Communication Systems Online Exam Quiz

Important questions about Communication Systems. Communication Systems MCQ questions with answers. Communication Systems exam questions and answers for students and interviews.

1. The velocity of sound waves in air

Options

A : is constant at all temperatures

B : varies directly as temperature

C : varies inversely as absolute temperature

D : varies directly as square root of absolute temperature

2. Counterpoise is used in coils having

Options

A : high resistivity

B : low resistivity

C : medium resistivity

D : both (b) and (c)

3. A modem is classified as low speed if data rate handled is

Options

A : upto 100 bps

B : upto 250 bps

C : upto 400 bps

D : upto 600 bps

4. A carrier wave carries information.

Options

A : True

B : False

C :

D :

5. A woofer should be fed from the input through a

Options

A : low pass filter

B : high pass filter

C : band pass filter

D : band stop filter

6. A generator is feeding power to a transmission line of characteristic impedance Z 0 . The line is terminated in impedance Z L . Standing waves will be set up if

Options

A : Z L = Z 0

B : Z L < Z 0

C : Z L > Z 0

D : both (b) and (c)

7. A 400 W carrier is amplitude modulated with m = 0.75. The total power in AM is

Options

A : 400 W

B : 512 W

C : 588 W

D : 650 W

8. In sound recording the degree of pre-emphasis is about 6 dB/ octave.

Options

A : True

B : False

C :

D :

9. Tracking of extra terrestrial objects requires

Options

A : high transmitting power

B : very sensitive receiver

C : fully steerable antenna

D : all of the above

10. A 1000 kHz carrier is simultaneously modulated with 300 Hz, 800 Hz and 2 kHz audio sine waves. Which of the following frequency is least likely to be present in the output?

Options

A : 1002 kHz

B : 1000 kHz

C : 999.2 kHz

D : 998.0 kHz

2. Which of the following cannot be the Fourier series expansion of a periodic signal?

Options

A : x ( t ) = 2 cos t + 3 cos 3 t

B : x ( t ) = 2 cos p t + 7 cos t

C : x ( t ) = cos t + 0.5

D : x ( t ) = 2 cos 1.5 p t + sin 3.5 p t

3. In colour TV receiver, varactor diode is used for

Options

A : detection

B : rectification

C : tuning

D : both (a) and (b)

4. Frequency shift keying is used mostly in

Options

A : telegraphy

B : telephony

C : satellite communication

D : radio transmission

5. Which of the following has the highest input impedance?

Options

A : CE

B : CB

C : CC

D : Push pull

6. Degaussing in a picture tube means

Options

A : Adding magnetism in mask and mounting frame

B : Removing residual magnetism in mask, shield etc...

C : Increasing resistance of coils to decrease time constant

D : Decreasing resistance of coils to increase time constant.

7. Space wave may be a direct wave or wave reflected from earth.

Options

A : True

B : False

C :

D :

8. If the bandwidth is increased by 2, the ? FM ? AM (where ? is the ratio of SNR of output to SNR at input, FM is frequency modulation and AM is amplitude modulation) is increased by a factor of

Options

A : 2

B : 3

C : 4

D : 6

9. When the channel is noisy, producing a conditional probability of error p = 0.5; the channel capacity and entropy function would be, respectively,

Options

A : 1 and 1

B : 1 and 0.5

C : 0.5 and 1

D : 0 and 1

10. c ( t ) and m ( t ) are used to generate an FM signal. If the peak frequency deviation of the generated FM signal is three times the transmission bandwidth of the AM signal, then the coefficient of the term cos [2 p (1008 x 10 3 t )] in the FM signal (in terms of the Bessel Coefficients) is

Options

A : 5 J 4 (3)

B : J 8 (3)

C : J 8 (4)

D : 5 J 4 (6)

1. A carrier is simultaneously modulated by two sine waves having modulation indices of 0.4 and 0.3. The total modulation index will be

Options

A : 0.1

B : 0.7

C : 0.5

D : 0.35

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