[RFI] Noise changes when room lights turn on / off

[Lee K7TJR]

  Most likely the reason the noise changes when you switch
 your light on is there is a small line voltage drop. This
 would cause a free running oscillator such as used in
 switching power supplies to shift frequency. I think that
 because your light changes this that the problem is very
 close to that circuit if not on the same one.
  You simply need to turn off all the breakers in your house
 and see which one stops the noise. There are hundreds of
 things this could be. Do you turn on the light in a fish
 aquarium  in the eve. Do you have a touch light in a china
 cabinet that gets turned on? Do you have a programmable
 temperature on your water heater, the list goes on and on.
 A small BC band radio and turning off your breakers will be
 very informative. Barring finding anything atyour house you
 need to do the same thing at your neighbors. Do you share
a power transformer with any of them?
  Lee  K7TJR  OR