[TenTec] Audio Hum on Omni-VII

[Stuart Rohre]

Bill, as others have alluded to, you have a pin 3 problem, the AC safety 
ground at the computer vs. that one at the radio.

You have a ground loop being created between the audio sections of the 
devices.  The adapter is a switching device too, probably.  It is not 
going bad, just its grounding must be carefully controlled.  Some of the 
interface cables have to be ground isolated at one end, to correct this, 
and certainly the rig and the computer power should come from the same 
outlet strip.

Try one change at a time. The big clue is that every thing is clean on 
computer battery power.  Keep interface cable grounded at one end, and 
lift the shield connection to radio at other to test that loop issue.

GL and 73,
Stuart Rohre
K5KVH