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[TowerTalk] Tower Grounding Query!

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Subject: [TowerTalk] Tower Grounding Query!
From: (
Date: Wed, 11 Aug 1999 21:25:55 PDT
Hi Gang,
  Got some questions that i would like to hear opinions on. 

 Building two towers-one will be 55 ft. high including a short mast with
tribander on it. Under it i expect to have a pretty good ground system. The
tower will be about 65 ft. from the back of the house, in the center of the
backyard.The other tower will be a shorter housebracketed tower at the back
of the house. It can be 21 ft. tall or 31 ft. tall. The 6 meter yagi will go
on it and will be at about 25 ft. or 35 ft. That tower will be tied into the
ground system of the higher one, as will the utility ground.
 1 )Seems likely that the shorter tower has as much probability of being hit
by lightning at either height(21 vrs. 31 ft.). and even though it will be in
the shadow of the taller tower. I've read over the years that a tower tends
to produce a cone of protection around it equal to a radius of about 2.5
times the tower height. At 21 ft. high, is it as likely, less likely, to be
struck as the taller tower? If as likely, then i see nothing to desire in
the 21 footer and will opt for the 31 footer. Or would both be less likely
to be hit by virtue of being in the shadow of the 55 footer?( hope the
question is clear!)

 2) I have acquired 200 ft. of #2 stranded(7 strands), 7 copper plated steel
ground rods(5/8th" x 8') and don't mind going on beyond that if its dictated
and worthwhile. Also have 10 Cadweld charges for #2 to #2 and 10 charges for
#2 to 5/8th" ground rods. I plan to install a halo ground about 16-20 ft. in
diameter with 6 ground rods 9ft. in the ground and 3 #2 wires comming off
the halo from equidistant points to the 3 tower legs and clamped with what
utility workers call Matthew clamps. Thought i would make a similiar
grounding setup at the base of the housebracketed tower, but with a
semi-circle instead of a halo. Would probably get
3 ground rods under it. Then bond the two ground systems together and tie in
the utility ground. Then, over the course of the next year or two, i want to
add at least 50 50-70 ft. radials of #10 or #12 bare copper(several per
month) as i want to also shunt feed the tower on 80 and 160.These radials
would provide an excellent r.f. ground and serve to augment the d.c. ground
also. Each anchor point for the guys will have a galvanized (5/8th" x 8')
ground rod and i assume i should use some of my 3/16th EHS to connect the
guy wire just above the turnbuckle to the rod(to prevent galvanic action?)
The guys will be broken up every 13 or 14 ft. with insulators).
  Would appreciate comment on whether i am making the best use of my
grounding components!

  3) The concrete is 12 days old. I'm inclined to wait for the full four
weeks for it to reach full strength. Any dissenting opinion?

  Thanks in advance for any comments! 73 Roy Lincoln WA4DOU Elm City, N.C.

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