How does a higher sunspot number affect HF propagation?
AHigher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies
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Subelement G3 question review
All 37 official questions with the exact winning phrase marked.
What effect does a sudden ionospheric disturbance have on the daytime ionospheric propagation?
BIt disrupts signals on lower frequencies more than those on higher frequencies
Approximately how long does it take the increased ultraviolet and X-ray radiation from a solar flare to affect radio propagation on Earth?
C8 minutes
Which of the following are the least reliable bands for long-distance communications during periods of low solar activity?
D15 meters, 12 meters, and 10 meters
What is the solar flux index?
DA measure of solar radiation with a wavelength of 10.7 centimeters
What is a geomagnetic storm?
DA temporary disturbance in Earth’s geomagnetic field
At what point in the solar cycle does the 20-meter band usually support worldwide propagation during daylight hours?
DAt any point
How can a geomagnetic storm affect HF propagation?
DDegrade high-latitude HF propagation
How can high geomagnetic activity benefit radio communications?
ACreates auroras that can reflect VHF signals
What causes HF propagation conditions to vary periodically in a 26- to 28-day cycle?
CRotation of the Sun’s surface layers around its axis
How long does it take a coronal mass ejection to affect radio propagation on Earth?
D15 hours to several days
What does the K-index measure?
BThe short-term stability of Earth’s geomagnetic field
What does the A-index measure?
CThe long-term stability of Earth’s geomagnetic field
How is long distance radio communication usually affected by the charged particles that reach Earth from solar coronal holes?
BHF communication is disturbed
What is a characteristic of skywave signals arriving at your location by both short-path and long-path propagation?
DA slightly delayed echo might be heard
What factors affect the MUF?
DAll these choices are correct
Which frequency will have the least attenuation for long-distance skip propagation?
AJust below the MUF
Which of the following is a way to determine current propagation on a desired band from your station?
AUse a network of automated receiving stations on the internet to see where your transmissions are being received
How does the ionosphere affect radio waves with frequencies below the MUF and above the LUF?
AThey are refracted back to Earth
What usually happens to radio waves with frequencies below the LUF?
CThey are attenuated before reaching the destination
What does LUF stand for?
AThe Lowest Usable Frequency for communications between two specific points
What does MUF stand for?
BThe Maximum Usable Frequency for communications between two points
What is the approximate maximum distance along the Earth’s surface normally covered in one hop using the F2 region?
C2,500 miles
What is the approximate maximum distance along the Earth’s surface normally covered in one hop using the E region?
B1,200 miles
What happens to HF propagation when the LUF exceeds the MUF?
APropagation via ordinary skywave communications is not possible over that path
Which of the following is typical of the lower HF frequencies during the summer?
DHigh levels of atmospheric noise or static
Which ionospheric region is closest to the surface of Earth?
AThe D region
What is meant by the term “critical frequency” at a given incidence angle?
AThe highest frequency which is refracted back to Earth
Why is skip propagation via the F2 region longer than that via the other ionospheric regions?
CBecause it is the highest
What does the term “critical angle” mean, as applied to radio wave propagation?
DThe 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?
CThe D region absorbs signals at these frequencies during daylight hours
What is a characteristic of HF scatter?
BSignals have a fluttering sound
What makes HF scatter signals often sound distorted?
DEnergy is scattered into the skip zone through several different paths
Why are HF scatter signals in the skip zone usually weak?
AOnly a small part of the signal energy is scattered into the skip zone
What type of propagation allows signals to be heard in the transmitting station’s skip zone?
BScatter
What is near vertical incidence skywave (NVIS) propagation?
BShort distance MF or HF propagation at high elevation angles
Which ionospheric region is the most absorbent of signals below 10 MHz during daylight hours?
DThe D region