[aprssig] Re: Problems with hum on TX audio.

[KC2MMi]

<<Check your DC power supply with a meter on AC if it shows voltage where is
your hum.>>

That can give a false positive. Someone who used to work for Fluke explained
this to me. Apparently some of the cheaper meters WILL show an AC voltage when
only pure DC is present, due to the way they are built. If you are testing for
AC on a DC circuit, be sure to reverse the test leads. If they only show AC in
one orientation--it is a cheap meter and there really is no AC on the line.

Who would figure.