[Heathkit] Differntial earth

[Jerry Lofstead]

Steve,

You are exactly correct on ... With proper grounding, everything goes 
high and comes back to earth potential when properly grounded.  I used 
to certify bonding and grounding for AT&T for PBX and computer 
installations.  Keep in mind... On a 2 inch diameter copper water pipe 
filled with water and going into the commercial water system, over a 1 
foot length, you will see a potential of 10,000 Volts appear during a 
strike!!!  That's why proper grounding is required...  single point!!!

This is why a SINGLE POINT GROUND is so important.  Each piece of gear 
needs to have ITS OWN ground wire to a "Ground Window" i.e. a single 
ground point that goes directly to earth.  This ground window is 
typically a rather thick and large copper plate with the earth ground 
located in the center of it.  All other ground wires are connected to 
bolts around it.  When "properly installed" with a direct lightning hit, 
no damage will be seen in anything attached to it!!  Seen that several 
times where even parts of a building were blown off near the telephone 
or computer room.

Jerry
W3CDE
Atlanta, GA

Steve Beveridge wrote:

> <SNIP...>
>
>It seems as though if everything goes "up" then "down" (with respect to
>genuine earth) at the same time, there is no (little?) damage. However, even
>a slight 'lag' in the return to true earth potential leads to damage. That
>energy has to go somewhere.
>
><SNIP>
>
>The 850 is nearly there, but this has been a valuable learning foray into
>something I had always taken as a fairly simple aspect of out hobby - the
>earth!
>
>Cheers
>Steve
>VK2XWL
>
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