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[TowerTalk] Info/Advice re: Exothermic Welds

Subject: [TowerTalk] Info/Advice re: Exothermic Welds
From: Art Greenberg <>
Date: Mon, 20 Aug 2012 13:54:36 -0400 (Eastern Daylight Time)
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I've recently moved to north-central Florida and want to get a couple of 
multi-band antennas going this fall. The plan is to install a 43-foot 
vertical and a 135-foot doublet fed with ladder line. In both cases I'll 
place a remote matching network at ground level, and run coax and control 
lines for the matching network from there into my shack in a shallow-ish 
trench (possibly with conduit) and through an entrance panel. I will run a 
ground wire in each trench with the coax, and will install ground rods at 
both ends of each trench and at intervals along the way. The entrance 
panel will contain a grounding plate on which lightning arrestors are 
located, and I'll run a ground wire (or a wide copper strap) from the 
grounding plate to that ground system, and to my electrical service ground 
rod. I'm looking for an acceptable way to bond the ground wire and copper 
strap to the ground rods. I've seen the term "cadweld" used, and I watched 
a utility crew use an exothermic weld technique to connect a ground wire 
to a ground rod at the base of a utility pole on my property. I have no 
direct experience with the process.

Looking at on-line catalogs I see reusable molds for various 
configurations, clamping "handles" and welding powder all sold a-la-carte. 
I have not seen a mold that would work to connect wide copper strap to a 
ground rod.

The utility crew didn't use a reusable mold, it was what looked like a 
ceramic cylinder that they placed over the connection and left in place 
when the weld was complete.

I imagine that the single-shot mold might be faster to use but more 
expensive than a reusable mold. If each trench run is 100 feet and I use 
10-foot ground rods spaced at 20 feet, that's a total of 12 ground rods to 
bond to including the existing electrical service ground. So its probably 
going to make sense to buy reusable molds and a clamping handle. Are there 
tradeoffs other than cost that I should consider? Does it really make 
sense to buy two different molds, one for "T" connections and another for 
a dead-end connection, or can I use the "T" mold for everything with just 
a stub of wire on the second port? Is there such a thing as a mold 
(one-shot or reusable) for bonding wide copper strap to a ground rod?

I'm looking for advice and opinions as well as information. Is my plan 
reasonable? Suggested reading and sources for the molds, etc. would be 


Art Greenberg

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