Chemically enhanced grounds are good for power line safety grounding, but
are of questionable use at rf and hence lightning related frequencies. The
problem is that the added conductivity is in a rather small area around the
rod and is due to ions that move relatively slowly. The key for dissipating
lighting is to spread it out to as much surrounding area as possible, 6-8
radials up to about 50' long buried no more than about 3' down are as good
as anything else, adding rods along their length doesn't hurt but probably
won't help that much either.
The biggest part of lightning protection for buildings and equipment is the
'single point ground'. while it may seem contradictory, a good perimeter
ground is also a valid method. The key is to make sure that all conductors
inside the protected structure are at the same potential. To do this takes
basically 2 steps. First provide a good common ground for all the equipment
cases, power grounds, and antenna/coax grounds... think low inductance, and
make sure that EVERYTHING is connected to it. The other step is to equalize
the non-grounded conductor voltages with the ground system. This is where
the arresters come in, get a whole house mov power entrance system,
arresters on the entrance for cable tv, phones, and all antenna/rotor/switch
control lines.
While none of this will stop lightning from hitting your station, if
everything is properly connected and equalized there will be no place for
the lightning currents to get in and damage equipment.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of Peter Grillo
> Sent: Saturday, March 19, 2005 17:26
> To: 'Jim Lux'; 'Tom Rauch'; jimjarvis@ieee.org; towertalk@contesting.com
> Cc: marketng@lightningeliminators.com
> Subject: [TowerTalk] porcupines and chemical ground
>
> Now that this thread has shot enough holes in spline balls made by
> www.ligtningeliminators.com , or so called porcupines, what can you all
> recommend for my situation on top of Buckhorn mountain, elevation 8350
> feet
> overlooking the front range of Colorado near Ft. Collins? My property has
> been hit three times in the past 5 years. None of these hits have been on
> a
> tower. One hit a power pole near the road. The latest hit (8/23/04)
> wiped
> out all my plugged in equipment. The strike hit the metal roof of my
> house
> (not grounded) and found a path to the neutral circuit. 7 breakers
> popped.
> Replacement cost for the damaged equipment was around $13,000 of which my
> insurance paid 80%.
>
> I am putting up a 120' Rohn 45 tower (obtained from K4XS) later in the
> spring and I want to do it right. I've dug the holes. The ground is
> mostly
> broken down granite. There is lots of pine tree growth in the area with
> very
> loose earth. All trees within 20 feet of the guy cables will have been
> cleared. The base of the tower sits in a nice bowl surrounded by two
> large
> boulders. It is located about 250' from the house, about 60' higher in
> elevation. I'm thinking of installing a Chem-rod grounding optimization
> system made by the same company listed above that makes spline balls. Is
> there any value in this? I know many of you will tell me that it all
> depends
> on the surrounding terrain. That I know, but I'm looking at attempting to
> improve the ground so as to direct the hits to the tower and not the
> house.
>
>
> My first thought is to run a solid copper cable from the tower down to the
> power pole ground stake (about 80 feet from the base of the tower). Then,
> I
> would stake ground rods along the length of this run about 8-10 feet apart
> depending on interference from surrounding boulders.
>
> Experienced help in this area is appreciated.
>
> Thanks,
> Pete
> W0RTT
>
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim Lux
> Sent: Saturday, March 19, 2005 7:48 AM
> To: Tom Rauch; jimjarvis@ieee.org; towertalk@contesting.com
> Subject: Re: [TowerTalk] Porcupines on commercial towers and stuff
>
>
> ----- Original Message -----
> From: "Tom Rauch" <w8ji@contesting.com>
> To: <jimjarvis@ieee.org>; <towertalk@contesting.com>
> Sent: Saturday, March 19, 2005 4:09 AM
> Subject: Re: [TowerTalk] Porcupines on commercial towers and stuff
>
>
> > > I observed that I'd counted 138 antennas on top, when I
> > > was last there. That's without porcupines. They were
> > > un-moved.
> > >
> > > My assumption would be that the porcupines pre-date the
> > > knowledge that they do no good.
> >
> > The fact government or private installations buy things and
> > install them doesn't mean they work as claimed. Governments
> > are also slow to learn anything.
>
> I concur with Tom,here.
>
> It's not necessarily that the govt is slow to learn. Here are two examples
> where there's a perfectly good reason to buy something that turns out
> useless.
>
> 1) The govt may buy the item for the purposes of testing or evaluating the
> claims. This is certainly true in the case of the lightning static
> dissipators. They bought them, installed them, did the tests, decided they
> didn't work, wrote the report and that was the end of it. They may or may
> not spend the money to uninstall them (if they do no harm, why bother).
> Of
> course the mfr of the device can now legitimately claim (as they do) "as
> purchased by NASA and the FAA" or even "tested by NASA", while leaving out
> the important extra words "...and found worthless". If you read the
> literature of the companies selling these things, they are VERY careful to
> not make claims that they have been tested to work. They describe a theory
> of operation, and cite lots of customer names, and even some anecdotal
> stories of apparent success.
>
> 2) The govt spends a fair amount of money on developing things that don't
> turn out in the end; called R&D. Perhaps someone has a bright idea, and
> has
> a promising almost-working prototype, but it's not clear whether it is
> feasible in a production environment. The govt may order up a bunch of
> these widgets, just because if it does work, it's going to be useful, and
> the overall cost is low, and there's no other way to find out, other than
> by
> making them and using them. DARPA describes this as "high risk, high
> reward". The SBIR program is similar..start with a 10 page concept, .
> invest 50-100K in some research and a paper report to take the idea a ways
> and figure out whether it's likely to work and how to test it, then invest
> 500K-1M in a Phase II to do some tests, then hopefully the small company
> goes into production in Phase III.
>
> There's a lot of things being done these days in the defense department
> and
> in homeland security that fit in the "it might work, and if it does,
> there's
> high payoff, so let's throw a few million at it". The problem of
> improvised
> explosive devices (IEDs) is prompting a lot of this... it's a very hard
> problem, it is very hard on morale, in the context of 100 billion dollars
> already sunk, investing a few tens of million in a bunch of really
> speculative ideas, one of which might work, might not be a bad strategy.
> (although some of the techniques I've seen proposed are pretty darn
> unrealistic, but hard to "prove" can't work, short of trying and failing..
> this is particularly true for the "demonstrated in the lab at 1 meter,
> we're
> going to ruggedize it and make it work in the field at 100 meters" kind of
> proposal.)
>
> And, of course, there's the plain old sucker problem. People buying
> things
> for government and business aren't always experts in what they're buying,
> and it might cost more or take unavailable resources to find out. There
> isn't infinite time and labor force available when planning a project. In
> the case of static dissipators, it might take a while, since there's no
> easy
> way to tell they don't work. If the light poles were properly installed,
> then the lightning strike won't do any harm, even if it does hit.
>
> _______________________________________________
>
> 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.
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