[600MRG] 630M Noise Reduction

[Michael Mussler]

I read an interesting article once about wall wart power supplies. I think it was published by Electronic Design News. The author obtained a half dozen wall warts, all manufactured off-shore in Asian countries. They removed the plastic enclosures (with difficulty) and discovered a number of interesting things:

PC Boards that had silk screened outlines of missing components relating to EMI suppression

Guts with PC board identifying information that didn’t match the information on the outside enclosure (power and current ratings)

Guts that had been removed from some other piece of equipment and re-packaged

Tests that indicated the FCC and CE marks on the enclosure were false

The sad state of affairs regarding compliance with FCC regulations in the US is caused by a shortage of funding and staff with technical backgrounds to police compliance to the rules. It has become a "complaint driven” system and like so many other government services, the squeaky wheel with big bucks and political clout gets the oil. There have been some published situations where more drastic consequences of FCC non-compliance have been identified (interference on aircraft caused by personal electronics) but these events are the exception. In reality, the EMI situation in our modern lives is akin to air, water, visible light and noise pollution. It is made worse because it is not something the general public can experience directly with their senses.  

The control of EMI in modern electronics is not rocket science. I’ve used switching mode power supplies salvaged from obsolete early generation PCs that were so “quiet” they could be used to power my HF radios with no interference issues whatsoever. It all comes down to proper designs with EMI suppression features that add cost without directly impacting efficiency and regulation of the supply.

Good luck, and don’t give up! Be sure to pass document your experiences and pass them along to the ARRL. They actually have people on their staff who are trying to work this problem. 

73
Mike Mussler, AI8Z
ex WD2XSH/12