In article , Rick wrote:
Of course. That's one of the first things I tried - reversing the radio
plug in the outlet - and the hum went from bad to slightly worse. It's a
transistor boom box thing with an internal power supply - not using an
AC/DC wall wart.

FWIW this is relatively new wiring in the building, circa 1981 the
entire building was gutted and all new services put in.

But this hum problem has only surfaced in the last 8 weeks or so.

1. Make sure the station (or an adjacent one) hasn't changed to IBOC/(HD
Radio), This is where they add a bunch of digital crap to the channel
that's a high compression digital (RealAudio style) stereo signal.
One test is that they don't run IBOC during the night because the skip
signals will really screw up the radio all over the continent.

2. It might be another device on the circuit with a tranformerless
power supply where the diodes in the power supply hooked right to
the power line switching on and off modulate any radio signals
picked up on power line.

Mark Zenier Washington State resident