Lightning emp

[Oznog]

As a slightly off question:
I live in a two story house at the top of a hill. I'm the tallest thing around and am at a somewhat elevated risk of being struck by lightning.

Now there is this old "wireless cable" antenna on my chimney that was there when I got the house. It has a ground strap and I would think this should provide some decent protection if lightning were to strike.

The only thing is, the strap runs down the outside wall right on the other side of where my computer sits, which is the most valuable piece of equipment I have to protect. I wonder, how much of a risk does this create? Even if the lightning is contained in the ground, is there an EMP at such close range that could still fry my computer?

 

[Dean Huster]

One thing that lightning isn't is predicable.

When we lived in Piedmont, Oklahoma, we lived on the highest hill (yes, in Oklahoma) around, actually about half-way up the municipal water tower which presented a lot of problems just with that. The house was on the top of the hill, nothing else of any height nearby. We were always getting fierce electrical storms where you'd swear that lightning would go through one bedroom window and out the other. Lightning would strike the barbed-wire fence around the house (steel posts) all the time. I had a long-wire antenna that was never struck and the house was never struck and we never lost any electronics to lightning. There was one time when I heard a periodic snapping and finally traced it to the BNC connector that I'd disconnected from the long-wire antenna. Even though an electrical storm was three or four miles away, that antenna was getting charged to over a thousand volts and then the BNC would arc over. I installed a neon lamp snubber on the antenna the next day.

Then we moved into the city. Houses and trees all around. We had our 5th wheel travel trailer parked in the driveway and plugged in to charge the battery. Storm comes through. Lightning strikes the gutter on the house behind the trailer, travels down the downspout, blows a hole in the ground and sprays mud all over everything. Zaps across to the trailer electrical cord, goes into the trailer and wipes out the refrigerator electronics, the CB radio and the auxiliary water heater element and blows a breaker. Traveled along the same trailer cable into the house and took out the garage door opener in five places and the digital combo lock I'd made and installed, on into the house where it took out a phone, phone anwering machine and a VCR.

Unpredictable unless you're out golfing and standing under a lone tree for protection from the rain.

Dean

 

[lord loh.]

... Even though an electrical storm was three or four miles away, that antenna was getting charged to over a thousand volts and then the BNC would arc over. I installed a neon lamp snubber on the antenna the next day. ...

What is a neon snubber and how does it help ?

And Oznog, as far as your computer is concerned, I suggest a safe thing to do is to move it away, a high DC potential traveling through a wire may generate enough magnetic field to damage your HDD.

OR Is it possible to shield the computer ? :?:

 

[dalt]

When lightning strikes it could easily cause a big enough electric field to do damage to your computer. I think themost frequent storm damage to computers is from the modems, so you might want to buy a protector for it.

I'm not quite sure if its the same thing but equipment is commonly protected from lightning strikes with a gas discharge arrester which is basically a gas filled tube with two electrodes - when a high voltage is applied the gas conducts causing a short circuit and the energy is put onto the ground instead of into your equipment.

 

[Dean Huster]

A neon snubber is nothing more than a standard NE-2 neon lamp with one lead connected to the antenna and the other to a ground you run up next to your feedline. I usually put it in a plastic box just for appearances. The neon lamp will conduct just under 100V and discharge the voltage on the antenna to around 50 or 60V. During nearby lightning discharges, you can go outside and watch that little lamp flashing as though flashing were about to go out of style (and it should for some perverts).

There is no known protection that we mere mortals can purchase for the income we make that will protect from a direct strike. Commercial radio and TV transmitters have a little larger investment to protect and one heckuva lightning draw, so will invest in equipment that for the most part, can protect from a direct strike.

Dean