Extra exam question E8C01
Subelement E8, SIGNALS AND EMISSIONS· Group E8C
What is Quadrature Amplitude Modulation or QAM?
- A.A technique for digital data compression used in digital television which removes redundancy in the data by comparing bit amplitudes
- B.Transmission of data by modulating the amplitude of two carriers of the same frequency but 90 degrees out of phase (correct answer)
- C.A method of performing single sideband modulation by shifting the phase of the carrier and modulation components of the signal
- D.A technique for analog modulation of television video signals using phase modulation and compression
WhyQuadrature Amplitude Modulation (QAM) transmits data by modulating the amplitude of two carriers of the same frequency but 90 degrees out of phase. Quadrature Amplitude Modulation transmits data by independently modulating the amplitude of two carriers at the same frequency but 90 degrees out of phase with each other, letting the combined signal represent more information per symbol than amplitude or phase modulation could alone, answer B. It isn't a data compression technique for digital TV, isn't an SSB generation method, and isn't an analog phase-modulation technique for video, QAM is specifically this two-carrier, phase-quadrature amplitude scheme.
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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