Owen Duffy wrote:

Bill, I often see the assertion that it is better to not bury radials.

Can you point me to any reputable texts or experimental evidence that
shows the difference between shallow buried radials and radials lying
"on top of the ground"?

Corrosion is often cited as a reason to use insulated buried radials,
but is corrosion a significant risk in most locations. We widely use
buried copper water pipes here, and copper clad earthing electrodes
for the MEN power supply earthing, yet they don't seem to suffer
significant corrosion in most places.

It seems to me that insulated buried radials are likely to be less
effective in a lightning protection role.

Owen

You're asking some good questions.

Many years ago, I was doing some ground system experiments with a
vertical antenna. I had strung a bunch of radials, consisting of small
insulated hookup wire, on the surface of the ground and I was measuring
antenna input impedance. I was surprised to discover distinct resonance
effects as the radial lengths were changed, something which I hadn't
expected -- they were acting more like elevated than buried radials. It
was summertime and the clay ground was pretty dry.

Then I took some pieces of mild steel wire and "stapled" the wires down
to conform with the ground and bring the wires into close contact with
it. The resonant effects disappeared and the radials acted more like
buried ones. I concluded that even a very small air gap between the
radials and the ground provided some independence from the ground.

More recently I've done some modeling to try and understand the
phenomenon a bit better. I'll give those results in my response to
another of your recent postings.

Oh, as for corrosion -- I'm sure it depends on the soil. But there's no
harm in using insulated wire, as far as RF ground effectiveness goes. I
suppose it would limit the lighning protection voltage to the insulation
voltage, however.

Roy Lewallen, W7EL