[Top] [All Lists]

RE: [RFI] Earth isolation

To: "rfi@contesting.com" <rfi@contesting.com>
Subject: RE: [RFI] Earth isolation
From: "Jim Brown" <jim@audiosystemsgroup.com>
Reply-to: Jim Brown <jim@audiosystemsgroup.com>
Date: Thu, 09 Sep 2004 09:10:06 -0500
List-post: <mailto:rfi@contesting.com>
On Thu, 9 Sep 2004 08:48:49 -0500, EDWARDS, EDDIE J wrote:

>If you place the choke on the AC mains ground you WILL create a change
>of that circuit's characteristic impedance 

Leave out the word "characteristic" -- it's not a transmission line. Just plain 
series impedance. Now the sentence is right on! 

>and it will no longer
>function as the AC safety ground whenever you need it.  


>You also violate
>the single point grounding principle since that circuit now sees other
>grounds as lower impedances (like thru your equipment circuit boards or
>through humans in some cases).  

Again, not the right words, but the right problem. The single point principle 
violated because the choke disconnects the power system from the single 
point. And the system is unsafe because the choke blocks the required 
connection at the frequency of potential power faults (spikes, lightning hits, 
etc.). You DO see the connection if you measure it with a DC ohmmeter (or 
audio frequency bridge), but lightning and power spikes aren't predominantly 
DC or audio, most of their energy is at much higher frequencies. 

Jim Brown  K9YC

RFI mailing list

<Prev in Thread] Current Thread [Next in Thread>