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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