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ECE :: Communication Systems

  1. The amplitude of a modulated RF aerial current is 6 A on the peaks of modulation and 4 A on the troughs of modulation. The value of carrier amplitude is

  2. A.
    5
    B.
    15
    C.
    20
    D.
    30

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  3. In practical commercial AM system channel bandwidth is

  4. A.
    150 kHz
    B.
    100 kHz
    C.
    15 kHz
    D.
    200 kHz

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  5. The currents fed to the two dipoles of turnstile antenna are

  6. A.
    in phase
    B.
    in quadrature
    C.
    in phase opposition
    D.
    either (a) or (c)

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  7. The circuit of figure give an output which is

  8. A.
    a frequency modulated signal
    B.
    an amplitude modulated signal
    C.
    a phase modulated signal
    D.
    none of the above

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  9. Which of the following microphones has lowest output impedance?

  10. A.
    Moving coil
    B.
    Ribbon
    C.
    Crystal
    D.
    Condenser

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  11. High frequency waves are

  12. A.
    absorbed by F2 layer
    B.
    affected by solar cycle
    C.
    reflected by D layer
    D.
    none of the above

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  13. During fast forward operation of a tape recorder

  14. A.
    all heads are withdrawn
    B.
    all amplifiers are shut off
    C.
    tape is not pressed against capstan
    D.
    all of the above

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  15. Homodyne detection means

  16. A.
    coherent detection
    B.
    non-coherent detection
    C.
    asynchronous detection
    D.
    none of the above

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  17. A radio station works at 800 kHz and uses AM. If this is a public broadcast system, it should transmit using

  18. A.
    parabolic reflector to transmit all round
    B.
    turnstile antenna for the required land
    C.
    half wave long horizontal wave
    D.
    a vertical antenna less than quarter for practical reasons

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  19. In a superheterodyne broadcast receiver, the frequency of local oscillator is __________ the incoming signal frequency.

  20. A.
    higher than
    B.
    lower than
    C.
    equal to
    D.
    not comparable to

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