SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hamg-bypass-capacitor

What might reduce RF interference to audio circuits?

A bypass capacitor.

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  1. A bypass capacitor ✔
  2. A bypass inductor
  3. A forward-biased diode

Why: A bypass capacitor gives unwanted RF a path to ground while letting the audio signal pass on. Small amounts of RF can otherwise get into audio circuits.

Huh, didn't know that: RF interference from a CW transmitter sounds like on-and-off humming or clicking in audio gear.

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References

Answer: A bypass capacitor. A bypass capacitor gives unwanted RF a path to ground while letting the audio signal pass on. Small amounts of RF can otherwise get into audio circuits.

  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
    Bypass capacitor
    Checked 2026-10-10.
  2. 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
    On-and-off humming or clicking
    Checked 2026-10-10.

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