I had one of those. I was getting some nasty RFI, which I eventually tracked down about a 1/4 mile away. Turned out to be a doorbell transformer. The homeowner yanked it out for me. That noise drove me insane, but the cancellator got rid of it. Took some fidgeting, but they do work.To this day I would be totally lost without my MFJ-1026 noise eliminating phase cancellation box.