Thanks Dick.
I see your comment on the silver solder. I wanted to see if you were
referring to plain silver solder (lower temp stuff like what you would use
with a big soldering iron), or if you were referring to the silver content
braising rods that require a torch.
The (affordable) silver rods have 15% silver and ~80% copper content and are
flux coated if I'm reading the spec right.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: Dick Blumenstein
Sent: Tuesday, October 17, 2017 10:53 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] FW: Tower Grounds
Hello Jeff-
Shortly, I am going to be using 2" wide copper strapping on my tower
legs. However, I am NOT attaching them to the tower leg bolts. Instead,
I will be clamping them on each tower leg about a foot up or so from the
base and in a GENTLE ARC, running them down to a ground rod near each
tower leg, attaching them with ground rod copper clamps below the Harger
CAD weld that attaches to the rod at the top where my #2 AWG stranded
goes out to additional ground rods (like a tree branch). I have read in
the past that silver solder might explode or melt (sorry Matt) from a
lightning strike and might not hold together. I will, of course, use
stainless shim stock between the copper and the galvanized tower leg to
reduce galvanic corrosion. Since I haven't done it at this time (soon,
though), it might be a little challenging to get the copper under a
couple of stainless radiator hose type clamps and then to proceed in a
"graceful" arc down to the ground rod. We'll see how that goes for me;
which is why I selected 2" wide (and not 3" wide) copper strapping. I
heard that lightning does not like to take sharp turns, hence, the arc
of copper and not bolting to the leg bolt. Every time I want to lower
my crank up tower horizontally to the ground to work on the antenna
system, I will obviously have to remove the copper from under the
stainless clamps. A bit of a pain, but so far I have not read of a
better way. At least it will allow me to look at any corrosion that
might have occurred since last time I lowered the tower.
(BTW, a little anecdote. The electrician I used for heavy duty projects
in FL, told me that he used to work at the Kennedy Space Center. He had
to CAD weld about 2,000 (as I recall) very long ground rods around the
Vertical Assembly Building. Now, that's one heck of a ground rod system!!!)
73,
Dick, K0CAT
===================
Matt wrote on 10/16/2017 12:04 AM:
Has anybody had any experience with grounding towers with flat copper
strap v.s. using stranded wire or copper braid (tinned or
ntinned)? --jeff
Wb7aht
Hi Jeff,
I feel that wide copper strap is an excellent choice because of its low
impedance and outdoor durability. I used 3" x.032" copper strap from each
tower leg to tie into my ground loop. I drilled 1.125" holes in the
strap
to fit over the anchor bolt to tower base connections (all crank-up towers
at my station). To make clean holes, I sandwiched the strap between two
scraps of plywood and used a forstner bit in a drill press. The copper
strap is dielectrically isolated from the galvanized base and bolts to
prevent galvanic corrosion using a pair of 1.125" ID stainless steel flat
washers at each connection. I also coated the connections with
antioxidant
compound and it will be easy to check and service them periodically since
they are above grade bolted connections. I also use a separate piece of
strap to ground the copper bulkhead bar at the tower base. It is tied
into
the ground loop with the shortest possible length.
The leg straps run the shortest path over the side of the concrete base
then
drop below grade where they are silver soldered to a wire ground loop that
encircles the concrete foundation. There are four radial grounds that
are
CAD welded to the ground loop at the four corners and these extend out
radially to about 50 ft each. There are 4' copper clad ground rods CAD
welded to the radials at about 8' intervals. The tops of the rods are
about 18" deep. I would have used 8' rods but I have really hard caliche
that starts at 18" deep and I just could not drive them any deeper even
using a full size jack hammer - so I cut the 8 footers in half and doubled
up the quantity at half the spacing.
I also use wide copper strap at the single point station ground panel to
connect to a similar ground loop at the station location.
Hope this info is of use to you & good luck on your project.
73
Matt
KM5VI
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