No subject

[n6tr at teleport.com]

> Late last night, while setting up for the ARRL SSB contest, I noticed a fair
> amount of hum in my monitored microphone audio, while hooked up through a
> DVP.

This type of problem is almost always the result of a ground loop.

If the ground for the microphone is connected to any other ground 
you will end up with hum 90 percent of the time.  

It is important to isolate the audio return so no other currents
flow through it.  If you have a relay somewhere to switch between
radios - or your microphone and the output of the DVK - you need
to use DPDT relays to switch the grounds as well.  

Tree N6TR
n6tr at contesting.com


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