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Thread: rfi problem

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  1. #1
    Join Date
    Jan 2000
    western upper penninsula michigan

    Default rfi problem

    just recently installed a 126 foot zepp end fed for hf and my neighbor is complaining of rfi on his computer speakers. so installed 2 splitshot ferrite cores on his computer speakers to try and minimize or get rid of the rfi on his speakers when i work hf. well the problem wasnt resolved and need another solution too what i can do too eliminate the rfi on his speakers signed ken(kc8lrq) in wisconsin

  2. #2


    PC speakers are notoriously poor. Even the so called 'shielded' speakers.

    You mention 2 ferrites, I assume you put them on the speaker leads - don't forget to add one to the power lead going to the speakers as well.

    Next would be to put bypass caps on the audio leads.

    However, chances are you'll never totally get rid of this.

  3. #3


    Also when using those snap-on ferrite filters, use one with a large center hole so you can "wrap" the leads (speaker and power) through each one several times. Simply snapping one on the wiring which makes a single pass through the core almost never helps at HF (might work at VHF): Wrap 3-4-5-6 turns of the wire through 1/2 the core before snapping it closed, and then make sure both sides of the ferrite inside make solid contact with each other (I use a couple of tie-wraps to help assure this, and close them really tightly). More "turns" through the core is much more effective at HF.
    What if soy milk is just regular milk introducing itself in Spanish?

  4. #4
    Join Date
    Jan 2011
    Houston Texas


    Sounds like your antenna is working good.

    You may want to put a ferrite filter on the Green audio out connection that feeds the Speakers if it is a Amplified Speaker system, The rf can be getting in on the input of the Speakers audio amp.
    "Theory only works perfect in a vacuum." KA9JLM Don

  5. #5
    Join Date
    Apr 2002
    Rochester, MN


    Amplified computer speakers can be a curse. Not only do they tend to rectify every radio signal for miles around, their wall wart power supplies tend to be horrendous broadband QRM generators. And since things that radiate are usually wide open to RF, the wall warts are sometimes the whole issue. If you have a power line filter handy, I'd try isolating the wall wart on it, and see if that helps.

    At lower HF, you need some real inductance to block RF, and it can be hard to achieve with the snap on ferrites. Be sure that the ferrite material you are using works well at the frequency you're having the most trouble with. The 'mix' used in the ferrite can make a big difference. Type 43 beads are useful mostly above 15 MHz.. Type 31 works well at lower frequencies.

    I think before investing a fortune in the proper beads, I'd consider moving or changing the feed on the antenna. End feeding the Zepp could be creating an imbalance on your feedline, and undesirable feedline radiation, increasing the RF field where it's not wanted - like in your neighbor's house.
    EchoLink, IRLP, Allstar and DSTAR linking - adding interest to repeaters worldwide 24X7

  6. #6
    Join Date
    Mar 2006
    Cincinnati, Ohio


    As others have said, these things are a curse. Often no number of beads and bypasses help. You may find that it will end up being less hassle and expense to buy your neighbor a set of these:

    Good luck.
    Bill WA8FOZ

  7. #7
    Join Date
    Jan 2002
    harms way


    In the end it's his prob, not yours. But it would be nice if you could get him sorted.
    now with true viterbi decoder!

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