Frenzel Chapter 4: Frequency Modulation

29 Questions | Total Attempts: 2935

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Frenzel Chapter 4: Frequency Modulation

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Questions and Answers
  • 1. 
    The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the modulating signal?
    • A. 

      Amplitude

    • B. 

      Frequency

    • C. 

      Phase

    • D. 

      Shape

  • 2. 
    Both FM and PM are types of what kind of modulation?
    • A. 

      Amplitude

    • B. 

      Phase

    • C. 

      Angle

    • D. 

      Duty Cycle

  • 3. 
    If the amplitude of the modulating signal decreases, the carrier deviation
    • A. 

      Increases

    • B. 

      Decreases

    • C. 

      Remains constant

    • D. 

      Goes to zero

  • 4. 
    On an FM signal, maximum deviation occurs at what point on the modulating signal?
    • A. 

      Zero crossing points

    • B. 

      Peak positive amplitude

    • C. 

      Peak negative amplitude

    • D. 

      Both B and C

  • 5. 
    In PM, a frequency shift occurs while what characteristic of the modulating signal is changing?
    • A. 

      Shape

    • B. 

      Phase

    • C. 

      Frequency

    • D. 

      Amplitude

  • 6. 
    Maximum frequency deviation of a PM signal occurs at
    • A. 

      Zero crossing points

    • B. 

      Peak positive amplitude

    • C. 

      Peak negative amplitude

    • D. 

      Peak positive or negative amplitude

  • 7. 
    In PM, carrier frequency deviation is not proportional to
    • A. 

      Modulating signal amplitude

    • B. 

      Carrier amplitude and frequency

    • C. 

      Modulating signal frequency

    • D. 

      Modulator phase shift

  • 8. 
    To compensate for increases in carrier frequency deviation with an increase in modulating signal frequency, what circuit is used between the modulating signal and the phase modulator?
    • A. 

      Low pass filter

    • B. 

      High pass filter

    • C. 

      Phase shifter

    • D. 

      Bandpass filter

  • 9. 
    The FM produced by PM is called
    • A. 

      FM

    • B. 

      PM

    • C. 

      Indirect FM

    • D. 

      Indirect PM

  • 10. 
    If the amplitude of the modulating signal applied to a phase modulator is constant, the output signal will be
    • A. 

      Zero

    • B. 

      The carrier frequency

    • C. 

      Above the carrier frequency

    • D. 

      Below the carrier frequency

  • 11. 
    A 100 MHz carrier is deviated 50 KHz by a 4KHz signal. The modulation index is
    • A. 

      5

    • B. 

      8

    • C. 

      12.5

    • D. 

      20

  • 12. 
    The maximum deviation of an FM carrier is 2KHz by a maximum modulating signal of 400Hz. The deviation ratio is
    • A. 

      0.2

    • B. 

      5

    • C. 

      8

    • D. 

      40

  • 13. 
    A 70 KHz carrier has a frequency deviation of 4KHz with a 1000Hz signal. How many significant sideband pairs are produced?
    • A. 

      4

    • B. 

      5

    • C. 

      6

    • D. 

      7

  • 14. 
    What is the relative amplitude of the third pair of sidebands of an FM signal with m=6?
    • A. 

      0.11

    • B. 

      0.17

    • C. 

      0.24

    • D. 

      0.36

  • 15. 
    A 200KHz carrier is modulated by a 2.5KHz signal. The fourth pair of sidebands are spaced from the carrier by
    • A. 

      2.5KHz

    • B. 

      5KHz

    • C. 

      10KHz

    • D. 

      15KHz

  • 16. 
    An FM transmitter has a maximum deviation of 12 KHz and a maxium modulating frequency of 12 KHz. The bandwidth by Carson's rule is
    • A. 

      24KHz

    • B. 

      33.6KHz

    • C. 

      36.8KHz

    • D. 

      48KHz

  • 17. 
    The maximum allowed deviation of the FM sound signal in TV is 25KHz. If the actual deviation is 18KHz, the percent modulation is
    • A. 

      43 percent

    • B. 

      72 percent

    • C. 

      96 percent

    • D. 

      139 percent

  • 18. 
    Which of the following is not a major benefit of FM over AM?
    • A. 

      Greater efficiency

    • B. 

      Noise immunity

    • C. 

      Capture effect

    • D. 

      Lower complexity and cost

  • 19. 
    The primary disadvantage of FM is its
    • A. 

      Higher cost and complexity

    • B. 

      Excessive use of spectrum space

    • C. 

      Noise susceptibility

    • D. 

      Lower efficiency

  • 20. 
    Noise is primarily
    • A. 

      High frequency spikes

    • B. 

      Low frequency variations

    • C. 

      Random level shifts

    • D. 

      Random frequency variations

  • 21. 
    The receiver circuit that rids FM of noise is the
    • A. 

      Modulator

    • B. 

      Demodulator

    • C. 

      Limiter

    • D. 

      Low pass filter

  • 22. 
    The phenomenon of a strong FM signal dominating a weaker signal on a common frequency is referred to as the
    • A. 

      Capture effect

    • B. 

      Blot out

    • C. 

      Quieting factor

    • D. 

      Domination syndrome

  • 23. 
    The AM signals generated at a low level may only be amplified by what type of amplifier?
    • A. 

      Op Amp

    • B. 

      Linear

    • C. 

      Class C

    • D. 

      Push-pull

  • 24. 
    Frequency modulation transmitters are more efficient because their power is increased by what type of amplifier?
    • A. 

      Class A

    • B. 

      Class B

    • C. 

      Class C

    • D. 

      All of the above

  • 25. 
    Noise interfere mainly with modulating signals that are
    • A. 

      Sinusoidal

    • B. 

      Nonsinusoidal

    • C. 

      Low frequencies

    • D. 

      High frequencies

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