[Elecraft] [K2} KIO2 Noise pickup

[Don Wilhelm]

  Brian,

There are two reasons for not grounding the computer to K2 at both ends.
1) A Faraday Shield often works better than a shield grounded at both 
ends.  (note that there is a signal ground wire on pin 5).
2) Connecting the K2 ground to the computer serial port shell may create 
circulating currents that can make the situation worse.

Many computer serial port shells are not well grounded to the computer 
chassis.
You may find some relief by connecting the computer case to the K2 case 
by a separate wire (not the cable shield).
Jim Brown (K9YC) may chime in with his sage advice to use twisted pair 
wires (CAT-5) instead of the shielded wire (or search for his past posts 
on the subject)  That may help.

Lastly, some computer and application combinations just create that 
polling noise.  Try another computer - desktops are usually better than 
laptops IMHO, or try relocating the computer if it is sitting near the 
K2.  Some experimentation may be in order - there is no one right answer 
to problems of that nature.

73,
Don W3FPR

On 12/7/2010 10:10 PM, Brian Denley wrote:
> I have installed the KIO2 and setup the K2 for computer control and
> everything works well but I hear chuffing noise as the control software
> polls the K2 (if I shut off the polling, the noise stops).  It's not my
> sound card picking up the noise: if I don't connect the K2 audio output to
> the computer, I still hear the noise from the K2 speaker.  The noise is
> strongest on 80 meters, weak on 40 and not audible on higher bands.  Any
> tips for eliminating this type of noise?  Why did we not ground the KIO2
> cable at both ends?
> Brian Denley
> http://home.comcast.net/~b.denley/index.html
>