Extra exam question E8B03
Subelement E8, SIGNALS AND EMISSIONS· Group E8B
What is the modulation index of an FM phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency if the highest modulating frequency is 1000 Hz?
- A.3 (correct answer)
- B.0.3
- C.6
- D.0.6
WhyAn FM phone signal with a maximum frequency deviation of 3000 Hz and a highest modulating frequency of 1000 Hz has a modulation index of 3. Modulation index equals frequency deviation divided by the modulating frequency: 3,000 Hz of deviation divided by a 1,000 Hz modulating tone works out to a modulation index of 3, answer A. The other figures come from inverting that ratio or applying an unrelated scaling factor to these same two values.
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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