Electromagnetic Wave Propagation Quiz 1

33 Questions

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Electromagnetic Wave Propagation Quiz 1

For COMMUNICATIONS 3 students


Questions and Answers
  • 1. 
    Ground-wave communications is most effective in what frequency range?
    • A. 

      300 kHz to 3 MHz

    • B. 

      3 to 30 MHz

    • C. 

      30 to 300 MHz

    • D. 

      above 300 MHz

  • 2. 
    The ionization causes the signal to be
    • A. 

      Diffused

    • B. 

      Absorbed

    • C. 

      refracted

    • D. 

      Reflected

  • 3. 
    The critical frequency at a particular time is 11.6 MHz. What is the MUF for a transmitting station if the required angle of incidence for propagation to a desired destination is 70°?
    • A. 

      12.3 MHz

    • B. 

      33.9 Hz

    • C. 

      33.9 MHz

    • D. 

      12.3 Hz

  • 4. 
    The ionosphere has the greatest effect on signals in what frequency range?
    • A. 

      300 kHz

    • B. 

      3 to 30 MHz

    • C. 

      30 to 300 MHz

    • D. 

      Above 300 MHz

  • 5. 
    The type of radio wave responsible for long-distance communications by multiple skips is the
    • A. 

      ground wave

    • B. 

      direct-wave

    • C. 

      surface wave

    • D. 

      Sky wave

  • 6. 
    Microwave signals propagate by way of the
    • A. 

      direct wave

    • B. 

      Sky wave

    • C. 

      surface wave

    • D. 

      Standing wave

  • 7. 
    Line-of-sight communications is not a factor in which frequency range?
    • A. 

      VHF

    • B. 

      UHF

    • C. 

      HF

    • D. 

      Microwave

  • 8. 
    A microwave-transmitting antenna is 550 ft high. The receiving antenna is 200 ft high. The maximum transmission distance is
    • A. 

      53.2 km

    • B. 

      53.2 ft

    • C. 

      53.2 mi

    • D. 

      53.2 m

  • 9. 
    To increase the transmission distance of a UHF signal, which of the following should be done?
    • A. 

      Increase antenna gain

    • B. 

      Increase antenna height

    • C. 

      Increase transmitter power

    • D. 

      Increase receiver sensitivity

  • 10. 
    _________ is the amount of voltage induced in a wave by an electromagnetic wave.
    • A. 

      Receiver voltage

    • B. 

      Field strength

    • C. 

      Magnetic induction

    • D. 

      Power density

  • 11. 
     An electromagnetic wave consists of ____________.
    • A. 

      Both electric field and magnetic field

    • B. 

      An electric field only

    • C. 

      A magnetic field only

    • D. 

      Non-magnetic field only

  • 12. 
    If a radio receiver needs 1 nW/m2 of power density to function, how far away from a 1-W point source will it continue to work?
    • A. 

      8.9 km

    • B. 

      8.9 m

    • C. 

      9.8 km

    • D. 

      9.8 m

  • 13. 
    What causes tropospheric ducting of radio waves?
    • A. 

      A very low pressure area

    • B. 

      An aurora to the north

    • C. 

      Lightning between the transmitting and receiving antenna

    • D. 

      A temperature inversion

  • 14. 
    What is a wavefront?
    • A. 

      A voltage pulse in a conductor

    • B. 

      A current pulse in a conductor

    • C. 

      A voltage pulse across a resistor

    • D. 

      A fixed point in an electromagnetic wave

  • 15. 
    • A. 

      595 nW

    • B. 

      595 pW

    • C. 

      56.9 nW

    • D. 

      56.9 W

  • 16. 
    What causes the ionosphere to absorb radio waves?
    • A. 

      The weather below the ionosphere

    • B. 

      The ionization of the D region

    • C. 

      The presence of the ionized cloud in the E region

    • D. 

      The splitting of the E region

  • 17. 
    Which ionospheric region is closest to the Earth?
    • A. 

      A region

    • B. 

      E Region

    • C. 

      D region

    • D. 

      F region

  • 18. 
    What causes the VHF radio waves to be propagated several hundred miles over oceans?
    • A. 

      An overcast of cirriform clouds

    • B. 

      A high pressure zone

    • C. 

      A polar air mass

    • D. 

      A widespread temperature inversion

  • 19. 
    Microwave and UHF systems have which of the following in common?
    • A. 

      Both provide fade-free communications

    • B. 

      Both are cheaper than HF radio

    • C. 

      They operate on the same frequency band.

    • D. 

      They are both line-of-sight (LOS) systems.

  • 20. 
    Troposheric scatter radio
    • A. 

      Uses molecules in the Earth’s troposphere to scatter some radio energy back to Earth

    • B. 

      Has a limited capability for data transmission

    • C. 

      Is not widely used commercially

    • D. 

      All of the above

  • 21. 
    Which of the following are electromagnetic?
    • A. 

      Radio waves

    • B. 

      Light

    • C. 

      Gamma rays

    • D. 

      All of the above

  • 22. 
    Sky wave cannot be “heard”
    • A. 

      Close to the transmitter

    • B. 

      Far from the transmitter

    • C. 

      In the silent zone

    • D. 

      In the skip zone

  • 23. 
    • A. 

      113 kW

    • B. 

      113 W

    • C. 

      131 W

    • D. 

      131 kW

  • 24. 
    Helical antennas are often used for satellite tracking at VHF because of
    • A. 

      Troposcatter

    • B. 

      Ionospheric refraction

    • C. 

      Subrefraction

    • D. 

      The Faraday effect

  • 25. 
     Diffraction of electromagnetic waves
    • A. 

      is caused by reflections from the ground wave

    • B. 

      arrives only with spherical wavefronts

    • C. 

      Will occur around edge of a sharp obstacle

  • 26. 
    The absorption of radio waves by the atmosphere depends on
    • A. 

      Their frequency

    • B. 

      Their distance from the transmitter

    • C. 

      The polarization of the wave

    • D. 

      The polarization of the atmosphere

  • 27. 
    The characteristic impedance of free space is
    • A. 

      Not known

    • B. 

      50Ω

    • C. 

      infinite

    • D. 

      377Ω

  • 28. 
    The largest frequency that will be returned to the Earth when transmitted vertically under ionospheric conditions is called the
    • A. 

      Critical frequency

    • B. 

      Optimum Working Frequency (OWF)

    • C. 

      Maximum Usable Frequency (MUF)

    • D. 

      Skip zone

  • 29. 
    As electromagnetic waves travel in free space, only one of the following can happen to them:
    • A. 

      Absorption

    • B. 

      Reflection

    • C. 

      Attenuation

    • D. 

      Refraction

  • 30. 
     In a vacuum, the speed of light
    • A. 

      Depends on its constant

    • B. 

      Depends on its wavelength

    • C. 

      Depends on its electric and magnetic field

    • D. 

      Is a universal constant

  • 31. 
    When the magnetic field is perpendicular to the surface of the Earth, what is the polarization of the TEM wave?
    • A. 

      Circular

    • B. 

      Elliptical

    • C. 

      Vertical

    • D. 

      Horizontal

  • 32. 
    What is the period of the solar cycle in which great electrical disturbance will occur?
    • A. 

      Every 11 years

    • B. 

      Every 4 years

    • C. 

      Every 5 years

    • D. 

      Every 10 years

  • 33. 
     Ducting occurs in which region of the atmosphere?
    • A. 

      F2

    • B. 

      Stratosphere

    • C. 

      Troposphere

    • D. 

      Ionosphere