I was on 40m, and noticed that the noise level had jumped 2 full S units overnight. It went from 5 to 7. Didn't know what was going on. Today I found the culprit. I have 12v track light in the kitchen. One of the lamps burned out, so I replaced it with a new LED lamp. The LED lamp is the source of the noise. So be careful using LED lamps in your house. Some generate lots of RFI. Glad I didn't replace all the lamps with those LEDs.