[TowerTalk] Fwd: Interesting Site

Mon Jun 26 08:52:13 EDT 2017

That is not a good assumption either… while the mathematical models may show that taller structures protect shorter ones, lightning is not known to have studied those models very well.  Lightning triggered cameras and high voltage power line lightning strike data shows that lower structures and wires, even wires that are predicted to be 100% shielded by higher wires do get hit.  And remember, it doesn’t take a direct hit to cause damage, a stroke to a higher tower can flash over sideways or the current in the ground system can inject current into the shorter structure causing damage to things connected to it.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net <http://wiki.k1ttt.net/> 
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373

From: Chuck Dietz [mailto:w5prchuck at gmail.com] 
Sent: Monday, June 26, 2017 12:20
To: David Robbins
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Fwd: Interesting Site

Well, I plan to build a 40' tower...  I don't expect it to get hit with or without the porcupine due to the three taller towers around it!

Chuck W5PR

:-)

On Mon, Jun 26, 2017 at 7:15 AM, David Robbins <k1ttt at verizon.net> wrote:

So, just how often does a tower get hit... lets look at some statistics and
physics.  A 40' tower guyed with steel wire may collect lightning strokes
from a 100' square area, more or less, but probably not much more.  This
accounts for some attraction, the rolling ball, ieee estimates of attraction
of strokes to tall structures, etc.  Now, how many strokes would you expect
in that area per year... from NLDN data there are about 25 lightning flashes
per square mile per year in central florida, the lightning capital of the
states.  Multiply, divide, invert, like 1/(((100*100)/(5280*5280))*25) gives
you something like 1 lightning strike every 100 years in that 100' square,
some rounding applied.  Now most of the rest of the country only has 5 to 10
flashes per square mile per year which makes that more like 1 strike every
250 to 500 years.  And lets see, most lightning causes little or no visible
damage if the tower is properly grounded... a small blackened crater may
show for a fresh one on a steel tower, maybe more obvious if it hits an
aluminum tower or antenna, but after a while they will look like a rust or
corrosion pock mark... so if you aren't watching you may not even know your
tower got hit, so factor in the percentage of time you are actually watching
your tower during thunder storms, and how likely does that make it that you
would see your tower get hit!

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Chuck
Dietz
Sent: Monday, June 26, 2017 11:48
To: David Gilbert
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Fwd: Interesting Site

Oh no, all u guys are wrong! I have had one of those on my 40 foot tower and
have never been struck by lightning...

Chuck W5PR

:-)

On Mon, Jun 26, 2017 at 1:35 AM, David Gilbert <xdavid at cis-broadband.com>
wrote:

>
> A good indication of the voodoo "science" involved in that link is the
> fact that he built it with 500 (!) points.  Ask yourself what 500
> sharp points would do that a few pointed different directions
> wouldn't.  In fact, pack enough points grouped close together and you
> make the static field effect approximate a smooth sphere.
>
> I'm always amazed that a hobby like ours, supposedly based in physics
> and the real world, perpetuates so much garbage like this ...
> especially when there are much more rigorous studies readily
> accessible out there on the internet to debunk it.
>
> Dave   AB7E
>
>
>
> On 6/25/2017 2:32 PM, Hans Hammarquist via TowerTalk wrote:
>
>> This topic has been discussed too may times and there seems to be
>> nobody with a definite answer. I have dissipators on my own tower.
>> They are rather easy to make. I haven't gotten any lightning strikes
>> in them during the few years the tower been up. That doesn't mean
>> they are effective. I have notice that I have had no strikes on my
>> house, something that happened on a relatively regular basis, since
>> the tower went up. I think the tower itself was the contributing factor
to that, though.
>>
>> I had a 0-0, stranded aluminum cable at hand when I raised the tower
>> and decided to put three, one on each leg, of them up. You can  view
>> they on my facebook page. Does it work? Honestly, I have no idea. I
>> do think that you can build these dissipators yourself for a much
>> lower price than what they are offered at.
>>
>> With 73 de,
>>
>> Hans - N2JFS/SM6BXX
>>
>>
>> -----Original Message-----
>> From: Don W7WLL <w7wll at arrl.net>
>> To: Towertalk <towertalk at contesting.com>
>> Sent: Sat, Jun 24, 2017 11:25 pm
>> Subject: [TowerTalk] Interesting Site
>>
>>
>> Ran across this looking for something else and noticed a section on
>> towers, grounding and other items we are all interested in. Sample
article.
>>
>> http://www.thebdr.net/articles/steel/twrs/TT-dissipators.pdf
>>
>> Don W7WLL
>> _______________________________________________
>>
>>
>>
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>
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