Home / ECE / Communication Systems :: Section 19

ECE :: Communication Systems

  1. On modulating a carrier of frequency fc by an audio signal fs, the following components has resulted:
    fc, fc + fs and fc - fs
    What is this type of modulation likely to be?

  2. A.
    Amplitude modulation (DSB)
    B.
    Single sideband modulation
    C.
    Frequency modulation only
    D.
    Amplitude modulation or frequency modulation

    View Answer

    Workspace

    Discuss Discuss in Forum


  3. Strength of space wave is not dependent on distance.

  4. A.
    True
    B.
    False

    View Answer

    Workspace

    Discuss Discuss in Forum


  5. Which of the following is not necessarily the advantage of SSB over double sideband, full carrier AM?

  6. A.
    The signal is more noise resistant
    B.
    More channel space is available
    C.
    Transmitter circuits must be more stable, given better reception
    D.
    Considerably less power is required for the same signal strength

    View Answer

    Workspace

    Discuss Discuss in Forum


  7. A signal m(t) = 5 cos 2p 100 t frequency modulates a carrier. The resulting FM signal is
    10 cos {(2p 105 t) + 15 sin (2p 100 t)}
    The approximate bandwidth of the FM would be

  8. A.
    0.1 kHz
    B.
    6 kHz
    C.
    3.2 kHz
    D.
    100 kHz

    View Answer

    Workspace

    Discuss Discuss in Forum


  9. Some possible functions of AGC in a TV receiver are

    1. To increase gain for weak signals
    2. To decrease gain for strong signals
    3. To change the contrast when we switch from one channel to other
    4. To reduce flutter
    Which of the above are correct?

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

    View Answer

    Workspace

    Discuss Discuss in Forum


  11. A monostable multivibrator is used to generate PWM because it can

  12. A.
    differentiator
    B.
    integrator
    C.
    voltage-to-frequency converter
    D.
    generate pulses

    View Answer

    Workspace

    Discuss Discuss in Forum


  13. Consider the following statements in amplitude modulation

    1. The harmonic and intermodulation distortion may occur in audio and RF amplifiers
    2. The sum and difference frequencies are present in the output of mixer
    3. The diode detector has audio frequencies in its output
    4. A balanced modulator cannot produce an AM with suppressed carrier
    Which of the above are true?

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

    View Answer

    Workspace

    Discuss Discuss in Forum


  15. A resistor R is in parallel with capacitance C. The rms noise voltage of resistor in the equivalent circuit can be written as

  16. A.
    B.
    kTC
    C.
    D.

    View Answer

    Workspace

    Discuss Discuss in Forum


  17. Assertion (A): In angle modulation the transmitted amplitude is constant.

    Reason (R): Angle modulation has good immunity to noise and interference.

  18. A.
    Both A and R are correct and R is correct explanation of A
    B.
    Both A and R are correct but R is not correct explanation of A
    C.
    A is correct but R is wrong
    D.
    A is wrong but R is correct

    View Answer

    Workspace

    Discuss Discuss in Forum


  19. A 1000 kHz carrier is simultaneously modulated with 300 Hz, 800 Hz and 2 kHz audio sine waves. The frequencies present in the output will be

  20. A.
    998 kHz and 1002 kHz
    B.
    998 kHz, 999.2 kHz, 1000.8 kHz, 1002.0 kHz
    C.
    998 kHz, 999.2 kHz, 999.7 kHz, 1000.3 kHz, 1000.8 kHz and 1000.2 kHz
    D.
    none of the above

    View Answer

    Workspace

    Discuss Discuss in Forum