-:PCE:-

MCQ   Question Principles of communication engineering :-

 

1. Modulation is done in …………..

Transmitter

Radio receiver

Between transmitter and radio receiver

None of the above 

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

Hartley

RC phase-shift

Wien-bridge

Crystal

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

Frequency

Amplitude

Phase

None of the above

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

Carrier

Sidebands

Both sidebands and carrier

None of the above

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

Thrice

Four times

Twice

None of the above

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

Amplitude

Frequency

Phase

None of the above

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

Lower sideband

Upper sideband

Carrier

None of the abo

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

50%

40%

60%

25%

9.Overmodulation results in …………..

Weakening of the signal

Excessive carrier power

Distortion

None of the above

10.Demodulation is done in …………

Receiving antenn 

Transmitter

Radio receiver

Transmitting antenna

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

Carrier

Sideband

Carrier as well as sideband

None of the above 

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

Frequency

Phase

Amplitude

None of the above

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

IF stage

Receiving antenna

Audio stage

RF stage

14. 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

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

Sensitivity

Selectivity

Distortion

Fidelity

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

IF

RF amplifier

Audio amplifier

Detector

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

IF and RF

RF and AF

IF and AF

RF and local oscillator signal

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

Reception is less noisy

Higher carrier frequency

Smaller bandwidth

Small frequency deviation 

19.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

 

20.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

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

20 %

40 %

50 %

10 % 

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

Crystal

Wien-bridge

Phase-shift

Hartle

23.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

24.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

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

Radio frequency

IF

Audio frequency

None of the above

26.What is the carrier frequency in an AM wave when its highest frequency component is 850Hz and the bandwidth of the signal is 50Hz?

a. 80 Hz

b. 695 Hz

c. 625 Hz

d. 825 Hz

27.Noise figure of merit in SSB modulated signal is

a. 1 

b. Less than 1

c. Greater than 1

d. None of the above 

28.For low level modulation, amplifier used is

a. Class A

b. Class C

c. Class A & C

d. None of the above

29.Function of RF mixer is

a. Addition of two signals

b. Multiplication of two signals

c. Rejection of noise

d. None of the above

30.Advantage of using VSB transmission is

a. Higher bandwidth than SSB

b. Less power required as compared to DSBSC

c. Both a and b

d. None of the above

31.Advantage of using a high frequency carrier wave is

a. Signal can be transmitted over very long distances

b. Dissipates very small power

c. Antenna height of the transmitter is reduced

d. All of the above

32.Bandwidth required in SSB-SC signal is (fm is modulating frequency):

a. 2fm

b. < 2fm

c. > 2fm

d. fm

33.For over modulation, the value of modulation index m is a. m < 1   

a. m < 1

b. m = 1

c. m > 1

34.Demodulation is:

a. Detection

b. Recovering information from modulated signal

c. Both a and b

d. None of the above

35.Calculate the side band power in an SSBSC signal when there is 50% modulation and the carrier power is 50W.

2/2

a. 50 W

b. 25 W

c. 6.25 W

d. 12.5 W:

36.Disadvantage of using a DSB or SSB signal modulation is

Difficult to recover information at the receiver

b. Carrier has to be locally generated at receiver

c. Both a and b are correct

d. None of the above 

37. Types of analog modulation are:

a. Phase modulation

b. Frequency modulation

c. Amplitude modulation

d. All of the above

 

38.Advantages of analog communication over digital communication are:

a. Data rate is low

b. Less transmission bandwidth is required

c. Synchronization is not needed

d. All of the above

39.Radio waves travel through

a. Electromagnetic waves

b. Water

c. Wires

d. Fiber optic cable

40. USB (Upper Side Band) is the band of frequency

a.Above the carrier frequency

b. Includes the carrier frequency

c. That lies in AM spectrum

d. Both a and c are correct

41.In PM the information is transmitted using _______ .

a. Change in frequency

b. Change in amplitude

c. Change in phase of the carrier

 

42.FM can be generated using PM by _______ .

a. Passing the modulating signal through a low pass filter

b. Passing the modulating signal through a high pass filter

 

c. Using the pre-emphasis

d. Using the de-emphasis

43. Noise immunity of PM is _______

a. Better than AM and FM

b. Worse than AM and FM

C. Better than AM but worse than FM

 

44.Amplitude of PM wave ______

a. remain constant

b. change in proportion with the modulating voltage

c. change in proportion with the modulating frequency 

45.The equation for the modulated PM wave is given by

a. 5 sin (2 π × 106 t )

b. 5 sin 1000 t + 5 sin 106 t

c. 5 sin ( 2 π × 106 t + 10 sin 6280 t )

d. 5 sin ( 2 π × 106 t – 10 sin 6280 t )

46.As compared to tuned radio frequency receivers which of the following is the advantage of using superheterodyne receivers?

A. High gain and better sensitivity

B. Better selectivity at high frequencies

C. Stability

D. Noise suppression

 

47.In a radio receiver, if the intermediate frequency is too low

A. High gain and better sensitivity

B. Better selectivity at high frequencies

C. Stability

D. Noise suppression

48.Which of the following oscillator is generally not used at VHF?

A. Colpitts oscillator

B. Clapp oscillator

C. Armstrong oscillator

D. Ultra Audio oscillator

49.The output of a diode detector contains

A. D.C. voltage

B. modulating signal

C. RF ripple

D. all of the above

50. In a radio receiver, if the intermediate frequency is too low

A. Image-frequency rejection will improve

B. Selectivity will be too sharp

C. The frequency selectivity of the local oscillator will have to be lowered

D. All of the above

     

 

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                                        ABHISHEK KUMAR MAURYA…..