[Elecraft] K2, PSK31 & microphone

[Stuart Rohre]

The transformer is to break the ground loop of having the computer ground 
connected to the RF chassis ground of the radio and producing possible 
ground loop currents.  In that case, you defeat the transformer if you 
connect the computer case to radio case.

The computer case ground should be the 3rd pin on AC plug, and use that one 
alone for computer.  That will correct any voltage difference due to a line 
filter in computer.

Some audio lines are floating, and the transformer gives them a reference 
known load.  The transformer is the way its done in commercial broadcasting 
to avoid hum problems.

Stuart
K5KVH