10
2-18. Electrically charged particles that affect
the propagation of radio waves are found
in what atmospheric layer?
1. Troposphere
2. Ionosphere
3. Chronosphere
4. Stratosphere
2-19. Most weather phenomena take place in
which of the following region of the
atmosphere?
1. Troposphere
2. Ionosphere
3. Chronosphere
4. Stratosphere
2-20. Radio wave propagation has the least
effect because of its constancy on which
of the following atmospheric layers?
1. Troposphere
2. Ionosphere
3. Chronosphere
4. Stratosphere
2-21. Long range, surface-wave
communications are best achieved when
the signal is transmitted over seawater
with (a) what polarization at (b) what
relative frequency?
1. (a) Vertical
(b) Low
2. (a) Vertical
(b) High
3. (a) Horizontal
(b) High
4. (a) Horizontal
(b) Low
2-22. The Navy’s long-range vlf broadcasts are
possible because of the advantages of
which of the following types of
propagation?
1. Diffraction
2. Ionospheric refraction
3. Repeated reflection and refraction
4. Both 2 and 3 above
2-23. A space wave (a) is primarily a result of
refraction in what atmospheric layer and
(b) extends approximately what distance
beyond the horizon?
1. (a) Ionosphere
(b) One-tenth farther
2. (a) Ionosphere
(b) One-third farther
3. (a) Troposphere
(b) One-third farther
4. (a) Troposphere
(b) One-tenth farther
2-24. The signal of a space wave is sometimes
significantly reduced at the receiving site
because of which of the following
interactions?
1. Space-wave refraction
2. Space-wave reflections
3. Ground-wave diffraction
4. Ground-wave reflections
2-25. For long-range communications in the hf
band, which of the following types of
waves is most satisfactory?
1. Sky wave
2. Space wave
3. Surface wave
4. Reflected ground wave
2-26. Ionization in the atmosphere is produced
chiefly by which of the following types of
radiation?
1. Alpha radiation
2. Cosmic radiation
3. Infrared radiation
4. Ultraviolet radiation
2-27. Ultraviolet waves of higher frequencies
produce ionized layers at what relative
altitude(s)?
1. Lower
2. Higher
3. Both 1 and 2 above
