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ECE :: Communication Systems

  1. If velocity of sound waves in air at 0°C is 330 m/s, the velocity at 40°C is about

  2. A.
    330 m/s
    B.
    334 m/s
    C.
    353 m/s
    D.
    380 m/s

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  3. A 5000 W signal is attenuated by - 196 dB. The resultant signal strength is

  4. A.
    1.26 x 106 W
    B.
    1.26 x 10-2 W
    C.
    1.26 x 10-8 W
    D.
    1.26 x 10-16 W

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  5. In FM, as bandwidth increases

  6. A.
    distortion increases
    B.
    distortion decreases
    C.
    distortion remains unaffected
    D.
    all

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  7. A 400 W carrier is amplitude modulated with m = 0.75. If single side band suppressed carrier is used the total power in modulated wave is

  8. A.
    400 W
    B.
    512 W
    C.
    112 W
    D.
    56 W

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  9. In TV transmitter, the function of duplexer is

  10. A.
    to amplify video signal
    B.
    to remove distortions in audio signal
    C.
    to combine outputs of visual and audio transmitters
    D.
    to amplify audio signal

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  11. Microwave link repeaters are typically 50 km apart in TV transmission due to

  12. A.
    atmosphere attenuation
    B.
    output power tube limitations
    C.
    attenuation of surface wave
    D.
    earth's curvature

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  13. Assertion (A): The colour signal consists of only luminance signal

    Reason (R): In India PAL colour signal system is used.

  14. A.
    Both A and R are correct and R is correct explanation of A
    B.
    Both A and R are correct but R is not correct explanation of A
    C.
    A is correct but R is wrong
    D.
    A is wrong but R is correct

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  15. To separate channels in FDM receiver we have to use

  16. A.
    integration
    B.
    AND gate
    C.
    band pass filter
    D.
    differentiation

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  17. A device with input x(t) and y(t) is characterized by y(t) = x2(t). An FM signal with frequency deviation of 90 kHz and modulating signal bandwidth of 5 kHz is applied to this device. The bandwidth of the output signal is

  18. A.
    370 kHz
    B.
    190 kHz
    C.
    380 kHz
    D.
    95 kHz

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  19. Assertion (A): Bandwidth of a TV signal is 5 MHz.

    Reason (R): TV systems use vestigial side band transmission.

  20. A.
    Both A and R are correct and R is correct explanation of A
    B.
    Both A and R are correct but R is not correct explanation of A
    C.
    A is correct but R is wrong
    D.
    A is wrong but R is correct

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