[Elecraft] Noise with KUSB

[Paul Christensen]

> I recently discovered the source of a very annoying noise in my K3. When
> unplugging the USB cable from my USB hub the noise in the receiver
> disappears.

I had posted on this topic a couple weeks ago.  I didn't discover my own 
noise problem until I was looking at the noise floor with a SDR-IQ and 
SpectraVue software.  In my case, most of the noise from the USB-to-RS232 
adapter is masked by band noise.

I managed to wind 10-turns of the USB adapter cable through a 0.75-inch I.D. 
#31 ferrite core.  The choke was placed as close as possible to the DB-9 
connector.  After winding, I detected no change which is unusual when using 
these cores.  It may be that the noise is induced in differential mode 
between the USB adapter and the K3.

I ended up discarding the adapter and went with a serial cable connected 
between the K3 and the one and only RS232 serial port on my PC.  Problem 
solved.

Paul, W9AC