[TowerTalk] Re: Concrete an insulator???

[Bill Hider, N3RR]

Ed,

Did you measure it with a device that generates 50,000 KV @ 30,000 Amps?

Com'on.  No one said concrete's a conductor at 12 V.

Concrete is a very good conductor (not as good as copper) to lightning and
static electricity. That's what we're talking about.  Don't you read the
literature about not being on a concrete floor and touching your equipment
during a lightning storm?  It's the lightning, not the DC voltage.

AND I never said to use this property of concrete as the sole means of
grounding a tower (as someone, not you Ed, said).  All I said when I
started this thread was you shouldn't insulate your tower base that is
embedded in the concrete because you will loose whatever conduction you
had through the concrete.  I, in fact, welded the joints between the legs,
horizontals, diagonals (which were bolted previously) together for that
part of the tower encased in the concrete.  That will help ensure equal
currents in each leg in the event of lightning.  It will also eliminate
any resistance in the joints.  50,000 Amps can cause a lot of voltage
across a little resistance inside the concrete.

wheeeww again.

Bill, N3RR

Edward W. Sleight wrote:

> OK guys, I happen to be in a very unique position. The base was poured
> for my new 89 footer yesterday. It's 5.5 x 6 x 7.5 feet. This evening,
> I measured the resistance between one of the ground rods (4) and the
> center of the base. At that time, the concrete was 36 hours old. The
> resistance was 1.47 Meg Ohms.
>
> I believe keeping the exposed section as wet as possible strengthens
> the concrete, so earlier today, I flooded the top with 2" of water.
>
> I'll flood it again tomorrow and repeat the test ( before and after )
> At that resistance, it won't even blow a .1 amp fuse.
>
> 73
>
> Ed
>
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