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ECE :: Communication Systems

  1. Consider the following types of distortions in diode detectors

    1. Distortion is caused due to the reason that dc and ac load impedances are unequal
    2. Distortion is caused because ac load impedance has a reactive component at high audio frequencies
    3. Audio frequency diode current is less than dc current
    Which of the above are true?

  2. A.
    1, 2 and 3
    B.
    1 and 2
    C.
    1 and 3
    D.
    2 and 3

  3. Satellites used for international communication are called

  4. A.
    cossort
    B.
    domsat
    C.
    marisat
    D.
    intelsat

  5. In a phase discriminator fc, is the IF to which primary circuit is tuned. Consider the following statements: The primary and secondary voltages are

    1. exactly 90° out of phase when input frequency is fc
    2. more than 90° out of phase when input frequency is higher than fc
    3. less than 90° out of phase when input frequency is lower than fc
    Which of the above statements is correct?

  6. A.
    1 only
    B.
    1 and 2
    C.
    1, 2 and 3
    D.
    2 and 3

  7. Electronic tubes used for transmitter differ from their counterparts in the receivers in respect that

  8. A.
    they are large in size
    B.
    they are capable of handling large powers
    C.
    they generate large amount of heat when in operation
    D.
    none of the above

  9. A plot of modulation index vs carrier amplitude yields a

  10. A.
    horizontal line
    B.
    vertical line
    C.
    parabola
    D.
    hyperbola

  11. In a certain '12 channel TDM' system it is found that channel no. 3 and channel no. 8 are connected to the same input signal. This technique

  12. A.
    wastes the channel capacity
    B.
    takes care of different sampling rate
    C.
    is required when different bandwidth signals are to be transmitted
    D.
    reduces noise

  13. Which wave is also called surface wave?

  14. A.
    Ground wave
    B.
    Sky wave
    C.
    Space wave
    D.
    Both (b) and (c)

  15. ADM stands for

  16. A.
    Angle Delta Modulation
    B.
    Angle Digital Modulation
    C.
    Adaptive Delta Modulation
    D.
    Adaptive Digital Modulation

  17. The atmospheric absorption of radio waves depends on

  18. A.
    frequency of wave
    B.
    the distance from transmitter
    C.
    wave polarisation
    D.
    atmospheric polarisation

  19. Efficiency of general AM signal with em = E1 cos ω1t + E2 cos ω2 tj ec = Ec cos ωct; E1 cos ω1t with modulation index m2 is __________ .