[R-390] computer swtiched source

[Robert Nickels]

On 1/31/2022 8:16 PM, GENE BALINSKI wrote:
> I have used a Radio Shack in-line AC noise filter.  It actually **did** make some difference, but not enough to reduce the 40 noise level much below ~ S-7. Perhaps the filter just reduced the power line conducted emissions while leaving the radiated emissions.

Roger all, Gene, good to hear you've at least identified the culprit.

Some years back the power supply in my Dell desktop failed so I bought 
an eBay replacement and had the same experience.  It took me part of a 
day to realize that no, the bands weren't all dead, but the noise floor 
was so high it sounded that way.   I took the p/s out and found that the 
IEC AC entry was not the line filter I thought it was, but just a 
connector for an IEC cordset. Filtering was probably the first thing 
they took out to reduce cost, after all the OEM was the one who had to 
worry about FCC, etc.

I scrounged up a line filter from my junk and with it inline the noise 
floor was back where it previously was.    You can find them online and 
it's not a big job to mount one in a metal box with suitable cords or 
connectors.   I found it a handy thing to have around when trying to 
identify noise sources.   Corcom and Schaffner are good brands to look for.

73, Bob W9RAN