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

[Leigh L. Klotz, Jr WA5ZNU]

Ken K0PP has pointed out I said it all wrong.  With my poor choice of 
the terms I have confused even myself, and produced gibberish.
I'll quote Ken because he said it clearly:

  Loops, if built correctly, have a NULL in both broadside directions 
... through the hole in the loop, so-to-speak.
 
  The nulls are -very- narrow, but deep and are essentially the only 
directivity exhibited by a loop.

I've successfully used the cardboard/test-lead loop antenna and TH-F6A 
HT I described to locate noise coming from a switching power supply for 
a lamp in a neighbors house, the charger on my robot vacuum cleaner (a 
menace surely no 1950's ham ever faced), a laptop power supply, and a 
home music player power supply.  Turning off the house breakers is a 
great first step to tell you what room it's in, but if you already know 
it's coming from the shack, the small loop helps a lot.

Leigh/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
>>
>>   
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