Topband: RE; Ground screen Question

[k3ky at radioprism.com]

No confusion at all, Jim. I know the difference between the two.
His reinforcing steel inside his driveway is probably way far
out of the realm of Ufer grounds, due to it being small gage
conductors. Aside from the great difficulty of boring into the
concrete and adequately bonding to those wires, I wouldn't try
this anyway out of concern that the current density during a
major lightning hit might be sufficient to produce widespread
cracking of the concrete.

Now I'll have to go re-read and brush up on Ufer grounds, but
as I remember, his driveway setup would be woefully inadequate
for the possible current levels involved in the event of a direct
lightning strike. Personally, I wouldn't go there. A concrete
drive would be a little pricey to replace, especially considering
the relatively small prospective gain in HF ground quality he
might see by connecting his radial field to it. I'd much rather
connect *over* that drive using strategically sawed grooves
and lightly concreting in a few wires at the surface in a few
places- this assuming he has somewhere to go on the far side of
the drive with those wires anyway.

I know a ham who thought his well pipe might make a dandy
addition to his ground radial system. He connected it, and
eventually had to replace a 600 dollar well pump after a strong
lightning hit on his property. This driveway question reminds me
of that. Properly designed Ufer grounds, fine- but I sure don't
want to invite lightning hits to dissipate through anything
concrete on my property. My two cents (two dollars, adjusted
for inflation...)

David K3KY



There is considerable confusion here with respect to radial systems for
antennas and an earth connection for lightning protection. They are VERY
different, and both are important. Properly bonded conductors buried in
concrete ARE acceptable as a ground for lightning protection -- it's
called a Ufer ground, after Herbert Ufer who developed the concept, and
it's now recognized in the National Electric Code. A Ufer ground works
because 1) concrete is conductive and 2) there is a large surface area
in contact with the earth. The downside is that the earth it makes
contact with is near the surface.

Like ALL earth electrodes, it must be bonded to all other grounds in
your home -- power system, Telco, CATV, your shack, and all driven rods.

I think Bob is on a pretty good track with his design.

For more ideas, see http://k9yc.com/160MPacificon.pdf

73, Jim K9YC