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Re: [TowerTalk] Grounding of Amateur Radio installations

To: "Tower Talk List" <>
Subject: Re: [TowerTalk] Grounding of Amateur Radio installations
From: "Jim Brown" <>
Date: Fri, 08 Dec 2006 09:21:33 -0800
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On Fri, 08 Dec 2006 15:47:18 +0000, Phil Camera wrote:

Each of Phil's posts have been right on about grounding. I'll add 
another important point that seems to be overlooked by many here on 
the topic of surge protection.  

MOV surge protection is a really bad idea on branch circuits. The 
only GOOD application of an MOV is a very beefy one AT THE SERVICE 

Let's say you have an MOV "protecting" a computer at one outlet, 
interconnected to a printer at another outlet, and a cable modem at 
another outlet. When the MOV fires, it conducts the surge (lightning 
or otherwise) on the green wire, and the resulting IR drop in that 
green wire raises the voltage on the chassis of equipment connected 
to THAT OUTLET to a very high value. The two ends of the cable 
connecting equipment powered from a different outlet will see the 
very high voltage at one end and a very low voltage at the other 
(or, if MOV "protected," a different very high voltage). That 
potential difference can, and usually will, blow up equipment at 
either end. This is the likely mechanism by which Pete's computers 
were toasted. 

Another reason MOV's are a really bad idea is that they fail or 
"work" at reduced capability after having dissipated some finite 
number of joules, but you often don't know this until it's too late.  

In the pro audio world, we have lots of expensive interconnected 
equipment at widely separated locations. Pro audio folks have 
learned the value of SERIES MODE surge protection. The SurgeX line 
of products use only series-mode surge protection, and have 
established an excellent track record. They are the only protection 
product I use on branch circuits. They are not cheap, and you won't 
find them at Sams Club or Costco. But neither is my ham gear, nor my 
computers, nor my home entertainment equipment. :) 

Full disclosure -- as a consultant, I occasionally do work for good 
manufacturers, and I have done work for SurgeX in the form of 
technical writing and occasional telephone support/troubleshooting. 
My recommendations are entirely independent of that -- indeed, I 
specified SurgeX products in all of the big audio systems I design, 
and bought and installed in my own home/office long before I did any 
work for them. 


Jim Brown K9YC


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