11
2-28. The density of ionized layers is normally
greatest during which of the following
periods?
1. At night
2. Before sunrise
3. Between early morning and late
afternoon
4. Between afternoon and sunset
2-29. Compared to the other ionospheric layers
at higher altitudes, the ionization density
of the D layer is
1. about the same
2. relatively low
3. relatively high
2-30. What two layers in the ionosphere
recombine and largely disappear at night?
1. D and F
2. D and E
3. E and F2
4. F1 and F2
2-31. For hf-radio communications covering
long distances, what is the most important
layer of the ionosphere?
1. C
2. D
3. E
4. F
2-32. Refraction of a sky wave in the ionosphere
is influenced by which of the following
factors?
1. Ionospheric density
2. Frequency of the wave
3. Angle of incidence of the wave
4. All of the above
2-33. A 10-MHz wave entering the ionosphere
at an angle greater than its critical angle
will pass through the ionosphere and be
lost in space unless which of the following
actions is taken?
1. The ground wave is canceled
2. The frequency of the wave is increased
3. The frequency of the wave is decreased
4. The ground wave is reinforced
2-34. The distance between the transmitter and
the nearest point at which refracted waves
return to earth is referred to as the
1. skip distance
2. return distance
3. reception distance
4. ground-wave distance
2-35. 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?
1. No sky-wave
2. Weak ground wave
3. A zone of silence
4. Strong ground wave
2-36. The greatest amount of absorption takes
place in the ionosphere under which of the
following conditions?
1. When sky wave intensity is the greatest
2. When collision of particles is least
3. When the density of the ionized layer
is the greatest
4. When precipitation is greatest
2-37. Which of the following layers provide the
greatest amount of absorption to the
ionospheric wave?
1. D and E
2. D and F1
3. E and F1
4. F1 and F2
