Lightning Protection for your Antenna

It's hard to know just what is "reasonable" when it comes to protecting your station from lightning.  Much of what is written by commercial vendors is aimed at the broadcast industry, with their 100 foot towers and millions of dollars worth of equipment.  Follow their guidelines, and you will have wonderful protection, but no money left for ham gear!  The other extreme is to have no protection at all.  Neither course seems prudent to me.

Lightning DOES come along, and here in west central Florida on an almost daily basis!  It's a bit daunting when you consider that a solid bolt can generate 30,000 amps at 750,000 volts.

My home is located on a small suburban lot, so an extensive system with multiple radials and the recommended commercial minimum of 10 ground rods is simply a pipe dream.  While I sometimes curse the huge oak trees that surround me for the signal that they absorb, I give thanks for and bless them during lightning storms, as they provide rather substantial NATURAL protection.

These factors persuaded me to adopt a simpler approach to lightning protection.  I decided to place a chemical ground rod at the antenna base, supplemented by a pair of standard ground rods where the coax enters the house.

The sandy soil here, with its poor conduction, was the reason for a chemical ground.  Now, if you purchase these from a commercial source, they are expensive - running around $1,000 each. As they are nothing more than a copper pipe with a few holes punched in it, filled with conductive "salts" which slowly leach into the surrounding earth over time, I decided to "homebrew" one. Commercial units use a six to twelve foot length of 2 1/2" pipe.  I found a 4' section of 4" diameter, and used that.  It was placed into the ground with a post hole digger, and then surrounded with a conductive backfill. I use Epsom salts (magnesium sulfate) for the filler.

I used #2 tinned copper wire to connect this creation to my antenna mast, but a wide strap would have been better.  While lightning is said to be DC current, it has such a fast rise time that it propagates like radio frequency - so low impedance connections are a must.

The coax to the antenna proper is also grounded (through its outer braid) to the same chemical rod, at the bottom of the mast, via a sturdy commercial kit supplied by Times Microwave.  It is then grounded again, before entering the house, to a pair of ground rods, connected via a #6 braided wire.  A commercial PolyPhaser surge arrestor takes care of the inner conductor.

Now, this little system is most definitely NOT the "ultimate"!  My intent in describing it here is to simply set YOU to thinking, and to encourage you to better it for your own system.  You will have much more peace of mind if you assess your lightning threat and do something about it!

"Ham" Radio