[RFI] Low voltage lighting solid state "transformers"

Tim Groat tcgroat at mesanetworks.net
Sun Dec 17 20:30:36 EST 2006

I have seen that, too. It has been quite common in low-end computer power 
supplies, as documented many tears back by W0UN. The same PC cards will be 
found in many "no-name" power supplies. The parts probably were in place to 
get an approval, then deleted to lower costs. I've also seen ones where the 
card was obviously designed to hold high voltage "Y2" disk capacitors with 
proper safety approvals, and much smaller, non-UL-approved, low cost caps 
were installed instead. I suspect that as soon as one "brand" would be 
pulled from the market, the same design re-appeared under a different name.

As for part 18 vs. Part 15, it makes no difference at HF amateur 
frequencies for *consumer* lighting equipment. The HF limits are identical 
outside of the designated ISM bands (based on the 1997 copy of Part 18 I 
have on hand): 250uV maximum in a 9kHz bandwidth. Unfortunately, 250uV 
still has a lot of interference potential (-61dBm at 50 ohms).

--Tim (KR0U)

>"Tom Rauch" <w8ji at contesting.com>:
>I see a lot of cheap SMPS that fail. Many of them even have spots on the 
>PC board for components that would make them pass, the parts just aren't 

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