Topband: RE; Ground screen Question

[Tom W8JI]

> 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.

If it was the sole ground, or the major part of a ground that might have to 
handle a direct hit, I wouldn't use it.

If it were simply something to augment an already good lighting ground or 
improve an RF buried ground system, I would not worry one bit about using 
it.

> 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.

Again, it is only a problem if that is the major part of the ground. If it 
is incidental and only an additional improvement, and the rests of the 
system was OK without it, I'd use it.

I've tied my heating ducts and water pipes in, in the past.  It does take 
some common sense in whether it is worth the work, and knowing if the rest 
of the system is large enough that it creates no hazard.

> 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...)

That is just asking for problems. Many well pipes are only metal at the 
head. Below the head or cap, they are often plastic. Well casings are almost 
always plastic today. The only guaranteed metal paths are the wires to the 
pump, even if it starts as metal at the top. Also, the wires are outside any 
metal pipes if metal pipes do exist, and lighting travels on the outermost 
surfaces. That would be the wires.

The well is nothing like concrete remesh. I would not bother connecting to a 
unknown rebar system, but if I knew it was bonded or remesh (screen) I sure 
would use it. Not as a primary ground, but to augment an existing pretty 
good ground in a direction the existing ground might not go.

I remember a few people who had houses in the way of a full system, and they 
ran the radials right under the floor joists. They used heating ducts, 
fences, water pipes, and everything else they could. The more they used, the 
stronger they got.

73 Tom