[TowerTalk] Cadweld vs clamps

Roger (K8RI) on TT K8RI-on-TowerTalk at tm.net
Sat Oct 25 22:06:22 EDT 2014



I'm well aware of the problem, but I've been trying to figure out how I 
can safely separate them.   Almost everything ties to a grounding plate 
where it enters the house and where it enters the shop.  I think I 
mentioned almost getting electrocuted when I lived in Breckenridge MI. I 
was holding a bare # 10 wire about 36' long that hooked to an 8' ground 
rod.  When my knees touched the wet ground, it had me.  That ground rod 
was about 75' W of the service ground.  The station ground was about 75' 
E of the service ground, yet the resistance in "WET" ground was high 
enough not to trip the breaker.

73

Roger (K8RI)



On 10/25/2014 7:35 PM, Bill Turner wrote:
> ------------ ORIGINAL MESSAGE ------------(may be snipped)
>
> On Sat, 25 Oct 2014 17:55:18 -0400, you wrote:
>
>> The antenna ground system ties
>> to both buildings, essentially tying their service grounds together
>> through a network of over 600 feet of bare #2 cad welded to 32 or 33 8'
>> ground rods.
> REPLY:
>
> And therein lies the problem. Multiple grounds which are physically
> separate but which are wired together.  That is asking for trouble and
> that is why the NEC requires a single point ground.  Having separate
> SPG's that are wired together is NOT a true SPG.
>
> The ground itself is not a perfect conductor, far from it. When
> lightning hits one of the grounds, it elevates that individual ground
> potential well above the other grounds in the area, and if they are
> wired together, guess what happens? Current flows between them and
> that is BAD NEWS.
>
> At my QTH, the tower and antennas have their own ground and the house
> has its own ground, and when lightning is present they are totally
> disconnected from each other. I believe that is the only safe way to
> go.
>
> 73, Bill W6WRT
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-- 

73

Roger (K8RI)




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