take-off angle of an 80m quarter-wave vertical 
> mounted over Sandy Soil varies as the radius of an excellent ground 
> screen (Salt water) is gradually extended outwards. It was produced by 
> using the capability of EZNEC to have two different radial ground media, 
> as I described earlier.
> 
> Please note that this is simply an exercise in determining how far from 
> the antenna, ground conditions affect the take-off angle; we're letting 
> EZNEC do the trig that we could otherwise easily do ourselves with some 
> simple maths.
> 
> Notice that as the ground screen grows from zero to about 100ft - the 
> range in which we might typically install a ground radial system - the 
> take-off angle barely changes. At the other extreme, above 500ft we are 
> beyond the Fresnel Zone in which reflections are taking place, and there 
> are no more improvements to be had. All the "action" takes place between 
> 100ft and 500ft.
> 
> Unfortunately, for many of us that's an area that might well be outside 
> our property boundary. Even if it is not, at that radius the areas are 
> so great that we would need to put down massive amounts of copper to 
> have any significant effect on the ground conductivity. Hence Rudy 
> Severn's comment: "Any practical ground system will not affect the 
> radiation angle or far-field pattern!"
> 
> 73,
> Steve G3TXQ
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