Years ago I heard W0UN's presentation at Dayton where he claimed that when
a thunderstorm would move over his multi-tower setup in Colorado that the
lightning would actually stop until the storm front would move beyond the
antenna farm. The towers were heavily grounded as I recall, but I don't
remember what else he did for lightning protection. I don't think he left
much undone on that front. This would support the theory of lightning rods
to prevent lightning strikes. And that is what I learned years ago in a
college meteorology class.
At 10:50 AM 6/1/03, Joe Giacobello wrote:
>You guys have raised an issue that I have wondered about for some time
>now. I also live out in the country and have noticed that the number of
>houses and other structures with lightning rods seems to have diminished
>over the years. Why has the use of lightning rods fallen out of favor?
>
>It was always my belief that the purpose of the rods was to slowly and
>continuously bleed off electrical charge in the air so that the likelihood
>of generating a voltage in excess of the the breakdown voltage for air in
>the vicinity of the structure was minimized. The ultimate objective was
>to prevent a sudden, instantaneous, potentially destructive, high current
>discharge through the structure itself. When I proposed on the Antennas
>mailing list that this mechanism most likely also applied to a properly
>grounded tower near one's house, my description was corrected by one of
>the readers. Apparently, the effectiveness of the rod or tower depends on
>the formation of a cloud of charge in the air surrounding the tip. In
>windy conditions, the cloud becomes unstable and must continually
>reform. (Although I'm not sure that it makes any practical difference, I
>was also informed that the flow of charge was from the ground through the
>rod into the cloud.) Is it because windy conditions reduce the
>effectiveness of lightning rods that they are less used today? I'd be
>interested in hearing some comments on this question.
>
>I should also add that I have a pointed multiwire attachment strapped to
>the top of my tower which (allegedly) provides multiple paths for
>discharge and reduces the voltage necessary for (slow) discharge to
>occur. (It can be purchased from the Wireman, and Pres swears that it
>works.) I also have a pretty good ground system with about eight ground
>rods connected in a large circle that includes the house ground. I have
>observed major lightning strikes on a ridge about the same height as mine
>and about 3/4 of a mile away, but I have never been hit. Have I been lucky
>or is the system really working?
>
>
>73, Joe
>
>Pete Smith wrote:
>
>>At 06:45 PM 5/31/03 -0700, Michael Tope wrote:
>>
>>>Actually it brings up a good question for the lightning technology experts
>>>on Towertalk. How come you only see lightning rods on barns and not
>>>houses? Is that just because most barns are old, and people have stopped
>>>using lightning rods, or is the their some other reason?
>>
>>
>>
>>My house -- a farmhouse -- came with an array of 6 lightning rods,
>>complete with woven aluminum down-conductors. Lightning rods are fairly
>>common on houses out here. I am very unclear on whether they offer any
>>protection at all, because the ground conductors seem to violate the
>>low-inductance requirement that we hear from Polyphaser.
>>It's not clear to me why lightning would "prefer" the rods to other
>>ground conductors that might be available in the neighborhood, or on
>>nearby power poles.
>>
>>
>>73, Pete N4ZR
>>The World HF Contest Station Database was updated 9 May 03.
>>Are you current? www.pvrc.org/wcsd/wcsdsearch.htm
>>
>>
>>
>>_______________________________________________
>>
>>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
>>any questions and ask for Sherman, W2FLA.
>>
>>_______________________________________________
>>TowerTalk mailing list
>>TowerTalk@contesting.com
>>http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
>any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
Jim Rhodes K0XU
jim@rhodesend.net
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