SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hame-nyquist-sampling

How often must an analog signal be sampled to be accurately reproduced?

At least twice the highest frequency in the signal.

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  1. At the highest frequency component rate
  2. At half the highest frequency component rate
  3. At least twice the highest frequency component ✔

Why: This is the Nyquist rule. Sample slower and high frequencies fold back as false lower ones, so you cannot rebuild the original signal.

Huh, didn't know that: A Fast Fourier Transform converts signals from the time domain to the frequency domain (E7F07).

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Why is it easier to measure a circuit in the time domain? It's not complex and there's only one step.
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References

Answer: At least twice the highest frequency component. This is the Nyquist rule. Sample slower and high frequencies fold back as false lower ones, so you cannot rebuild the original signal.

  1. NCVEC 2024-2028 Amateur Extra Question Pool, E7F05 (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
    B. At least twice the rate of the highest frequency component of the signal
    Checked 2026-10-11.
  2. NCVEC 2024-2028 Amateur Extra Question Pool, E7F07 (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. Converting signals from the time domain to the frequency domain
    Checked 2026-10-11.

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