Basic concepts of modulation and demodulation MCQs January 8, 2026November 20, 2024 by u930973931_answers 20 min Score: 0 Attempted: 0/20 Subscribe 1. What is modulation in a communication system? (A) Suppressing unwanted noise from a signal (B) Converting analog signals to digital (C) Amplifying a weak signal (D) Varying a carrier wave to encode information 2. Which of the following is NOT a type of modulation? (A) Amplitude Modulation (AM) (B) Frequency Modulation (FM) (C) Phase Modulation (PM) (D) Rectified Modulation (RM) 3. Which of the following is the main advantage of modulation? (A) Enables long-distance signal transmission (B) Reduces bandwidth requirement (C) Eliminates noise completely (D) Simplifies signal encoding 4. In amplitude modulation (AM), the modulating signal affects the: (A) Frequency of the carrier wave (B) Bandwidth of the carrier wave (C) Phase of the carrier wave (D) Amplitude of the carrier wave 5. Frequency modulation (FM) involves varying the: (A) Amplitude of the carrier wave (B) Frequency of the carrier wave (C) Phase of the carrier wave (D) Wavelength of the carrier wave 6. In phase modulation (PM), the modulating signal causes variations in the: (A) Frequency of the carrier wave (B) Amplitude of the carrier wave (C) Power of the carrier wave (D) Phase of the carrier wave 7. Which type of modulation is least susceptible to noise? (A) Frequency Modulation (FM) (B) Amplitude Modulation (AM) (C) Phase Modulation (PM) (D) Pulse Modulation 8. Which type of modulation is used in AM radio broadcasting? (A) Frequency Modulation (B) Phase Modulation (C) Amplitude Modulation (D) Pulse Modulation 9. The bandwidth requirement for an AM signal is: (A) Equal to the carrier frequency (B) Half the highest frequency of the modulating signal (C) Twice the highest frequency of the modulating signal (D) Independent of the modulating signal 10. Which type of modulation has the largest bandwidth requirement? (A) AM (B) FM (C) Both FM and PM (D) PM 11. Demodulation is the process of: (A) Encoding information into a carrier wave (B) Extracting the original information signal from a modulated carrier wave (C) Amplifying a weak signal (D) Reducing the noise in a signal 12. Which of the following devices is used for AM demodulation? (A) Envelope detector (B) Phase-locked loop (PLL) (C) Frequency discriminator (D) Quadrature detector 13. FM signals are demodulated using: (A) Rectifiers (B) Envelope detectors (C) Frequency discriminators or PLL (D) Filters 14. The role of a demodulator in a communication system is to: (A) Filter noise from the signal (B) Convert a digital signal into an analog signal (C) Enhance the signal power (D) Recover the original information signal from the carrier wave 15. Which modulation technique is commonly used in TV broadcasting? (A) AM (B) FM (C) QAM (D) PM 16. Which of the following systems uses frequency modulation (FM)? (A) Longwave radio (B) FM radio broadcasting (C) Morse code transmission (D) AM radio broadcasting 17. Phase modulation (PM) is commonly used in: (A) Wi-Fi networks (B) GPS communication (C) AM radio broadcasting (D) Long-distance telephony 18. Which modulation technique encodes both amplitude and phase into a single signal? (A) AM (B) Quadrature Amplitude Modulation (QAM) (C) PM (D) FM 19. In digital communication, which modulation technique is widely used? (A) ASK (Amplitude Shift Keying) (B) PSK (Phase Shift Keying) (C) FSK (Frequency Shift Keying) (D) All of the above 20. Which modulation technique is used in cellular networks for efficient bandwidth utilization? (A) QAM (B) AM (C) PM (D) SSB (Single Sideband Modulation)