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ECE :: Communication Systems

  1. In the spectrum of an FM wave

  2. A.
    When modulation index is large, carrier frequency disappears
    B.
    carrier frequency cannot disappear
    C.
    amplitude of any side band depends on modulation index
    D.
    the total number of side bands depend on modulation index

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  3. The reactance of bypass capacitor in a CE amplifier circuit should be

  4. A.
    equal to the resistance in parallel with it
    B.
    equal to 10% or less of the resistance in parallel with it
    C.
    equal to 50% of the resistance in parallel with it
    D.
    independent of the resistance in parallel with it

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  5. In a radar system the solution to blind speed problem is to

  6. A.
    use MTI
    B.
    use monopoles
    C.
    vary PRF
    D.
    change Doppler frequency

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  7. For a FM wave carrier modulating frequency is 10 kHz and bandwidth is 2 MHz. If the modulating signal amplitude is doubled, the bandwidth will be

  8. A.
    0.5 MHz
    B.
    1 MHz
    C.
    2 MHz
    D.
    4 MHz

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  9. In band III of TV, distant reception (beyond line of sight range) is possible due to

  10. A.
    tropospheric bending by refraction
    B.
    reflection of waves
    C.
    ionospheric scattering
    D.
    none of the above

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  11. In amplitude modulation the rms value of radio frequency voltage after 40% modulation is 60 mV. If modulation is 80% the rms value after modulation will be about

  12. A.
    50 mV
    B.
    60 mV
    C.
    66 mV
    D.
    80 mV

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  13. 1 GHz is equal to

  14. A.
    106 Hz
    B.
    108 Hz
    C.
    109 Hz
    D.
    1010 Hz

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  15. Consider the following statements

    1. In a pulsed radar, the transmitted pulses are of high frequency
    2. In a pulsed radar, the transmitted pulses are of high power
    3. In a pulsed radar, the transmitted pulses are of brief duration
    4. In a pulsed radar, the transmitted pulses are of square wave shape.
    Of the above statements the correct statements are

  16. A.
    1 only
    B.
    1, 2 and 3 only
    C.
    1, 2, 3, 4
    D.
    1 and 3 only

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  17. Probability density function of thermal noise is

  18. A.
    Poisson
    B.
    Binomial
    C.
    Gaussian
    D.
    None of the above

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  19. In a colour TV receiver AFT stands for

  20. A.
    Automatic Fine Tuning
    B.
    Automatic Frequency Tuning
    C.
    Automatic Field Tuning
    D.
    Alignment Frequency Tuning

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