I can't help but make a few comments found below:
Sean rf wrote:
Suggestions for grounding:
When attaching your #4 solid copper to the ground rod, use a non-oxidizing compound between your ground clamp and the ground rod. This is available at Home Depot in the electrical department, made by Ideal, it is called No-Alox, $5-$7. Make certain that you "shine" or "buff" the ground rod first with some emery cloth or sandpaper.
Or use Kopr-Shield, which is a copper-based compound.
You should also consoder the spacing between your ground rods. If you are using 8' long rods, be certain that they are no closer than 8', otherwise, they will cancel each other out.
No, No, they won't "cancel" each other out. The effectiveness is an
inverted cone which is 8 ft. in diameter at the surface. Overlapping
the cones will just reduce the effectiveness. Space them two times the
diameter from each other or 16 ft apart for 8 footers.
Same with 10' long ground rods, no less than 10' from the next ground rod.
10 x 2 = 20 ft apart. Read the technical articles on the Polyphaser web
site for the definitive info.
The best attachment for your #4 to the ground rods is ultimately a Cad-Weld connection, but these can be pricey.
No not really, just an industrial myth. Spec out CadWeld OneShots from
the www.erico.com website and order them from your local industrial
electrical supply house (not Home Depot ). I had to buy a case of 12
minimum and they cost me about $5.50 each. Now consider that price for
a maintenance free, weatherproof connection that can be buried versus a
$2.50 all brass/bronze ground clamp that you will have to retighten at
least four times a year (after every thermal cycling they will loosen
up) and I think they're real cheap. Or Hargar or Harger sells similar
units called UniShots, same thing.
Tnx for my 2 cents, 73 Phil KB9CRY
-Sean
Floyd Sense <sentek@sprintmail.com> wrote:
In regard to the stainless steel shims - I recently did the same, after
spending a lot of time finding the darned stainless steel. I finally
located some at a large sheet metal shop. They had some .002 and .005 stock
on hand, rolled up in tubes. According to them, they'd had it for several
years and no one had ever asked for it before. I also ran across some
small stainless strips in a local "old fashioned" hardware store that
carried very small diameter tubing and strips for hobby use.
----- Original Message -----
From: "Bill Ralston"
To:
Cc:
Sent: Friday, November 14, 2003 11:24 AM
Subject: Re: [Towertalk] Connecting grounds to towers
From: Bill Ogden
What is a reasonable way to connect ground wires to a tower (a TX-455,
in
this case, with the tilt-over feature)? I plan on three ground rods and
about 50 radials. I'll probably use insulated #14 wire (from Home
Depot)
for the radials and #8 bare for the ground rods.
I'd think about using #4 solid Cu or Cu strap - bigger the better. #4 is
avail at Home Depot.
I would run three wires from the base or tower leg to the ground rods, and
then run a ring around the base tying all three ground rods together.
Most
folks here seem to thing the cadweld one shots are the way to go, but I've
haven't tried that and have just been using standard ground clamps and
split
bots to make connections.
One way to attach the ground lead to the tower is to buy a Polyphaser
clamp.
Another way is to put wrap stainless steel around the tower leg and then
lay
the ground wire against the stainless and hold in down with stainless
steel
hose clamps. I did this, which gave me about 6" of contact between the #4
ground wire and the tower leg, with the stainless to prevent the galvanic
corrosion. This is similar to the polyphaser clamp. The building
inspector
vetoed that, insisting upon an "approved ground clamp"
I replaced this with standard ground clamps designed to go on a pipe (also
available at home depot). As these are made of bronze, there is still a
concern about galvanic action, so I placed shims of stainless between the
tower leg and the clamp. Since the area of contact between the clamp and
the grounding wire is quite small, I used three of these in parallel for
ground lead. The problem is that most building codes / inspectors are
really only concerned with DC grounding, and do not understand RF or
lightning.
Another option might be to find a large enough terminal (again, look in
the
electrical dept at Home Depot) that will go onto the bolt that is designed
to receive a large wire. Again, be careful about galvanic mismatches.
You
might even machine something out of stainless if you are really ambitious.
I am surprised about how little mention there is of practical mechanical
problems in the handbooks.
No kidding - I struggled with this for quite some time
de Bill N7VM
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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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