Finally, I have received my building permit for my tower and home remodel and
am excavating for the tower, a 70 foot crank-up by Tashjian Towers. The base
will be located at the inside corner of a U-shaped home (visualize the lower
right inside corner of the "U"), approximately 8-10 feet from adjacent walls.
The home's power panel will be located about 55 feet away (visualize the end of
the upper left arm of the"U") and will utilize a new concrete garage floor with
rebar as a Ufer ground. The radio room will be located about 65 feet away from
the tower (visualize the lower left outside corner of the "U").
After reading the archives and reviewing the PolyPhaser site information, I was
considering the following approach to grounding my system and would appreciate
any suggested modifications and good sources for material.
The dimension of the tower base will be 4x4x8.5 feet. I would like to extend
three 52 foot radial lines away from the tower, approximately 11-12 degrees
apart from one another, running away from the structure, using 1.5 inch copper
strapping and an 8 foot 5/8" ground rod every 13 feet. I'm not sure if I
should take all of the radials from one leg, one from each leg, or from a strap
loop interconnecting all three legs. Also, I'm unsure how I best connect the
strap to the tower and the ground rods. I would like to use a Cadweld (or
similar) connection for the ground rods because they will be covered by a new
concrete patio after installation. My tower manufacturer doesn't recommend
tying into the base rebar (Ufer). The radials may need to circumvent a large
tree planter in the center of the courtyard area. I suspect that the ground
conductivity in our area isn't great, (although I have no formal measurements).
I was planning on grounding the coaxial cable ground at the top and base of the
tower, although I have to figure out a good way to do this. I would like to
place a metal box at the tower base to house PolyPhaser protectors. I wonder
if that could also serve as the ground for the coax shield at the base?
Anyway, from the bottom of the box, I will have a sweep of conduit which will
go underground to a hole in the homes foundation wall. From there to the
shack, the coxial cables will be on the surface of the crawl space and enter
the radio room directly from the floor OR through a grounded metal plate on the
wall. I was going to use copper strapping from the tower ground to the plate
and radio room equipment bus bar (copper pipe on the back side of the desk).
I also plan to run a 55 foot 1.5 inch copper strap to the home's panel ground
(again a Ufer ground). Lastly, I was going to run either #6 copper wire or
again copper strapping around the house perimeter, WITHIN the crawl space,
against the foundation wall, slightly buried beneath the soil if possible. I
don't think it is possible to loop a wire outside the entire house due to
existing concrete pads, driveway, etc. I hope this is ok.
Now compared to several amateur installations I have seen locally, this is
overkill. Some have advised me to put three spirals of #6 wire spanning the
vertical length of hole, one for each leg, and then just pore the concrete... a
Ufer type ground NOT using the rebar cage. Some just have one to three ground
rods surrounding the tower base. Of these folks, none have had problems (so
far) after many years of service.
Sorry about the long message, but I will be pouring concrete within 2-3 weeks
and all of the radials will be permanently out of my reach under a new patio
concrete surface!
Craig, AE7I
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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