SUBELEMENT G3 - RADIO WAVE PROPAGATION Flashcards
G3A01 (A)
What is the significance of the sunspot number with regard to HF propagation?
A. Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies
G3A02 (B)
What effect does a Sudden Ionospheric Disturbance have on the daytime ionospheric propagation of HF radio waves?
B. It disrupts signals on lower frequencies more than those on higher frequencies
G3A03 (C)
Approximately how long does it take the increased ultraviolet and X-ray radiation from solar flares to affect radio propagation on the Earth?
C. 8 minutes
G3A04 (D)
Which of the following are least reliable for long distance communications during periods of low solar activity?
D. 15 meters, 12 meters and 10 meters
G3A05 (D)
What is the solar flux index?
D. A measure of solar radiation at 10.7 centimeters wavelength
G3A06 (D)
What is a geomagnetic storm?
D. A temporary disturbance in the Earth’s magnetosphere
G3A07 (D)
At what point in the solar cycle does the 20-meter band usually support worldwide propagation during daylight hours?
D. At any point in the solar cycle
G3A08 (B)
Which of the following effects can a geomagnetic storm have on radio propagation?
B. Degraded high-latitude HF propagation
G3A09 (C)
What effect does a high sunspot number have on radio communications?
C. Long-distance communication in the upper HF and lower VHF range is enhanced
G3A10 (C)
What causes HF propagation conditions to vary periodically in a 28 day cycle?
C. The Sun’s rotation on its axis
G3A11 (D)
Approximately how long is the typical sunspot cycle?
D. 11 years
G3A12 (B)
What does the K-index indicate?
B. The short term stability of the Earth’s magnetic field
G3A13 (C)
What does the A-index indicate?
C. The long term stability of the Earth’s geomagnetic field
G3A14 (B)
How are radio communications usually affected by the charged particles that reach the Earth from solar coronal holes?
B. HF communications are disturbed
G3A15 (D)
How long does it take charged particles from coronal mass ejections to affect radio propagation on the Earth?
D. 20 to 40 hours
G3A16 (A)
What is a possible benefit to radio communications resulting from periods of high geomagnetic activity?
A. Auroras that can reflect VHF signals
G3B01 (D)
How might a sky-wave signal sound if it arrives at your receiver by both short path and long path propagation?
D. A well-defined echo might be heard
G3B02 (A)
Which of the following is a good indicator of the possibility of sky-wave propagation on the 6-meter band?
A. Short skip sky-wave propagation on the 10-meter band
G3B03 (A)
Which of the following applies when selecting a frequency for lowest attenuation when transmitting on HF?
A. Select a frequency just below the MUF
G3B04 (A)
What is a reliable way to determine if the MUF is high enough to support skip propagation between your station and a distant location on frequencies between 14 and 30 MHz?
A. Listen for signals from an international beacon in the frequency range you plan to use
G3B05 (A)
What usually happens to radio waves with frequencies below the MUF and above the LUF when they are sent into the ionosphere?
A. They are bent back to the Earth
G3B06 (C)
What usually happens to radio waves with frequencies below the LUF?
C. They are completely absorbed by the ionosphere
G3B07 (A)
What does LUF stand for?
A. The Lowest Usable Frequency for communications between two points
G3B08 (B)
What does MUF stand for?
B. The Maximum Usable Frequency for communications between two points
G3B09 (C)
What is the approximate maximum distance along the Earth’s surface that is normally covered in one hop using the F2 region?
C. 2,500 miles
G3B10 (B)
What is the approximate maximum distance along the Earth’s surface that is normally covered in one hop using the E region?
B. 1,200 miles
G3B11 (A)
What happens to HF propagation when the LUF exceeds the MUF?
A. No HF radio frequency will support ordinary sky-wave communications over the path
G3B12 (D)
What factor or factors affect the MUF?
A. Path distance and location
B. Time of day and season
C. Solar radiation and ionospheric disturbances
D. All of these choices are correct
G3C01 (A)
Which ionospheric layer is closest to the surface of the Earth?
A. The D layer
G3C02 (A)
Where on the Earth do ionospheric layers reach their maximum height?
A. Where the Sun is overhead
G3C03 (C)
Why is the F2 region mainly responsible for the longest distance radio wave propagation?
C. Because it is the highest ionospheric region
G3C04 (D)
What does the term “critical angle” mean as used in radio wave propagation?
D. The highest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions
G3C05 (C)
Why is long distance communication on the 40-meter, 60-meter, 80-meter and 160-meter bands more difficult during the day?
C. The D layer absorbs signals at these frequencies during daylight hours
G3C06 (B)
What is a characteristic of HF scatter signals?
B. They have a wavering sound
G3C07 (D)
What makes HF scatter signals often sound distorted?
D. Energy is scattered into the skip zone through several different radio wave 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
G3C09 (B)
What type of radio wave propagation allows a signal to be detected at a distance too far for ground wave propagation but too near for normal sky-wave propagation?
B. Scatter
G3C10 (D)
Which of the following might be an indication that signals heard on the HF bands are being received via scatter propagation?
D. The signal is heard on a frequency above the Maximum Usable Frequency
G3C11 (B)
Which of the following antenna types will be most effective for skip communications on 40-meters during the day?
B. A horizontal dipole placed between 1/8 and 1/4 wavelength above the ground
G3C12 (D)
Which ionospheric layer is the most absorbent of long skip signals during daylight hours on frequencies below 10 MHz?
D. The D layer
G3C13 (B)
What is Near Vertical Incidence Sky-wave (NVIS) propagation?
B. Short distance MF or HF propagation using high elevation angles
