With the new 45G (concrete arrives at 0730 tomorrow) I'm trying something I
haven't seen mentioned, hope it works ok. I placed a 6' long strip of 8"
wide heavy gauge solid copper roofing material in the base hole, covered
with a few inches of gravel. The strip runs across the bottom of the hole
under the gravel, then up and out one side of the hole with about 6" to
spare outside the hole. It's spiked to the side of the hole with a half
dozen 8" spiral bridge nails (just to hold it solid while the concrete's
poured). I plan to tie this copper sheet into the other ground setup for the
tower legs, which will be several (at least 6) copper clad ground rods in a
circle about a 6' radius around the base of the tower, all tied in with #4
copper to all three legs. Don't know if the copper sheet under the tower
base will help dissipate strikes, but I figured it wouldn't hurt and I had
it on hand. My theory is anything that adds copper contact to the ground,
especially down deeper where things stay fairly damp, can only help. Has
anybody that's tried this got any comments? The tower will sit on a Rohn
pier pin in the center of a concrete pad that will measure about 3' square
by 3-1/2 feet deep. Concrete will be a fairly stiff mix of 3000 psi 28-day.
No rebar in the base pad (compression load only), but lots of rebar in the
guy anchor pads. The fun part will be trying to properly finish the base top
around the pier pin area with an ever-so-slight slope in all directions away
from the pier pin, so that water doesn't collect and stand under the tower
base plate. Needless to say, a concrete finisher I ain't. :-)
Jerry W5KP
----- Original Message -----
From: EUGENE SMAR <SPELUNK.SUENO@prodigy.net>
To: Milcarsky <jamvet@bellsouth.net>; TowerTalk <towertalk@contesting.com>
Sent: Friday, July 20, 2001 8:46 PM
Subject: Re: [TowerTalk] Routing cables - tower to shack
>
> Ed:
>
> I'm planning on putting the arrestors at the base of my tower, bolted
> to the insides of a metallic Hoffman box or similar. From the box the
coax
> and control cable runs will be in 3 inch sch 40 buried conduit to the
> house/shack. The alternative is to put the arrestors in a box just
outside
> the house at the end of the conduit run and ground at that point, as most
> commercial installations have it.
>
> My thinking is that the ground field for a lightning strike
originates
> at the tower, where all the underground radials connect to the tower legs.
> Here the inductance of multiple parallel ground legs will be less than at
> the entrance to the house/shack, fifty feet from the tower, where I will
> have only one radial to which to connect the arrestors' grounds. (I'm not
> planning on encircling my house with buried copper ground wires.) I'd
> rather have the arrestors far away from the house and let them do their
work
> in a low-inductance part of the ground field, rather than close to the
> house.
>
> I agree with Steve, though - keep the single-point ground outside of
> your house. Its connection into earth will be shorter and the lightning
> energy is less likely to get into your house wiring. And don't put a
bend
> in your ground wire from the coax runs. Keep it as straight as possible
> such that the lightning energy continues to move in a downward direction
to
> a metallic ground connection.
>
> GL es 73 de
> Gene Smar AD3F
> -----Original Message-----
> From: Milcarsky <jamvet@bellsouth.net>
> To: TowerTalk <towertalk@contesting.com>
To: <towertalk@contesting.com>
> Date: Friday, July 20, 2001 7:03 PM
> Subject: Re: [TowerTalk] Routing cables - tower to shack
>
>
> >
> >Steve,
> >
> >It's clear that grounding the coax at the tower base, before it bends
> toward
> >the shack is the right thing to do. However, I have only heard that the
> >coax shield should be grounded at this point. Why not also place an
> >arrestor for the center conductor at this point as well? It would seem
> that
> >this would afford a certain amount of extra protection. What are your
> >thoughts?
> >
> >Ed KG4ARN
> >
> >----- Original Message -----
> >From: <K7LXC@aol.com>
> >To: <kq2m@mags.net>; <towertalk@contesting.com>
> >Sent: Friday, July 20, 2001 6:14 PM
> >Subject: Re: [TowerTalk] Routing cables - tower to shack
> >> Commercial specs call for grounding cables that come down the tower
> >> *before* they turn towards the building. The cables should be grounded
> >> directly to the tower at that point to offer the lowest resistance path
> to
> >> ground. The bend in the cables introduces inductance at that point so
you
> >> want to be grounded before that so the lightning energy will go there
to
> >> ground.
> >
> >
> >
> >
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> >-----
> >FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> >Submissions: towertalk@contesting.com
> >Administrative requests: towertalk-REQUEST@contesting.com
> >Problems: owner-towertalk@contesting.com
> >
>
>
> List Sponsor: Are you thinking about installing a tower this summer? Call
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> -----
> FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
>
>
List Sponsor: Are you thinking about installing a tower this summer? Call us
for information on our fabulous Trylon Titan self-supporting towers - up to
96-feet for less than $2000! at 888-833-3104 <A
HREF="http://www.ChampionRadio.com";>
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