[Elecraft] Switching noise "hash" story (was Radio Shack power supply)

[Ken Lotts]

Interesting story about the Switching noise "hash"..
I have six computers in my house..  I had never given any thought to the QRN
I was picking up until one day I shut two of my servers off while I was
listening to 40 mtrs on my K2.  I had spectrogram running and was able to
clearly see and hear what those computer were doing to my radio.

The noise was a series of signals (possibly 12 or more) exactly 60 hz apart.
They were very unstable and therefore drifted (all together) up and down at
random..

My solution was to buy new power supplies from a discount computer store I
found on the net.. BUT, when they arrived, I placed them in service and they
both had a very pronounced 60 hz pulse noise that was worse than the hash!
Luckily, I finally found some old power supplies from work and all has been
quiet ever since.

Ken aa7jc
http://www.lotts.net/ken/ham