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ECE :: Communication Systems

  1. LCD uses

  2. A.
    nematic crystals
    B.
    sematic crystals
    C.
    cholesteric crystals
    D.
    twisted nematic crystal

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  3. Which of the following stage is not present in AM receiver as compared to FM receiver?

  4. A.
    AM amplifier
    B.
    Demodulator
    C.
    Amplitude limiter
    D.
    AF amplitude

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  5. The function of duplexer in a RADAR is

  6. A.
    to permit the use of same antenna for transmission and reception
    B.
    to provide gain to the transmitted power
    C.
    to amplify the received signal
    D.
    both (b) and (c)

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  7. If e = 10 cos (2p x 108t + 20 cos 2p 103t). The bandwidth is

  8. A.
    108 Hz
    B.
    42 kHz
    C.
    21 kHz
    D.
    108 ± 103 Hz

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  9. In FM, as the modulating frequency decreases and the modulating voltage amplitude

  10. A.
    increases, the modulation index increases
    B.
    decrease, the modulation index increases
    C.
    remains constant, the modulation index increases
    D.
    remains constant, the modulation index decreases

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  11. Modulation system used for video-modulation in television broadcast is

  12. A.
    SSB AM with carrier
    B.
    SSB with carrier suppressed
    C.
    DSB AM with carrier
    D.
    a modified form of SSB with carrier called vestigial sideband

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  13. The highest modulation frequencies typically used in FM broadcast is

  14. A.
    5 kHz
    B.
    10 kHz
    C.
    15 kHz
    D.
    25 kHz

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  15. The intermediate frequency of a superheterodyne receiver is 450 kHz. If it is tuned to 1200 kHz, the image frequency will be

  16. A.
    750 kHz
    B.
    900 kHz
    C.
    1600 kHz
    D.
    2100 kHz

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  17. In the above case the modulation index will be

  18. A.
    9.6
    B.
    28.8
    C.
    57.6
    D.
    100

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  19. Which of the following statement regarding single-sideband (SSB) transmission is not correct?

  20. A.
    In such transmission only or sideband is transmitted, leaving of the other sideband and the carrier
    B.
    It has gained general acceptance of use in home-entertainment equipment
    C.
    It is generally reserved for point-to-point communication
    D.
    The amount of power and bandwidth necessary to be transmitted for a given amount of information are appreciable reduced

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