Hi JC,
> Roger,
>
> Five direct hits already this year? That's amazing! I've had exactly
> zero
That's just this year. The system was basically finished late in 2001. The
last climb was in temperatures of well below freezing and it was windy. It
was so cold the electrical tape wouldn't stick to itself.
I was up there for between two and three hours.
So the tower has been up for 2002, 3, 4, 5, and this year. The previous
years it has averaged about 3 hits a year so that's a minimum of 17 times
the tower has been hit.
> hits since 1961. Don't you get damage? Can you tell the point the strike
http://www.rogerhalstead.com/ham_files/Tower29.htm shows the entire antenna
system atop the tower.
Early on I had some damage, but I think it was more due to the ground
system, or rather lack of a single point ground. I lost this computer which
I had just finished building (in a different incarnation than present) and a
couple of Polyphasors. Since then, with the exception of two Polyphasors
(always for the 440 array), and one N-type barrell connector to the SW 75
meter sloper, I've lost a couple of remote preamps for the TV antennas. The
Polyphasors and N-connector would have been lightning, but I'm not so sure
the preamps didn't die from RF exposure.
With the price of copper I hesitate to say my ground system now consists of
33, 8' ground rods Cadwelded (TM) to over 600 feet of bare #2 which also
ties into the house system.
I've been running this machine while transfering large files across a Cat5e
gigabit network to the storage computer in the shop when the tower took a
hit. The lights went out, the UPSs squealed in protest, the lights came back
on and the file transfer resumed almost as if nothing had happened. (The
switch was not on a UPS)
The 135 feet of Cat5e runs within 10 feet of the base of the tower. There
are 4 late model, high capacity computers tied together through a switch and
router. Total storage is now over 5 Terabytes, but a good portion of that
is on external drives that don't run all the time.
BTW, I use CORDLESS keyboards and mice. <:-))
The "Old tower" which was up prior to the current one took one hit that
literally blew the tape and seal off all the connectors at the top of the
tower. At that time I used all 9913. Within 15 minutes I had water running
out of one rig. BTW, it not only removed all the tape and seal, it removed
all the plating as well, blew out the 7/8" Heliax about 20 feet down from
the top and shortened the repeater antenna by about a foot or so. The
fiberglass sheath at the end of that big vertical looked like an exploded
cigar. I lost the front end out of a Kenwood 221 and as I recall that was
connected to one of the antennas on the old tower.
> hits? My SD friend, K0TY, has no trouble. I was there when one hit a few
> years ago and it literally blew apart the antenna, apparently vaporizing
> part of it (or blowing it so far away we couldn't find it). However, I
When doing the occasional antenna maintenance I've noticed exposed
connectors look like they'be been exposed to a lot of corona. Either that or
a strong acid rain. <:-)) The Aluminum looks good except for that white
platina of age and there are a few small burn marks at various locations. So
far, nothing serious.
I am amazed at the number of hits the thing takes. OTOH I should put up a
photo of what the system looks like from a distance. From the town hall
about a half mile east you see the trees and then the antennas sticking way
up above them all by them selves.
> don't think any of his electronics were ever damaged, or the tower or
> coax,
> just the antennas where the strikes hit and "damage" is not an adequate
> word
> to describe what happened to them.
>
> I do recall hearing static discharging during storms when I lived in South
> Dakota. I think the device was called a Blitz Bug Lightning Arrestor or
I used to have a number of those. They are just a spark gap with two or
three extending toward the center conductor.
> something like that. It would occasionally make a loud buzzing noise,
> which
> I always assumed was static discharging from my antennas to ground. This
> was many years ago, mind you, and some things from those days are getting
> a
> little fuzzy, but that's the way I remember it. Still, never had a direct
A *lot* of things form those days are fuzzy except for my hairline which has
gone down the back of my neck.
73
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
> strike as far as I know.
>
> 73 - JC, K0HPS
>
>
>
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com]On Behalf Of K8RI on Tower talk
> Sent: Tuesday, July 04, 2006 10:09 AM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] Grounding base slab and pier tower bases
>
> Whether the prevention works or not I can't say, but this is mixing apples
> and oranges so to speak. This post is referencing the energy in the
> strike.
> The theory behind the porcupine is to *prevent* the strike by dissipating,
> or rather letting the charge leak off before it can build up. The energy
> at
> this stage is much lower than that contained in the strike.
>
> As the storm moves over the landscape localized (size depends on how you
> define localized) charged areas move across the surface with corresponding
> charged areas in the clouds. These areas may be well separated
> horizontally
> by as much as 10 miles. The charged area on the ground doesn't even have
> to
> be under the storm. I've seen lightning strike the ground over 10 miles
> from
> the cloud/storm with the hit out in bright sunlight.
>
> We have to define charged areas as there are charge gradients across the
> surface most of the time. So some how we need to define an elevated charge
> versus the day-to-day stuff, so I'm going to stick with generalities..
>
> The charged areas are *probably* on average on the order of 5 to 10 acres
> with a *substantial* gradient across the area. These charged areas can
> *flow* or move at substantial speeds. Typical is going to be the average
> speed of the storm, but they can move faster or slower. Due to soil
> resistance even a major strike is not going to entirely neutralize the
> charge. More than likely a substantial charge will remain.
>
> So we have not only a charge build up, but it's also a moving target which
> we generally think of as being stationary. Unfortunately we are thinking
> of
> that object as being the target (which it isn't) rather than the moving
> charge (which it is). When we find our tower is in the elevated charge
> zone, it *may* be the highest charged point, BUT the strongest charge may
> not be the tower. It might be no more than a few hundred feet away. All
> things being equal height does make a big difference, but things are
> seldom
> equal. The charge which is certainly the most important is not equal, or
> even uniform.
>
> I've seen the average tower height dismissed as it is considered
> insignificant compared to the length of the lightning bolt. That height
> can
> make a considerable difference, but it may or may not in the real world
> under specific conditions.
>
> As an experiment: hook two plates to a Vandegraf Generator and place them
> just close enough to each other so that at the maximum charge build up
> they
> will arc over. Now put a couple of sharp points on each of the surfaces.
> It depends on how fast the generator can build the charge (coulombs per
> second), but corona should develop around the points preventing the plates
> from reaching the point where they can arc over. BUT "at times' like in
> the
> real world, if the generator can build the charge faster than it can be
> bled
> off the strike will occur any way.
> In that particular case the point does provide a source for a feeder and
> the
> porcupine does provide a discharge, or leakage path for preventing or
> slowing the charge build up on the tower. Whether that is a fast enough
> discharge rate is do any good is pure conjecture. OTOH blunt objects do
> prevent the corona, or leakage current and should allow for the minimum
> charging time.
>
> Much, if not most of the information on lightning strikes is antidotal. I
> don't have a bunch of pointy objects on top of my tower unless you count
> the
> element ends, in which case I have a lot of them. <:-))
> http://www.rogerhalstead.com/ham_files/Tower29.htm This system has been
> taking about three verified direct hits a season. It's well past that for
> this year with it up to five and it's only the beginning of July. I know
> it
> took two hits a couple nights ago. I think it took three (maybe even
> more),
> but I'm not counting that third one because I don't know for sure.
>
>> No need to present facts available to you. Just look up measured energy
>> of
>> a strike and compare it to the ability of the porcupine to dissipate this
>
> The measured energy of the stike is not the point here. The point is to
> try
> and prevent the charge build up to where the strike ocurrs. It takes far
> less current to beed off a charge or prevent the build up within limits
> than
> is contained in a strike. The point (no pun intended) is to bleed off the
> charge faster than the ground charge builds, whether it be moving into the
> area, building up, or both. If that charge is building on the object
> faster
> than it can be bled off and a feeder is produced that connects then the
> object will be hit. When that strike ocurrs the current comes from an
> area
> considerably larger than the tower and contains far more energy than would
> have been available from the tower.
>
>> energy. BTW, while you are looking for facts, try to determine the
>> amount
>> of charge that can be dissipated by the porcupine.
>>
>
> To be effective the porcupine would most likely have to dissipate very
> little energy. That is not its job.
>
> Now, as to whether the porucpine actually does do its job is some thing
> else
> entirely, but has little to do with the arguments presneted here.
>
> Roger Halstead (K8RI and ARRL 40 year Life Member)
> N833R - World's oldest Debonair CD-2
> www.rogerhalstead.com
>> 73, Keith NM5G
>>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com] On Behalf Of Doug Renwick
>> Sent: Tuesday, July 04, 2006 9:57 AM
>> To: towertalk@contesting.com
>> Subject: Re: [TowerTalk] Grounding base slab and pier tower bases
>>
>> I did not say that porcupines will stop all lightning strikes.
>> I said "In other words, my addition of the porcupine did not have a
>> negative
>> effect."
>> Scientific experiment will only trump experience IF the scientific
>> experiment can exacting duplicate the experience and conditions!
>> Please present your scientific experiment that proves porcupines will not
>> stop strikes, any strike.
>>
>> Doug
>>
>> Subject: Re: [TowerTalk] Grounding base slab and pier tower bases
>>
>> Experience may trump theory, but scientific experiment trumps experience
>> EVERY time! porcupines on towers have been shown to not stop strikes.
>> Not
>> any more than an owl stops birds.
>>
>>
>> David Robbins K1TTT
>>
>>
>> --
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>> Date: 6/30/2006
>>
>>
>>
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