Newly passed my foundation a week or two ago but as yet still haven't got on air properly due to HF interference. I have S9 or higher noise floor which makes all but the strongest signals impossible to read. I have an Diamond GZV 4000 (switching) 857d with LGD auto tuner and AV600 meter. I have noticed that when the problem is present my SWR is higher. Investigation so far: Running rig with home as normal, s9 or higher noise on 10m through 40m (may be more but I dont have antenna for that) Isolated mains supply entirely and ran off battery. Noise gone, as low as S1 but sometimes S4/5 at worst. Great to find out its at least inside my own house. Put ferrites on all my cables and connectors, and a few cables I could access around the house. brought it down to S8 at best but still often higher. Unplugged and switched off every item in the house one by one including fridge, shower, lighting, oven, plug sockets, powerlines etc etc. Nothing plugged or switched on at all still s8/9 +. Isolated garage mains connection too, no change still s8/9+. With everything off or unplugged, removed fuses one by one, identified ring main fuse as the one causing interference. Appears to be the wiring itself? So I guess the question for me is what next? It seems to be my mains itself and specifically the ring main. With nothing plugged in or switched on but the fuse in place I have S9, so how to I work out what it is to resolve it? Could it be the wiring itself? Or is it likely to be a socket or switch? Is there anything I could try? Are filters worth considering or are they snake oil? The house is an 80s one so I assume will have PME earthing. Disheartening start but I am hoping to get it resolved and get my first contacts soon Any advice appreciated.