Re: Bitx40 very loud, high-pitched, low frequency noise

Woody
 

The PC supply is also a switcher.  It may also require a "power good" signal to operate and a minimum load to work properly.
I recommend trying a linear regulated supply or battery for trouble shooting.  Your wall-wart switcher may work if the problem is gone with good pure DC if a big filter capacitor (like >1000 uf) and enough ferrite choke beads/sleeves are added to the feed line - and it is not dropping out of regulation.
Woody 

--

Join BITX20@groups.io to automatically receive all group messages.