MCQs in Modulation Part I

(Last Updated On: December 8, 2017)

MCQs in Modulation - Part I

This is the Multiples Choice Questions Part 1 of the Series in Modulation as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

Online Questions and Answers Topic Outline

  • MCQs in Amplitude Modulation
  • MCQs in Phase Modulation
  • MCQs in Sound Pressure Level
  • MCQs in Frequency Modulation
  • MCQs in Pulse Modulation

MCQs in Modulation Series

Following is the list of multiple choice questions in this brand new series:

Modulation MCQs
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III
PART 4: MCQs from Number 151 – 200                 Answer key: PART IV
PART 5: MCQs from Number 201 – 250                 Answer key: PART V
PART 6: MCQs from Number 251 – 300                 Answer key: PART VI
PART 7: MCQs from Number 301 – 350                 Answer key: PART VII
PART 8: MCQs from Number 351 – 400                 Answer key: PART VIII
PART 9: MCQs from Number 401 – 450                 Answer key: PART IX
PART 10: MCQs from Number 451 – 500                 Answer key: PART X

Start Practice Exam Test Questions Part I of the Series

1. ______ is the maximum sideband suppression value using filter system.

  • A. 50 dB
  • B. 60 dB
  • C. 40 dB
  • D. 30 dB

2. _______ determines the number of sideband components in FM.

  • A. carrier frequency
  • B. modulation frequency
  • C. modulation index
  • D. deviation ratio

3. One of the following transmits only one sideband.

  • A. H3E
  • B. R3E
  • C. A3E
  • D. B8E

4. What produces the sidebands on FM?

  • A. signal amplitude
  • B. carrier harmonics
  • C. baseband frequency
  • D. broadband frequency

5. Which test instrument displays the carrier and the sidebands amplitude with frequency to frequency?

  • A. oscilloscope
  • B. spectrum analyzer
  • C. frequency analyzer
  • D. amplitude analyzer

6. Mixer is also known as a ________.

  • A. modulator
  • B. suppressor
  • C. converter
  • D. beater

7. Which one of the following emission transmits the lower sideband and half of the upper sideband?

  • A. A5C
  • B. J3E
  • C. A3J
  • D. A3H

8. An FM receives signal ______.

  • A. vary in amplitude with modulation
  • B. vary in frequency with modulation
  • C. vary in frequency and amplitude with wideband modulation
  • D. is not immune to noise

9. The process of impressing intelligence on the carrier is called

  • A. modulation
  • B. detection
  • C. mixing
  • D. impression

10. ______ is an electronic instrument used to show both the carrier and the sidebands of a modulated signal in the frequency domain.

  • A. spectrum analyzer
  • B. oscilloscope
  • C. digital counter
  • D. frequency counter

11. What part of the carrier is varied by the intelligence during modulation in an AM system?

  • A. phase
  • B. frequency
  • C. amplitude
  • D. both a and c

12. The difference between the RF carrier and the modulating signal frequencies is called the

  • A. USB
  • B. LSB
  • C. Sideband
  • D. Carrier frequency

13. What stage in a radio transmitter isolates the oscillator from the load?

  • A. Oscillator
  • B. Buffer
  • C. Separator
  • D. Mixer

14. The frequency of the unmodulated carrier in FM system is

  • A. modulating frequency
  • B. center frequency
  • C. carrier frequency
  • D. deviation frequency

15. The ratio of maximum deviation to the maximum modulating frequency is called

  • A. carrier swing
  • B. deviation ratio
  • C. modulation factor
  • D. modulation index

16. A carrier signal has

  • A. constant amplitude
  • B. a frequency of 20 kHz and above
  • C. a varying amplitude
  • D. the information content

17. The modulated peak value of a signal is 125 V and the unmodulated carrier value is 85 V. What is the modulation index?

  • A. 0.47
  • B. 0.68
  • C. 0.32
  • D. 1.47

18. An 891 kHz carrier having an amplitude of 80 V is modulated by a 4.5 kHz audio signal having an amplitude of 45 V. The modulation factor is

  • A. 0.56
  • B. 0.65
  • C. 1.78
  • D. 1.25

19. What is the modulation index of an FM signal having a carrier swing of 75 kHz when the modulating signal has frequency of 3 kHz?

  • A. 25
  • B. 12.5
  • C. 0.04
  • D. 0.08

20. In a FM system, if modulation index is doubled by having the modulating frequency, what will be the effect on the maximum deviation?

  • A. No effect
  • B. Maximum deviation doubles
  • C. Decreases by ½
  • D. Increases by ¼

21. Which of the following is considered as an indirect method of generating FM?

  • A. Reactance modulator
  • B. Balanced modulator
  • C. Varactor diode modulator
  • D. Armstrong system

22. To generate an SSB or DSB signal one must use a circuit known as

  • A. filter modulator
  • B. ring modulator
  • C. balanced modulator
  • D. reactance modulator

23. Which is the first radio receiver?

  • A. TRF receiver
  • B. Superheterodyne receiver
  • C. Crystal radio receiver
  • D. Heterodyne receiver

24. An interfering signal with a frequency equal to the received signal plus twice the IF is called

  • A. image frequency
  • B. center frequency
  • C. rest frequency
  • D. interference frequency

25. Double sideband full carrier emission type

  • A. A3J
  • B. H3E
  • C. R3A
  • D. A3E

26. Single sideband reduced carrier emission type

  • A. H3E
  • B. R3E
  • C. J3E
  • D. B8E

27. A single sideband suppressed carrier emission type.

  • A. H3e
  • B. R3E
  • C. J3E
  • D. B8E

28. Independent sideband emission type

  • A. H3E
  • B. R3E
  • C. J3E
  • D. B8E

29. Vestigial sideband emission type

  • A. C3F
  • B. J3E
  • C. R3E
  • D. B8E

30. Single sideband full carrier emission type.

  • A. R3E
  • B. H3E
  • C. J3E
  • D. B8E

31. Phase modulation emission type.

  • A. F3E
  • B. F3C
  • C. F3F
  • D. G3E

32. Which one is not an advantage of SSB over AM?

  • A. Power saving
  • B. Requires half the bandwidth
  • C. Wider area of reception
  • D. Better fidelity

33. The advantage of a high level modulated AM transmitter is

  • A. Less audio power required
  • B. Better fidelity
  • C. Higher value of operating power
  • D. Less distortion

34. The advantage of a low-level modulated AM transmitter is

  • A. Less audio power required
  • B. Better fidelity
  • C. Higher value of operating power
  • D. Less distortion

35. _____ is the bad effect caused by overmodulation in AM transmission.

  • A. Increase in noise
  • B. Deviation in the operating frequency
  • C. Interface to other radio services
  • D. Decrease in the output power

36. Which characteristic of a radio receiver refers to its ability to reject an unwanted signal?

  • A. Sensitivity
  • B. Selectivity
  • C. Fidelity
  • D. Quality

37. What type of emission is frequency modulation?

  • A. F3E
  • B. G3E
  • C. A3E
  • D. B3E

38. AM transmission power increases with ________.

  • A. Frequency
  • B. Source
  • C. Load
  • D. Modulation

39. _______ locks the FM receiver to a stronger signal.

  • A. Hall effect
  • B. Capture effect
  • C. Image frequency
  • D. Homing

40. What is the highest percentage of modulation for AM?

  • A. 50 %
  • B. 75 %
  • C. 100 %
  • D. 80 %

41. In FM, the Carson’s Rule states that the bandwidth is equal to twice the sum of the modulating frequency and ______.

  • A. Carrier signal
  • B. Modulating signal
  • C. Frequency deviation
  • D. Image frequency

42. What is the carrier swing of an FM transmitter when modified by 75%?

  • A. 53.2 kHz
  • B. 48 kHz
  • C. 56.25 kHz
  • D. 112.5 kHz

43. The modulation system inherently more resistant to noise

  • A. Single sideband suppressed carrier
  • B. Frequency modulation
  • C. Pulse-position modulation
  • D. Amplitude shift keying

44. Subcarriers that are arranged so that the channels occupying adjacent frequency bands with some frequency space between them is known as

  • A. Guard bands
  • B. AM bands
  • C. Band gap
  • D. Void band

45. Modulation of an RF amplifier carrier results in

  • A. Multiple channels
  • B. Smaller antennas
  • C. Directional propagation
  • D. All of the above

46. A process which occurs in the transmitter

  • A. Mixing
  • B. Modulation
  • C. Heterodyning
  • D. Demodulation

47. A process which occurs in the receiver

  • A. Beating
  • B. Modulation
  • C. Mixing
  • D. Demodulation

48. One part of the transmitter that protects the crystal oscillator from “pulling”.

  • A. Buffer amplifier
  • B. Modulator
  • C. Power amplifier
  • D. Antenna coupler

49. What aspect of the carrier is changed by modulation?

  • A. Frequency
  • B. Phase
  • C. Amplitude
  • D. Depends on the type of modulation

50. The amplitude of a sine wave which is modulated by a musical program will

  • A. Be complex
  • B. Contain fundamental frequencies
  • C. Contain harmonic frequencies
  • D. All of the above

Complete List of MCQs in Communications Engineering per topic

MCQs in Modulation Part I
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