rfi noise

I moved after owning a house many years to a rental with a high-RFI environment and I'm still, three years later, trying to come to terms with it. The RFI manifests as a persistent wockwockwockwock that drowns out most signals above 8mhz. tracing it with a portable, it's all around the building...

I would appreciate any ideas on the interference shown on the attached photo. The RFI is fairly consistent all the way from around 3.8Mhz to 4.8Mhz with a central drop. The pattern seems quite different from switcher power supply RFI which tends to happen mainly on harmonics. I am wondering...