? on grounding TV antenna

[gfretwell]

>

If you don't find a way to bond them together the lightning will find it for you.

[bud--]

You guys really can't figure out this is gargbage from the retarded google newsreader that is of no interest to anyone?

An "average" lightning strike is 20,000 amps. If you have a ground rod with a resistance of 10 ohms to earth it is a near miracle. The lightning strike will then lift the isolated ground rod 200,000 volts above "absolute" earth potential. (There can be arcing across the ground surface away from the rod.) The rest of the house electrical will be many thousands of volts from that. The coax will "be bringing lightning into the house".

If you have lightning rods (now called air terminals), the down conductor will be far larger than you would use on the TV antenna. An there will probably be at least 2 of them. The earthing system of a lightning rod system *must* be connected to the earthing system for the building electrical. The NEC has a note referencing NFPA780, the standard on lightning rod installations. The standard may require metal

6 feet from lightning rod conductors be bonded to the rod conductors (for instance a rooftop A/C unit on a flat roof). There may be enough voltage from the rod conductors to the metal to cause a side flash across 6 feet, even with the rod and building earthing systems connected.

The provisions of the NEC for TV antennas, which are more than what is used on some installations, are not intended to protect from a direct lightning strike to the antenna. If you want to protect from a direct strike find out what hams use for protection.

In gfretwell's post, a large conductor goes to the house grounding electrode system. The house grounding system will be raised above "absolute" earth potential, but all the wiring rises together. (That also requires service panel suppressors (which are required by NFPA780) and good connection to phone and cable entry protectors.)

[JRStern]

I believe that charge builds up on the ground over a fairly large area in advance of even the beginning of a strike, so the question is what kind of tall objects conduct it effectively up to where the charges in the cloud can "see" it. Does it matter if you run a copper rod from ground to steeple, or give it an air gap or insulator gap of an inch or three? I wonder. My guess is, it doesn't matter much, that the fields and charges are actually fuzzy and distributed.

Too bad someone can't figure out a way to actively attract - and capture! - all that energy.

J.

[The Daring Dufas]

If you've ever listened to any sort of shortwave broadcasts on a whip antenna, you may have heard static discharges that make a zip, zip, zip sound through the speaker at regular intervals.

TDD