wrote in message
oups.com...
I am trying to gain a better understanding of the issues associated
with lightning and grounding, particularly for an amateur radio
station. I would greatly appreciate any answers to my questions, given
below.

1.) It seems like lightning "finds" a path before actually discharging
through it. Is this correct? How fast is the process of finding the
path?

Logic says no. As a charge starts to build, it also starts to flow. If the
discharge path has high enough resistance, it wont flow until the charge
reaches a certain potential. That may be what you were trying to ask. Then
we are speaking of a dielectric. When the potential becomes large enough to
punch through the dielectric, then the discharge occurs.

2.) Does lightning discharge over one path or many paths? In other
words, if lightning strikes a point, and there are two paths from that
point to ground, is the energy shared - like a current divider? One
would think that this is what happens, with the sharing based upon
relative impedances to ground.

No need to make lightening too mysterious. It is electricity, and if there
are two solid paths of basically equal resistant, it will flow in both. It
is important to note that I did say basically EQUAL. Two paths may be equal
at low voltages, but at high voltages, in bends of wire, the lightening has
been known to burn off one path.

3.) This talk about "single point ground" can be confusing, especially
when the solution involves multiple ground rods. I believe we are
really saying that the station (equipment) should be connected to
ground at only one point - but you can have any number of ground
connections (i.e., like ground rods) otherwise.

I cant tell you much about this. Its safer for the equipment to have only
one ground connection as the surge caused by lightening can enter from any
of the grounds if its not a direct hit to the antenna itself.

4.) Does the size of an antenna affect the probability of its being
struck by lightning, all else being equal? What is the governing
relationship?

Again, logic dictates that a bigger antenna can be closer to a charged area
than a small one. That being said, it probably doesnt make much difference
unless youre running some very longwire type of antennas. A yagi or a quad
will probably not change the chance of getting a hit very much.

5.) Finally, consider an amateur antenna on a pole, located some
distance from the service entrance of the house. Let's say there is a
copper cold water pipe right at the service entrance. Is it wise to
place a lightning rod (or rods) right under the antenna, place an
arrestor on the coax there and then another arrestor where the coax
enters at the service entrance? Is a ground wire needed between the
remote ground rod and the cold water pipe?

Thanks in advance,

-JJ

Don't connect it to your water pipe. That's a good way to get a damaged
water pipe if you take a hit. Use grounding at the antenna support. You CAN
use arrestors, but the way our hardline at work is grounded, they just trim
off the outer jacket and connect a clamp for grounding, then cover it with
weatherproof putty. They are grounded at the base of the antenna tower, then
at the point of entry to the cellsite. Then there is a ring ground inside
the cellsite, and that ring ground is connected to a groundrod outside the
site at the opposite corner from where the antenna feedlines enter. Cant
explain how it works all that well, but we seldom have much lightening
damage to our equipment, and its directly connected all the time. We do use
surge protection to protect the power wiring to the equipment as well. There
are probably others on here that can give you more info than I can. There
are also standards that are set up by NEC that need to be followed as well,
if I'm not mistaken.
B