[Elecraft] K2 - NOISY POLLING

[Rich Lentz]

My radio was unusable until I added an isolation transformer between the
mike input and audio output (1 each).  Just used junk box transformers with
no idea of the input/output impedance.  The PC Sound card is very high
impedance so no need to assume you need to have a 1:1 or 20K to 4 ohm,
picked for their size (SMALL )  Signal level was such that I had to add a
100K/1K divider feeding the Sound card.  Got rid of all noise except the
noise from the oscillators in the PC and monitor.  Since you end up adding
the CAT-IO interface it is kind of hard to eliminate any ground return (and
associated ground-loop) unless you also add an optical isolator. 

Rich,
KE0X