[time-nuts] Standards sought for immunity of shielded cable links to power-frequency ground loops

[Joe Gwinn]

At 4:59 AM +0000 1/7/09, time-nuts-request at febo.com wrote:
>
>Message: 6
>Date: Tue, 06 Jan 2009 21:54:41 -0600
>From: Brian Kirby <kirbybq at bellsouth.net>
>Subject: Re: [time-nuts] Standards sought for immunity of shielded
>	cable links to power-frequency ground loops
>To: Discussion of precise time and frequency measurement
>	<time-nuts at febo.com>
>Message-ID: <49642781.2020305 at bellsouth.net>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>During my experiences involving audio/phone, video and data
>transmission, we were taught to ground the shield at one end only so we
>would not cause a ground loop.

Yes, it's impossible to do this in a system of any size.  In my 
experience, the RF cables connect the arms of the star-grounding 
system, causing loops.  So, the receivers had to be immune.  The 
problem is to quantify and specify the required degree of immunity.


>I ran into problems everywhere I went with this and as much as folks
>disdain transformers, they are your friend in this type of problem.

DC blocks (usually a series capacitor) also work at RF.  But we would 
have a lot of them.  And we would still need some kind of spec to 
require, to know when we are done.


>Don White Consultants/Interference Control Technology published a whole
>series on EMI, Grounding, and EMC for the military.  They are located in
>Gainesville, VA.

But do they publish formal and official requirements documents? 
That's what I need, versus training.

Thanks,

Joe