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Subject: [TowerTalk] FOOTING -- GROUNDING
From: (Jerry Liley)
Date: Fri, 21 Nov 1997 16:07:06 -0600
                        A story from Missouri
Dear Jim,
I am not an expert but I do have some experience.   You cannot have
too much grounding provided that it does not "route" the charge to the
wrong place.  I once placed a coax switch in the window well outside my
basement shack to switch between towers.   It was placed on an eight foot
ground rod.   I thought I was doing good.....WRONG!   Every charged cloud 
that passed over my house seemed to discharge right into that switch.  
After several repairs to switches I put the switch on a wooden stake.  End
of problem.  (I should add that there was an air gap between the switch
and the rig).   All of the problems stayed in the window well outside.

On grounding towers:  I also heard forty years ago that you never direct any
"charge" through concrete.  I did not listen.  I have built three towers
(Rohn 45 and 55) that began life in a seven foot deep, square hole.   When
the hole is dug and cleaned out,  I set a tower section down in the bottom
of the hole and mark a tower leg footprint on the floor of the hole.  I
then take the section out and sink three eight foot ground rods right in the
middle of each leg mark.  About a foot of each ground rod pokes up out of
the bottom of the hole.  A 15 degree bend is put in each ground rod so that
the tower section or ground section  (done it both ways)  is pushed down 
over the ground rods that there is good contact between ground rod and
tower.   One inch gravel is then placed in the bottom of the hole 12 inches
deep.  The tower section is then raised up about six inches off of the bottom
of the hole  (the gravel fills in under it)   and the rest of the re-bar
and concrete preparation is done and the concrete is poured.  I use two 
tower sections to get a good plumb and hold them in place with temp guys.
My towers have been struck by lightning several times over the years.  
(The name of my QTH is Holts Summit and is the highest place for miles

This is not necessarily a recommendation but is a true experience.  So far
I have not had any damage to the concrete bases.   I figure that the bottom
of the hole with that foot of gravel and those three ground rods are always
wet from the water draining down through the tower legs.   If you could
see it, there may even be some standing water because Missouri has clay at
that depth and the water does not seep away very fast.   If there is some
other explanation as to why there has been no damage,  I don't know what it

73,  Jerry,   K0GUG

J.  Bradshaw,  AC6TK
At 10:16 AM 11/21/97 -0800, you wrote:
>I have noticed several replies (and I thank you all) mention attaching the
>J-bolts to the rebar cage.  In my visits to other tower manufacturers
>webpages, the issue of proper grounding was raised.
>It seems that there is a danger of the concrete being shattered in a
>direct hit if the grounding path is through the concrete, resulting in
>collapse of the tower.  It was mentioned that J-bolts should NOT be
>attached to the rebar cage, and that the cage should not protrude from the
>In addition, HEAVY ground wire should be bolted to tower feet and run
>beyond the perimeter of the foundation to ground rods.
>Check out the recent thread by M.G.Brafford.  It sounds like he lives on a
>One should also know that his insurance should be paid up,  because
>lightning just plain wrecks things and kills people no matter what you do.
>I don't live anywhere near the top of the hill, but I've been zapped by
>just STATIC when the wind blows.  The time to disconnect is BEFORE the
>storm, not during.  Its been interesting to watch the end of the coax to
>one of my antennas just dance from not being DC grounded.  I'd hate to
>think that was being dissipated in the front end of my radio!  A low pass
>filter may help, by virtue of series L, but caps to ground might not break
>down before the first RF stage!
>Food for thought.
>73 de Jim,

***   Jerry Liley, K0GUG, Holts Summit, MO -- ARRL LIFE -- NRA LIFE  ***
***                     5BDXCC-CW    Honor Roll-CW                   ***

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