Electronics Systems And Technologies

1277 Questions | Total Attempts: 31098

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Electronics Systems And Technologies - Quiz

Priority Level: High (ECE) & Low (ECT)


Questions and Answers
  • 1. 
    The reflected wave
    • A. 

      Arrives in phase with the direct wave

    • B. 

      Arrives out of phase with the direct wave

    • C. 

      Arrives in a variable phase compared with the direct wave

    • D. 

      Is always horizontally polarized

  • 2. 
    An advantage of FSK over on/off keying is the fact that FSK
    • A. 

      Offers better frequency stability

    • B. 

      Can provide faster data rates

    • C. 

      Reduces the number of receiving errors

    • D. 

      Forget it! On-off keying is just as good as FSK

  • 3. 
    The highest layer of the ionosphere is
    • A. 

      The D layer

    • B. 

      The E layer

    • C. 

      The F layer

    • D. 

      None of the above

  • 4. 
    An LSB, suppressed-carrier signal can be demodulated by
    • A. 

      An envelope detector

    • B. 

      A diode

    • C. 

      A ratio detector

    • D. 

      A product detector

  • 5. 
    Which of the following modes is used to send image data over telephone lines?
    • A. 

      On/off keying

    • B. 

      Fax

    • C. 

      AM

    • D. 

      Product detection

  • 6. 
    The S/N ratio is a measure of
    • A. 

      The sensitivity of a receiver

    • B. 

      The selectivity of a receiver

    • C. 

      The dynamic range of a receiver

    • D. 

      The efficiency of a transmitter

  • 7. 
    A receiver that responds to a desired signal, but not to another signal very close by in frequency, has good
    • A. 

      Sensitivity

    • B. 

      Noise figure

    • C. 

      Dynamic range

    • D. 

      Selectivity

  • 8. 
    An FM detector with built-in limiting is
    • A. 

      A ratio detector

    • B. 

      A discriminator

    • C. 

      An envelope detector

    • D. 

      A product detector

  • 9. 
    In which mode of PM does the peak power level of the pulses vary?
    • A. 

      PAM

    • B. 

      PDM

    • C. 

      PIM

    • D. 

      PFM

  • 10. 
    Which of the following modes can be demodulated with an envelope detector?
    • A. 

      AM

    • B. 

      CW

    • C. 

      FSK

    • D. 

      USB

  • 11. 
    The bandwidth of a fax signal is kept narrow by
    • A. 

      Sending the data at a slow rate of speed

    • B. 

      Maximizing the number of digital states

    • C. 

      Optimizing the range of colors sent

    • D. 

      Using pulse modulation

  • 12. 
    The dynamic range in a superhet is largely influenced by the performance of the
    • A. 

      Local oscillator

    • B. 

      Product detector

    • C. 

      Front end

    • D. 

      Selectivity in the IF chain

  • 13. 
    Frequency sweeping can be used to get a transmitter to produce
    • A. 

      Spread-spectrum signals

    • B. 

      Time division multiplexed signals

    • C. 

      Narrowband AM signals

    • D. 

      Double sideband, suppressed carrier signals

  • 14. 
    A radio wave has a frequency of 1.55 MHz. The highest modulating frequency that can be used effectively is about
    • A. 

      1.55 kHz

    • B. 

      15.5 kHz

    • C. 

      155 kHz

    • D. 

      1.55 MHz

  • 15. 
    If an AM signal is modulated with audio having frequencies up to 5 kHz, then what is the complete signal bandwidth?
    • A. 

      10 kHz

    • B. 

      20 kHz

    • C. 

      50 kHz

    • D. 

      500 kHz

  • 16. 
    Suppose an SSB suppressed carrier is at 14.335 MHz, and audio data is contained in a band from 14.335 to 14.338 MHz. What is this mode?
    • A. 

      DSB

    • B. 

      LSB

    • C. 

      USB

    • D. 

      AFSK

  • 17. 
    The deviation of a narrowband voice FM signal normally extends up to __________ either side of the unmodulated-carrier frequency.
    • A. 

      3 kHz

    • B. 

      5 kHz

    • C. 

      10 kHz

    • D. 

      3 MHz

  • 18. 
    A continuously variable signal (such as music audio) can be recovered from a signal having only a few discrete levels or states by means of
    • A. 

      A ratio detector

    • B. 

      A D/A converter

    • C. 

      A product detector

    • D. 

      An envelope detector

  • 19. 
    Transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern.
    • A. 

      FDM

    • B. 

      AFSK

    • C. 

      PCM

    • D. 

      TDM

  • 20. 
    It states that a signal can be exactly reconstructed from its samples if the sampling frequency is greater than twice the highest frequency of the signal; but requires an infinite number of samples.
    • A. 

      Nyquist–Shannon sampling theorem

    • B. 

      Maxwell's theorem

    • C. 

      Hartley's sampling theorem

    • D. 

      Pascal-Blaise theorem

  • 21. 
    Imagine a center-fed, straight wire antenna in free space, whose length can be varied at will. At which of the following lengths is the radiation resistance at the feed point the highest?
    • A. 

      λ/4

    • B. 

      λ

    • C. 

      λ/3

    • D. 

      λ/2

  • 22. 
    What is the approximate length, in meters (m), of a center-fed, λ/2 wire antenna at a frequency of 18.1 MHz? Assume the velocity factor is typical for wire.
    • A. 

      7.90 m

    • B. 

      8.29 m

    • C. 

      13.6 m

    • D. 

      25.9 m

  • 23. 
    What is the approximate height, in feet (ft), of a ground-mounted, λ/4 vertical antenna, made of aluminum tubing, at a frequency of 7.025 MHz? Assume the velocity factor is 92 percent.
    • A. 

      64.43 ft

    • B. 

      32.22 ft

    • C. 

      19.64 ft

    • D. 

      9.822 ft

  • 24. 
    In order to obtain reasonable efficiency with a λ/4 vertical antenna mounted over poorly conducting soil at a frequency of 10 MHz, it is necessary to
    • A. 

      Minimize the loss resistance by installing numerous ground radials

    • B. 

      Make the antenna out of large-diameter aluminum or copper tubing

    • C. 

      Suspend the antenna from a kite or balloon

    • D. 

      Feed the antenna with a waveguide

  • 25. 
    A driven element in a parasitic array is
    • A. 

      Grounded for dc

    • B. 

      A loop with a circumference of λ/2

    • C. 

      Connected to the feed line

    • D. 

      A straight length of wire

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