Connect with us

Computer Generated Noise

Discussion in 'Electronic Repair' started by rijo101, Nov 20, 2006.

Scroll to continue with content
  1. rijo101

    rijo101 Guest

    Hi Group , I have a problem with my home computer and or monitor
    generating noise that is picked up on my HF ham radio rig . In order to
    cancel the generated noise , how might be the best way to ground or
    choke out the noise directly from my home PC ? I presume I first need to
    determine the frequency of the unwanted noise signal and then build a
    balun or a choke to ground or cancel the noise, maybe !!!
    One thing is for sure , the problem exists when the computer is on
    and it generates harmonics that interfere with HF radio on Amateur Radio
    Frequencies .
    Thanks for any good help in advance , rijo
  2. James Sweet

    James Sweet Guest

    Is your computer plugged into a properly grounded outlet? Got all the
    metal slot covers in place? Computers produce a lot of RFI, it can be
    tricky to keep it contained.
  3. Adrian C

    Adrian C Guest

    This has to be an FAQ on amateur radio groups, or answered in full on a
    ham related website.

    The answer is basically clip-on ferrite chokes for external leads,
    ensuring that the motherboard is grounded at all mounting points (no
    plastic standoffs), ensuring the back plates of add-on cards and sockets
    firmly and electrically contact the backplane slots, ensuring the edges
    of the metal case cover firmly and electrically meet the rest of the
    case, covering up holes larger than 1cm diameter etc. Get plenty of
    adhesive copper tape/foam.

    If all else fails, turn on "Spread Spectrum" in the BIOS setup ;-)
  4. This is a tough problem because, generally, the noise is radiated from the
    computer circuit boards. The waveforms in computers are rich in harmonics,
    thus there is no easy way to filter the noise out. However, you can try:

    1/ Physical separation between the computer and the antenna. (Sometimes a
    simple reorientation of the equipment can help.)
    2/ Is your antenna feedline coaxial? If so, a balun at the antenna can help
    (this is because balanced currents in the coax helps to prevent the shield
    from acting as an antenna).
    3/ Use separate ac supplies and line filters.
    4/ Use ferrite decoupling cores on all of the computer leads.
    5/ Replace long leads with short leads.
  5. rijo101

    rijo101 Guest

    Thanks to everyone who replied . I will take all the replies into
    consideration . Thanks again.
  6. I had this problem largely resolved by replacing the power supply in the
    cheapo computer box with a higher quality power supply. Before replacing the
    PS, I couldn't listen to AM radio anywhere in the building, now I can.

    Mark Z.
  7. PhattyMo

    PhattyMo Guest

    This is a biggie,I've seen a large variance in PSU filtering...
    Some cheaper PSU's don't even fit the filtering components to the
    PCB's,they jumper over the common-mode chokes,and leave the caps off the

    Some PSU's have 2 common mode chokes in series,and alot of filtering...
    It depends.

    Another tip,If you can fit one,use one of the IEC sockets with the
    built-in filtering can on the back on everything in your house that uses
    an IEC socket,all the SMPS's in everything now days are nasty.

    Ferrite every cable on your PC,at both ends of the cables.
    (okay,maybe just one ferrite on the mouse and keyboard,or else it might
    get annoying.)

    Basically filter the hell out of everything-go overboard with it.
    PC's are *horribly* noisy beasts to tame..
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day