50 TOP MODULATION & DEMODULATION Questions and Answers pdf | MCQs

MODULATION & DEMODULATION Questions and Answers pdf :-

1. Modulation is done in …………..

Transmitter
Radio receiver
Between transmitter and radio receiver
None of the above
Answer : 1

2. In a transmitter ……………. oscillator is used

Hartley
RC phase-shift
Wien-bridge
Crystal
Answer : 4

3. In India, ……………. modulation is used for radio transmission

Frequency
Amplitude
Phase
None of the above
Answer : 2

4. In an AM wave useful power is carrier by ………….

Carrier
Sidebands
Both sidebands and carrier
None of the above
Answer : 2

5. In amplitude modulation, bandwidth is ……………. the audio signal frequency

Thrice
Four times
Twice
None of the above
Answer : 3

6. In amplitude modulation, the ………… of carrier is varied according to the strength of the signal.

Amplitude
Frequency
Phase
None of the above
Answer : 1

7. Overmodulation (amplitude) occurs when signal amplitude is …………. carrier amplitude

Equal to
Greater than
Less than
None of the above
Answer : 2

8. In an AM wave, the majority of the power is in …………….

Lower sideband
Upper sideband
Carrier
None of the above
Answer : 3

9. At 100% modulation, the power in each sideband is ………………… of that of carrier

50%
40%
60%
25%
Answer : 4

10. Overmodulation results in …………..

Weakening of the signal
Excessive carrier power
Distortion
None of the above
Answer : 3

11. If modulation is 100% then signal amplitude is ………….. carrier amplitude

Equal to
Greater than
Less than
None of the above
Answer : 1

12. As the modulation level is increased, the carrier power …………..

Is increased
Remains the same
Is decreased
None of the above
Answer : 2

13. Demodulation is done in …………

Receiving antenna
Transmitter
Radio receiver
Transmitting antenna
Answer : 3

14. A high Q tuned circuit will permit an amplifier to have high ……………

Fidelity
Frequency range
Sensitivity
Selectivity
Answer : 4

15. In radio transmission, the medium of transmission is ……………..

Space
An antenna
Cable
None of the above
Answer : 1

16. If level of modulation is increased ……………. power is increased

Carrier
Sideband
Carrier as well as sideband
None of the above
Answer : 2

17. In TV transmission, picture signal is ……………… modulated

Frequency
Phase
Amplitude
None of the above
Answer : 3

18. In a radio receiver, noise is generally developed at ………….

IF stage
Receiving antenna
Audio stage
RF stage
Answer : 4

19. Man made noise are …………. variations.

Amplitude
Frequency
Phase
Both phase and frequency
Answer : 1

20. The signal voltage induced in the aerial of a radio receiver is of the order of …………….

mV
µV
V
None of the above
Answer : 2

21. Superhertodyne principle refers to

Using a large number of amplifier stages
Using a push-pull circuit
Obtaining lower fixed intermediate frequency
None of the above
Answer : 3

22. If a radio receiver amplifies all the signal frequencies equally well, it is said to have high …………

Sensitivity
Selectivity
Distortion
Fidelity
Answer : 4

23. Most of the amplification in a superhetrodyne receiver occurs at ………. stage

IF
RF amplifier
Audio amplifier
Detector
Answer : 1

24. The letters AVC stand for …………..

Audio voltage control
Abrupt voltage control
Automatic volume control
Automatic voltage control
Answer : 3

25. The superhetrodyne principle provides selectivity at ………. stage

RF
IF
audio
Before RF
Answer : 2

26. In superhetrodyne receiver, the input at mixer stage is ……….

IF and RF
RF and AF
IF and AF
RF and local oscillator signal
Answer : 4

27. The major advantage of FM over AM is …………..

Reception is less noisy
Higher carrier frequency
Smaller bandwidth
Small frequency deviation
Answer : 1

28. When the modulating signal controls the frequency of the carrier, we get……….

Phase modulation
Amplitude modulation
Frequency modulation
May be any one of the above
Answer : 3

29. Modulation refers to a low-frequency signal controlling the …………

Amplitude of the carrier
Frequency of the carrier
Phase of the carrier
May be any of the above
Answer : 4

30. The IF is 455 kHz. If the radio receiver is tuned to 855 kHz, the local oscillator frequency is ………….

455 kHz
1310 kHz
1500 kHz
1520 kHz
Answer : 2

31. If Amin = 40 and Amax = 60, what is the percentage of modulation?

20 %
40 %
50 %
10 %
Answer : 1

32. The function of ferrite antenna is to …………….

Reduce stray capacitance
Stabilise d.c. bias
Increase the Q of tuned circuit
Reduce noise
Answer : 3

33. In a radio receiver, we generally use ………….. oscillator as a local oscillator

Crystal
Wien-bridge
Phase-shift
Hartley
Answer : 4

34. A 100 V carrier is made to vary between 160 V and 40 V by the signal. What is the modulation factor?

3
6
5
None of the above
Answer : 2

35. A 50 kW carrier is to be amplitude modulated to a level of 85%. What is the carrier power after modulation?

50 kW
5 kW
8 kW
25 kW
Answer : 1

36. In the above question, what is the power in sidebands?

8 kW
6 kW
06 kW
9 kW
Answer : 3

37. In a superhetrodyne receiver, the difference frequency is chosen as the IF rather than the sum frequency because …………….

The difference frequency is closer to oscillator frequency
Lower frequencies are easier to amplify
Only the difference frequency can be modulated
None of the above
Answer : 2

38. The diode detector in an AM radio receiver is usually found ………….

Before the first RF stage
After the first RF stage
After several stages of amplification
None of the above
Answer : 3

39. In a TRF radio receiver, the RF and detection stages are tuned to …………

Radio frequency
IF
Audio frequency
None of the above
Answer : 1

40. In TV transmission, sound signal is ………………… modulated

Amplitude
Frequency
Phase
None of the above
Answer : 2

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