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ECE :: Communication Systems

  1. For demodulating PCM; it is first converted into

  2. A.
    PDM
    B.
    PPM
    C.
    PWM
    D.
    PAM

  3. One of the advantages of base modulation over collector modulation in a class C transistor amplifier is

  4. A.
    higher efficiency
    B.
    more linear operation
    C.
    more power output per transistor
    D.
    lesser requirement of modulating power

  5. In an AM transmitter after the modulation stage, class C amplifier

  6. A.
    can be used
    B.
    cannot be used
    C.
    may be used, but it has no use
    D.
    can't be determine to use

  7. The maximum number of AM broadcast stations that can be accommodated in a 100 kHz bandwidth for the highest modulating frequency of 5 kHz will be

  8. A.
    100
    B.
    20
    C.
    10
    D.
    1

  9. For a short dipole having an effective length less than half the wavelength the radiation resistance is

  10. A.
    proportional to length
    B.
    proportional to square root of length
    C.
    proportional to square of length
    D.
    none of the above

  11. In a low level amplitude modulated system, the amplifier modulated stage must be

  12. A.
    class C
    B.
    linear
    C.
    non linear
    D.
    harmonic

  13. A noise can be represented as superposition of spectral components. When this noise is passed through a narrow band filter, the output of filter should look like

  14. A.
    sinusoidal
    B.
    rectangular
    C.
    triangular
    D.
    none of the above

  15. A narrow band noise show

  16. A.
    AM only
    B.
    AM and FM
    C.
    FM
    D.
    PCM

  17. The upper and lower side frequencies for 3 kHz audio modulation with a 27 MHz carrier frequency will be

  18. A.
    30 and 24 MHz
    B.
    27.3 and 26.7 MHz
    C.
    27.3 and 26.97 MHz
    D.
    27.3 and 26.97 MHz

  19. Consider the following advantages of phase array radar

    1. simple circuitry
    2. ability to track and scan simultaneously
    3. ability to track many targets together
    4. very fast scanning
    Which of the above are correct?

  20. A.
    1, 2, 3
    B.
    1, 3, 4
    C.
    2, 3, 4
    D.
    1, 4 only