[Elecraft] OT: Ground rods and concrete

Ken G Kopp kengkopp at gmail.com
Tue Apr 18 19:39:24 EDT 2017


I was the first to use the term "exploding tower base" in this discussion.
The term "exploding" was probably not correct.  As several others have
phrased it, an instant expansion of steam is more correct.  Concrete is
never totally "dry" in the context of this conversation.

I witnessed lightening blowing apart the two tower bases I spoke of in
person, directly, and in real-time. It happened in the mid-sixties at the
St. Petersburg, FL Coast Guard base.  As someone else has mentioned;
the Tampa Bay region has the highest incidence of lightening in the
Western Hemisphere.  To the one of you who accused my of lying ...
I was there ... you weren't.

At the time I was an ET aboard the USC&GS (Now NOAA) Oceanographic
Survey ship Hydrographer/WTEI and we were in the area deliberately
attracting lightening with balloon-hoisted cables.  I -do- know something
about the infinite uncertainty of lightning.

I'm a retired electric power company two-way radio tech and have probably
dealt with more types of towers than most of you.  Large electric
transmission
line towers are almost always set on four concrete piers, and are grounded
with (usually) copper straps cad-welded to each tower leg and connected to
ground rods a bit away from the cement.  Each of us can search long enough
to find "facts" that support our various positons, especially on today's
Internet.

Here in the mountains of the West ... as well other regions ... finding and
maintaining a "good" ground at a radio site atop a mountain can be a
"challenge".  It's almost never done with ground rods.  My power company
employer has several hundred mountain-top microwave and/or radio sites.
Been there, done that, as they say.

One responder spoke of fitting a copper pipe with a garden hose fitting and
"flushing" it into the ground.  That works very well, and is how some of my
14 grounds are installed.  It helps if the downward end is partly
flattened, BTW.

A much bigger problem overall than lightening is water collecting in tower
legs,
especially in climates where it can rust (undetected) from the inside and /
or
freeze and split one or more legs.  There's an accepted way to avoid this.

73!

Ken Kopp - K0PP


On Apr 18, 2017 at 4:30 PM, <w5sum at comcast.net> wrote:

> some 40 years ago, maybe longer I put up a 50' rohn 25G tower. Dug the
> hole

    and set the tower base in it alone with a 12' 3/4" ground rod and
poured the
    cement, left about 6" of ground rod protruding. I bonded to that rod
and grounded
    the tower. 3 years later I had a huge lightning strike on my tower and
yes.. it cracked
    that base.

    never again

    Ronnie W5SUM

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