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SESK: Stuff Everyone Should Know · sesk.info/hame-cw-bandwidth-13wpm

What is the approximate bandwidth of a 13-WPM International Morse Code transmission?

About 52 Hz.

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  1. 52 Hz ✔
  2. 13 Hz
  3. 104 Hz

Why: A CW signal takes roughly 4 Hz of bandwidth for each word per minute of speed. At 13 words per minute that comes to about 52 Hz.

Huh, didn't know that: Keying speed and the shape of the rise and fall times affect the bandwidth of a CW signal (E8C12).

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References

Answer: 52 Hz. A CW signal takes roughly 4 Hz of bandwidth for each word per minute of speed. At 13 words per minute that comes to about 52 Hz.

  1. NCVEC 2024-2028 Amateur Extra Question Pool, E8C05 (4th errata, Feb. 4, 2026) www.ncvec.org/downloads/2024-2028%20Extra%20Class%20Question%20Pool%20and%20Syllabus%20Public%20Release%20with%204th%20Errata%20Feb%204%202026.pdf
    C. 52 Hz
    Checked 2026-10-11.
  2. NCVEC 2024-2028 Amateur Extra Question Pool, E8C12 (4th errata, Feb. 4, 2026) www.ncvec.org/downloads/2024-2028%20Extra%20Class%20Question%20Pool%20and%20Syllabus%20Public%20Release%20with%204th%20Errata%20Feb%204%202026.pdf
    C. Keying speed and shape factor (rise and fall time)
    Checked 2026-10-11.

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