Jim Brown K9YC is the author of an excellent guide to solving RFI issues around the radio shack. His very useful article “A Ham’s Guide to RFI, Ferrites, Baluns, and Audio Interfacing” has much information useful to SWLs looking for a way to reduce noise and there are a lot of instances where the noise-source is in the home. You’ll find a lot of interesting material on Jim’s website.