[TowerTalk] Yet more grounding questions

Jim Brown jim at audiosystemsgroup.com
Thu Oct 5 13:26:07 EDT 2006

On Wed, 04 Oct 2006 20:47:44 -0400, Peter Dougherty wrote:

>UPSs with MOVs. I'm reading that MOV surge suppressors are NOT a 
>good thing in terms of lightning protection. On the other hand, UPSs 
>are needed for all the PCs in the house. How can I get the UPS 
>protection I need and still have solid lightning protection?

Three recommendations -- do all of them. 

1. Bond ALL of the grounds together using connections of the lowest 
possible impedance at RF. Remember, the energy in lightning peaks 
broadly around 1 MHz. All grounds means your ground rods, your plumbing 
(if it's metal), structural metal, and your radial system. Note that a 
radial system helps provide a low impedance to earth at RF by virtue of 
the capacitance between it and the earth, and is probably more 
important in that regard that the DC connection provided by ground 

2. Use a whole-house TVSS at your service entrance. This will be a 
shunt mode device, and it needs to be bonded to that big ground bus 
noted in #1. This provides primary protection for stuff coming in on 
the power service.

3. Series-mode TVSS products made by SurgeX (near Philadelphia) are 
designed for use on branch circuits. These products overcome all of the 
shortcomings of MOV devices. They are not cheap, but neither is the 
equipment they protect. They are useful whether or not #2 is present -- 
they protect your gear (ham gear, office equipment, entertainment gear, 
etc.) from stuff coming in from the power service AND stuff induced on 
branch circuits. 

A discussion of all of this is part of the Power And Grounding "white 
paper" tutorial that is on my website.  http://audiosystemsgroup.com. 
Click on the link for Publications. 


Jim Brown K9YC

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