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ECE :: Communication Systems

  1. The tuned circuit of the oscillator in a simple AM transmitter employs a 50 H coil and a 1 nanofarad capacitor. If the oscillator output is the carrier frequency will be

  2. A.
    448 kHz
    B.
    555 kHz
    C.
    625 kHz
    D.
    712 kHz

  3. In a low level AM system, the amplifier which follows the modulated stage must be the

  4. A.
    linear device
    B.
    harmonic device
    C.
    class C amplifier
    D.
    non-linear device

  5. In a square law modulator, the carrier frequency should be __________ times than the highest modulating frequency.

  6. A.
    1
    B.
    2
    C.
    4
    D.
    3

  7. CSSB stands for

  8. A.
    Compatible Single Sideband
    B.
    Compressed Single Sideband
    C.
    Carrier Single Sideband
    D.
    Coded Single Sideband

  9. Tropospheric scatter is used with frequencies in the range of

  10. A.
    VLF
    B.
    HF
    C.
    UHF
    D.
    VHF

  11. The PAM Signal can be detected by

  12. A.
    Band pass filter
    B.
    Band stop filter
    C.
    High pass filter
    D.
    Low pass filter

  13. FM is named so because

  14. A.
    it restrains the frequency excursions of FM
    B.
    it increases the frequency excursions of FM
    C.
    it decreases the amplitude of FM signal
    D.
    it increases the amplitude of FM signal

  15. Which statement is incorrect for the signal x(t) = 5 sin (2p x 103t) sin (2p x 106t)?

  16. A.
    Upper side band frequency is 1001000
    B.
    Carrier amplitude is 5
    C.
    Lower sideband frequency is 990000
    D.
    x(t) is DSB-SC

  17. In radio receivers, the value of IF is

  18. A.
    100 kHz
    B.
    225 kHz
    C.
    455 kHz
    D.
    850 kHz

  19. If F(ω) is Fourier transform of f(t), then Fourier transform of f(t) cos2 ωct is

  20. A.
    F(ω) + [F(ω + 2ωc) + F(ω - 2ωc)]
    B.
    F(ω) + [F(ω + 2ωc) + F(ω - 2ωc)]
    C.
    F(ω) - [F(ω + 2ωc) + F(ω - 2ωc)]
    D.
    F(ω) - [F(ω + 2ωc) + F(ω - 2ωc)]