[Elecraft] [K2] K2 KIO2 Polling Noise in PC Speakers w/ HRD

[Don Wilhelm]

Brian,

The wire actually diminished ground loops. 
A ground loop forms between two chassis at different potentials, and 
that potential difference causes current to flow on conductors that 
normally carry signals.  There may still be a slight potential 
difference between the two chassis - it depends on the 
resistance/impedance of the connecting wire.  You might reduce the noise 
even further with a larger wire or a strap, but one quickly reaches a 
point of diminishing returns.

Other similar noise can occur because of what audio pros call a "pin 1 
problem".  It does not always relate to an actual pin 1 (except for 
audio XLR cables).  The shield of a cable *should* connect to the 
outside enclosure of a device, so any noise carried on the shield will 
be conducted on the outside of the enclosure.  With the advent of PC 
boards and the ease of making shield connections to the ground plane of 
those PC boards (mounting the jack on the PC board rather than the 
enclosure, the shield connection often goes to the PC board ground plane 
first, and then afterward it may (or may not) be connected to the 
enclosure case.  That situation is common, and does create the "pin 1 
problem" which can induce noise onto the PC board ground plane and will 
modulate all signals on that board.

Many (most) amateur transceivers and computer sound cards have this "pin 
1 problem".  Extraordinary steps must be taken to eliminate such "sneak 
paths".

73,
Don W3FPR

Brian N5BCN wrote:
> Hi Don,
>
> Thanks for the tip (why didn't I think of that?!?).  I tied a wire between
> the PC and K2 chassis and the polling noise dropped dramatically.  Although
> it is still audible, it is diminished to the point where I can "live with
> it."  Hopefully the wire wouldn't introduce any ground loops........
>
> THANKS!
>
> 73
>
> Brian N5BCN
>   
>