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Re: [TowerTalk] Vertical antennas and lightning

To: "David Gilbert" <>, <>
Subject: Re: [TowerTalk] Vertical antennas and lightning
From: "Bill Aycock" <>
Date: Sun, 1 Aug 2010 12:36:24 -0500
List-post: <">>
This argument has always had holes, as far as I am concerned. It is  not the 
strike energy that "Bleeding" will handle, but the static charge that helps 
create an ionized path, that the strike can follow.  Diminishing that path 
HAS to help.
Additionally, I know this is not absolute; I merely want to improve the odds 
a little.  Other protection is also needed.

----- Original Message ----- 
From: "David Gilbert" <>
To: <>
Sent: Sunday, August 01, 2010 11:35 AM
Subject: Re: [TowerTalk] Vertical antennas and lightning

> Look at it this way ... the magnitude of arcing you get across the end
> of the coax if you don't have the antenna DC-shorted to ground is rather
> tiny.  My experience over the years (when I had a dipole or vertical
> that was not DC-shorted to ground) was that I'd get a spark across the
> end of a PL-259 (roughly half inch spacing) every few seconds.  Add up
> the energy from all those little arcs over maybe a ten or fifteen minute
> period and compare it to the energy from a single lightning strike.
> Then consider the likelihood that the portion of the cloud system that
> generated the lightning strike wasn't even near your QTH ten or fifteen
> minutes ago.
> It's like trying to drop the level of a flowing river by removing water
> with a teacup.
> DC-shorting an antenna to ground is important to protect both equipment
> and people from static buildup.  I once drew a really thick (lots of
> current) 2 inch long bright blue arc to my left hand from the shack end
> of the coax coming from an unterminated 80m dipole (my right hand was on
> the floor) ... that calculates out to about 300,000 volts and the biceps
> of both arms were sore for three days.  Imagine what the energy that is
> capable of generating those half inch arcs might do to a receiver front
> end or the contacts of a small relay.
> But grounding the antenna isn't going to even come close to bleeding off
> enough charge from the clouds overhead to prevent a lightning strike.
> 73,
> Dave   AB7E
> On 8/1/2010 8:40 AM, Bill Aycock wrote:
>> Gene--
>> In your message to Dan, you say:
>>   "you'll be draining off the static electricity (DC charge) to
>> ground, hopefully thus minimizing the likelihood of a strike to begin 
>> with."
>> I have always believed this to be true, but whenever I even hint at it,
>> someone on this reflector jumps on me. Do you have a reference for me?
>> Thanks--Bill--W4BSG
>> --------------------------------------------------
>> From: "Gene Smar"<>
>> Sent: Friday, July 30, 2010 5:40 PM
>> To: "Dan Schaaf"<>; "Tower and HF antenna construction
>> topics."<>
>> Subject: Re: [TowerTalk] Vertical antennas and lightning
>>> Dan:
>>>      If the inductor is the correct value (high enough XL at the 
>>> vertical's
>>> lowest frequency of operation so as not to upset the feedpoint impedance
>>> appreciably) you can permanently connect it to the feedpoint.  In that
>>> configuration you'll be draining off the static electricity (DC charge) 
>>> to
>>> ground, hopefully thus minimizing the likelihood of a strike to begin
>>> with.
>>>      I'd recommend XL>  10 X 50 Ohm = 500 Ohms at the lowest frequency.
>>> 73 de
>>> Gene Smar  AD3F
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