General exam G3: Radio Wave Propagation

All 37 questions in subelement G3. The exam asks 3 of them, one from each group (G3A, G3B, G3C). Answers are hidden until you open them.

G3A

1. G3A01 How does a higher sunspot number affect HF propagation?

   1. Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies
   2. Lower sunspot numbers generally indicate greater probability of sporadic E propagation
   3. A zero sunspot number indicates that radio propagation is not possible on any band
   4. A zero sunspot number indicates undisturbed conditions
   Show answer

   A. Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies

2. G3A02 What effect does a sudden ionospheric disturbance have on the daytime ionospheric propagation?

   1. It enhances propagation on all HF frequencies
   2. It disrupts signals on lower frequencies more than those on higher frequencies
   3. It disrupts communications via satellite more than direct communications
   4. None, because only areas on the night side of the Earth are affected
   Show answer

   B. It disrupts signals on lower frequencies more than those on higher frequencies

3. G3A03 Approximately how long does it take the increased ultraviolet and X-ray radiation from a solar flare to affect radio propagation on Earth?

   1. 28 days
   2. 1 to 2 hours
   3. 8 minutes
   4. 20 to 40 hours
   Show answer

   C. 8 minutes

4. G3A04 Which of the following are the least reliable bands for long-distance communications during periods of low solar activity?

   1. 80 meters and 160 meters
   2. 60 meters and 40 meters
   3. 30 meters and 20 meters
   4. 15 meters, 12 meters, and 10 meters
   Show answer

   D. 15 meters, 12 meters, and 10 meters

5. G3A05 What is the solar flux index?

   1. A measure of the highest frequency that is useful for ionospheric propagation between two points on Earth
   2. A count of sunspots that is adjusted for solar emissions
   3. Another name for the American sunspot number
   4. A measure of solar radiation with a wavelength of 10.7 centimeters
   Show answer

   D. A measure of solar radiation with a wavelength of 10.7 centimeters

6. G3A06 What is a geomagnetic storm?

   1. A sudden drop in the solar flux index
   2. A thunderstorm that affects radio propagation
   3. Ripples in the geomagnetic force
   4. A temporary disturbance in Earth’s geomagnetic field
   Show answer

   D. A temporary disturbance in Earth’s geomagnetic field

7. G3A07 At what point in the solar cycle does the 20-meter band usually support worldwide propagation during daylight hours?

   1. At the summer solstice
   2. Only at the maximum point
   3. Only at the minimum point
   4. At any point
   Show answer

   D. At any point

8. G3A08 How can a geomagnetic storm affect HF propagation?

   1. Improve high-latitude HF propagation
   2. Degrade ground wave propagation
   3. Improve ground wave propagation
   4. Degrade high-latitude HF propagation
   Show answer

   D. Degrade high-latitude HF propagation

9. G3A09 How can high geomagnetic activity benefit radio communications?

   1. Creates auroras that can reflect VHF signals
   2. Increases signal strength for HF signals passing through the polar regions
   3. Improve HF long path propagation
   4. Reduce long delayed echoes
   Show answer

   A. Creates auroras that can reflect VHF signals

10. G3A10 What causes HF propagation conditions to vary periodically in a 26- to 28-day cycle?

    1. Long term oscillations in the upper atmosphere
    2. Cyclic variation in Earth’s radiation belts
    3. Rotation of the Sun’s surface layers around its axis
    4. The position of the Moon in its orbit
    Show answer

    C. Rotation of the Sun’s surface layers around its axis

11. G3A11 How long does it take a coronal mass ejection to affect radio propagation on Earth?

    1. 28 days
    2. 14 days
    3. 4 to 8 minutes
    4. 15 hours to several days
    Show answer

    D. 15 hours to several days

12. G3A12 What does the K-index measure?

    1. The relative position of sunspots on the surface of the Sun
    2. The short-term stability of Earth’s geomagnetic field
    3. The short-term stability of the Sun’s magnetic field
    4. The solar radio flux at Boulder, Colorado
    Show answer

    B. The short-term stability of Earth’s geomagnetic field

13. G3A13 What does the A-index measure?

    1. The relative position of sunspots on the surface of the Sun
    2. The amount of polarization of the Sun’s electric field
    3. The long-term stability of Earth’s geomagnetic field
    4. The solar radio flux at Boulder, Colorado
    Show answer

    C. The long-term stability of Earth’s geomagnetic field

14. G3A14 How is long distance radio communication usually affected by the charged particles that reach Earth from solar coronal holes?

    1. HF communication is improved
    2. HF communication is disturbed
    3. VHF/UHF ducting is improved
    4. VHF/UHF ducting is disturbed
    Show answer

    B. HF communication is disturbed

G3B

1. G3B01 What is a characteristic of skywave signals arriving at your location by both short-path and long-path propagation?

   1. Periodic fading approximately every 10 seconds
   2. Signal strength increased by 3 dB
   3. The signal might be cancelled causing severe attenuation
   4. A slightly delayed echo might be heard
   Show answer

   D. A slightly delayed echo might be heard

2. G3B02 What factors affect the MUF?

   1. Path distance and location
   2. Time of day and season
   3. Solar radiation and ionospheric disturbances
   4. All these choices are correct
   Show answer

   D. All these choices are correct

3. G3B03 Which frequency will have the least attenuation for long-distance skip propagation?

   1. Just below the MUF
   2. Just above the LUF
   3. Just below the critical frequency
   4. Just above the critical frequency
   Show answer

   A. Just below the MUF

4. G3B04 Which of the following is a way to determine current propagation on a desired band from your station?

   1. Use a network of automated receiving stations on the internet to see where your transmissions are being received
   2. Check the A-index
   3. Send a series of dots and listen for echoes
   4. All these choices are correct
   Show answer

   A. Use a network of automated receiving stations on the internet to see where your transmissions are being received

5. G3B05 How does the ionosphere affect radio waves with frequencies below the MUF and above the LUF?

   1. They are refracted back to Earth
   2. They pass through the ionosphere
   3. They are amplified by interaction with the ionosphere
   4. They are refracted and trapped in the ionosphere to circle Earth
   Show answer

   A. They are refracted back to Earth

6. G3B06 What usually happens to radio waves with frequencies below the LUF?

   1. They are refracted back to Earth
   2. They pass through the ionosphere
   3. They are attenuated before reaching the destination
   4. They are refracted and trapped in the ionosphere to circle Earth
   Show answer

   C. They are attenuated before reaching the destination

7. G3B07 What does LUF stand for?

   1. The Lowest Usable Frequency for communications between two specific points
   2. The Lowest Usable Frequency for communications to any point outside a 100-mile radius
   3. The Lowest Usable Frequency during a 24-hour period
   4. The Lowest Usable Frequency during the past 60 minutes
   Show answer

   A. The Lowest Usable Frequency for communications between two specific points

8. G3B08 What does MUF stand for?

   1. The Minimum Usable Frequency for communications between two points
   2. The Maximum Usable Frequency for communications between two points
   3. The Minimum Usable Frequency during a 24-hour period
   4. The Maximum Usable Frequency during a 24-hour period
   Show answer

   B. The Maximum Usable Frequency for communications between two points

9. G3B09 What is the approximate maximum distance along the Earth’s surface normally covered in one hop using the F2 region?

   1. 180 miles
   2. 1,200 miles
   3. 2,500 miles
   4. 12,000 miles
   Show answer

   C. 2,500 miles

10. G3B10 What is the approximate maximum distance along the Earth’s surface normally covered in one hop using the E region?

    1. 180 miles
    2. 1,200 miles
    3. 2,500 miles
    4. 12,000 miles
    Show answer

    B. 1,200 miles

11. G3B11 What happens to HF propagation when the LUF exceeds the MUF?

    1. Propagation via ordinary skywave communications is not possible over that path
    2. HF communications over the path are enhanced
    3. Double-hop propagation along the path is more common
    4. Propagation over the path on all HF frequencies is enhanced
    Show answer

    A. Propagation via ordinary skywave communications is not possible over that path

12. G3B12 Which of the following is typical of the lower HF frequencies during the summer?

    1. Poor propagation at any time of day
    2. World-wide propagation during daylight hours
    3. Heavy distortion on signals due to photon absorption
    4. High levels of atmospheric noise or static
    Show answer

    D. High levels of atmospheric noise or static

G3C

1. G3C01 Which ionospheric region is closest to the surface of Earth?

   1. The D region
   2. The E region
   3. The F1 region
   4. The F2 region
   Show answer

   A. The D region

2. G3C02 What is meant by the term “critical frequency” at a given incidence angle?

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

   A. The highest frequency which is refracted back to Earth

3. G3C03 Why is skip propagation via the F2 region longer than that via the other ionospheric regions?

   1. Because it is the densest
   2. Because of the Doppler effect
   3. Because it is the highest
   4. Because of temperature inversions
   Show answer

   C. Because it is the highest

4. G3C04 What does the term “critical angle” mean, as applied to radio wave propagation?

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

   D. The highest takeoff angle that will return a radio wave to Earth under specific ionospheric conditions

5. G3C05 Why is long-distance communication on the 40-, 60-, 80-, and 160-meter bands more difficult during the day?

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

   C. The D region absorbs signals at these frequencies during daylight hours

6. G3C06 What is a characteristic of HF scatter?

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

   B. Signals have a fluttering sound

7. G3C07 What makes HF scatter signals often sound distorted?

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

   D. Energy is scattered into the skip zone through several different paths

8. G3C08 Why are HF scatter signals in the skip zone usually weak?

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

   A. Only a small part of the signal energy is scattered into the skip zone

9. G3C09 What type of propagation allows signals to be heard in the transmitting station’s skip zone?

   1. Faraday rotation
   2. Scatter
   3. Chordal hop
   4. Short-path
   Show answer

   B. Scatter

10. G3C10 What is near vertical incidence skywave (NVIS) propagation?

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

    B. Short distance MF or HF propagation at high elevation angles

11. G3C11 Which ionospheric region is the most absorbent of signals below 10 MHz during daylight hours?

    1. The F2 region
    2. The F1 region
    3. The E region
    4. The D region
    Show answer

    D. The D region

Questions: NCVEC Question Pool Committee (public domain). Pool valid July 1, 2023 – June 30, 2027.