Topband: 160 meter radials

[Tom Rauch]

Hi Paul,

> I got to thinking about this and have a question about it--
> 
>  My 160 meter Inv L has 90 raidals on it- about two miles of wire....if I
>  add 
> it to my 80 meter 4 square radial system, that will give it another 3
> miles of radials,  but how is this good??  

Radial do two jobs. One is they give the feedline something to 
"push" against to force current up in the antenna. The other is they 
distribute the strong fields and effectively "shield" the antenna from 
lossy earth.

The "push" thing is easy. Even a few elevated radials solve that 
problem.

The second problem is complex and only solved by a lot of wire 
covering a large area so fields are distributed evenly below the 
radial system. This effect does not require the wires be tied back to 
the feedpoint in any way for the wires to "improve things", nor is 
symmetry an issue.

It does require the radials NOT be resonant in order to minimize 
loss.

ON4UN's book covers this in a similar way by giving an example 
where a small elevated system has greatly improved performance 
by adding a conventional system below it, even though they are not 
connected.

If your ground system is large enough to have a stable and low 
terminal impedance, tying in the other system will make no 
significant difference at all.... although just HAVING it there will 
reduce losses. The biggest advantage in bonding through a wide 
strap, in systems that are large enough to provide a low terminal 
impedance, is for low frequency resistance or lightning protection.

 
73, Tom W8JI
w8ji@contesting.com



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