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Author Topic: Lightning Arrestor's Which one?  (Read 5679 times)
KB1LKR
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Posts: 1898




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« Reply #15 on: October 10, 2009, 10:43:42 AM »

In that vein, I was flying out of Birmingham, AL a few weeks ago and was delayed due to a crew doing repairs to the middle of the main runway (6/24, 12,000 ft, asphalt) due to a lightning strike to it!

You never know what it'll hit or what it'll do once it does. I would have bet on the tower, radar antennas, VHF antennas, terminal buildings, the trees just to the NW, any number of other things before the middle of the tarmac. All you can do is do the best you can to divert the energy to ground as quickly as possible, and keep everything at approximately the same potential while it's being diverted.

Meanwhile they were operating at reduced capacity w/ their short secondary (18/36, 7,100 ft) runway.

Of course it also didn't help that Atlanta, my next stop, was closed for several hours for severe WX too.
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W8JI
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Posts: 9296


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« Reply #16 on: October 16, 2009, 05:35:52 AM »

A lightning strike path to an object does NOT seek the "best ground around". That is a silly old wife's tale.

Lightning is an arc. The initial ionization or hit starts with virtually no current at all, so any object that has any ability to give up charges, like for example a tree or tall wet wooden structure, is a target just as much as a copper pipe connected to a deep well.

Once the giant arc starts, high current brings lower resistances and impedances into play. All that current creates a big voltage drop across higher impedances, and at that point a "better ground" is meaningful because more of the current flows that path.

The problem with an arc, or starting an arc, is the electric field gradient varies greatly with the shape of the object as well as the height. It does NOT vary much with conductivity, because initial leakage currents are localized and are in microamperes. For example my 300 foot tall insulated base tower has a few hundred MICROamperes to a few dozen milliamperes leakage current when sizzling at the top with corona.

Obviously the ground resistance doesn't mean much up to the point the strike starts, and once it starts it will generally stay where it is when it starts.

I have all these towers:

http://www.w8ji.com/transmitting%20antennas.htm

and I can assure you the tallest 318 foot tower with only thirty 50-80 foot radials in drier soil gets hit nearly all of the time. The 220 foot tall tower that is on 20 foot lower ground, even though it has 100 200' long radials many of which run right into a creek, gets hit about once a year.

One of the big problems listening to people talk about what lightning "hits" is they have good intentions, but often are clueless where the lightning actually hit. Unless you are standing there watching and waiting with a broad focus, you can't tell. There is so much light from the short flash you really have to be looking for its direction.

I would bet not a single person was looking with a clear view of that well, and instead just saw a big flash in some general direction. then they see the well is all "tore up" and assume it was a direct strike.

Here is another clue the data is corrupt. It was said lightning hit the well because it is a good ground and lightning seeks the best ground. It was also said lightning did not like that ground, and ran through the pipes into the basement and house where there is hardly any grounding at all.

Which is the truth? Is the well such an overpowering attractive ground it can be the only target for a charge exchange with a cloud thousands of feet away? Is the well such a poor ground the charge had to run though a long buried pipe (probably plastic if modern)or wires, and ground itself to unburied metal in the house with such intensity it started a fire?

Factually, most lightning hits are on above ground utility lines or trees. Despite have 300 foot towers and all these radials, about half the hits around here are on trees or power mains. This is because even though statistically the tower is a better target, the trees and power wires are a big wide target. The other hits that do occur almost exclusively hit the tallest tower. They hit the sharpest tallest point on that tower, a 2 meter antenna.

Now here's a good one to think about. I have no ICE or Polyphaser lightning protection devices, all my radios and TV sets are connected all the time, and I never have problems with equipment. The same is true for repeaters in the shed at the base of the 300 ft tower.

I have had coax melt, for example the shield of RG8X in an air-wound choke balun feeding my 160 dipole at the top of the 300 footer has melted, but no other damage. Nearly 100% of any occasional damage is from a shield melting, and there is a logical reason why that happens.

I have no modem failures, no TV set damage (other than the screens being magnetized), no computer damage, no well damage, and no ham gear equipment damage.

The key is in wiring and grounding and avoiding ground loops.

Tom
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KA7LCO
Member

Posts: 1




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« Reply #17 on: October 16, 2009, 12:13:25 PM »

Did you ever receive your ICE units? I have had an order in for several months and am about to abandon them and look for something else, no response to emails, they dont answer there phones, nuttin....
If anybody has an inside track to contacting them please let me know...
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K9AMA
Member

Posts: 17




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« Reply #18 on: October 16, 2009, 06:14:37 PM »

Ive always had good luck calling them toll free at
1-800-423-2666

Ask for Mike.

I called them yesterday about a question I had.

73!  Dan
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W7CNK
Member

Posts: 38




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« Reply #19 on: October 24, 2009, 07:46:31 AM »

The only Lighting Arrestor that works is "DISCONNECT".
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K9KJM
Member

Posts: 2415




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« Reply #20 on: October 24, 2009, 07:54:49 PM »

Quote:
"The only Lighting Arrestor that works is "DISCONNECT"."

B.S.!!!!!!

Commercial stations, Cell site towers, etc etc do NOT "disconnect" during storms, And do not suffer damage when they are properly protected.

To "disconnect" without moving that coax far outdoors, or properly GROUNDING it is very dangerous!
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