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Grounding attic antenna?

Discussion in 'Electronic Repair' started by mm, Dec 10, 2009.

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  1. mm

    mm Guest

    Do I need to ground an antenna in my attic? (The web page talks about
    outdoors and putting the ground right where the cable comes into the
    house, which implies I don't need one for the attic, afaict. :) )

    I installed an electric circuit straight from the breaker box to the
    attic, and I know I connected the ground wire. Can I use the electric
    ground?

    Or do I have to run a new wire?

    Thanks.
     
  2. 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:

    http://www.radioshack.com/product/index.jsp?productId=2150597

    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.
     
  3. GregS

    GregS Guest


    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
     
  4. mm

    mm Guest

    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.
     
  5. 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.
     
  6. GregS

    GregS Guest

    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
     
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