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