69 lines
3.2 KiB
Markdown
69 lines
3.2 KiB
Markdown
G3C – Ionospheric regions; critical angle and frequency; HF scatter; near vertical incidence skywave (NVIS)
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- [[G3C01]] (A)
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Which ionospheric region is closest to the surface of Earth? #card
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- A. The D region
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- B. The E region
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- C. The F1 region
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- D. The F2 region
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- [[G3C02]] (A)
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What is meant by the term “critical frequency” at a given incidence angle? #card
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- A. The highest frequency which is refracted back to Earth
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- B. The lowest frequency which is refracted back to Earth
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- C. The frequency at which the signal-to-noise ratio approaches unity
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- D. The frequency at which the signal-to-noise ratio is 6 dB
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- [[G3C03]] (C)
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Why is skip propagation via the F2 region longer than that via the other ionospheric regions? #card
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- A. Because it is the densest
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- B. Because of the Doppler effect
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- C. Because it is the highest
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- D. Because of temperature inversions
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- [[G3C04]] (D)
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What does the term “critical angle” mean, as applied to radio wave propagation? #card
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- A. The long path azimuth of a distant station
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- B. The short path azimuth of a distant station
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- C. The lowest takeoff angle that will return a radio wave to Earth under specific ionospheric conditions
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- D. The highest takeoff angle that will return a radio wave to Earth under specific ionospheric conditions
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- [[G3C05]] (C)
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Why is long-distance communication on the 40-, 60-, 80-, and 160-meter bands more difficult during the day? #card
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- A. The F region absorbs signals at these frequencies during daylight hours
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- B. The F region is unstable during daylight hours
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- C. The D region absorbs signals at these frequencies during daylight hours
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- D. The E region is unstable during daylight hours
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- [[G3C06]] (B)
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What is a characteristic of HF scatter? #card
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- A. Phone signals have high intelligibility
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- B. Signals have a fluttering sound
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- C. There are very large, sudden swings in signal strength
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- D. Scatter propagation occurs only at night
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- [[G3C07]] (D)
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What makes HF scatter signals often sound distorted? #card
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- A. The ionospheric region involved is unstable
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- B. Ground waves are absorbing much of the signal
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- C. The E region is not present
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- D. Energy is scattered into the skip zone through several different paths
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- [[G3C08]] (A)
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Why are HF scatter signals in the skip zone usually weak? #card
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- A. Only a small part of the signal energy is scattered into the skip zone
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- B. Signals are scattered from the magnetosphere, which is not a good reflector
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- C. Propagation is via ground waves, which absorb most of the signal energy
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- D. Propagation is via ducts in the F region, which absorb most of the energy
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- [[G3C09]] (B)
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What type of propagation allows signals to be heard in the transmitting station’s skip zone? #card
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- A. Faraday rotation
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- B. Scatter
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- C. Chordal hop
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- D. Short-path
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- [[G3C10]] (B)
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What is near vertical incidence skywave (NVIS) propagation? #card
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- A. Propagation near the MUF
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- B. Short distance MF or HF propagation at high elevation angles
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- C. Long path HF propagation at sunrise and sunset
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- D. Double hop propagation near the LUF
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- [[G3C11]] (D)
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Which ionospheric region is the most absorbent of signals below 10 MHz during daylight hours? #card
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- A. The F2 region
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- B. The F1 region
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- C. The E region
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- D. The D region
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