Lightning

[Scott]

Lightning

Now that I have an excellent conductor of copper and galvanized pipe jutting 23 feet into the air from my house, which will eventually be connected to my computer, how worried should I be about lightning?

There are many trees around my yard that are much taller, so perhaps they’d get struck first.

Are there any certain lightning precautions I should be taking?

Regards,

Scott

[Ebacherville]

RUN a copper groud rods in the ground by yout trees and run coper wire up to the top of the trees.. this will make them get hit first… but that may not always be the case..you could get hit, but that help lower the odds

Jason

[radio8z]

Hi,

Yes, you should be concerned about lightning. A Google search on grounding and lightning protection will get you information.

Here is a link to start:

http://members.cox.net/pc-usa/station/ground0.htm

I cannot claim expertise on this subject, but I can tell you my experience. I have an amateur station and use two antennas. One is a dipole 20 feet up in the trees behind my house, the other is a 2 meter vertical mounted to my chimney. I also have a DSS dish on the roof. All three of these were installed according to our local (and national) electric code which states that the lead wires and masts be grounded as close as practical to the electrical service ground stake when entering the building. I was able to ground all three (easy because they are coaxial leads….just ground the shield using an approved coaxial ground connector) directly to the electrical service ground stake where they enter my house. The idea here is to have a single point ground.

If you read the link above, you will see a discussion of this. Putting wires in trees and ground stakes all over the place does not conform to the single ground approach and can make things worse.

About four years ago I had a lightning strike. It hit a large ash tree next to my porch. The tree was 10 feet from the ground stake, and my dipole lead was buried within 3 feet of the tree. I was standing in my house watching the storm through our french door windows and was also about 10 feet away. The tree exploded, throwing large branches and bark thirty feet across the yard, and the concussion damaged the roof of my porch splitting a 4 x 8 roof beam. I saw a ball of plasma lightning which looked like a basketball on fire slowly bounce across my yard away from the house. My neighbor saw this too.

Most of the electrical damage was to our telephones. I lost 3 cordless phones, and two modems which were connected to the line. No damage to my computers and no damage to my radios or DSS equipment, which I attribute to the single point grounding (and some luck).

The best thing is to disconnect and ground any wires going outside BEFORE the storm arrives. Don’t even think of it while lightning is active. You could be damaged.

There are no guarantees with lightning, only some steps you can take with proper grounding to limit the damage.

Neil

[Scott]

Hi Neil:

Thanks for the information.

I took a look around the house today and wasn’t able to find the electrical service ground rod. An addition was added to my house many years before we bought it, and I think the construction folks added the addition over the place where I would find the rod and the electrical service entrance

In the basement where the fusebox is, the conduit disappears through what used to be the the external wall of the house. There is no crawlspace or basement underneath the addition. Brilliant, huh?

I was thinking of installing an electrical outlet on the outside of my house where the transmitter is. Would connecting the ground of this outlet to my antenna ground rods achieve this single point ground?

Thanks,

Scott

[techpuppy]

Lightning can cause some strange damage. I had a lightning hit in the yard (a one foot crater) that then went over to buried electric and phone lines and then inside. The yard is surrounded by 40 – 50 foot trees. Apparently they didn’t do much to attract the lightning as it hit about 10 feet from the base of one of the trees. The strike had to curve around the canopy of the tree. It vaporized the phone wiring. All that was left was a black trace along the walls. I eventually had to have much of the wiring replaced. A UPS was destroyed as well as a computer, scanner, phones, and every surge protector in the place. So based on that experience and what I’ve learned here we’ve taken the following steps.

First of all thanks to this site and 12man who tried and tested using an FM link to the transmitter rather than audio lines. There went half the problem and improved safety now that there’s no direct electrical connection between the studio equipment and the transmitter.

We chose not to bury the power lead to our transmitter due to research done in Florida in regard to lightning strikes. The research found that lightning tended to flow to buried lines. It does not take a direct strike for dangerous and damaging lightning to enter buried cables. (That was also my experience.)

That leaves our power lead going from inside to the transmitter on the tower. First of all inside we use a dedicated outlet for the plug in power supply. Into that outlet is a surge protector with fusible links. Then we plugged a UPS into that protector. The UPS provides power to keep us on the air for most power interruptions. It also provides some surge protection. Into that we have our power supply for the transmitter. The power leads go outside. Immediately outside the negative lead is grounded. Then we have made a loop consisting of about 8 loops of the power lead which is supposed to be viewed as a high impedance path for lightning. Coming out of the loop are two inline fuses (one in each lead).

Our next step was to use carefully grounded copper pipe. It sticks out of the ground. On top of that is a T fitting with two lengths of copper pipe about 12″ long each coming out of each side. They are soldered in place. At each end of the pipes are plastic pipe caps cemented in place. We drilled a small hole in the middle of each of these caps and ran a piece of aluminum rod through the inside. The rod does not make contact with the copper pipe as it is supported by the end caps and sticks out about an inch on each side. The positive lead coming from the fuse attaches to one end of the rod. The lead continuing on to the transmitter connects on the other end. The idea was that lightning could arc across the small air gap into the copper ground yet not provide any hinderance to our power supply normally.

And for a bit more protection (and because we got a great buy on the cable) we have another loop adjacent to the tower before the wire goes up to the transmitter.

This system may not save our transmitter or antenna, but hopefully would reduce the effects of lightning on inside equipment and wiring.

[radio8z]

Scott,

I don’t know what to tell you about your situation. Other than what I previously posted, I would rather give no advice than wrong advice.

Techpuppy,

Very interesting approach to the problem, especially the spark gaps and fuses. In light of the Florida research about buried wires, I am surprised that my strike did not cause more damage. The phones that were damaged were connected to the underground feed which was also next to the base of the tree.

Hope you never have to test your protection scheme.

Neil

[Author]

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