[RFI] Dimmer Switch Help

Paul Christensen w9ac at arrl.net
Fri Mar 13 17:32:43 PDT 2009

My own tests indicate that the Lutron dimmers produce far less RFI than 
those made by Leviton.  I recently installed a Leviton dimmer that was 
boldly branded as having an RFI filter.  But on 160m-80m, its filtering was 
much less effective than the comparable Lutron model.  I have since replaced 
all Leviton dimmers in our household.

For years, my shack's 120VAC equipment was simply plugged into the nearest 
shack wall outlets.  These outlets share the same circuit with a couple 
other rooms on a common breaker.  Running 100W from an HF rig resulted in a 
slight dimming of the room's incandescent lights.

About a year ago, I decided to run two dedicated 20A circuits into the shack 
fed from a tandem breaker -- each breaker feeding one 20A duplex outlet in 
the shack.  Each outlet subsequently feeds an isolation transformer, which 
is then routed to a two-circuit, 16-outlet Ethernet-controlled power strip. 
Gone is the room light dimming and almost miraculously, other RFI/EMI has 
also disappeared.

FYI - I put a bit of money into the outlets.  They are Leviton 
hospital-grade, isolated ground, with built-in surge protection (Catalog 
8380-IGW).  At first glance they seem absurdly expensive, but comparing the 
cost to a high-quality surge-protected power strip, the cost was comparable.

Paul, W9AC

----- Original Message ----- 
From: "Charlie Gallo" <Charlie at TheGallos.com>
To: "Hardy Landskov" <n7rt at cox.net>
Cc: <rfi at contesting.com>
Sent: Friday, March 13, 2009 8:09 PM
Subject: Re: [RFI] Dimmer Switch Help

> On 3/13/2009 Hardy Landskov wrote:
>> Hi Bob and Everyone else,
>> Garry, NI6T (Big 160 guy) made a paper study of dimmer switches and put 
>> it
>> out on the Topband Reflector if I remember. And there is quite a 
>> difference!
>> I have it around somewhere but emailing Garry might be faster 
>> garry at ni6t.com
>> 73 Hardy N7RT
> OK Guys,
> I have a good friend who works for Lutron, and a while back I emailed him, 
> asking these very questions.  He gave me permission to put his answer up 
> on the list.  I've redacted his name, and "family" news (weddings etc)
>>On 11/19/2006 Redacted wrote:
>> Hi!
>> To paraphrase the racing guys, RFI suppression costs money. How low do 
>> you
>> want to go?
>> There are a couple of factors involved--one is how the device responds to
>> noise on the line before we dim, the other is how we do the dimming.
>> The best possible solution is made for hospitals and MRI centers--zero 
>> RFI.
>> Lotsa bucks. The next best solution is our GP dimming panels--very little
>> RFI, but lotsa bucks. Then comes our LP dimming panels, with the new
>> FET-based A-series dimming module. Much more modestly priced, but this is
>> still Lutron. (Depending upon how much the electrical contractor marks it
>> up, you're still probably around a hundred dollars per circuit or so.)
>> Want more? Here's the Lutron FAQ for RFI:
>> http://www.lutron.com/default.aspx?pid=6#faq8
>> Note the last suggestion--install an electronic low-voltage lighting
>> system, with an ELV dimmer. Then comes the big tip: a separate neutral.
>> Lots of times these days electricians will wire a building with a common
>> neutral--combining the white wires and running a lot of circuits back to
>> the panel on a single white wire. This is a bad thing to do--because you
>> get all kinds of nasty noise on the line, and the noise appears on all of
>> the circuits. But it happens (it saves the contractor wire).
> -- 
> 73 de KG2V
> For the Children - RKBA!
> Be wary of strong drink.
> It can make you shoot at tax collectors -- and miss.
> --R.A.H.
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