I would run 10 or 12 radial wires out 15'-20' to your ground rods. I would
make one longer run from tower ground over to you main entrance point.
I would adjust the number and lengths of radial wire so that you would use
up all your #2 wire with the tower radials and the run to your main entrance
point.
-------------------
Wes Attaway (N5WA)
(318) 393-3289 - Shreveport, LA
Computer/Cellphone Forensics
AttawayForensics.com
-------------------
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Art
Greenberg
Sent: Monday, May 18, 2020 2:29 PM
To: TowerTalk@contesting.com
Subject: [TowerTalk] Tower lightning ground system layout
I am working on the layout for my tower lightning ground system.
I have on hand about 275 feet of #2 bare solid copper. I also have 17 8-foot
ground rods.
I've read that lightning protection "radials" reach the point of rapidly
diminishing returns at lengths beyond about 70 feet.
Originally I planned to have three runs of 50 feet about 120 degrees apart
and make a fourth run go to my entrance panel and mains ground. But it seems
my distance estimating skills are lacking. I just measured that distance and
its more than 100 feet, and well beyond being an effective length.
If I instead go with four runs of about 65 feet spaced at about 90 degrees,
the fourth run will be limited in length by a driveway. I can't rotate the
whole pattern very much to improve that due to another obstacle. My apparent
options:
1 - I can abandon the idea of equal angular spacing to make that run a bit
longer. I think I can get the full 65 feet but I'll be going into a wooded
area with the possibility of having to deal with shallow tree roots and I
definitely won't be able to make a perfectly straight line of it.
2 - I can turn it into two or three shorter runs in a fan configuration
(also abandoning equal angular spacing), but the angular spacing between the
fan runs will result in the set ground rods on each run that are 16 feet
from the base of the tower being much less than 16 feet apart. I imagine the
optimal spacing rule of 2 times rod length still applies.
3 - I can put a bend in a single run to turn it parallel to the driveway to
get the full 65 feet. I would have to abandon equal angular spacing to avoid
an acute (less than 90 degrees) bend. What would be the best way to lay out
this bend (e.g., multiple gentler bends vs. a single bend, smooth curve or
something else, what about ground rod placement, etc.)?
Any of these options means acquiring more ground rods. I think I have a
sufficient number of Uni-Shots already.
I'm thinking option 1 is best, but I'm uncertain. Is there a clear advantage
to one approach vs. the other?
While I'm asking ... Should I be thinking about using more shorter runs, say
5 runs of 55-ish feet spaced 70 degrees apart, or 6 runs of 45-ish feet
spaced 60 degrees apart?
Yeah, I'm probably over thinking this. But I live in Florida and summer
thunderstorm season is about to begin.
Thanks.
--
Art Greenberg
WA2LLN
art@artg.tv
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