Ex. Module 10 Ch. 2&4

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Ex. Module 10 Ch. 2&4
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2012-02-13 18:30:04
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  1. The induction field is made up of which of
    the following fields?
    H and E field
  2. After the radiation field leaves an antenna,
    what is the relationship between the E and
    H fields with respect to (a) phase and
    (b) physical displacement in space?
    (a) In phase (b) 90 degrees
  3. What is the first harmonic of a radio wave
    that has a fundamental frequency of 2,000
    kHz?
    2,000 kHz
  4. A radio wave with a frequency of 32 kHz
    is part of which of the following frequency
    bands?
    The lf band
  5. A frequency of 3.5 GHz falls into what rf
    band?
    Super high
  6. A radio wavelength expressed as 250
    meters may also be expressed as how
    many feet?
    820
  7. An increase in the frequency of a radio
    wave will have what effect, if any, on the
    velocity of the radio wave?
    None
  8. An increase in frequency of a radio wave
    will have what effect, if any, on the
    wavelength of the radio wave?
    Increase
  9. Energy radiated from an antenna is
    considered horizontally polarized under
    which of the following conditions?
    • If the magnetic field is in the horizontal
    • plane
  10. The ability of a reflecting surface to reflect
    a specific radio wave depends on which of
    the following factors?
    Striking angle
  11. The bending of a radio wave because of a
    change in its velocity through a medium isknown as
    diffraction
  12. Radio communications can be diffracted
    to exceptionally long distances through the
    use of (a) what frequency band at (b) whatrelative power level?
    • (a) Very low frequency
    • (b) High power
  13. Electrically charged particles that affect
    the propagation of radio waves are found
    in what atmospheric layer?
    Ionosphere
  14. Most weather phenomena take place in
    which of the following region of the
    atmosphere?
    Troposphere
  15. Radio wave propagation has the least
    effect because of its constancy on which
    of the following atmospheric layers?
    Stratosphere
  16. Long range, surface-wave
    communications are best achieved when
    the signal is transmitted over seawater
    with (a) what polarization at (b) what
    relative frequency?
    (a) Vertical (b) Low
  17. The Navy’s long-range vlf broadcasts are
    possible because of the advantages of
    which of the following types of
    propagation?
    Diffraction
  18. A space wave (a) is primarily a result of
    refraction in what atmospheric layer and
    (b) extends approximately what distance
    beyond the horizon?
    • (a) Ionosphere
    • (b) One-third farther
  19. The signal of a space wave is sometimes
    significantly reduced at the receiving site
    because of which of the following
    interactions?
    Ground-wave reflections
  20. For long-range communications in the hf
    band, which of the following types of
    waves is most satisfactory?
    Space wave
  21. Ionization in the atmosphere is produced
    chiefly by which of the following types of
    radiation?
    Infrared radiation
  22. Ultraviolet waves of higher frequencies
    produce ionized layers at what relative
    altitude(s)?
    Higher
  23. The density of ionized layers is normally
    greatest during which of the following
    periods?
    • Between early morning and late
    • afternoon
  24. Compared to the other ionospheric layers
    at higher altitudes, the ionization density
    of the D layer is
    relatively low
  25. What two layers in the ionosphere
    recombine and largely disappear at night?
    D and E
  26. For hf-radio communications covering
    long distances, what is the most important
    layer of the ionosphere?
    F
  27. Refraction of a sky wave in the ionosphere
    is influenced by which of the following
    factors?
    • Ionospheric density
    • Frequency of the wave
    • Angle of incidence of the wave
  28. The distance between the transmitter and
    the nearest point at which refracted waves
    return to earth is referred to as the
    skip distance
  29. When ground-wave coverage is LESS
    than the distance between the transmitter
    and the nearest point at which the
    refracted waves return to earth, which of
    the following reception possibilities
    should you expect?
    A zone of silence
  30. The greatest amount of absorption takes
    place in the ionosphere under which of the
    following conditions?
    • When the density of the ionized layer
    • is the greatest
  31. If the signal strength of an incoming signal
    is reduced for a prolonged period, what
    type of fading is most likely involved?
    Absorption
  32. Radio waves that arrive at a receiving site
    along different paths can cause signal
    fading if these waves have different
    phase relationships
  33. The technique of reducing multipath
    fading by using several receiving antennas
    at different locations is known as what
    type of diversity?
    Space
  34. Receiving sites located near industrial
    areas can expect to have exceptionally
    large losses in signal quality as a result of
    which of the following propagation
    situations?
    Man-made interference
  35. Which of the following ionospheric
    variation causes densities to vary with the
    axial rotation of the sun?
    27-day sunspot cycle
  36. Which of the following ionospheric
    variation causes densities to vary with the
    position of the earth in its orbit around the
    sun?
    Seasonal variation
  37. Which of the following ionospheric
    variation causes densities to vary with the
    time of the day?
    Daily variation
  38. What factor significantly affects the
    frequency of occurrence of the sporadic-E
    layer?
    Latitude
  39. A sudden and intense burst of ultraviolet
    light is especially disruptive to
    communications in which of the following
    frequency bands?
  40. Hf
  41. For a radio wave entering the atmosphere
    of the earth at a given angle, the highest
    frequency at which refraction will occur is
    known by which of the following terms?
    Maximum usable frequency
  42. The most consistent communications can
    be expected at which of the following
    frequencies?
    Optimum working frequency
  43. In determining the success of radio
    transmission, which of the following
    factors is the LEAST predictable?
    • Weather conditions along the path of
    • communication
  44. At frequencies above 100 MHz, the
    greatest attenuation of rf energy from
    raindrops is caused by which of the
    following factors?
    Scattering
  45. Under certain conditions, such as ducting,
    line-of-sight radio waves often propagate
    for distances far beyond their normal
    ranges because of which of the following
    factors?
    Temperature inversions
  46. When ducting is present in the
    atmosphere, multihop refraction of
    line-of-sight transmission can occur
    because of which of the following factors?
    Angle of incidence of the radio wave
  47. A propagation technique used to extend
    uhf transmission range beyond the horizon
    uses which of the following propagation
    characteristics?
    Tropospheric scatter
  48. What effect, if any, does the radiation
    angle of a transmitting antenna have on
    the reception of communications by
    tropospheric scatter?
    • The lower the angle, the stronger the
    • signal
  49. Radio energy is transmitted through
    which of the following mediums?
    Space
  50. Energy is transmitted from a transmitter
    into space using which of the following
    devices?
    A transmitting antenna
  51. Transmitted rf energy takes what form as
    it is sent into space?
    An electromagnetic field
  52. The dimensions of a transmitting antenna
    are determined by which of the following
    factors?
    Transmitted frequency
  53. A device used to radiate or receive
    electromagnetic wave energy is referred
    to as a/an
    antenna
  54. An antenna that can be mounted to
    radiate rf energy either vertically or
    horizontally is classified as which of the
    following types?
    Hertz
  55. A complete antenna system consists of
    which of the following components?
    • A feeder line, a coupling device, and
    • an antenna
  56. What component in an antenna system
    transfers energy from the transmitter to
    the antenna?
    A feeder
  57. The type, size, and shape of an antenna
    are determined by which of the following
    factors?
    • Power output of the transmitter
    • Transmitter frequency
    • Direction to the receiver
  58. Moving electric and magnetic fields in
    space have what (a) phase and
    (b) angular relationships?
    • (a) In phase
    • (b) Perpendicular
  59. What is the length of each half of the
    wire for a dipole antenna?
    1/4 wavelength
  60. On a standing wave, the points of high
    current and voltage are identified by
    which of the following terms?
    Loops
  61. The presence of standing waves indicates
    which of the following conditions of an
    antenna?
    Resonance
  62. The antenna property that allows the
    same antenna to both transmit and
    receive energy is
    reciprocity
  63. There is a ratio between the amount of
    energy propagated in certain directions
    by a directional antenna compared to the
    energy that would be propagated in these
    directions if the antenna were not
    directional. This ratio is known as which
    of the following antenna characteristics?
    Gain
  64. The polarization plane of the radiation
    field is determined by which of the
    following fields?
    Electric field only
  65. For best reception of a signal from a
    horizontally polarized antenna, the
    receiving antenna should be mounted so
    that it has what relationship with the
    transmitting antenna?
    90 degrees
  66. An electric field that rotates as it travels
    through space exhibits what type of
    polarization?
    Elliptical
  67. For ground-wave transmissions, what
    type of polarization is required?
    Vertical
  68. For high-frequency operation, which of
    the following antenna polarization
    patterns is preferred?
    Horizontally polarized
  69. Omnidirectional transmission is obtained
    from which of the following antennas?
    Vertical half-wave
  70. An isotropic radiator radiates energy in
    which of the following patterns?
    Omnidirectional
  71. An ordinary flashlight is an example of
    what type of radiator?
    Anisotropic
  72. The area enclosed by the radiation
    pattern is the
    lobe
  73. Inserting an inductor or capacitor in
    series with an antenna is one method of
    electrically changing the electrical length
    of an antenna. What is this method
    called?
    Loading
  74. Many complex antennas are constructed
    from what basic antenna?
    The half-wave antenna
  75. On an energized half-wave antenna,
    which of the following electrical
    conditions exist?
    Voltage is maximum at the ends
  76. A method of feeding energy to a halfwave
    antenna is to connect one end
    through a capacitor to the output stage.
    What is this method of feeding called?
    • End feed
    • Voltage feed
  77. An antenna supplied by the center-feed
    method is fed at what point?
    Low voltage and high current
  78. The basic Marconi antenna has which of
    the following characteristics?
    • One-quarter wavelength and
    • grounded at one end
  79. A series of conductors arranged in a
    radial pattern and buried in the ground
    beneath the antenna is referred to as a
    ground screen
  80. A folded dipole can be used instead of a
    simple, center-fed dipole for which of the
    following purposes?
    Matching impedance
  81. An antenna arrangement that has
    elements aligned in a straight line is
    referred to as what type array?
    Unidirectional
  82. To select a desired signal and
    discriminate against interfering signals,
    the receiving antenna should have which
    of the following characteristics?
    Be vertically polarized
  83. What is the maximum number of
    elements ordinarily used in a collinear
    array?
    Four
  84. Compared with collinear arrays,
    broadside arrays have which of the
    following advantages?
    Sharper tuning
  85. What is the range of electrical spacing
    between the elements of an end-fire
    array?
    1/8 to 1/4 wavelength
  86. Assuming that the elements are correctly
    spaced, the directivity of an end-fire
    array may be increased by which of the
    following actions?
    Increasing the number of elements
  87. The ratio of energy radiated by an array
    in the principal direction of radiation to
    the energy radiated in the opposite
    direction describes which of the
    following relationships?
    Front-to-back ratio
  88. The Yagi antenna is an example of what
    type of antenna array?
    Multielement parasitic
  89. An antenna which is designed especially
    for vertically-polarized ground waves at
    low frequencies is the
    Beverage antenna
  90. A rhombic antenna is essentially a
    combination of which of the following
    antennas?
    Two collinear arrays in parallel
  91. A rhombic antenna has which of the
    following advantages?
    • Simple construction
    • Wide frequency range
    • Noncritical adjustment
  92. The principal disadvantage of the
    rhombic antenna is its
    large antenna site
  93. The unidirectional radiation pattern of
    the rhombic antenna is caused by which
    of the following antenna characteristics?
    Termination resistance
  94. Horizontal half-wave antennas mounted
    at right angles to each other in the same
    horizontal plane make up which of the
    following antennas?
    Turnstile
  95. The most common means of obtaining a
    low-radiation angle from a vertical
    quarter-wave antenna is by what
    procedure?
    Adding a ground plane
  96. A corner reflector antenna is used for
    which of the following purposes?
    To produce a unidirectional pattern
  97. If a corner-reflector antenna is
    horizontally polarized, its radiation
    pattern will take on what shape?
    A narrow beam in the vertical plane
  98. When radio or radar antennas are
    energized by transmitters, you must not
    go aloft until which of the following
    requirements are met?
    • A working aloft "chit" has been filled
    • out and signed by proper authority

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