Cross Country Wireless has released a filter designed to remove noise and interference on the incoming mains feed to radio equipment or high-quality audio equipment.
The filter first uses a differential filter on the live and neutral conductors to remove LF and HF noise from switch mode power supplies on the same circuit, ring main or phase. The filter then has a common mode filter to stop HF and VHF interference on all three conductors.
This also stops any RF signal or interference from the radio or audio equipment being fed back to the mains supply.
The combined filter system provides a reliable filtering system that can cope with almost any situation where severe electromagnetic interference is present on the incoming mains supply.
Mains Filter - http://www.crosscountrywireless.net/mains_filter.htm