Which ionospheric region is closest to the surface of Earth?

1. A The D region
2. B The E region
3. C The F1 region
4. D The F2 region

What is meant by the term "critical frequency" at a given incidence angle?

1. A The highest frequency which is refracted back to Earth
2. B The lowest frequency which is refracted back to Earth
3. C The frequency at which the signal-to-noise ratio approaches unity
4. D The frequency at which the signal-to-noise ratio is 6 dB

Why is skip propagation via the F2 region longer than that via the other ionospheric regions?

1. A Because it is the densest
2. B Because of the Doppler effect
3. C Because it is the highest
4. D Because of temperature inversions

What does the term "critical angle" mean, as applied to radio wave propagation?

1. A The long path azimuth of a distant station
2. B The short path azimuth of a distant station
3. C The lowest takeoff angle that will return a radio wave to Earth under specific ionospheric conditions
4. D The highest takeoff angle that will return a radio wave to Earth under specific ionospheric conditions

Why is long-distance communication on the 40-, 60-, 80-, and 160-meter bands more difficult during the day?

1. A The F region absorbs signals at these frequencies during daylight hours
2. B The F region is unstable during daylight hours
3. C The D region absorbs signals at these frequencies during daylight hours
4. D The E region is unstable during daylight hours

What is a characteristic of HF scatter?

1. A Phone signals have high intelligibility
2. B Signals have a fluttering sound
3. C There are very large, sudden swings in signal strength
4. D Scatter propagation occurs only at night

What makes HF scatter signals often sound distorted?

1. A The ionospheric region involved is unstable
2. B Ground waves are absorbing much of the signal
3. C The E region is not present
4. D Energy is scattered into the skip zone through several different paths

Why are HF scatter signals in the skip zone usually weak?

1. A Only a small part of the signal energy is scattered into the skip zone
2. B Signals are scattered from the magnetosphere, which is not a good reflector
3. C Propagation is via ground waves, which absorb most of the signal energy
4. D Propagation is via ducts in the F region, which absorb most of the energy

What type of propagation allows signals to be heard in the transmitting station's skip zone?

1. A Faraday rotation
2. B Scatter
3. C Chordal hop
4. D Short-path

What is near vertical incidence skywave (NVIS) propagation?

1. A Propagation near the MUF
2. B Short distance MF or HF propagation at high elevation angles
3. C Long path HF propagation at sunrise and sunset
4. D Double hop propagation near the LUF

Which ionospheric region is the most absorbent of signals below 10 MHz during daylight hours?

1. A The F2 region
2. B The F1 region
3. C The E region
4. D The D region