[Skimmertalk] ground loop reduction?

[Mark n2qt]

well one nice thing about having a battery powered rig is you can just keep
disconnecting things and see what happens.   So, I pulled the external 
power, the rs 232 cable, and the antenna cable, leaving only the I/Q to
the sound card (which was still isolated with transformers).

The only thing noted is that with the band noise removed, the noise at
0 was more noticeable but not by much.   

I did add a bonding cable with no affect.  

If I pull the audio to the sound card it also stays pretty much the same.  

I think that the problem is related to the sound card in the pc chassis so 
I may open it up and see if there is any sensitivity to grounds or perhaps
another card next to the sound card.  

It also may be that it may just be the near DC response of the sound card
and that the skimmer will display down to the noise floor. 

Mark n2qt


-----Original Message----- 
From: David Gilbert 
Sent: Wednesday, November 21, 2012 9:11 PM 
To: skimmertalk at contesting.com 
Subject: Re: [Skimmertalk] ground loop reduction? 


Presumably you have an RS-232 connection to the KX3, right?  That can be 
problematic for this sort of thing.   Just for grins, try bonding the 
chassis of your computer to the chassis of the KX3 with the shortest 
copper strap or heavy braid you can manage.  I mean really short ... as 
in six or eight inches of something 1/2 inch wide.  If it makes a 
difference you'll know what to work on.

73,
Dave   AB7E



On 11/21/2012 6:36 PM, Mark n2qt wrote:
> I'm using cw skimmer with a non offset I/Q feed (from a Elecraft KX3).
> I have excessive ground loop noise regardless of the sound card I use
> (EMU-0202 USB or Quartet).  Using transformers for ground isolation
> doesn't help, in fact the ground noise is there regardless of connection
> to the sound cards.   The noise sidebands go out about +/- 300 hz from
> 0.
> Normally the ground noise is offset from the signal and hasn't bothered
> me when using an LP-PAN (6khz offset) or Softrock (23Khz offset) but 
> with the kx3 it's a real annoyance since it's so close to the desired.
> Looking for positive experiences on fixing this....
>
> Mark n2qt
>
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