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SESK: Stuff Everyone Should Know · sesk.info/hamg-ferrite-choke

What helps reduce RF interference caused by common-mode current on an audio cable?

A ferrite choke on the cable.

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  1. Add another insulating jacket
  2. Connect the center conductor to the shield
  3. Place a ferrite choke on the cable ✔

Why: Common-mode RF flows along the outside of the cable. A ferrite choke adds impedance to that current, so less RF gets into the audio equipment.

Huh, didn't know that: Bonding equipment enclosures together helps minimize ground loops.

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References

Answer: Place a ferrite choke on the cable. Common-mode RF flows along the outside of the cable. A ferrite choke adds impedance to that current, so less RF gets into the audio equipment.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    Place a ferrite choke on the cable
    Checked 2026-10-10.

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