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ECE :: Communication Systems

  1. In a system using QASK and 4 bits to form a symbol, the required bandwidth is

  2. A.
    same as BPSK
    B.
    half of that in BPSK
    C.
    one-fourth of that in BPSK
    D.
    none of the above

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  3. Each of the following statements regarding frequency modulation is true except

  4. A.
    amplitude of the modulated wave remains the same as that of carrier wave
    B.
    the amount of variation of deviation from the original carrier frequency is determined by the frequency of the modulating signal
    C.
    the rate at which the frequency of modulated wave varies is determined by the frequency of the modulating signal
    D.
    frequency of modulated wave increases as the signal voltage increases and vice-versa

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  5. Assertion (A): Radio transmission is by sky waves

    Reason (R): Waves having frequencies higher than 30 MHz penetrate the atmosphere and do not return to earth.

  6. 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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  7. During playback the take up reel is

  8. A.
    in clockwise motion
    B.
    in anticlockwise motion
    C.
    either clockwise or anticlockwise motion
    D.
    none of the above

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  9. To avoid objectionable noise in a microwave TV link, the SNR should be about

  10. A.
    50 or more
    B.
    10 or more
    C.
    25 or more
    D.
    200 or more

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  11. Foster Seeley discriminator uses a

  12. A.
    single tuned circuit
    B.
    double tuned circuit with primary and secondary tuned to the same frequency
    C.
    double tuned circuit with primary and secondary tuned to the different frequency
    D.
    none of the above

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  13. Which of the following statement about modulation is correct?

  14. A.
    It avoid use of antennas
    B.
    It reduces bandwidth
    C.
    It ensures transmission over long distances
    D.
    It combines different transmissions

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  15. Sound wave travels as

  16. A.
    longitudinal waves
    B.
    transverse waves
    C.
    both longitudinal and transverse waves
    D.
    either longitudinal or transverse wave

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  17. FM signal can be generated by

  18. A.
    diode reactance modulator
    B.
    saturable reactor modulator
    C.
    reactance tube modulator
    D.
    none of the above

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  19. A planar array radar uses a high gain planar array antenna.

  20. A.
    True
    B.
    False

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