[TowerTalk] Re: Ground radials

[Didier Juges <didier@cox.net>]

It's true that capacitance will help bridge the gap, and the higher the 
frequency, the more effect from capacitance. At higher frequencies, most 
models I saw for soil make capacitance (rather the dielectric constant) the 
dominant factor.
Of course the type of insulation would also make a big difference, with 
enamel insulated wire (think magnet wire) probably much better than plastic 
insulated wire.

It seems like it's time to go through some numbers and compare resistive 
versus capacitive impedance of the wire to the surrounding soil.

There are not complex maths (at least to get a first order approximation), 
and all that's needed is some typical resistivity and dielectric constant 
data for common soil.

On the other hand, I believe we agree that the only question is how  much 
better a non-insulated wire would be. As long as corrosion does not get 
into the picture, non-insulated wire will always be better than insulated 
wire. Bare copper wire would be my choice (will be when I get around to 
wiring my 50' tower as a 160m vertical)

73,
Didier KO4BB

At 02:11 PM 12/24/2003, Jim Lux wrote:
> But, what's the capacitance between the soil and the wire, through the
> insulation.  If it's enameled wire, the capacitance will be quite large, and
> the impedance quite low. You've got lots of surface area, too...
>
> The soil impedance will probably dominate over the interface
> resistance/impedance. (probably is the operative word here... I'm too lazy
> to run the calculation just now..)


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