[Elecraft] RX IQ USB Noise

[Jim Brown]

Loop is absolutely the wrong way to view this problem, and transformers 
are NOT the easiest or cheapest solution.

The solution is 1) proper chassis-to-chassis BONDING between all of the 
equipment being interconnected and 2) get power for all of the 
interconnected equipment from the same mains outlet, or from outlets 
that share the same "green wire" (what is called the "protective earth" 
in Europe).

73, Jim K9YC

. On Wed,8/31/2016 1:58 AM, Andrew Hebden wrote:
> This sounds like a 'hum loop' problem, the scourge of audio enthusiasts.
> In effect there are two earth connections between the KX3 and PC and it
> forms a small loop aerial where by it picks up mains interference. You could
> try running the cables from the KX3 to the PC very close together.
> It doesn't affect most people but I did get this problem a bit ago, but not
> with my KX3. The solution for me was to fit two small audio isolation
> transformers (one for each channel) in the IQ line, fitted in a small
> project box, and the problem went away. This has long been the recommended
> procedure for most audio lines between a PC and a rig.