Mike Chambers wrote:
Unfortunately that didn't solve the problem.

The transformer should have fixed the problem. The noise is most likely
coming from the laptop switched-mode power supply. Have you tested it
while running on batteries alone?

I have several radios connected to computers, and for this I use the
Buxcomm Rascal GLX (www.buxcomm.com) and this works for both of my pc's
and my laptop.
The Rascal is also available as a kit for transceivers and you can
build just the receive side if you wish. That said, the transformer
alone should be enough, and there is the possibility that you did not
assemble the cable shielding correctly or add sufficient bypassing.

My computers receive audio, decode it and post it to my webpage. This
system does work, do not despair.

Brad
www.vk2qq.com