General Class License Exam Questions

Subelement G3

Radio Wave Propagation

Groups

G3A - Sunspots and solar radiation; ionospheric disturbances; propagation forecasting and indices
G3B - Maximum Usable Frequency; Lowest Usable Frequency; propagation
G3C - Ionospheric layers; critical angle and frequency; HF scatter; Near-Vertical Incidence Skywave

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Group G3A Sunspots and solar radiation; ionospheric disturbances; propagation forecasting and indices

G3A01 What is the significance of the sunspot number with regard to HF propagation?

Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies
Lower sunspot numbers generally indicate greater probability of sporadic E propagation
A zero sunspot number indicate radio propagation is not possible on any band
All of these choices are correct

G3A02 What effect does a Sudden Ionospheric Disturbance have on the daytime ionospheric propagation of HF radio waves?

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

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

28 days
1 to 2 hours
8 minutes
20 to 40 hours

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

80 meters and 160 meters
60 meters and 40 meters
30 meters and 20 meters
15 meters, 12 meters and 10 meters

G3A05 What is the solar flux index?

A measure of the highest frequency that is useful for ionospheric propagation between two points on the Earth
A count of sunspots which is adjusted for solar emissions
Another name for the American sunspot number
A measure of solar radiation at 10.7 centimeters wavelength

G3A06 What is a geomagnetic storm?

A sudden drop in the solar flux index
A thunderstorm which affects radio propagation
Ripples in the ionosphere
A temporary disturbance in the Earth's magnetosphere

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

At the summer solstice
Only at the maximum point of the solar cycle
Only at the minimum point of the solar cycle
At any point in the solar cycle

G3A08 Which of the following effects can a geomagnetic storm have on radio propagation?

Improved high-latitude HF propagation
Degraded high-latitude HF propagation
Improved ground-wave propagation
Improved chances of UHF ducting

G3A09 What effect does a high sunspot number have on radio communications?

High-frequency radio signals become weak and distorted
Frequencies above 300 MHz become usable for long-distance communication
Long-distance communication in the upper HF and lower VHF range is enhanced
Microwave communications become unstable

G3A10 What causes HF propagation conditions to vary periodically in a 28 day cycle?

Long term oscillations in the upper atmosphere
Cyclic variation in the Earth's radiation belts
The Sun's rotation on its axis
The position of the Moon in its orbit

G3A11 Approximately how long is the typical sunspot cycle?

8 minutes
40 hours
28 days
11 years

G3A12 What does the K-index indicate?

The relative position of sunspots on the surface of the Sun
The short term stability of the Earth's magnetic field
The stability of the Sun's magnetic field
The solar radio flux at Boulder, Colorado

G3A13 What does the A-index indicate?

The relative position of sunspots on the surface of the Sun
The amount of polarization of the Sun's electric field
The long term stability of the Earth's geomagnetic field
The solar radio flux at Boulder, Colorado

G3A14 How are radio communications usually affected by the charged particles that reach the Earth from solar coronal holes?

HF communications are improved
HF communications are disturbed
VHF/UHF ducting is improved
VHF/UHF ducting is disturbed

G3A15 How long does it take charged particles from coronal mass ejections to affect radio propagation on the Earth?

28 days
14 days
4 to 8 minutes
20 to 40 hours

G3A16 What is a possible benefit to radio communications resulting from periods of high geomagnetic activity?

Auroras that can reflect VHF signals
Higher signal strength for HF signals passing through the polar regions
Improved HF long path propagation
Reduced long delayed echoes

Group G3B Maximum Usable Frequency; Lowest Usable Frequency; propagation

G3B01 How might a sky-wave signal sound if it arrives at your receiver by both short path and long path propagation?

Periodic fading approximately every 10 seconds
Signal strength increased by 3 dB
The signal might be cancelled causing severe attenuation
A well-defined echo might be heard

G3B02 Which of the following is a good indicator of the possibility of sky-wave propagation on the 6-meter band?

Short skip sky-wave propagation on the 10-meter band
Long skip sky-wave propagation on the 10-meter band
Severe attenuation of signals on the 10-meter band
Long delayed echoes on the 10-meter band

G3B03 Which of the following applies when selecting a frequency for lowest attenuation when transmitting on HF?

Select a frequency just below the MUF
Select a frequency just above the LUF
Select a frequency just below the critical frequency
Select a frequency just above the critical frequency

G3B04 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?

Listen for signals from an international beacon in the frequency range you plan to use
Send a series of dots on the band and listen for echoes from your signal
Check the strength of TV signals from Western Europe
Check the strength of signals in the MF AM broadcast band

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

They are bent back to the Earth
They pass through the ionosphere
They are amplified by interaction with the ionosphere
They are bent and trapped in the ionosphere to circle the Earth

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

They are bent back to the Earth
They pass through the ionosphere
They are completely absorbed by the ionosphere
They are bent and trapped in the ionosphere to circle the Earth

G3B07 What does LUF stand for?

The Lowest Usable Frequency for communications between two points
The Longest Universal Function for communications between two points
The Lowest Usable Frequency during a 24 hour period
The Longest Universal Function during a 24 hour period

G3B08 What does MUF stand for?

The Minimum Usable Frequency for communications between two points
The Maximum Usable Frequency for communications between two points
The Minimum Usable Frequency during a 24 hour period
The Maximum Usable Frequency during a 24 hour period

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

180 miles
1,200 miles
2,500 miles
12,000 miles

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

180 miles
1,200 miles
2,500 miles
12,000 miles

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

No HF radio frequency will support ordinary sky-wave communications over the path
HF communications over the path are enhanced
Double hop propagation along the path is more common
Propagation over the path on all HF frequencies is enhanced

G3B12 What factor or factors affect the MUF?

Path distance and location
Time of day and season
Solar radiation and ionospheric disturbances
All of these choices are correct

Group G3C Ionospheric layers; critical angle and frequency; HF scatter; Near-Vertical Incidence Skywave

G3C01 Which ionospheric layer is closest to the surface of the Earth?

The D layer
The E layer
The F1 layer
The F2 layer

G3C02 Where on the Earth do ionospheric layers reach their maximum height?

Where the Sun is overhead
Where the Sun is on the opposite side of the Earth
Where the Sun is rising
Where the Sun has just set

G3C03 Why is the F2 region mainly responsible for the longest distance radio wave propagation?

Because it is the densest ionospheric layer
Because it does not absorb radio waves as much as other ionospheric regions
Because it is the highest ionospheric region
All of these choices are correct

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

The long path azimuth of a distant station
The short path azimuth of a distant station
The lowest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions
The highest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions

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

The F layer absorbs signals at these frequencies during daylight hours
The F layer is unstable during daylight hours
The D layer absorbs signals at these frequencies during daylight hours
The E layer is unstable during daylight hours

G3C06 What is a characteristic of HF scatter signals?

They have high intelligibility
They have a wavering sound
They have very large swings in signal strength
All of these choices are correct

G3C07 What makes HF scatter signals often sound distorted?

The ionospheric layer involved is unstable
Ground waves are absorbing much of the signal
The E-region is not present
Energy is scattered into the skip zone through several different radio wave paths

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

Only a small part of the signal energy is scattered into the skip zone
Signals are scattered from the magnetosphere which is not a good reflector
Propagation is through ground waves which absorb most of the signal energy
Propagations is through ducts in F region which absorb most of the energy

G3C09 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?

Faraday rotation
Scatter
Sporadic-E skip
Short-path skip

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

The communication is during a sunspot maximum
The communication is during a sudden ionospheric disturbance
The signal is heard on a frequency below the Maximum Usable Frequency
The signal is heard on a frequency above the Maximum Usable Frequency

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

A vertical antenna
A horizontal dipole placed between 1/8 and 1/4 wavelength above the ground
A left-hand circularly polarized antenna
A right-hand circularly polarized antenna

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

The F2 layer
The F1 layer
The E layer
The D layer

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

Propagation near the MUF
Short distance MF or HF propagation using high elevation angles
Long path HF propagation at sunrise and sunset
Double hop propagation near the LUF