[arm-allstar] the hum

[Ken]

I will add yet one more.

 

The basic issue is that the URI has a direct connection through it on the 0
VDC of the USB to the so-called ground connections on the DB25 side.  What
this does - in most cases - is to connect the negative lead of the DC
Switching supply of your computer to the negative terminal of the power
supply feeding your repeater/radio - with the URI audio device right in the
middle.  That might be OK except, of course, that all of these things are
also grounded in various other places like the third pin of the AC wiring,
etc.

 

What worked for me was to add a short/heavy (#10) wire between the computer
chassis and the transmitter chassis - my hum was on repeater transmit.
Ground loop currents can still flow, but now 99.99% of them do not flow in
the audio "ground" leads.

 

73

Ken

KE2N