[Premium-Rx] AC Mains Filter Observation

[bob boroughs]

Info to the Group,
 
I have been following the AC Mains Filter thread with great interest.
For several years I was an engineer on a team doing instrumented surveys
on computer facilities including screen rooms, all of which included
filters on the AC mains. There are a great number of filter types and
installation methods and to make a long story tedious, most of them
provide very little filtering benefit due to faulty installation.
 
It is not the filters which are the problem, merely their installation.
The problem comes from the grounding of the filters themselves. It is
imperative that the case of the filters be bonded to an excellent ground
with VERY short conductors with WIDE widths. During our surveys we found
AC filtering problems whenever the length of the grounding straps was
more than four times the width. For example if your ground lead from the
filter is four feet long it would need to be at least one foot wide. 
 
In screen rooms this is usually overcome by mounting the filter on the
shield itself, with similar sizing on the screen room ground leads.
Incidentally it is not the cross section area or impedance of the ground
lead that was most important, merely the width. For example even a 2/0
welding cable would not be a large enough width for a four foot ground
lead. 
 
Good luck on your filtering installations, but remember to provide an
excellent ground source, locate the filters as close as possible to it,
and use WIDE conductors such as thin copper sheet or foil for your
ground connections.
 
Bob, kg6mc at cox.net
 
 
----- Original Message ----- 
From: Edward <mailto:navydude1962 at yahoo.com>  Sylvester 
To: premium-rx at ml.skirrow.org 
Sent: Monday, September 04, 2006 12:35 PM
Subject: [Premium-Rx] AC Mains Filter Recommendation Needed
 
Hello to the Group!
 
Though only indirectly pertinent to Premium receivers, I'd like to get
some recommendations as to which filter to use at my electrical junction
box.  I am building a radio room from the ground up and will have a
dedicated electrical sub panel for the room.
 
I want to purchase a heavy duty EMI/RFI filter to put in-line, so that
every AC outlet in the room has this benefit.  I figure, why not have
the quietest scenario possible so that I can maximize
performance/reception of each premium receiver?
 
Your input is appreciated.
 
73,
Ed NI6S
Los Angeles

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