1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Proper Ferrite choke diameter?

Discussion in 'Home Brew' started by curlyjo, Jul 8, 2017.

  1. curlyjo

    curlyjo
    Expand Collapse
    Supporting Member

    Joined:
    Nov 13, 2009
    Messages:
    164
    Likes Received:
    27
    20170708_120258.jpg Can anyone tell me what is the right snap on ferrite diameter I need for 12 gauge speaker / power cord? I hooked up a vintage stereo system in my radio room last night. When I turned on my radio this morning I got talk back through my speakers.


     

  2. Captain Kilowatt

    Captain Kilowatt
    Expand Collapse
    Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    13,994
    Likes Received:
    5,241
    There is no proper size. The more turns you can put thru the ferrite the better hence choose a size and fill it. Install it as close to the amp as possible as the speaker leads are acting as antennas and feeding the RF back into the amp where it is causing problems. Also try a 0.001 microfarad capacitor accross the speaker leads at the amp output.
     
    sp5it likes this.
  3. curlyjo

    curlyjo
    Expand Collapse
    Supporting Member

    Joined:
    Nov 13, 2009
    Messages:
    164
    Likes Received:
    27
    Thanks for your reply. I have a few that snap on LMR 400 and some that snap on rg8. I was not experiencing speaker bleed over until I actually mounted the stereo speakers about 3 feet from my ICOM that is shown in my pic. So in my aplacation should in snap one on each antenna feed line on the back of the ICOM. Then wrap the speaker wire through a ferrite as close to I can get to the stereo speaker termial? I was thinking I was supposed to snap on a proper size ferrite on the stereo speaker wire close up to the speaker. Kind of like the molded on ferrites on computer cables.
     
  4. Captain Kilowatt

    Captain Kilowatt
    Expand Collapse
    Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    13,994
    Likes Received:
    5,241
    Snapping a ferrite core on results in essentially a single turn and may help. try it and see. If not wind as many turns as you can around the open half and then snap it shut and try again. Again.....as close to the amp as you can get it.
     
  5. Paul-W5lz

    Paul-W5lz
    Expand Collapse
    New Member

    Joined:
    Jul 12, 2017
    Messages:
    22
    Likes Received:
    9
    Another trick that may be helpful is to use coax as the speaker lead(s), grounding that shield via the speaker jack in the radio. That 0.001 cap from center to the shield won't hurt either... nor those ferrites.

    Use smaller coax, that LMR400 would be the pits as a speaker cable.
     
    Captain Kilowatt likes this.

Share This Page