[Premium-Rx] AC Mains Filter Observation

[Carcia, Francis A HS]

A good ground strap is at least 20% wide X length. I was also involved in
the same type of project. We needed a quiet place to put our screen room so
I talked my boss into putting copper screen on the walls before the
sheetrock went up. Then we had all the joints soldered. Next the screen was
bonded to the super structure. We even put in under the epoxy floor. Next we
installed the screen room with filters mounted on the screen room wall near
the breaker panel. This was back in 461A days when we did radiated emissions
to starting at 14 KHz. We had ambient problems and had to come in on Sunday
and shut most of the building down. The new set up was very quiet. Dumping
conducted noise into the chassis ground just gives it a different place to
go and radiate from. fc

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From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of bob boroughs
Sent: Tuesday, September 05, 2006 9:43 PM
To: premium-rx at ml.skirrow.org
Subject: [Premium-Rx] AC Mains Filter Observation


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 <mailto: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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