On Sun, 13 Jun 2004 13:57:17 -0000, Larry W4CSC
wrote:

Gary Schafer wrote in
:


Larry, I really don't believe you are that dumb to hold on to a tower
in the middle of a lightning storm. I do see that you are a great
story teller though. However please remember that there are a lot of
folks that read this group that may not be too technically savvy and
may not be able to tell the difference.

Regards
Gary


Not dumb at all. Under my feet were 36 pile-driven ground rods connected
with bridge cables to the tower in a ring about 100' in diameter, "driven
to refusal", in other words, bed rock.

The several megohms of body resistance is no path at all when in parallel
with a few MICROOHMS to such a ground system. With currents high enough to
heat the tower beyond what my hand could tolerate, there is no shock, at
all.

It was a most amazing afternoon.....(c;

Larry


With the high current traveling through the tower and the relatively
high impedance that the tower and ground leads present, it is possible
to have thousands of volts differential in only a few feet length. The
larger the tower the less impedance of course. But the ground system
is never 100% and it has it's own impedance problems.

All conductors have impedance and a high current applied to that
impedance will produce a large voltage drop across it. Even the tower
itself.

Ground rods driven past 8 to 10 feet do little good for lightning.
Even if they are into the water table past that depth. The impedance
of that long of a rod gets to high to be of much value. (I know, lots
of people have long deep rods or pipes in their installations and
think they have the best ground in the world)

If you really want to know why go look at the polyphaser site. They
even tell you how to calculate what the voltage drop in a few feet of
tower length will be with a typical lightning strike.

You are right about the tower providing a "cone of protection" but
that cone only means that the lightning will probably strike the tower
before it strikes you directly. It does not tell you anything about
how effective the tower / ground system is at getting the lightning
current dissipated safely to ground.

Don't be grabbing on to those towers during a storm Larry. We will
miss you here.

Regards
Gary