3c251 Volume 4

100 Questions | Total Attempts: 344

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Volume Quizzes & Trivia

3C251 Volume 4. UREs only.


Questions and Answers
  • 1. 
    What led to the development of very high frequency (VHF) and ultra high frequency (UHF) radio systems during World War II?
    • A. 

      The longer distances involved in communications with forces of Europe

    • B. 

      The need for more reliable high-capacity communications

    • C. 

      The development of line of sight (LOS) communications

    • D. 

      The need for more resistance to nuclear blast

  • 2. 
    The two primary types of radio waves are
    • A. 

      Direct and surface

    • B. 

      Sky and surface

    • C. 

      Ground and sky

    • D. 

      Direct and sky

  • 3. 
    What condition causes the downward bending of a radio wave as it grazes the top of an obstruction such as a mountain peak?
    • A. 

      Reflection

    • B. 

      Refraction

    • C. 

      Diffraction

    • D. 

      Diffusion

  • 4. 
    During periods of maximum sunspot activity, what is the density level and altitude effect of the F layer?
    • A. 

      Less dense and at a lower altitude

    • B. 

      More dense and at a lower altitude

    • C. 

      Less dense and at a higher altitude

    • D. 

      More dense and at a higher altitude

  • 5. 
    What type of frequency is the highest frequency that returns to earth when it is transmitted vertically under given ionospheric conditions?
    • A. 

      Frequency of optimum traffic

    • B. 

      Maximum usable frequency

    • C. 

      Most usable frequency

    • D. 

      Critical frequency

  • 6. 
    A satellite system that requires numerous satellites in randomly spaced orbits to provide acceptable coverage is
    • A. 

      An active system

    • B. 

      A passive system

    • C. 

      A synchronous system

    • D. 

      A low-altitude system

  • 7. 
    What is a major disadvantage of a geostationary satellite?
    • A. 

      It can't amplify signals

    • B. 

      It orbits the earth in a figure eight pattern

    • C. 

      The transmitted frequency is below 10-gigahertz (GHz)

    • D. 

      The two-way propagation delay is about 0.6 seconds

  • 8. 
    Above what frequency does the propagation loss because of oxygen and water absorption become very serious in satellite communication?
    • A. 

      10 gigahertz (GHz)

    • B. 

      8 GHz

    • C. 

      6 GHz

    • D. 

      4 GHz

  • 9. 
    The reduction in amplitude of a radio signal as it travels away from the source through a propagation medium that's free of obstructing, scattering, or reflecting effects is called
    • A. 

      Faraday effect

    • B. 

      Doppler effect

    • C. 

      Free space attenuation

    • D. 

      None of the above

  • 10. 
    The Doppler effect, inherent to satellite communications, is caused by
    • A. 

      Transmit frequency drift

    • B. 

      Transmit frequency drift off phase-lock ground receivers

    • C. 

      The satellite's motion in space relative to ground stations

    • D. 

      Rotation of the polarization of radio waves

  • 11. 
    Which satellite communications subsystem consist of a satellite antenna array and a transponder?
    • A. 

      Earth

    • B. 

      Space

    • C. 

      Orbital

    • D. 

      Control

  • 12. 
    What satellite device receives, amplifies, and retransmits signals from earth to terminals?
    • A. 

      Station keeper

    • B. 

      Satellite amplifier

    • C. 

      Satellite transponder

    • D. 

      Regenerative repeater

  • 13. 
    At a minimum, a typical link involves
    • A. 

      An active satellite and one earth terminal

    • B. 

      An active satellite and two earth terminal

    • C. 

      Two active satellite and one earth terminal

    • D. 

      Two active satellite and two earth terminal

  • 14. 
    Maintaining optimum performance of a satellite's transponder is a function of
    • A. 

      Satellite control

    • B. 

      Station keeping

    • C. 

      Satellite ground track

    • D. 

      Communications control

  • 15. 
    What type of multiple-access service used in satellite communications provides each earth terminal exclusive use of the satellite transponder for a specified time interval?
    • A. 

      Spread spectrum multiple access (SSMA)

    • B. 

      Frequency division multiple access (FDMA)

    • C. 

      Demand assignment multiple access (DAMA)

    • D. 

      Time division multiple access (TDMA)

  • 16. 
    Two system control problems with time division multiple access are in the area of network timing and
    • A. 

      Power

    • B. 

      Frequency

    • C. 

      Synchronization

    • D. 

      Transponder complexity

  • 17. 
    What satellite access system lets several users occupy the same frequency spectrum in the transponder simultaneously?
    • A. 

      Frequency division multiple access (FDMA)

    • B. 

      Time division multiple access (TDMA)

    • C. 

      Spread spectrum multiple access (SSMA)

    • D. 

      Band spreading multiple access

  • 18. 
    Which organization is responsible for the design, acquisition, and single systems management of the Defense Switched Network?
    • A. 

      Defense Logistics Agency

    • B. 

      Communications Squadron

    • C. 

      Air Force Communications Agency

    • D. 

      Defense Information Systems Agency (DISA)

  • 19. 
    How is survivability provided in the Defense Switched Network (DSN)?
    • A. 

      End offices are multiple-homed

    • B. 

      End offices do not interoperate with allied networks

    • C. 

      The DSN offers precedence access thresholding (PAT)

    • D. 

      The DSN offers single multilevel precedence and preemption (MLPP)

  • 20. 
    How is responsiveness provided in the Defense Switched Network (DSN)?
    • A. 

      End offices are multiple-homed

    • B. 

      End offices do not interoperate with allied networks

    • C. 

      The DSN offers precedence access thresholding (PAT)

    • D. 

      The DSN offers single multilevel precedence and preemption (MLPP)

  • 21. 
    What type of Defense Switched Network (DSN) precedence call cannot be preempted?
    • A. 

      Flash

    • B. 

      Priority

    • C. 

      Intermediate

    • D. 

      Flash Override

  • 22. 
    What type of precedence is assigned to Defense Switched Network (DSN) calls pertaining to situations that gravely affect the security of national and allied forces?
    • A. 

      Flash

    • B. 

      Priority

    • C. 

      Intermediate

    • D. 

      Flash Override

  • 23. 
    Which encryption device makes end-to-end encryption available to any user of the Defense Switched Network (DSN)?
    • A. 

      KG-84

    • B. 

      KG-94

    • C. 

      KIV-7

    • D. 

      Secure telephone unit-III (STU-III)

  • 24. 
    What is the primary difference in the Defense Switched Network (DSN) subsystems?
    • A. 

      Access line protocol functions

    • B. 

      Network management functions

    • C. 

      Internal call processing features and functions

    • D. 

      Administrative, operations and maintenance functions

  • 25. 
    Why should high-priority users not be terminated on a remote switching unit (RSU)?
    • A. 

      A Secure telephone unit-III (STU-III) cannot make calls through a RSU

    • B. 

      Precedence calling is not available with a RSU

    • C. 

      RSU can become saturated and deny all service

    • D. 

      RSU can become isolated from the parent switch