[RFI] Low voltage lighting solid state "transformers"

Jim Brown jim at audiosystemsgroup.com
Sun Dec 17 16:04:00 EST 2006

On Sun, 17 Dec 2006 11:07:56 -0700, Steven Farmer wrote:

>Since my rfi seems to be mostly a common mode problem, some 
>sort of emi filtering at their breaker panel might also work. 

I doubt it. The AC wiring between the noise source and the filter will 
act as an antenna, and in a typical building, is likely to be long 
enough to be a pretty effective radiator on the HF bands. Now, IF the 
AC wiring happens to be in grounded metallic conduit that is properly 
bonded at both ends (or at least bonded to the noise source), you are 
in FAR better shape. That's more likely to be the case in an industrial 
building, less likely in residential. And even in industrial buildings, 
I'm seeing a lot more PVC pipe rather than EMT, because it's a lot 
cheaper to install. That, of course, provides no shielding at all. 

The depressing thing about all of this is that everyone involved is 
playing cheap, and we pay the price. Cheap power supplies, cheap 
electrical, no filters, cheap Congress (no funding for FCC to enforce 
its rules), and in the case of these devices, rules (Part 18) that seem 
to allow this garbage equipment to be sold. 

Perhaps someone working in the EMC world might venture an opinion as to 
whether there might be grounds for approaching FCC on this issue. The 
lighting people will tell you that their stuff is exempt under Part 18. 


Jim K9YC

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