At some point, reconnecting a device will cause the interference to return. This is the offending item. Once in a while, more than one item will contribute to the overall interference heard. Only the items causing the problem need to be addressed. These items will need an interference filter.
Filters are available from a variety of sources.
Contact the engineering department at one of the local radio or television stations. They usually know where filters can be purchased. And the correct type of filter must be used. Installing the wrong filter will not correct the problem. Radio and television stations are frequently expected to furnish filters or otherwise make repairs needed to solve the problems related to interference.