Tom wrote: "99% of this is how you route cables and how you wire =
things.73, Tom W8JI"
Don't be bashful Tom, tell us how in detail please. With all this talk =
about SPG's, etc., it is still hard to visualize. I do have the 'Grounds =
for lightning' and have looked at all of the web pages, but it is still =
difficult to determine what is right.
I have a 5 foot 1" by 1/4" copper bus bar running on the wall on =
stand-offs behind my equipment and the equipment grounded to it (in =
different places along its length) with webbed straps and it connected =
to my outside ground system with about 7 feet of 3/0 copper wire, but, =
no bulkhead panel.
My cables come to the house from the tower at an eight foot height, =
which is frowned upon, but it clears everything.=20
Also, if you disconnect everything, as Pete said, what do you plug the =
inside cables into when disconnected? Grounded females on the bulkhead??
Any explanations will be much appreciated. Thank you.
73, Carl VE9OV
----- Original Message -----=20
From: Tom Rauch=20
To: firstname.lastname@example.org ; Pete Smith=20
Sent: Monday, July 29, 2002 9:08 AM
Subject: Re: [Towertalk] grounding system
> At 05:03 PM 7/28/02 -0400, Glenn Little wrote:
> >Acording to some data that I got from a surge suppressor company
> >concerning lightning induced voltages, a lightning strike one Km =
> >will induce 200 volts per meter of wire. The second floor of you
> >house appears to be about 10 feet or about 3 meters above actual
> >ground. That three meter ground wire could have 600 volts on it =
> >a strike one Km away. If the strike is 100 meters away, the figure
> >goes to 1KV per meter of wire.
> These numbers seem a bit extreme, or at least a bit categorical. =
> many times have you seen a lightning bolt and counted less than 3
> before the thunder came. Did it fry your phone? Your modem? Your
Part of the problem with taking things literally is people who market=20
things always try do the best job they can in pitching the need for=20
their devices. What we read, even though traceable to facts, are=20
often the extreme.
The induced voltage would be influenced by many things including what=20
is around the conductor, the impedances loading the conductor, the=20
density and angle of the strick, the position of the conductor, and=20
For example the guy lines on my 300 foot tower will often "pop"=20
across the insulators with distant flashes, yet I can have a receiver=20
on and running and connected to that tower without ANY lightning=20
protection and nothing is hurt.
There is a lot of available potential across an open circuit with a=20
conductor high and in the clear, but not much current available to=20
drive any load. Voltage decreases dramatically even with extremely=20
high values of load resistance.
99% of all of this is how you route the wires into the house and how=20
the connections are all made.=20
> I suspect these numbers could represent worst case, but there are =
> many variables (orientation of wire, neight above ground, etc.) for =
> to believe that one voltage fits all.
If that were true, I'd be in deep "poo" here. I have 4 or 5 miles of=20
antenna wire spread over a half-mile square area, and 100-300 foot=20
tall antennas. I leave everything connected all the time, and don't=20
have a single lightning arrestor in any feedline or control cable. I=20
live next to the worse area in the USA for lightning, we have=20
afternoon thunderstorms like clockwork during the summer.
99% of this is how you route cables and how you wire things.73, Tom=20
Self Supporting Towers, Wireless Weather Stations, see web site: =
Call 888-333-9041 to place your order, mention you saw this ad and =
take an additional 5 percent off
any weather station price.
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