"very frequently on Saturday afternoons"
I think that's your big clue. There's plenty of power tools and equipment that folks use on weekends to do various jobs that create mains interference beyond the scope of many conditioners to deal with.
It may pay to go for a walk around your immediate area when you notice the hum at it's worst and see if you can hear any obvious power tools or equipment nearby.
I think that's your big clue. There's plenty of power tools and equipment that folks use on weekends to do various jobs that create mains interference beyond the scope of many conditioners to deal with.
It may pay to go for a walk around your immediate area when you notice the hum at it's worst and see if you can hear any obvious power tools or equipment nearby.