[TowerTalk] Grounding Wire/Strip

[Bob Wanderer]

See comments below.
73, Bob AA0CY
(ex PolyPhaser Technical Consultant)

----------
From:  Richard Spindler[SMTP:spindoc@digital.net]
Sent:  Tuesday, October 26, 1999 9:42 AM
To:  TowerTalk Reflector
Subject:  [TowerTalk] Grounding Wire/Strip


Boy.  This just gets complicateder and complicateder.

I was all set to do my ground system and grounding radials with #6 wire,
and then in reading another treatise on grounding, I am told that this
is a major mistake because of the inductance which will cause lightning
to look for another route to ground.  The PolyPhaser literature says
that what really should be used is minimum 1-1/2" flat copper strip, and
I have read another couple sources which repeat that, and say that if
wire is to be used, the minimum size should be 2/0.

The thing is: that kind of shoots my neat plan with the CADWelding of
the ground rods, unless one can CADWeld the copper strip.  Also, the
copper strip is REALLY expensive.  I think I am looking at around $400
for the amount I would need, and I wonder how long it would last
underground versus big wire; I would think a lot less long.

First step is to measure the pH of your soil.  The testing products sold for
pools and spas will work..  PolyPhaser has a kit specifically designed for this
purpose if you want to go that route.  Their catalog shows how to perform this
test.  If your soil is alkaline or base (and, generally, the US west of the
Mississippi is alkaline, acidic east of there), use copper-based grounding
material, otherwise go with aluminum, tinned, or galvanized materials.  
The longevity of your system, whether copper based or not, will depend on how
alkaline or acidic your soil is.  I believe the range is from 3 to 20 years
depending on many factors (including which "expert" you choose to believe),
but IMHO 6~10 years is a good average.  This longevity would be irrespective
of whether strap or wire was used.

Erico has a CADweld(TM) mold for the 1-1/2" copper strap if memory serves.
PolyPhaser has a mechanical attachment which should work satisfactorily for
amateur purposes.

Costwise, check with Ron Block (I THINK his # is 800 421 7170).  He's a Poly
distributor and a ham and has his own source for the copper which he sells at
a good price to hams.  Also try DavisRF.

I recall reading something somewhere about "copper flashing."  Sounds
like something that might be used in construction, and maybe on the same
principle, but cheaper than the PolyPhaser strip?

Yes, copper flashing would be a good alternative.  Again, first ascertain
your soil's pH.

I might be back to brazing copper strip to ground rods instead of the
pyrotechnics, after all.  I have a little common sense voice in the back
of my head that says wire would probably be OK if I get big wire, but
2/0?

I believe PolyPhaser has a mechanical wire-to-ground rod connection
which will handle up to 4/0.

This system is certain to take lightning strikes, so I do want to do it
right.  Anybody got some ideas or data on this dilemma?

Yes, mount a #1 Iron golf club at the top of the tower.  As Lee Trevino
once said, 'Not even God can hit a #1 Iron."  (Or was it a #2?).  All seriosuness
aside, the better your ground system the less likely damage will occur.  However,
you need to balance that with the fact that you're not a 24/7/365 service and
reasonable systems (cost-wsie) will probably suffice.

Good luck.
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