[Elecraft] K2 - Isolation box construction for digital modes

[Don Wilhelm]

Euan,

Your grounds should not be connected between the K2 and the computer - 
that will "un-isolate" your isolation box.  At the isolation box, use 
stereo plugs and jacks at your interface box and connect the 
transformers to the tip and ring.  Similar if you are using an 
opto-isolator on the PTT circuit - use a stereo jack and plug there too.
If you wish to use shielded cables between the box and the K2, ground 
the shield only at the K2 end (use 2 conductor plus shield cable).  
Actually twisted pair conductors will be as good or better than shielded 
cable - CAT-5 wires are good for self shielding.

73,
Don W3FPR

Euan McPherson wrote:
> I'm building an isolation box (between K2 and computer with external
> soundcard) for digital operations, containing two 1:1 transformers and
> voltage divider resistors. The box is metal. All input and output sockets
> are 3.5mm mono and are grounded to the box, hence all input and output
> braids are connected together via the box. Is this likely to create a ground
> loop problem? Advice would be appreciated before I solder it all together.
>
> 73, Euan M0GBZ
>   
>