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From: Barry Kutner[SMTP:w2up@itw.com]
Sent: Sunday, July 27, 1997 10:04 AM
To: towertalk@contesting.com
Subject: [TowerTalk] ground rods and connections
Hi gang - I was re-reading some of the archives on ground rods, etc.
on the reflector today, in preparation for some impvement in the
tower ground. This brought up a few questions:
1. When you have mulitple ground rods in series (spaced at twice
their depth) what is the best way to connect them, and with what
material? For example, if you use #4 solid copper, do you run it as
one long piece (meaning, not cutting it) and clamping it, and
intersperse the ground rods, or do you cut it to length and clamp
each piece with a separate clamp (meaning two clamps on each
"middle" rod)?
While probably an "ask 10 experts and get 11 answers" type query, I
think either way would work although I'd suggest the first way to maintain
continuity.
2. If using copper strap instead of round wire (this
is better, isn't it?) MUCH how do you bury it? Same way as cable-in a trench.
and how do you connect it
to the rods? PolyPhaser 58R112S for a mechanical method.
Can the strap be Cadwelded? Yes. Erico sells the molds for both 1.5 & 3" widths
BTW Cadweld(TM) is a trademark of Erico for their exothermic welding products.
Exothermic is the correct generic name. However, like Xerox for
photocopying and even PolyPhaser for lightning protection,
people use Cadweld to mean exothermic welding.
3. Speaking of Cadweld, I'd like to hear from someone who has
actually done this and find out the details. Easy as pie. Put the mold
around the materials to be welded, pour in the "gunpowder" (comes in
pre-measured single-shot bags), close the mold and put the primer
"gunpowder" in the top of the mold. Then fire it with the igniter. BANG!
Great stress reliever (almost as good as taking your .45 to target practice and
pretending the target's somebody you dislike).
4. How long do 8 ft copper ground rods last in average soil?
Anywhere from 5-15 years, maybe more and maybe less. Best thing to do, Barry,
is measure the pH of your soil. Adequate results can be obtained from using the
same measurement devices sold by pool and spa shops. PolyPhaser sells a
measuring kit (SPT, about $50) designed specifically for this measurement. If
the pH is neutral to alkaline, it is a copper-friendly environment. If however,
it is
acidic, you would be better off using galvanized/tinned/aluminum rather than
copper. The soil found in the eastern part of the U.S. is generally acidic,
whereas it is alkaline in the western part. Realize that the pH may vary by
depth and that you may, for example, have an alkaline stratum sandwiched between
acidic strata. Without starting the thread again, this can cause corrosion to
occur
on the ground or guy anchor rod itself (as can the part of the anchor rod in
concrete
versus the part which is in soil).
My system has been in 7 years now. Should I just start over
with more rods, assuming corrosion has done its thing, or try to find
where I left off 7 years ago (may not be easy with it all buried)
and continue the daisy chain?
If you've not done PM in 7 years (something which ought to be done yearly),
I would check the condition of what is already in place first. If it looks in
good
shape (make a ground resistance [Megger or equivalent] test), employ it as
part of your upgraded system. Otherwise, pull it out and restart.
73,
Bob Wanderer AA0CY
Senior Applications Engineer
PolyPhaser Corp.
Tnx/Barry
--
Barry Kutner, W2UP Internet: w2up@itw.com
Newtown, PA FRC alternate: barry@w2up.wells.com
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