12
2-38. If the signal strength of an incoming signal
is reduced for a prolonged period, what
type of fading is most likely involved?
1. Selective
2. Multipath
3. Absorption
4. Polarization
2-39. Radio waves that arrive at a receiving site
along different paths can cause signal
fading if these waves have different
1. velocities
2. amplitudes
3. phase relationships
4. modulation percentages
2-40. The technique of reducing multipath
fading by using several receiving antennas
at different locations is known as what
type of diversity?
1. Space
2. Receiver
3. Frequency
4. Modulation
2-41. The amount of rf energy lost because of
ground reflections depends on which of
the following factors?
1. Angle of incidence
2. Ground irregularities
3. Frequency of the wave
4. Each of the above
2-42. 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?
1. Absorption
2. Multihop refraction
3. Natural interference
4. Man-made interference
2-43. Which of the following ionospheric
variation causes densities to vary with the
axial rotation of the sun?
1. Daily variation
2. Seasonal variation
3. 27-day sunspot cycle
4. 11-year sunspot cycle
2-44. Which of the following ionospheric
variation causes densities to vary with the
position of the earth in its orbit around the
sun?
1. Daily variation
2. Seasonal variation
3. 27-day sunspot cycle
4. 11-year sunspot cycle
2-45. Which of the following ionospheric
variation causes densities to vary with the
time of the day?
1. Daily variation
2. Seasonal variation
3. 27-day sunspot cycle
4. 11-year sunspot cycle
2-46. What relative range of operating
frequencies is required during periods of
maximum sunspot activity?
1. Lower
2. Medium
3. Higher
2-47. What factor significantly affects the
frequency of occurrence of the sporadic-E
layer?
1. Seasons
2. Latitude
3. Weather conditions
4. Ionospheric storms
