COMMUNICATION SYSTEMS QUIZ

For a low level AM system, the amplifiers modulated stage must be

Class C amplifiers

Linear devices

Harmonic devices

Non-linear devices

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Commercial Frequency deviation of FM is

70 kHz

80 kHz

75 kHz

65 kHz

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A telephone channel requires a bandwidth of about

1 kHz

3 kHz

10 kHz

50 kHz

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Assertion (A): In FM the frequency of the carrier is varied by the modulating voltageReason (R): FM and PM are two forms of angle modulation.

A is wrong but R is correct

Both A and R are correct and R is correct explanation of A

A is correct but R is wrong

Both A and R are correct but R is not correct explanation of A

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In Pulse Code Modulation system

Quantising noise can be overcome by companding

Large bandwidth is required

Suffers from the disadvantage of its incompatibly with TDM

Quantising noise can be reduced by decreasing the number of standard levels

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Skip distance depends on time of day and angle of incidence.

True

False

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In case of frequency modulation, modulating voltage remains constant if the modulating frequency is lowered, then

Amplitude of distant sidebands increases

Amplitude of distant sidebands first increases, then decreases

Amplitude of distant sidebands decreases

Amplitude of distant sidebands remains constant

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A zero mean white Gaussian noise is passed through an ideal low pass filter of bandwidth 10 kHz. The output of the samples so obtained would be

Correlated

Statistically independent

Uncorrelated

Orthogonal

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If sampling is done at the rate of 10 kHz. The bandwidth required is

1280 kHz

10 kHz

35 kHz

70 kHz

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In practical commercial FM system, channel bandwidth is

150 kHz

88 MHz

108 MHz

100 kHz

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