It peaks at about -70dB on my FDM-S2 and therefore kills all weak DX while creating an unpleasant racket on stronger signals. I know the approximate direction of the noise. It sounds (and looks) like a cheap psu. It has also been suggested that it could be a plasma TV.
At first, the noise was audible around 1500 when I would start to look for Asiatic signals, but had gone by 1600 and did not return in the evenings. For the last two weeks, however, it has existed non-stop, around the clock.
Only the strongest signals can be heard through the noise.
So my medium wave DXing is now out of the question from home. Maybe this will encourage me to venture out more and stretch out some longwires in remote locations again.