[Elecraft] serial interface noise on 160m -- propagates through K3 to coax cables and grounds...

[Leigh L. Klotz, Jr WA5ZNU]

Mitch,
You may be doing this already, but you can make a small loop antenna for 
your HT (TH-F6A?) to DF the noise.
A really simple one is just a short SMA to BNC jumper with a square wire 
loop (alligator test leads?) taped to a piece of cardboard.
When the loop is broadside to the noise, it will be the loudest, and 
when parallel, the null will be sharpest.
This type of antenna is inefficient, and so it work well to DF noise 
sources to a few inches.
So you can tell where noise is being radiated inside your shack.  (It 
might be created in one spot and radiated elsewhere, of course.)

If you need a better DF antenna for RFI, make a better version that is 
shielded, by using a piece of scrap coax:
http://lists.contesting.com/_rfi/2005-01/msg00078.html

Leigh/WA5ZNU
> Hello, 
>
> I have been hearing an annoying noise on 160m that has a pulse rate of about 1/3 of a second.   After observing the behavior when I do certain things with my K3 and my computer I found that the source of the pulsing is Ham Radio Deluxe polling the K3 for VFO changes -- it polls every 300ms.  However, when HRD is shut down (no other serial port activity) the noise is still present as a constant tone with no pulsing effect.  My first suspicion is the USB to Serial adapters on the computer, but I am also thinking that maybe the noise is coming from the USB hubs or their wall warts.  I can hear the noise on the K3, my winradio, and my handheld (which is picking up the noise on 80m).  I was wondering if anyone has seen something like this and whether this might be coming from inside the computer or the USB hubs.  I am going to pull out my desk from the wall and start tracking this down to the source but I wanted to see if anyone else had experience with this sort of thing and any 
>  thoughts or recommendations?
>
> Best Regards,
>
> Mitch Mitchell
> AE5HO
> mitchmitchell1616 at msn.com
>
>