Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Household noise from AC line, lights etc.

  1. Oct 23, 2011 #1
    What is the main frequency components of noise from AC line, florescent lights, appliances and other common household stuff? I know there are 60Hz and 120Hz from rectifying. Do I have to worry about 180, 240, 300, 360 ( 60X1, X2, X3, X4, X5......) etc.?

    Which one are the strong ones?
  2. jcsd
  3. Oct 23, 2011 #2

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

    used to be 60 plus odd harmonics
    even harmonics infer asymmetry like half-wave rectification

    nowadays electronics have input filters to make them draw sinewave current for purpose of easing harmonic load on distribution in the end user's facility. In 3 phase third harmonic all returns via neutral so that's why it is now reqiiured inside buildings to be same size conductor as lines.

    i think if you make an antenna you will now find major noise at switching frequency of power supplies - tens to a few hundred khz and not sync'd with line
    and of course backplane noise from embedded computers. My digital FM tuner wipes out the analog one nearby.

    that's my casual observations

    tune a transistor radio between stations and walk around the house.
    in my power plant the computer room was 100X noisier to a radio than the main generator, which was a significant 60hz machine-- 24kv @ 22kiloamps..
  4. Oct 23, 2011 #3


    User Avatar
    Gold Member

    When I turn on the TV it causes a flickering on the computer monitor for a second. I think that is the de-gausing circuit on the TV
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook