[Hallicrafters] Antenna Lightning Protection

[Tom NØJMY]

Lightning is a lot like deer. Deer never seem to pay any attention to 
the deer crossing signs.

I use to live on one of those lightning-magnet hills north of Cedar 
Rapids.  My tower never showed any signs of having been hit over the 13 
years I lived there. But my well, which was about 50' away and protruded 
out of the ground about 18", got blasted on a regular basis.

I guess I had an "inverted cone" of protection, hi HI.  My house was 
also hit once, blowing one of the garage doors in, as well as a few 
other things.  And a medium-sized Chinese elm out in the pasture was 
destroyed by a bolt that I happened to get on tape (long story)!

73,
Tom NØJMY.  .

www.hayseedhamfest.com
Multi-section Can Capacitors
for Heathkit, Drake, more...

Bob Macklin wrote:
> In the 80's I was the chief engineer on a NASA telescope on a 10K ft
> mountain near Tucson. This place is a lightening magnet.
> 
> I received a grant from NASA for a lightning protection study.
> 
> We ended up with a LARGE knife switch that would break all lines between the
> internal wiring and the power into the building including the ground. All
> the incoming lines had gas discharge clamps and semiconductor (Transorbs) on
> them.
> 
> There is a CONE OF PROTECTION. We put a ham radio crankup tower in the
> corner near the building and ran it up during thunderstorms. This protected
> the telescope building from a direct hit.
> 
> This facility also had a NASA tracking station used for the Space Shuttle
> program.
> 
> Bob Macklin
> K5MYJ
> Kent (Seattle), Wa,
> "Real Radios Glow in the Dark"
> 
> ----- Original Message ----- 
> From: "Glen Zook" <gzook at yahoo.com>
> To: <hallicrafters at mailman.qth.net>; "Waldo Magnuson" <magnuson at mac.com>
> Sent: Tuesday, January 06, 2009 8:14 AM
> Subject: Re: [Hallicrafters] Antenna Lightning Protection
> 
> 
>> I do regular presentations on lightning protection and r.f. grounding.
> You can find synopsis of my presentations (in Word format) and some
> rudimentary diagrams at
>> http://k9sth.com/Page_2.html
>>
>> Scroll down to the heading "Grounding Articles" and the first 4 links are
> appropriate.  There are definitely several ways to accomplish a good
> grounding system and what I recommend is just one of those.  However, my
> recommendations are among the cheapest, if not "the" cheapest, ways to
> achieve a good grounding system because you can fabricate most of the
> devices yourself for a fraction of what they cost from commercial sources.
> Now the websites for the commercial manufacturers often do offer some very
> good information on grounding.  Of course the methods described "just
> happen" to use the devices manufactured by that company.
>> I do recommend installing dissipation devices in addition to a proper
> grounding system.  There are instructions as how to build your own devices
> at a cost under $10 each rather than purchasing such devices from commercial
> sources that generally cost several hundred dollars each.  The ones that you
> make yourself will probably not be as "pretty" as the commercial sources but
> they do work.
>> Now there is nothing now known to man that can prevent a lightning strike.
> However, dissipation devices do reduce those chances considerably.  There
> are those who say that such devices are "snake oil" and there are those who
> swear by them.  I am among the latter.  Those companies who manufacture the
> dissipation devices often will "guarantee" that you will "never" take a
> strike.  But, if you do take a strike then they usually say that you did not
> install the devices correctly.  As I said before, there is nothing that can
> prevent a strike from possibly happening.  However, you can greatly reduce
> that chance.
>> I live 1/2 block from the highest point in the City of Richardson, Texas,
> and although no where near as bad as Florida, we definitely get our share of
> lightning.  The top antenna on my main tower is 67 feet above ground (see
> http://k9sth.com/uploads/newantenna.JPG for photos) and in over 36 years of
> the tower being installed I have never taken a lightning strike.  The "pole
> pig" (electric company distribution transformer) that is about 40 feet from
> the tower and about 40 feet lower than the tower has been struck.  Also, my
> across the street neighbor has lost 3 trees and a chimney to lightning but
> none of my antennas have ever been struck.  Now that is not to say that I
> will never take a strike for, again, there is nothing now known that will
> prevent a strike absolutely.  But I am a firm believer in dissipation
> devices.
>> In the past, when I was not retired, I oversaw the installation of
> dissipation devices on over 200 two-way radio and microwave radio towers
> ranging from around 100 feet to over 500 feet tall here in the State of
> Texas.  Some of those towers recorded several lightning hits per year and
> after the devices were installed none of the towers were hit, at least
> during around 10 years that I kept track of them.  But, again, there is
> nothing that will prevent a strike absolutely.
>> You do have to install a proper ground system, there is no question as to
> that.  Then adding dissipation devices is an added protection.  The ground
> system comes first and then add dissipation devices.
>> As I pointed out before, there are several ways to get a good ground
> system.  The system that I recommend has been adopted by a couple of
> television transmitter manufacturers and by at least one agency of the U.S.
> government.  Of course the systems recommended by most of the manufacturers
> of grounding equipment work well, they are just relatively expensive to
> employ.
>> Remember that commercial radio installations have to operate 24/7/365 and
> they do not have the ability to disconnect the antennas during storms.  The
> vast majority of those installations do not suffer damage from lightning
> because of proper grounding systems and amateur radio operators need to take
> note.
>> Glen, K9STH
>>
>> Website:  http://k9sth.com
>>
>>
>> --- On Mon, 1/5/09, Waldo Magnuson <magnuson at mac.com> wrote:
>>
>> From: Waldo Magnuson <magnuson at mac.com>
>>
>> I just read an article on gas discharge tubes (GDTs) and again thought I
> should have some kind of lightning protection for my radios other than (when
> I remember) disconnecting my antenna when I'm not using it.  What do others
> have for lightning protection (if any)?  Any recommendations?  GDTs sound
> good.
>>
>>
>> ______________________________________________________________
>>
> 
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