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ECE :: Communication Systems

  1. If the target cross-section is changing, the best scanning system for accurate tracking is

  2. A.
    lobe switching
    B.
    monopulse
    C.
    sequential lobing
    D.
    conical scanning

  3. If e = 10 sin(108 t + 3 sin 104 t) then the modulation index is

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

  5. Frequency modulation consists in

  6. A.
    varying the frequency and amplitude of the carrier in accordance with the instantaneous value of modulating signal
    B.
    varying the amplitude of the carrier in accordance with the instantaneous value of the modulating voltage
    C.
    varying the frequency of the carrier voltage in accordance with the instantaneous value of the modulating voltage
    D.
    vary the frequency of the carrier voltage

  7. Pulse modulation is often used in

  8. A.
    microwave band
    B.
    FL band
    C.
    telegraphy
    D.
    telephony

  9. Thermal noise has a power spectral density which is quite uniform upto frequencies in the order of

  10. A.
    100 Hz
    B.
    106 Hz
    C.
    109 Hz
    D.
    1013 Hz

  11. In cell communication

  12. A.
    carrier frequency change
    B.
    carrier frequency constant
    C.
    depend upon location
    D.
    depend upon geographical area

  13. A ground wave travels along surface of ground.

  14. A.
    True
    B.
    False

  15. In narrowband FM, the modulation index is

  16. A.
    near unity
    B.
    about 100
    C.
    about 0.1
    D.
    about 300

  17. Waves of frequencies higher than 30 MHz penetrate the atmosphere.

  18. A.
    True
    B.
    False

  19. Armstrong modulator generates

  20. A.
    AM signals
    B.
    FM signals
    C.
    PM signals
    D.
    both (b) and (c)