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ECE :: Communication Systems

  1. When the length of antenna is a whole wavelength

  2. A.

     The radiation at right angles is zero

    B.

     The radiation at right angles is maximum

    C.

     The radiation is zero in all directions

    D.

     The radiation is maximum in all directions


  3. Under ordinary circumstances, impulse noise can be reduced in

  4. A.

     FM only

    B.

     AM only

    C.

     Both AM and FM

    D.

     None of the above


  5. Which of the following is used to generate PDM?

  6. A.

     Free running multi-vibrator

    B.

     Monostable multi-vibrator

    C.

     JK flip-flop

    D.

     Schmitt trigger


  7. A zero mean white Gaussian noise is passed through an ideal low pass filter of bandwidth 10 kHz. The output of the samples so obtained would be

  8. A.

     Correlated

    B.

     Statistically independent

    C.

     Uncorrelated

    D.

     Orthogonal


  9. A three stage telephone switching structure is to have 128 input and 128 output terminals. There are 16 first stage and 16 third stage matrices. To avoid blocking the number of intermediate paths required is

  10. A.

     16

    B.

     15

    C.

     8

    D.

     1


  11. For a low level AM system, the amplifiers modulated stage must be

  12. A.

     Linear devices

    B.

     Harmonic devices

    C.

     Class C amplifiers

    D.

     Non-linear devices


  13. In case of low level amplitude modulation system, the amplifiers following the modulated stage must be

  14. A.

     Class C amplifiers

    B.

     Linear devices

    C.

     Non-linear devices

    D.

     Harmonic devices


  15. Commercial Frequency deviation of FM is

  16. A.

     70 kHz

    B.

     75 kHz

    C.

     80 kHz

    D.

     65 kHz


  17. An FM radio receiver which is tuned to a 91.6 MHz broadcast station may receive an image frequency of __________ MHz.

  18. A.

     102.3

    B.

     113

    C.

     70.2

    D.

     80.9