[Elecraft] RFI noise

[William Carver]

I lost a PC power supply, ordered a pair of replacements from Tiger
Direct. They were neither half-KW monsters nor their cheapest supply. It
had VDE/UL/FCC stickers, ALL of the agency certifications.

Suspecting a line surge had killed the original supply I decided to
stuff some MOV at the input connector of the new supplies before I even
installed them. I opened the cases and found The PCB silkscreen showed
RFI filter components, but none were installed: the board had direct
wire jumpers from power in to the switching circuits. 

I connected it to the motherboard and found switcher EMI over the HF
spectrum. For the record, my shop is in the garage, powered from
seperate breakers, shop strips have 30A/230V encapsulated line filters
and their own MOV. The radio gear was in a bedroom with coax feedlines
goubg directly outside, buried for 250 feet to a yagi 50 feet in the
air. No open wire feeders, no longwires direct to the shack. 

It seemed pretty clear the supplies had passed agency approvals with the
filter components in place, but once they had the sticker they stopped
putting those parts on the board. 

Bill - W7AAZ