[Elecraft] Re: K3 in NAQP SSB

[Jim Brown]

Thanks Lee. What you've described is a classic example of a "pin 1 problem," 
and your solution was a good one. That is, you gave the cable shield a good RF 
path to the chassis and removed the path to the circuit board. The cap from 
the hot to ground MAY have mattered, but I'd guess a lot less than you think. 

73,

Jim K9YC

On Mon, 18 Aug 2008 12:03:29 -0700, Lee Sawkins wrote:

>Hi Bob.

>I am not subscribed to the list, so I cannot post there.

>I had exactly the same problem as you with my DX Doubler.  Going through
>the box, RF feedback.  Going direct, no feedback.

>The main difference between these two methods of connecting the mike was
>that the DX Doubler had small capacitors to its circuit board from both
>the mike hot and ground lines.  I clipped one lead of each cap on the
>top of the circuit board to remove them from these lines.    I only
>clipped one lead in case I wanted to re-install them.  This cleared up
>almost all of the problem.  A small capacitor (.001) across the mike and
>ground lines at the connector of the K3 completely elimated the problem,
>even when running a TL922 amp with my K3.

>The problem appears to be that the small bypass caps inside the DX
>Doubler are coupling RF "into" the mike leads rather than getting it
>out!

>73 Lee VE7CC


>>Unfortunately, I was not able to go full SO2R with my new microHAM MK2R SO2R
>>box and N1MM DVK because of RF feedback getting into the audio lines.  I had
>>the same problem with my DXdoubler, so I know it is not the microHAM box,
>>but something in my setup is causing a hollow echo distortion effect in my
>>headphones even though it is not too bad on the air according to reports.
>>When I plug the headset directly into the K3, no problems at all.    I've
>>got to figure this problem out so I can use all this fancy gear.  ;-)

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6:51 AM