[RFI] Dealing with RFI from light dimmers

[Frank O'Donnell]

I was interested in the recent posts regarding light dimmers, as this is 
a significant issue for me. We have three dimmers in our house, and 
three more in a guest house directly behind. As of yet, the brand name 
on all of these is unknown. Banning dimmers from these houses is not an 
option.

Currently I'm operating on 630m and listening across the MF/LF spectrum, 
where RFI from these devices seems much stronger than at HF. The 
strongest RFI is getting into a receiver in our main house from dimmers 
in the guest house, which is physically closer to the receiver's antenna 
but on a different power service drop. So I'm wondering if the RFI is 
traveling through AC wiring, or if it might be getting from the dimmers 
to the antenna. The shack gear's power is all filtered, through 
Tripp-Lite power strips and wrapping AC cords through FT240 toroids.

I noticed that one or two people here mentioned having good luck with 
Lutron dimmers, but others cited issues with these.

I see the ARRL RFI Book states, "The best cure is to replace the control 
with a better one that has a built-in RFI filter. (Beware of dimmers in 
plastic cases!)" It also discusses placing an AC line filter at the 
dimmer, as well as one or two common-mode chokes made by wrapping AC 
wiring around an F(T)-240 or F(T)-140 ferrite core.

Lutron has this application note on RFI and dimmers:

http://www.lutron.com/TechnicalDocumentLibrary/360484.pdf

It mentions Lamp Debuzzing Coils (LDCs) as "the most effective way to 
reduce RFI."

So I'm wondering about the best things to try as next steps. Are some 
Lutron models more effective than others? If the RFI is originating in 
our guest house on a different service drop, is it likely that adding 
filters to the AC supply to the dimmers there would help? Has anyone had 
any luck with LDCs?

Thanks for any suggestions,

Frank K6FOD