[RFI] Ground Rod Placement

[k0il@qsl.net]

W6jzu wrote: 
>IF I haven't gone to extraordinary efforts to establish a true ground 
>system as the ones Dale and others describe, and IF I have no identifiable 
>problems as a result, should I, "just to be safe" (whatever that means), go 
>to all that effort? 
 
Hi Smitty, 
 
You obviously have a good "RF" ground.  I see you have a 6-land call.  If 
you're in 6-land, do you get alot of lightning storms? (I've never been 
there!)  If you do, are you located on high ground or relatively flat ground 
making your tower the tallest object around? 
 
If you said yes to both of both of these, you're an lightning strike waiting 
to happen!  It'll just depend on how often you have lightning storms as to how 
often you'll take a strike.  It may be once every year, or once every 10 
years.  Then it's almost completely random chance with a poor safety ground as 
to if/when/how much damage you will get from a strike. 
 
I once lived at the bottom of a valley when I was first licensed at age 15.  
Only had one thin FOUR foot rod for the antenna and one FOUR foot rod for 
shack equipment!!!  Never had a problem in 10 years, but I also almost NEVER 
left equipment hooked up when not in use.  All I had was some old "spark gap" 
arrestors that were actually junk.  I felt darn lucky when the neighbors old 
tall tree in their front yard took a direct hit splitting it into two.  I was 
extremely lucky to have never taken a direct hit. 
 
Now I live on a very high point and my antennas are a little higher than the 
nearest power line.  First week in the house, before any antennas went up, I 
saw the line take a direct hit!  I knew things would be different at my new 
location right then.  So I've taken alot of extra precautions at this QTH.  I 
learned alot about grounding on my job as a communications engineer that 
opened my eyes also.  It's best to reduce the randomness of lightning's damage 
by giving it what it wants: a path to a large area of ground/earth for it 
dissipate its energy.  It'll find a path or a number of paths, usually through 
your household electrical system and equipment, if you don't give it a good 
enough controlled path to start with. 
 
A ham friend of mine who lives 1 mile away and 100 ft lower in elevation has 
been hit 3 times in last 4 years.  One hit took out every electronic item in 
the house that was plugged into the AC power system and caused the fiberglass 
2 meter antenna on top of his tower to explode into tiny pieces.  Other hits 
only took out the PacketCluster radios and computers in a "random" fashion.  
He had never had a hit in 10+ years before that. 
 
Proper grounding isn't only for RFI/EMI, although it can help RFI/EMI problems 
when properly installed.  It's mainly for safety.  There are 3 types of 
grounding in a ham's shack or house: RF ground for RF equipment, lightning 
dissipation ground for antennas, and AC power system "SAFETY" ground.  And 
there's also ground system on the telco and cable TV for any transiants (like 
lightning) and safety.  These should all be tied to a single point grounding 
system if at all possible.   
 
If anyone wants to learn more about grounding, the book "The Grounds for 
Lightning and EMP Protection" sold by PolyPhaser really has some good stuff in 
it and is easy to read (few equations).  Another pretty good book is 
"Lightning and Lightning Protection" by William C. Hart and Edgar W. Malone, 
published by Don White Consultants, Inc. although it's a bit dated now and may 
be hard to find. 
 
73, 
de ed -- K0iL 
k0il@qsl.net 
Omaha, NE


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