Fiberglass invites lightning?!?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KX4O, Jul 31, 2020.

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  1. KX4O

    KX4O Ham Member QRZ Page

    From the current makers of the Isopole...

    As it is well-known, the fiberglass antennas are too prone to receiving lightening discharges. The friction of the wind with the fiberglass increases the production of ozone in the air which is the chosen way for the lightening to discharge.

    Fiberglass + wind = ozone generation? Anyone else heard of this phenomena?

    The rest of the FAQ page looks like gibberish from non-technical marketing department folks so might have to take the above at arms length. Still if there is some truth to the above claim, I wonder if any of you can corroborate their premise.
     
  2. W6MK

    W6MK Ham Member QRZ Page

    Wiki "How Many Angels Can Dance on the Head of a Pin?"
     
  3. WJ4U

    WJ4U Ham Member QRZ Page

    Let me know when there are subterranean tremors involved.
     
    AJ5J likes this.
  4. WR2E

    WR2E Ham Member QRZ Page

    I think the ozone idea is crap. and what? Lightening?

    BUT... over the past 30 years or so I have heard of what seems to be a disproportionate number of Antron 99s and before that Shakespere "Big Sticks" being struck.

    Including one of mine... direct hit. It was on the roof of a triplex and the tip had to be about 70' up.

    I have a feeling that they are prone to building static charges on them and if anything THAT is what could potentially form a 'feeler' that connects with the leader and causes the strikes.

    But Ozone? naaahhhhh... unless... the static charge they build creates the ozone.

    Maybe if we put up enough fiberglas antennas we can close up the ozone hole? o_O
     
    KB3UWC and AJ5J like this.
  5. KP4SX

    KP4SX Premium Subscriber QRZ Page

    Hard to ground fiberglas. :eek:
    In the USVI they have installed (or still installing) 5000 'composite' utility poles very much made from fiberglas. Maybe at that scale they can tell us if the theory has any validity.
     
  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    I think that ham fiberglass-encased VHF antennas are more vulnerable because they tend to be mounted at the highest point on a tower, so that they stick up above the "cone of protection" offered by the grounded tower. That means that the lightning current pulse(s) (35kA to 150kA) strikes the tip of the antenna and current pulse travels down inside the antenna.

    Here are some pictures of one that I use as a prop during my "lightning protection" seminar I run at hamfests... It came from a local ham's place. He had it mounted on a 30 ft metallic support pipe clamped to the eave of his garage. The bottom end of the metallic pole was grounded with a ground rod, but that rod was not bonded to his electrical service, which is about 100ft away on his detached house.

    The coax came off the bottom of the support pole and went back up to a window sill to enter the garage. There was no gas-gap or ADU on the coax The coax was connected directly to a VHF/UHF solid-state rig powered by a three-prong AC-powered Astron supply (both of which survived intact). The coax had holes blown in the vinyl jacket along its entire length (it was taped to the mast) and had to be replaced.

    After the strike, the innards of the Diamond X-50A were laying on the ground, and all that was left on the mast was the hollow fiberglass tube shown in the pictures...
    tag.png tracks.png tip.png hole1.png hole2.png Innards2.png innards3.png
    Click to enlarge photos.

    The burned holes are where the antenna base was clamped to the mast with u-bolts.
     
    Last edited: Aug 1, 2020
    N0TZU likes this.
  7. W3ATV

    W3ATV XML Subscriber QRZ Page

    They may be able to test that theory this weekend! :eek:
    Aren't you getting sick of this hurricane stuff Bill?
    Let's hope this one is a dud.
     
  8. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    I call BS on the “as it is well known, the fiberglass antennas are too prone to receiving lightning discharges.”

    Oh yeah? Show how many radome antennas are struck vs. bare antennas per unit time, per square area, normalized by the number of each type installed in the same geographic area. Come on, nobody has that information.

    As for static electric charge making a difference, that is very far fetched. The electric field which causes upward streamers from objects on the ground is so high that the air is strongly ionized at the tip of an object and the streamers are feet in length. When was the last time you saw a natural static electricity spark that was feet long? Never.

    It’s all just marketing hype.
     
    Last edited: Aug 1, 2020
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  9. AJ5J

    AJ5J Ham Member QRZ Page

    Shakespeare Co. has made quite a lot of fiberglass radome-style antennas for the marine market for ages. IF this idea had merit I don't think they'd still be in business (their customers would go on strike because of all the strikes :))
     
  10. PA5COR

    PA5COR Ham Member QRZ Page

    My Imax 2000was up 18 yearss and through many thunderstorms and succombed to the last storm because the tip fell off through delaminating the fiberglass.
    Put up a spare one with 2 coats of marine grade polyester paint for the next 18 years.
    My Diamond X51oN was on top of the roof mounted mast at 21 meters top for 10 years as highest antenna beefore i took that mast down and now is at 17 meters high.
    My 23 meter vertical L fed at the base with autotuner is connected to the ground system ( 17 earth rods 10 feet deep in silty sea clay) and house ground when there is a thunderstorm, never had any problem, is the highest point here for 500 yards around.
    lightning did strike an house 300 yards away into the attick where the central heating system was mounted though...
     
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