Extra exam question E8B01
Subelement E8, SIGNALS AND EMISSIONS· Group E8B
What is the modulation index of an FM signal?
- A.The ratio of frequency deviation to modulating signal frequency (correct answer)
- B.The ratio of modulating signal amplitude to frequency deviation
- C.The modulating signal frequency divided by the bandwidth of the transmitted signal
- D.The bandwidth of the transmitted signal divided by the modulating signal frequency
WhyThe modulation index of an FM signal is the ratio of frequency deviation to modulating signal frequency. An FM signal's modulation index is the ratio of frequency deviation to the modulating signal's own frequency, a dimensionless number that describes how much the carrier swings relative to how fast the modulating signal itself is changing, answer A. It isn't the ratio of modulating amplitude to deviation (that inverts the relevant quantities), and it isn't a bandwidth-to-modulating-frequency ratio in either direction, those describe different concepts like deviation ratio instead.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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