[Elecraft] K3 in NAQP SSB

[W8JI Tom]

>>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,
>
> Don't be so sure of that. MOST ham rigs and ham accessory boxes are built
> with pin 1 problems, which are the primary cause of RFI.

Be especially aware that rigs with external 12V supplies can develop what 
sounds exactly like RFI from "pin 1" problems.

This is because the power supply leads of the SSB radio are current 
modulated at an audio rate. If the 12V supply has a ground connection common 
to the negative lead post on the supply (or through other gear) the V- lead 
voltage drop can cause a "pin 1" issue from dc potential that varies at an 
audio rate.

As Jim says this is a common problem and might not actually be RF feedback. 
We've had that problem here on several contesting accessories. I'm 
disappointed to have to say most popular interface equipment has that 
problem.

73 Tom