Well, thank you all for your ideas. I did check my dimmers and electric
blankets but found no RFI from them. It didn't seem to be anything from the
thermostat either. I do have a battery charger which maintains a lead acid
battery for my sump pump. I don't know about that yet. Of course, since
yesterday all has been quiet.

And, by way of full disclosure, I live within spitting distance of a massive
array of radar antennas associated with our Distant Early Warning system
that supplies input to NORAD in Cheyenne Mt. and who knows what sort of RF
they might be putting out occasionally?

Thanks again, Pete