This High Pass Filter design by Mark Gluch is very effective – see  2017jun10_HF_HPF – he writes that it solved overloading caused by very powerful local AM broadcast transmitters. His other issue  is sometimes high HF noise level from  power lines or when certain lights or appliances are turned on.  The filter was built using ordinary axial lead inductors and leaded ceramic capacitors on a piece of FR4 pcb material. Using BNC  connectors in-out.