[Hallicrafters] Antenna Lightning Protection

[Glen Zook]

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.