Residential lightning strikes, a statistical question

Discussion in 'Amplitude Modulation' started by WB2CAU, Mar 27, 2021.

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  1. WB2CAU

    WB2CAU Ham Member QRZ Page

    I would like to pose a question, but first explain my understanding of lightning protection.

    A well-grounded air terminal on a structure serves two purposes. First, it should provide a low impedance current path to ground in the event of a strike.

    Secondly, it provides a “cone of protection” around the air terminal to reduce the possibility of a strike by bleeding off any built-up charge.

    Functionally, an air terminal can be a dedicated lightning rod or could be your well-grounded ham radio antenna or tower. TV antennas installed properly could also perform the same secondary function.

    Since the mid-20th century, most suburban and rural homes had grounded TV antennas. In the last 35 to 40 years, TV antennas have gradually disappeared as cable TV has taken their place.

    You would think that without grounded TV antennas on homes, the incidence of lightning strikes onto residences would be dramatically increased.

    The question is this; do statistics, perhaps from insurance companies, support my theory that without a grounded TV antenna in place, a residential lightning strike probability is greatly increased?
     
    Last edited: Mar 27, 2021
  2. KL7KN

    KL7KN Ham Member QRZ Page

    The number and intensity (so-called superbolts) of lightening strikes are increasing. Ben brings this up fairly often.

    As to your question. The number of strikes over time is the same - it's just the target (for lack of a better word) that takes the hit.

    My son lives in Texas hill country, had a neighbor take a direct hit on a roof vent pipe. Pieces of roofing were found 3 blocks away...

    Lightening rods, properly installed, may reduce your insurance costs in some areas. You should ask your carrier's agent.
     
    K0UO likes this.
  3. KL7AJ

    KL7AJ Ham Member QRZ Page

    It's been a while since I've seen any numbers but it used to be assumed that rural areas had more (or bigger) superbolts because there were fewer structures to provide a slow bleed-off. We probably have much better data these days
     
    K0UO likes this.
  4. W7TFO

    W7TFO Premium Subscriber QRZ Page

    Static dissapators are the better alternative.

    The analogy is it is better to have it go away than to try and withstand the strike.

    http://www.nottltd.com/

    73DG
     
    KB0MNM and WD4ELG like this.
  5. KL7AJ

    KL7AJ Ham Member QRZ Page

    Even Ben Franklin understood this
     
  6. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Actually, that's how residential lightning rods are supposed to function. They were never designed to take a direct hit.

    Most homeowners don't understand this, and most residential lightning rods are poorly or improperly installed, often by fly-by-night scammers.

    I knew a guy in Illinois who had a direct hit to the 80m dipole he had strung just above his roof. The entire thing was vaporised, not a trace could be found. Fortunately, he had minimal damage to his house or radio equipment inside. No clue whether the dipole attracted lightning to the house, or protected it from damage.

    I have heard tales (unverified) of the top of entire residential TV antenna towers being vaporised from a direct hit.
     
  7. WB2CAU

    WB2CAU Ham Member QRZ Page

    Perhaps I should've been clearer. I didn't mean lightning strikes in general. Obviously that's not going to change. I meant lightning strikes to residences more now than when TV antennas were common. In other words, has the trend away from TV antennas for the general population (not hams, of course) made a home more vulnerable to a damaging home strike? Did TV antennas provide a benefit that is now gone with the bulk of the population no longer having one? A well-grounded TV antenna (emphasis on grounded) would likely provide that cone of protection for the area around it. I want to know if there is a higher percentage of lightning damage claims now that most homes have no grounded masts sticking up from their roofs. I would think this would be a good way to determine the effectiveness of a TV antenna (or any grounded antenna) beyond pulling in over-the-air RF signals.

    The sheer number of TV antennas that existed at one time compared to now should provide the means for some statistical correlation... I would think. We as hams with our varied antennas are too small a sample to provide any meaningful conclusion, being such a tiny portion of the total population.

    Have we shot ourselves in the foot migrating our entertainment from an antenna to cable TV?

     
    Last edited: Mar 27, 2021
    KL7KN likes this.
  8. WB2CAU

    WB2CAU Ham Member QRZ Page

    Ah, but perhaps the antenna took a hit that would have done more damage if it wasn't there at all. I would rather it destroy an antenna than burn down my house. And who really knows if that antenna that was vaporized was properly grounded. There are some hams (and non-hams) who believe it's better not to ground than to ground. They believe a grounded antenna is an invitation for a strike.
     
  9. W0JKT

    W0JKT Premium Subscriber QRZ Page

    Wonder why more ham discussion of this since if it works could be useful. HOWEVER:
    Maybe for a different thread but is there any scientific evidence dissipators even work. While article linked below is based on boating the technical detail seems good and also talks about antenna towers etc. Their bottom line in the article is that they do not work and are just a marketing gimmick.

    https://www.practical-sailor.com/blog/lightning-protection-the-truth-about-dissipators
     
    WA7ARK likes this.
  10. W7TFO

    W7TFO Premium Subscriber QRZ Page

    I have no knowledge of lightning on water.

    With over half a century in broadcast engineering I can tell you, without question, they do work on towers.

    Several with just a slender lightning rod on top were hit, and suffered severe damage.

    We rebuilt everything and this time used the Nott product as directed.

    Not one hit since, even in the heavy thunderstorm seasons.

    The 6-story building next door to the identical one I worked in took several hits, and suffered damage to most electronic systems even tho it was fully equipped with rods and heavy ground cables.

    My building, that held a 22-studio radio complex and a large IT department system, suffered no hits/damage with a properly installed constellation of dissapators.

    73DG
     
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