[Elecraft] KX3-PCKT or Sound Card Interface

[Lynn W. Taylor, WB6UUT]

I bought the KX3-PCKT cable kit along with my KX3 -- my primary interest 
is digital modes.

I also see on the list that a lot of you use a sound card interface 
instead of cables.

If the KX3 has enough isolation, is more isolation needed?

What am I missing?

Thanks in advance....

-- Lynn