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An FM signal deviates 3,000 Hz each side of the carrier with a highest modulating frequency of 1,000 Hz. What is the modulation index?

A modulation index of 3.

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  1. 0.3
  2. 6
  3. 3 ✔

Why: FM modulation index is the frequency deviation divided by the modulating frequency. That is 3,000 divided by 1,000, which equals 3.

Huh, didn't know that: A phase-modulated signal's modulation index does not depend on the RF carrier frequency (E8B02).

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References

Answer: 3. FM modulation index is the frequency deviation divided by the modulating frequency. That is 3,000 divided by 1,000, which equals 3.

  1. NCVEC 2024-2028 Amateur Extra Question Pool, E8B03 (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
    A. 3
    Checked 2026-10-11.
  2. NCVEC 2024-2028 Amateur Extra Question Pool, E8B02 (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
    D. It does not depend on the RF carrier frequency
    Checked 2026-10-11.

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