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

[N5BCN]

(K2 #6800 w/ KSB2 KIO2 KAT2 KNB2)

Hi,

My first post to the reflector. :-)

I recently completed the KIO2 module (without KPA100) and have been
controlling the K2 via HRD v5.0.  I'm passing the K2 audio via the K2 EXT
SPKR connection to the the PC Mic In and out to PC Speakers.  All is well
EXCEPT for an annoying buzzing noise coming through the PC Speakers that is
caused by HRD polling the K2.  I know this because when I change the polling
interval, the noise changes accordingly.  Also, when I disconnect HRD from
the K2, the noise goes away.  Even holding down a button, which pauses the
HRD/K2 polling, causes the noise to cease.  Of course it starts up as soon
as I release the mouse button.

I believe the noise is being picked up by the PC Sound Card.  When I connect
the PC Speakers directly to the K2 EXT SPKR port (bypassing the PC sound
card), there is no polling noise.  I've also tried the following to no
avail:

1)  Tried both Line In and Mic In on the PC.  No difference.
2)  Connected the KIO2 Serial Cable to both a USB/Serial adapter and a PCI
Card with a DB9 Serial connector.  No difference.
3)  Tried connecting the KIO2 Serial Cable Pin 1 to the bare shield wire on
the PC side vs no connection to Pin 1.  No difference.
4) Tried "dressing" the cables inside the K2 so the KIO2 wires were far from
the RF Board.  No difference, despite holding the KIO2 and cabling as
physically far away as possible from the RF Board.
5) Tried routing the audio patch cable from the K2 to the PC as far away as
possible from the KIO2 Serial Cable.  No difference.

Has anyone else experienced this, and if so, have you found a solution?  Any
suggestions would be most appreciated.

73

Brian N5BCN
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