# MCQ in Modulation Part 1 | ECE Board Exam

(Last Updated On: April 15, 2020) 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.

#### MCQ Topic Outline included in ECE Board Exam Syllabi

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

#### Start Practice Exam Test Questions Part 1 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

Solution:

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

A. carrier frequency

B. modulation frequency

C. modulation index

D. deviation ratio

Solution:

3. One of the following transmits only one sideband.

A. H3E

B. R3E

C. A3E

D. B8E

Solution:

4. What produces the sidebands on FM?

A. signal amplitude

B. carrier harmonics

C. baseband frequency

Solution:

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

Solution:

6. Mixer is also known as a ________.

A. modulator

B. suppressor

C. converter

D. beater

Solution:

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

Solution:

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

Solution:

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

A. modulation

B. detection

C. mixing

D. impression

Solution:

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

Solution:

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

Solution:

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

A. USB

B. LSB

C. Sideband

D. Carrier frequency

Solution:

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

A. Oscillator

B. Buffer

C. Separator

D. Mixer

Solution:

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

A. modulating frequency

B. center frequency

C. carrier frequency

D. deviation frequency

Solution:

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

Solution:

16. A carrier signal has

A. constant amplitude

B. a frequency of 20 kHz and above

C. a varying amplitude

D. the information content

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

Solution:

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

Solution:

25. Double sideband full carrier emission type

A. A3J

B. H3E

C. R3A

D. A3E

Solution:

26. Single sideband reduced carrier emission type

A. H3E

B. R3E

C. J3E

D. B8E

Solution:

27. A single sideband suppressed carrier emission type.

A. H3e

B. R3E

C. J3E

D. B8E

Solution:

28. Independent sideband emission type

A. H3E

B. R3E

C. J3E

D. B8E

Solution:

29. Vestigial sideband emission type

A. C3F

B. J3E

C. R3E

D. B8E

Solution:

30. Single sideband full carrier emission type.

A. R3E

B. H3E

C. J3E

D. B8E

Solution:

31. Phase modulation emission type.

A. F3E

B. F3C

C. F3F

D. G3E

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

A. Sensitivity

B. Selectivity

C. Fidelity

D. Quality

Solution:

37. What type of emission is frequency modulation?

A. F3E

B. G3E

C. A3E

D. B3E

Solution:

38. AM transmission power increases with ________.

A. Frequency

B. Source

D. Modulation

Solution:

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

A. Hall effect

B. Capture effect

C. Image frequency

D. Homing

Solution:

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

A. 50 %

B. 75 %

C. 100 %

D. 80 %

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

45. Modulation of an RF amplifier carrier results in

A. Multiple channels

B. Smaller antennas

C. Directional propagation

D. All of the above

Solution:

46. A process which occurs in the transmitter

A. Mixing

B. Modulation

C. Heterodyning

D. Demodulation

Solution:

47. A process which occurs in the receiver

A. Beating

B. Modulation

C. Mixing

D. Demodulation

Solution:

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

A. Buffer amplifier

B. Modulator

C. Power amplifier

D. Antenna coupler

Solution:

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

A. Frequency

B. Phase

C. Amplitude

D. Depends on the type of modulation

Solution:

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

Solution:

#### Questions and Answers in Modulation Series

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

MCQ in Modulation
PART 1: MCQ from Number 1 – 50                        Answer key: PART 1
PART 2: MCQ from Number 51 – 100                   Answer key: PART 2
PART 3: MCQ from Number 101 – 150                 Answer key: PART 3
PART 4: MCQ from Number 151 – 200                 Answer key: PART 4
PART 5: MCQ from Number 201 – 250                 Answer key: PART 5
PART 6: MCQ from Number 251 – 300                 Answer key: PART 6
PART 7: MCQ from Number 301 – 350                 Answer key: PART 7
PART 8: MCQ from Number 351 – 400                 Answer key: PART 8
PART 9: MCQ from Number 401 – 450                 Answer key: PART 9
PART 10: MCQ from Number 451 – 500                 Answer key: PART 10

### Complete List of MCQ in Communications Engineering per topic

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