Ask A Scientist© Engineering Archive

Index Key:   ENG021
Author:      pati
Subject:     E/M interference
Text:        What might be the cause of static interference inside a home that 
prohibits the use of a stereo, battery operated radio, car radio, and 
television?  The type of static interference is compatible to the static 
interference when a blender, mixer, or microwave oven is turned on only they 
are not being used and the static interference occurs at varies times during 
the day and night and come and go at different intervals.  I thought it might 
be someone using a C. B. radio but I do not hear any voices.  If you could 
tell me what you think it might be or recommend a good book to read on this 
topic, I would greatly  appreciated it.

Response #:  1 of 1
Author:      dipper
Text:        It is very difficult to tell what is causing the interference 
without knowing some more specifics, like proximity to neighbors, what type of 
neighbors (industrial or residential), how many people on a single 
transformer, frequency of the interference, and so on.  It does sound like, if 
you are getting so much interference that it even makes the car radio 
inoperable, that there is a tremendous source of radiated electrical noise in 
the area.  If that is the case, a call to the local FCC office should get the 
ball rolling.  It could be that the operator of the source does not even know 
that it is happening.  It is unlikely that it is a CB radio because of the 
power levels required to do what you describe, and it probably is not a HAM 
operator, because they would be able to tell that there was something wrong 
and do something about it.  A good start to finding out where or what is 
causing the problem, is to get in your car, tune the radio to a low frequency 
on the AM dial, and drive.  Note the strength of the noise at different 
locations, and use a map to pinpoint where the source may be.  It may even be 
a factory with a big horsepower motor that has bad brushes.  The FCC can help 
you out though, so give "Uncle Charlie" a call.