I didn't think about dimmers but I bet if this dimmer is tripping an AFCI it would make an AM radio painful to listen to.
There are some old "non-RF friendly" dimmers that put nasty stuff back into the power line.
IBM's dirty little secret was the "noise" everyone had their panties in a wad about in the computer room came from phase control power supplies (in our machines) that were not unlike a cheap dimmer.
They basically just chopped 3VDC or 5VDC straight off of the 208v phases with SCRs and used a big bank of capacitors to turn it into usable DC. When you looked at these spiky wave forms on a scope it was hard to believe it used to be sine waves.
