Grounding attic antenna?

What are you using the antenna for? There is a big difference between a ground for electrical safety and an RF ground for signals. If it is just for reception e.g. a TV antenna, then there is no need for an RF ground.

For electrical saftey, the antenna should be connected to a lightening arrestor and that connected to ground. I don't know US electrical codes, but I think that it has to be a separate yellow green wire.

Since you are inside a house, it is almost impossible for lightning to strike your antenna, but a nearby lightning strike can still do a lot of damage.

For an antenna that is directly coax fed, i.e. one side of the antenna is connected directly to the coax, a "ground block" will do.

Here is an example:

Most TV antennas consist of a metal boom, with elements that are insulated from it. In that case, you should put the grounding block directly on the boom, and connect a short coax from the feed point to it.

Run a ground wire from it common ground rod where the electricity enters your house.

Note that you do not have to run the ground wire from the antenna, you can ground the boom to the coax using a grounding block, and at the other end run a ground block and grounding wire to the main ground. This works electrically, it may not be legal in the US.

BTW, it is never a good idea to use the ground wire for an outlet for an antenna, someome may disconnect the outlet without realizing they are disconnecting the antenna too.

Geoff.

Lighting will hit things in the attic including AC wiring. A friend had it happen to him. I think there was some smoke involved. Another friend had his old outside antenna hit, and started a fire in the basement where the TV was. It would be nice to a a lightning rod above and around all metal in the house to form more of a diversion down the house and into the ground.

Don't use the AC grounding conductor. Run new wire out the roof and into the ground.

greg

This is dubious, since a lightning strike in a rainstorm will not likely penetrate the wet roof.

That's only just barely acceptable; the heaviest wire in the RF cable is grounded anyhow, at the TV set, but it can be run to a ground block and wired to (for instance) plumbing vents that penetrate most attics.

The "new wire out the roof and into the ground" has to fulfill all the requirements for a building's lightning-rod system. Much work. Scant benefit.

Sorry, G. But yes, I did mean a tv antenna.

Another weird story!

When I first bought the house 26 years ago, I called an 800 number advertised in public service announcements on tv about lightning rods, and at the time, I was sure they were non-profit and didnt' sell them, but when they found out I didnt' live in Florida, they pooh-poohed the idea. I am only doubting this now because I can't remember any details of the phone call. But since then I have never heard or read a word about anyone in Baltimore or its suburbs having lightening protection, other than a grounding block.

And over the years, I decided to take comfort/assurance in that I live in shallow valley with lots of trees taller than my house, so they'll protect me even more than in many of the other parts of town.

OKay.

Thanks and thanks Geoffrey.

You still can have damage from lightning. A nearby strike will produce an EMP which will damage equipment. At one time I had one that wiped out two computers, two modems (one of them on the shelf), a keyboard (also on the shelf) and a some other small items.

This was in the early 1990's and I had a Radio Shack telephone line surge protector which inside was an MOV and a FUSE and it did it's job. The fuse blew, saving the modem that was behind it and a fax machine.

Never trust someone else (or even yourself) to remember that something serves two purposes when saftey is involved.

You're welcome and good luck.

Geoff.

Michael Jackson needed lightening protection, you need lightning protection.

Some more weirdness. That house happens to be the first American home with a bomb shelter. The roof is made out of steel. That didn't stop the lightning from going down the TV antenna feed.

greg