[Elecraft] K3 Power supply

[Paul Christensen]

> Wonder what supplies are being used with the K3?

Merv,

For the shack, I gave up on switch-mode power supplies since I could not 
find one that produced a low noise floor on all bands.  For years, I was 
unknowingly putting up with a high-level noise floor until I purchased the 
SDR-IQ and began seeing broad "bumps" in the viewed spectra response.  The 
bumps were attributed to switch mode power supplies, switch-mode wall 
supplies, and some USB adapters.  By changing switch-mode back to old linear 
technology and a combination of changing the USB adapters as well as using 
multi-wound #31 ferrite cores (wound K9YC style) on both ends of the USB 
cables, I finally have a flat noise floor on all bands.

I am sure there are quiet switch-mode supplies out there.  But with all the 
other noise sources I have to contend with, I don't want to be asking myself 
if some new grunge I'm hearing in the future is attributed to my power 
supply.

My guess is that many of us are living with high noise floors from 
switch-mode products and do not realize it -- until a PAN adapter is added 
and the noise floor can be seen.  Spotting sharp switch-mode and LAN-type 
grunge is easy without a PAN adapter, but it's the very broad noise (e.g., 
gentle rise and fall over 100 kHz) that's deceptive when one tunes the band.

The shack supply here is now a surplus linear Agilent 6652A.  These sell new 
in the $4K range but are only a few hundred $$ if you catch the right 
on-line sales for surplus product.

Paul, W9AC