Locating the source of local HF interference

In recent weeks my reception of HF radio, particularly on 40m (7MHz band), has been marred by nasty broad band interference. I had thought it was from a neighbour's TV.

Using a portable shortwave radio with a strength meter, I walked around the house trying to find the cause but it just seemed to be strong everywhere that mains wiring went.

After shutting down all computers I turned off the house main switch and the interference was gone.

By plugging things back in, one by one, I found the culprit.

Many of us suffer HF interference and the more computers and appliances we have the more likely it is, but this experience shows that it can be located and removed.