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Mast as Lightning Rod

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD9VV, Jun 9, 2021.

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  1. KD9VV

    KD9VV Ham Member QRZ Page

    Completely agree.
    Just attempting to give a possible strike a easier path to ground rather than jumping to my house.
    My thought was, and perhaps incorrect, is a good earth ground from the mast would be better than nothing.
    Also agree with another post I need a better was to attach the copper wire to the mast.
     
  2. W9IQ

    W9IQ Ham Member QRZ Page

    In order for multiple ground rods to be effective, they must be located at least 8 feet from each other. It is better to run the grounds out like radials from the mast with the ground rods appropriately spaced. The buried ground rod wires should be bare and at least 6 gauge - larger is better. Use exothermic welding cups to attach the ground wires to each ground rod. Use exothermic or proper pipe ground clamps on the mast to attach the ground wire(s).

    Make certain your coax cable (and any other cable) is grounded to the same spot where the ground system attaches to the mast. A discharge type device(s) at that point would be better than a simple shield ground.

    - Glenn W9IQ
     
    Last edited: Jun 9, 2021
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  3. W6KCS

    W6KCS Ham Member QRZ Page

    This might work, Polyphaser makes them to connect solid copper to 1-1/2" to 2-1/4" galvanized tower legs. I think they call it a "J-2".

    polyphaser j-2.jpg
     
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  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    OWT!
     
  5. AA4PB

    AA4PB Ham Member QRZ Page

    The coax shield needs to be grounded to a nearby ground rod just before it enters the house. Otherwise you have a parallel path for a strike on the pole or inductive coupling into the coax run from a nearby strike. That path would typically be from the coax to the back of the radio, through the DC power connection to the power supply, out the AC ground wire in the power cord and back to the electrical panel and to it's ground wire and rod. You need to give lightning currents on the coax a lower impedance path to ground outside the house in order to minimize what flows through the radio equipment and house wiring.

    A typical way to do that is to cut the coax just before it enters the house (close to ground level). Put coax connectors on the cut ends and attach them to a surge protector. Run a short ground wire from the surge protector ground screw to a ground rod. Also bond that ground rod back to the electrical service ground to prevent a possible shock hazard from touching two ground connections inside the radio shack. The coax connectors and surge protector are often mounted inside a waterproof plastic utility box in order to prevent water damage.

    That coax cable shield should also be connected to the support mast near ground level. You can also do that with connectors inside a water-tight box or you can purchase a water-proof clamp assembly made for the purpose. Run a ground wire from the base of the mast to one (or more) ground rods close by.

    Remember, lightning does not have to directly strike your support mast in order to get into the system. It could also strike a tree in the vicinity and magnetically couple currents into the metal mast and/or coax cable.
     
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  6. AA4PB

    AA4PB Ham Member QRZ Page

    The DX Engineering web site has a variety of grounding options.
     
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  7. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    You beat me to it!

    These are also available at home improvement stores in the electrical department for grounding water pipes. Make sure you get bronze, not zinc.

    The rod at the mast must be bonded back to the AC service ground. It must also be bonded to the rod at the coaxial cable entry into the house where the cables are grounded. Ideally that is the same as the AC service rod if the coax entrance is co-located, but for many of us it’s a separate rod.

    Here is a list of good resources for grounding, if you aren’t already familiar with them.

    https://forums.qrz.com/index.php?threads/resources-for-antenna-and-station-grounding.756419/
     
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  8. KD9VV

    KD9VV Ham Member QRZ Page

    Oh boy.
    Looks like I have a summer project.
    As said, my 2 masts are 75 feet from the AC service entrance/ ground.
    ..and it wont because straight run.
     
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  9. AK5B

    AK5B Ham Member QRZ Page

    Yes, you opened an expensive can of worms---but that can opening could prove to be very beneficial to you and your insurance company someday.

    73,

    Jeff (also currently putting together good static/surge protection at my new QTH)
     
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  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    If possible, I'd relocate the "masts" so they're closer.:)

    Of course, once someone invests the time and money to install a 100' tower, that's not so easy; but with masts it might be.

    I worked on K2BPP's tower in NNJ a lot back in the early 1980s. Dave had a 180' Rohn 45G with stacked 20m beams rotated by a prop pitch motor and the tower was 200' behind his house. My job was to climb past everything and install a Stationmaster repeater antenna on the very top, above everything...and since it was "my" repeater I was highly motivated to get that done. Thankfully Dave already had the coax in place, buried, running to the top of the tower and into his basement ham shack so I didn't have to deal with that. But scary standing atop the beacon plate to install the antenna without being tethered to the tower itself (my harness was only tethered to the mast and although I couldn't really "fall," it was scary anyway).

    His grounding system was six 8' rods, two bonded per tower leg, spread out over about 25' radius around the tower and then a "cable" back to the house utility panel ground. That cable was as big as a utility power drop, probably #2 or #0 stranded copper, with more 8' ground rods along the route, all welded connections. The damned ground cable probably cost $1000.:p

    Not my money. Interesting to see such an installation, though. I remember telling Dave, "When I grow up, I want to do it like this.":)
     
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