[Elecraft] Use of PC power supplies with K2

[John Ragle]

  Ken...

     The general subject of RFI/switching power supplies has been 
bruited about on this list server several times. I personally have had 
excellent experience with the several that I use. These include a 20 
amp, 13.8 V supply from pyramid and two 25 amp, 13.8 volt supplies from 
Radio Shack. These supplies sit within inches of my K3/100 and my ICOM 
910H and cause no interference that I can detect.

     On the other hand, I have a circline fluorescent lamp with a 
magnifier that I transplanted from my workbench to my operating site, 
about which I made the following discovery. The lamp itself runs off a 
power supply at the base of the "tensor" arms. Turning the lamp on and 
off produces no change in interference, but unplugging the lamp from the 
wall outlet reduces hash noise on 20 meters by about 3 S units !!!. The 
wall-wart-like power supply in the base of this lamp is very noisy, and 
the lamp has accordingly been banished to a less sensitive site.

     My summary comment would be that power supplies run the gamut wrt 
RFI problems, and that one might well have to proceed by 
trial-and-error. I have always rejected use of the PC-type power supply 
because they usually come with a spaghetti of different wires intended 
for different functions within the computer. The small Radio Shack 25 
amp supplies are about the same volume as a typical PC supply, and a 
great deal more congenial (cosmetically) than the latter.

John Ragle -- W1ZI

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On 10/3/2010 1:47 PM, Kenneth Moorman wrote:
> I would like to hear from anyone who has attempted to use one of the small
> external PC AC adapter power supplies with a K2.  They are, of course,
> switchers, so I am not very hopeful.