Not sure what radio you're using ... but if possible, make a small loop of wire
on the end of a long piece of coax as a RF sniffer. The pickup will be
extremely poor requireing you to be close to the source, thereby helping you
identifying the source.

Run the sniffer by the power cords, see if it's there.

I did this in finding the source of my computer noise _inside_ the computer.

Post your results !

jw
wb9uai
milwaukee