SUBELEMENT G3 - RADIO WAVE PROPAGATION

Question 1

G3A01 (A)

What is the significance of the sunspot number with regard to HF propagation?

Answer 1

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

Question 2

G3A02 (B)

What effect does a Sudden Ionospheric Disturbance have on the daytime ionospheric propagation of HF radio waves?

Answer 2

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

Question 3

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?

Answer 3

C. 8 minutes

Question 4

G3A04 (D)

Which of the following are least reliable for long distance communications during periods of low solar activity?

Answer 4

D. 15 meters, 12 meters and 10 meters

Question 5

G3A05 (D)

What is the solar flux index?

Answer 5

D. A measure of solar radiation at 10.7 centimeters wavelength

Question 6

G3A06 (D)

What is a geomagnetic storm?

Answer 6

D. A temporary disturbance in the Earth’s magnetosphere

Question 7

G3A07 (D)

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

Answer 7

D. At any point in the solar cycle

Question 8

G3A08 (B)

Which of the following effects can a geomagnetic storm have on radio propagation?

Answer 8

B. Degraded high-latitude HF propagation

Question 9

G3A09 (C)

What effect does a high sunspot number have on radio communications?

Answer 9

C. Long-distance communication in the upper HF and lower VHF range is enhanced

Question 10

G3A10 (C)

What causes HF propagation conditions to vary periodically in a 28 day cycle?

Answer 10

C. The Sun’s rotation on its axis

Question 11

G3A11 (D)

Approximately how long is the typical sunspot cycle?

Answer 11

D. 11 years

Question 12

G3A12 (B)

What does the K-index indicate?

Answer 12

B. The short term stability of the Earth’s magnetic field

Question 13

G3A13 (C)

What does the A-index indicate?

Answer 13

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

Question 14

G3A14 (B)

How are radio communications usually affected by the charged particles that reach the Earth from solar coronal holes?

Answer 14

B. HF communications are disturbed

Question 15

G3A15 (D)

How long does it take charged particles from coronal mass ejections to affect radio propagation on the Earth?

Answer 15

D. 20 to 40 hours

Question 16

G3A16 (A)

What is a possible benefit to radio communications resulting from periods of high geomagnetic activity?

Answer 16

A. Auroras that can reflect VHF signals

Question 17

G3B01 (D)

How might a sky-wave signal sound if it arrives at your receiver by both short path and long path propagation?

Answer 17

D. A well-defined echo might be heard

Question 18

G3B02 (A)

Which of the following is a good indicator of the possibility of sky-wave propagation on the 6-meter band?

Answer 18

A. Short skip sky-wave propagation on the 10-meter band

Question 19

G3B03 (A)

Which of the following applies when selecting a frequency for lowest attenuation when transmitting on HF?

Answer 19

A. Select a frequency just below the MUF

Question 20

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?

Answer 20

A. Listen for signals from an international beacon in the frequency range you plan to use

Question 21

G3B05 (A)
What usually happens to radio waves with frequencies below the MUF and above the LUF when they are sent into the ionosphere?

Answer 21

A. They are bent back to the Earth

Question 22

G3B06 (C)

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

Answer 22

C. They are completely absorbed by the ionosphere

Question 23

G3B07 (A)

What does LUF stand for?

Answer 23

A. The Lowest Usable Frequency for communications between two points

Question 24

G3B08 (B)

What does MUF stand for?

Answer 24

B. The Maximum Usable Frequency for communications between two points

Question 25

G3B09 (C) What is the approximate maximum distance along the Earth's surface that is normally covered in one hop using the F2 region?

Answer 25

C. 2,500 miles

Question 26

G3B10 (B) What is the approximate maximum distance along the Earth's surface that is normally covered in one hop using the E region?

Answer 26

B. 1,200 miles

Question 27

G3B11 (A) | What happens to HF propagation when the LUF exceeds the MUF?

Answer 27

A. No HF radio frequency will support ordinary sky-wave communications over the path

Question 28

G3B12 (D) | What factor or factors affect the MUF?

Answer 28

A. Path distance and location B. Time of day and season C. Solar radiation and ionospheric disturbances D. All of these choices are correct

Question 29

G3C01 (A) | Which ionospheric layer is closest to the surface of the Earth?

Answer 29

A. The D layer

Question 30

G3C02 (A) | Where on the Earth do ionospheric layers reach their maximum height?

Answer 30

A. Where the Sun is overhead

Question 31

G3C03 (C) | Why is the F2 region mainly responsible for the longest distance radio wave propagation?

Answer 31

C. Because it is the highest ionospheric region

Question 32

G3C04 (D) | What does the term "critical angle" mean as used in radio wave propagation?

Answer 32

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

Question 33

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

Answer 33

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

Question 34

G3C06 (B) | What is a characteristic of HF scatter signals?

Answer 34

B. They have a wavering sound

Question 35

G3C07 (D) | What makes HF scatter signals often sound distorted?

Answer 35

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

Question 36

G3C08 (A) | Why are HF scatter signals in the skip zone usually weak?

Answer 36

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

Question 37

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?

Answer 37

B. Scatter

Question 38

G3C10 (D) Which of the following might be an indication that signals heard on the HF bands are being received via scatter propagation?

Answer 38

D. The signal is heard on a frequency above the Maximum Usable Frequency

Question 39

G3C11 (B) | Which of the following antenna types will be most effective for skip communications on 40-meters during the day?

Answer 39

B. A horizontal dipole placed between 1/8 and 1/4 wavelength above the ground

Question 40

G3C12 (D) | Which ionospheric layer is the most absorbent of long skip signals during daylight hours on frequencies below 10 MHz?

Answer 40

D. The D layer

Question 41

G3C13 (B) | What is Near Vertical Incidence Sky-wave (NVIS) propagation?

Answer 41

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