> Now we need to layout a bunch of radials. Has there been
any discussion on
> using electric fence wire vs. copper wire?
Depending on soil and any direct current flowing in the
ground radials, you can eat up aluminum or galvanized or cad
plated steel wire pretty fast.
I'd stay with copper. Bare or insulated, it makes little
difference. I'd avoid stranded wire for life concerns.
> Does the gauge of the wire have
> any impact on the installation?
As long as it's big enough to not break it is OK. I use #16
tinned bare buss wire. Never had a problem.
>Finally just how long should the radials be?
> I have seen 5 percent longer than 1/4 wave.
With a buried wire, there really aren't any resonant effects
Mike. The general rule I follow is I make the wires as long
as I reasonably can and I keep the open ends about .025 wl
apart.
My 200 ft 160 vertical has 100 radials about 200 ft or
longer in most directions. I'm sure that's overkill. My
130ft verticals have about 50 radials about 100 ft long.
You can spend your life over-analyzing radials, but the
bottom line is I've never seen a system with about 50
radials a few tenths of a wavelength long be any less than
in the upper 90% efficiency range and I doubt anyone else
has either. On the other hand I've seen several systems with
four or six elevated radials that were 2.5-6 dB down from
the same antenna with 50 or more radials.
I'm also more than a little reluctant to base decisions on
models of radials, because models are without a doubt the
least accurate when dealing with wires near or buried in the
soil. I go by the "safe rather than sorry" philosophy, and
don't waste a lot of time planning how to save .5 dB based
on a model when the model itself might be off 5 dB.
73 Tom
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