[Hallicrafters] Antenna Lightning Protection

Wed Jan 7 10:40:45 EST 2009

Interesting Bob.  Ive been arguing about the Cone concept for decades 
but the established orthodoxy  rebels violently whenever it is 
mentioned. Ive left several antenna forums in disgust over this.

Carl
KM1H

----- Original Message ----- 
From: "Bob Macklin" <macklinbob at msn.com>
To: <hallicrafters at mailman.qth.net>
Sent: Wednesday, January 07, 2009 9:03 AM
Subject: Re: [Hallicrafters] Antenna Lightning Protection

> 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.
>>
>>
>>
>> ______________________________________________________________
>>
>
> ______________________________________________________________ 