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Grounding roof antenna?

Discussion in 'Electronic Repair' started by Sudy Nim, Oct 27, 2008.

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  1. Sudy Nim

    Sudy Nim Guest

    Installed new roof antenna, with new tripod mount and 10 foot pole (about 30ft.
    roof to soil). Instructions say nothing about grounding. I have lived here (far
    Chicago suburbs) 44 years and always connected tripod to soil pipe about 20 feet
    away. Never had a problem with lighting strike, excluding several power line
    incidents. Question to ground or not to ground? TIA
     

  2. Actually, the instructions likely do detail the grounding requirements. If
    not you will likely find them in the first pages of any television, or any
    other receiving equipment. The mast for the antenna and the coax shield
    must both be grounded to the ground electrode on your electrical service.

    Leonard
     
  3. PeterD

    PeterD Guest

    Code usually requires grounding.
     
  4. Sudy Nim

    Sudy Nim Guest

    Thanks to all, appreciate your replies. I wired it to ground today.
    Sudy Nim
     
  5. hr(bob)

    hr(bob) Guest

    I hope you used a wire somewhat bigger than 26 gauge. Altho a direct
    lightning strike of 20,000 amps or more will vaporize anything you
    could reasonably use, the ground will help in the event of a nearby
    strike. How far west of Chicago are you. I'm 28 miles out and we
    get some humdingers here.
     
  6. GregS

    GregS Guest

    Like the warming trend here in Pittsburgh, well this last summer was not as hot
    as the previous two, but all the leaves are usually on the ground, or at
    least thats the way it was 10 years ago. Its been unusually quiet
    as thunder storms go. I sort of miss them. We have hill after hill, after hill, etc.
    The worst and most trecherous sounding storm I have encountered, was up
    right off Lake Erie, on flat land. I was scarred.

    I was installing some guy poles off my new deck for a sun shade, out
    of steel piping. I also attached some wiring to a ground post.
    First time I ever put one of those long things in the ground. I still want to ground the steel
    roof of my shed attached to the garage.


    greg
     
  7. Bob Shuman

    Bob Shuman Guest

    My understanding is that the antenna ground wire is to provide an
    "alternate" path for the very large, near instantaneous current (either
    from ground to the sky/lightnining or from the lightning to the ground,
    depending on the difference in the voltage potentials) that occurs when the
    lightning "strikes" the metal mast.

    Too small a conductor and it will be quickly vaporized leaving the current
    to find its way to ground via some other (more destructive) path. Even if
    the ground wire is of sufficient diameter to withstand the lightning strike,
    it also needs to be as low of a resistance on that path as possible since
    some portion of the current will nonetheless follow the path down the coax
    based on the impedances seen in those two "parallel" paths to ground. The
    goal here is simply to minimize any current down the coax so proper
    attention needs to be given to the construction and length of the ground
    conductor as well as the terminations on both ends too.

    Bob
     
  8. GregS

    GregS Guest

    I would agree with the path of least resistance, but as far as a single strike,
    vaporizing the conductor is not going to stop the lightning like a fuse.. The vapor or plasma
    probably has some conductivity anyway.

    greg
     
  9. Sudy Nim

    Sudy Nim Guest

    I hope you used a wire somewhat bigger than 26 gauge. Altho a direct
    lightning strike of 20,000 amps or more will vaporize anything you
    could reasonably use, the ground will help in the event of a nearby
    strike. How far west of Chicago are you. I'm 28 miles out and we
    get some humdingers here.
    influenced some related interesting discussions. My property is in kind of a
    valley, I'm about 20 feet lower than the surrounding area. The only lighting
    problems I experienced at home are power line strikes, which resulted in blown
    power line transformers, damaged TV's, appliances and burned out wall outlets.
    Prior to retirement I made my living in the TV service industry so I have
    personally seen the results of lighting. I often pondered if grounding the
    antenna just attracts lighting? Just as I can not visualize how a radio or TV
    dropped into a bathtub of water would electrocute you. But, I'll let someone
    else experiment with that. Looks, as if we could be neighbors, you must know of
    DuPage County?
     
  10. Sjouke Burry

    Sjouke Burry Guest

    Lightning is 100...1000 ths of amps.
    A low resistance part to ground means less damage on
    attached equipment, and less chance of starting a fire inside.
    That also means, no curves and bends, to lessen inductivity.
     
  11. Bob Shuman

    Bob Shuman Guest

    Neighbor,

    I too am living west of Chicago, IL in western Dupage County.

    Bob
     
  12. hr(bob)

    hr(bob) Guest

    Bob H is Bob Hofmann retired from Bell Labs EMC group in Naperville,
    IL. I put myself thru college in the 1950's installing towers and
    antennas and vacuum tube antenna boosters in Fort PIerce, Florida.
    After a good summer storm, we could count on getting calls from people
    whose tower amplifiers had been blown apart and whose 300 ohm twin
    lead if intact had no conductivity because the copper had ben
    vaporized into the poyethelene or what poastic was used for the
    downleads. Nearest tv station was Miami, 125 miles away, so
    amplifiers on towers was the only way to get signals. When West Palm
    Beach went on the air, only 57 miles away, people began to get serious
    about buying tv's since roofotp antennas becanme somewhat
    practical.....
     
  13. Bob Shuman

    Bob Shuman Guest

    We were likely working at the Naperville, IL (Indian Hill) facility at the
    same time and probably passed each other in the cafeteria or in the
    hallways... BTW, I started there in 1979 and just a few months ago, moved
    back to the same old building. So now it is ~30 years later and I work an
    aisle away on the same floor and in the same building that I started in.
    But it is an entirely different company now as you well know.

    (Another) Bob

    Bob H is Bob Hofmann retired from Bell Labs EMC group in Naperville,
    IL. I put myself thru college in the 1950's installing towers and
    antennas and vacuum tube antenna boosters in Fort PIerce, Florida.
    After a good summer storm, we could count on getting calls from people
    whose tower amplifiers had been blown apart and whose 300 ohm twin
    lead if intact had no conductivity because the copper had ben
    vaporized into the poyethelene or what poastic was used for the
    downleads. Nearest tv station was Miami, 125 miles away, so
    amplifiers on towers was the only way to get signals. When West Palm
    Beach went on the air, only 57 miles away, people began to get serious
    about buying tv's since roofotp antennas becanme somewhat
    practical.....
     
  14. Sudy Nim

    Sudy Nim Guest

    Hi guys. I too climbed a few towers in my youth! I was with the big mother
    (Motorola) from mid 50's until retirement. Started in consumer products (TV) in
    Franklin Park. During my 35 years moved through various divisions, automotive,
    military, communication etc. Last days at headquarters campus in Schaumburg.
    Do not wish to get too personal here for all the world to see. Sudy Nim
     
  15. Bob Shuman

    Bob Shuman Guest

    Franklin Park = Quasar! With the works in the drawer for easy
    serviceability?

    Bob
     
  16. Sudy Nim

    Sudy Nim Guest

    Yep, that was the birth of the all transistorized color TV and last of the
    breed. Division sold to a Japan Company and they continued under the Quasar name
    for a short time in the Franklin Park plant before moving everything to Japan. I
    was one of the fortunate few that did not lose my job and continued employment
    in a different division. The main building is still there but empty for several
    years and was supposed to be converted to rental apartments, condos or something
    similar.

    Sudy Nim
     
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