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[TowerTalk] Lightning solution

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Subject: [TowerTalk] Lightning solution
Date: Wed, 03 Jun 1998 12:17:32 -0400
Very good Barry,

    I really liked some of your points.  Think some of them were TIC, but
here is my Lightning anti-strike theory:
        Sometime back I visited shack of NS5M, whereby I saw a huge knife
switch on side of his desk.  I jokingly advised that if lightning strikes
a mile from cloud to ground, how the heck could adding 5 inches of air
gap with the knife switch help.  After much lightning damage, Rod found
that by disconnecting rig and tower from ground, and unplugging it,
lightning refused to hit his tower.
    Months later, we were having the worst lightning summer ever in
central Florida.  Two people had been killed, workers struck, etc.  At
work I consulted the Transmission & Protection Engineer about my theories
and he handed me a big brown book to study.  This book was the product of
years of research on lightning strike prevention for the NASA Space
Center at Titusville, FL.
    Here is what I found:  Lightning is almost always a negetive charge
that strikes from the ground up.  A cloud looses electrons and becomes
positively charged.  As it travels over the earths surface, a mass of
free electrons in the earth gather under this cloud and follow it.  When
the two charges are close enough, a dangling chain of coherent air ions
begins to form from the cloud down.  The actual lightning strike takes
place when the end of this chain is only 35 to 50 feet above the free
electron source.
    I then devised a gadget i called "Strike Alert" which was a static
potential rise detector.  The output was a 48vdc signal used to throw a
relay.  Centel Cellular installed two of these at sites that had been
devastated by lightning.  When a static buildup was detected (positive
cloud overhead), the tower was isolated from ground & the main line power
was cut off by relay.  Lightning did NOT strike.  I worked closely with a
Centel rep to conclude over and again that the lightning was coming from
the ground up to the closest point to the cloud, the ion chain then
dangled close enough to this negatively charged point and discharge took
    Applying this to ham radio can present some real safety hazards,
however, as Barry points out.  A ground isolated tower may direct a
lightning strike through your coax right into shack.  Isolating the tower
and pumping the free electrons out of if would make it positive, so as
not to attract positive lightning cloud, but what if the cloud was
negative.  What has worked for me is to keep tower grounded and
disconnect all wires near tower base.  It has been struck, but there is
no metallic path from shack to tower for electrons to follow.
    I believe that if there were two towers 50 feet from each other and
the same height, one grounded, the other isolated, the grounded one would
receive the lightning strike each incidence.  I thought of creating
Strike Alert circuitry to verify positive or negative charge of cloud,
and then charging an isolated tower the same as detected cloud charge,
but a charged tower would almost surely noise up reception as electrons
migrated between antenna and air (insulated antenna elements might stop
    Hope i didnt cloud up an already cloudy issue.  I just find lightning
fascinating, and had to add my two cents.
    73/dx, Doug - Nx4d

Barry Kutner wrote:

> There have been some interesting theories proposed lately, such as
> leaving your tower and antennas ungrounded so as not to attract
> lightning. Here's a better one, follow my logic...
> The W2UP thereom of lightning protection:
> 1. Like charges repel each other.
> 2. Lightning is a negative charge (or is it a positive charge?)
> 3. Take a D cell (yes, it MUST be a D cell. Those AA cells will
> never take the charge) out of your flashlight.  Attach it
> across your coax.
> 4. Since like charges repel, by polarizing your antenna with a like
> charge, you have now repelled the lightning. No need for spiny balls
> or anything like that.
> 5. This is even more effective if you wrapped your concrete base in
> Saran Wrap to further insulate it from ground.
> 73 Barry
> P.S. Good luck - you will need it as much as if you leave your
> tower ungrounded, and the charge has to find its own path to
> ground.
> --
> Barry Kutner, W2UP              Internet:
> Newtown, PA         FRC         alternate:
> --
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