[RFI] Finding house noise sources

[David Robbins]

> So how might I best localize a source of internal house RFI when 
> nothing is plugged in? Is there something like a stud finder that 
> will allow me to follow the path of wiring behind walls?

yes there is... https://www.google.com/#q=circuit+tracer
usually you turn the breaker off, plug in one of the units to an outlet on the circuit and that puts a signal on the wire that you can trace.  
effective ranges vary, some work on hot circuits some are better on dead ones.  I have only limited experience but prefer the dead
circuit method as the signal 'should' stop at the breaker in the box and not carry over to other circuits.

the obvious questions are, what kind of bulb is in that overhead light?  and, is it on a dimmer?  other bad possibilities could be a dying
switch or socket that is arcing.  I have even seen incandescent lights generate noise, a small gap in the filament can arc for quite a while
before the bulb completely dies.  taking out the switch from the box to check for wires heading somewhere other than to the light might
point to hidden loads... doing the same for the outlets might be useful also.