[TowerTalk] FW: Tower Grounds

[Dick Blumenstein]

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 untinned)?  --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
>
>
>   
>
> _______________________________________________
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>