Sorry, sent a blank one somehow by accident...
I would suggest Tom's statistical conclusion that these don't prevent
strikes is backed up by the physics of a lightning strike.
The two poles, as it were, or the anode and cathode, are not the tower and
the cloud nor the tower and ground. It is the ground and the cloud. Your
tower is merely part of the path.
Dissipating static off the tower might serve a purpose in preventing
naturally occuring static (from wind, etc.) from damaging components, I
don't know. It's certainly why airplanes trail little conductive ropes
behind their wings. But I have great difficulty believing these things will
dissipate the charge that's in the Earth, and if it did dissipate it, where
would it go?
This is as fallacious, IMHO, as the wrist-strap argument from a few weeks
ago: if you could connect the wrist strap to the cloud and to ground, it
would probably serve a useful purpose, but grounding the tower itself isn't
going to do anything but provide the path of least resistance to Earth. In
lightning protection, that's a good thing, but it doesn't lessen the
likelihood of a strike any more than strapping a 2-iron to the top of the
tower. (God may not be able to hit a 2-iron, but lightning surely could.)
73, kelly
ve4xt
----- Original Message -----
From: "Grillo's" <ah3c@frii.com>
To: "Towertalk Reflector" <towertalk@contesting.com>
Cc: "CQ Contest" <cq-contest@contesting.com>
Sent: Tuesday, July 27, 2004 7:46 PM
Subject: [TowerTalk] spider balls
> Since we are on the subject of lightning, has anyone ever used "spider
> balls" to dissipate energy thereby eliminating strikes on the structure?
> These are a steel rod with over 200 fine spiked elements about 2 ft. long
> each that create a cluster of very sharp spikes.
>
> Can you visualize this? I have three spider balls and am considering
> installing one each about 40 feet up from the guy anchors on the steel
guys
> that would be connected to the anchor rods. The balance of the guy lines
up
> to the top of the 120' tower are polyphaser cable, so are insulated. I
> would install three copper ground grids at each guy point and link them
> together with underground copper cable.
>
> The other thought is to mount them on top of the 120' tower and put one
> ground grid under the tower.
>
> I'm looking for alternatives before the concrete gets poured in 2
weeks....
>
> Pete
> W0RTT
>
>
> ----- Original Message -----
> From: "Tom Rauch" <w8ji@contesting.com>
> To: <keith@dutson.net>; "'TowerTalk'" <towertalk@contesting.com>
> Sent: Tuesday, July 27, 2004 2:18 PM
> Subject: Re: [TowerTalk] Lightning Strike - Epilogue
>
>
> > > Analysis of the damage has revealed that the lines running
> > from main house
> > > to shack need to be grounded. But I have decided on a
> > better solution. The
> > > telephone line will be replaced with a new connection that
> > will enter the
> > > shack in a different location that is far from the power
> > entrance. The LAN
> > > connection will be wireless. The TV connection will be
> > removed and a new
> > > dish will be installed for the shack.
> >
> > Keith, I think you are making a mistake. You should bring
> > all lines in at the same point, and bypass and ground them
> > at that point.
> >
> > Moving a telephone line to the opposite end of the building
> > is asking for trouble.
> >
> > Adding a separate small dish is OK, as long as it too enters
> > near the power line and all share a common ground.
> >
> > > BTW, the bolt apparently hit the power lines in front of
> > the house, after
> > > the transformer. The lines enter a weatherhead on another
> > pole and run
> > > through underground conduit to the main breaker panel.
> > The 200 amp main
> > > breaker did not get tripped.
> >
> > Maybe it there, but most likely not. The problems occured
> > because current passed through your equipment on the way to
> > different "grounds". From the extent of the damage when
> > considering the nearly total lack of protection, it doesn't
> > sound at all like a direct hit on your service entrance.
> >
> > Lightning might hit your tower and a large portion of the
> > strike current will flow from the power line, since it is
> > such a massive ground. It may hit a power line, and current
> > flow from your tower ground through your equipment. It may
> > have hit tree down the street, or a mile away.
> >
> > The wireless LAN is good because it totally eliminates a
> > path. The TV feed change at best won't help very much, and
> > if you install a dish away from the power line entrance it
> > can make the problem much worse than simply having a
> > properly installed cable follow the power line to the shack.
> > Moving the telco line away from the power line entrance will
> > certainly make things much worse.
> >
> > The last thing we ever want to do is to isolate devices, and
> > intentionally create multiple grounds and entrance points
> > into a structure or equipment cluster. It is the worse
> > possible thing to do. This is why everyone universally
> > recommends common point grounds and single point entrances.
> > It's why telco and CATV lines enter near the utility
> > entrance and share the same ground.
> >
> > You might consider looking at commercial installations and
> > rethinking your plans. The next hit could be a disaster.
> >
> > 73 Tom
> >
> >
> > _______________________________________________
> >
> > 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
_______________________________________________
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
|