How to use ferrite beads

Written by andrew hazleton
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A ferrite bead is an electronic component which functions as a low-pass filter in many types of circuitry. Low-pass filters are designed to allow low frequency signals to pass but will attenuate (lessen the intensity of) higher frequency signals.

In simple terms, a ferrite bead acts as a very high value resistor for high frequencies, and a low value resistor for low frequencies. They are commonly found at the ends of cables for earphones, power cords, USB cables, headsets and other devices. Ferrite beads are usually designed to work on RF (radio frequency) noise that can be picked up by long cords.

Common sources of RF interference are cell phone towers, AM/FM radio towers and some electronic equipment. The National Cancer Institute of the U.S. National Institutes of Health has indicated concerns that RF energy near your head is a health risk.

Skill level:
Moderately Easy

Things you need

  • Ferrite bead

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  1. 1

    Procure a ferrite bead designed to clamp on to the wire you wish to protect. These are available from electronics and hobbyist suppliers, as well as some cellular phone equipment suppliers.

    Ferrite beads come in many sizes, and you should be able to find the size required.

  2. 2

    Open the ferrite bead. They typically snap together with a plastic tab. Release this tab and the bead should separate lengthwise into two halves.

  3. 3

    Place the wire you wish to shield in the channel which runs through the centre of the ferrite bead. The bead should be mounted as close as possible to the end of the wire where protection is desired.

    For a phone headset, mount the wire as near as possible to the earpiece.

  4. 4

    Snap the ferrite bead closed and secure any locking mechanisms.

Tips and warnings

  • A small dot of glue may help secure the ferrite bead to the wire, and will not affect electrical performance.
  • Mounting additional ferrite beads on the same headset will not provide significantly greater protection.

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