Radio Wave Propagation
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General Class Exam Question Pool

effective 7/01/2011 thru 6/30/2015

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Topic G3: Radio Wave Propagation


G3A-2011: Sunspots and solar radiation; ionospheric disturbances; propagation forecasting and indices

G3A01-2011: What is the sunspot number?

A measure of solar activity based on counting sunspots and sunspot groups

A 3 digit identifier which is used to track individual sunspots

A measure of the radio flux from the Sun measured at 10.7 cm

A measure of the sunspot count based on radio flux measurements



G3A02-2011: What effect does a Sudden Ionospheric Disturbance have on the daytime ionospheric propagation of HF radio waves?

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

It enhances propagation on all HF frequencies

It disrupts communications via satellite more than direct communications

None, because only areas on the night side of the Earth are affected



G3A03-2011: Approximately how long does it take the increased ultraviolet and X-ray radiation from solar flares to affect radio-wave propagation on the Earth?

8 minutes

28 days

1 to 2 hours

20 to 40 hours



G3A04-2011: Which of the following amateur radio HF frequencies are least reliable for long distance communications during periods of low solar activity?

21 MHz and higher

3.5 MHz and lower

7 MHz

10 MHz



G3A05-2011: What is the solar-flux index?

A measure of solar radiation at 10.7 cm

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



G3A06-2011: What is a geomagnetic storm?

A temporary disturbance in the Earth's magnetosphere

A sudden drop in the solar-flux index

A thunderstorm which affects radio propagation

Ripples in the ionosphere



G3A07-2011: At what point in the solar cycle does the 20 meter band usually support worldwide propagation during daylight hours?

At any point in the solar cycle

At the summer solstice

Only at the maximum point of the solar cycle

Only at the minimum point of the solar cycle



G3A08-2011: Which of the following effects can a geomagnetic storm have on radio-wave propagation?

Degraded high-latitude HF propagation

Improved high-latitude HF propagation

Improved ground-wave propagation

Improved chances of UHF ducting



G3A09-2011: What effect do high sunspot numbers have on radio communications?

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

High-frequency radio signals become weak and distorted

Frequencies above 300 MHz become usable for long-distance communication

Microwave communications become unstable



G3A10-2011: What causes HF propagation conditions to vary periodically in a 28-day cycle?

The Sun’s rotation on its axis

Long term oscillations in the upper atmosphere

Cyclic variation in the Earth’s radiation belts

The position of the Moon in its orbit



G3A11-2011: Approximately how long is the typical sunspot cycle?

11 years

8 minutes

40 hours

28 days



G3A12-2011: What does the K-index indicate?

The short term stability of the Earth’s magnetic field

The relative position of sunspots on the surface of the Sun

The stability of the Sun's magnetic field

The solar radio flux at Boulder, Colorado



G3A13-2011: What does the A-index indicate?

The long term stability of the Earth’s geomagnetic field

The relative position of sunspots on the surface of the Sun

The amount of polarization of the Sun's electric field

The solar radio flux at Boulder, Colorado



G3A14-2011: How are radio communications usually affected by the charged particles that reach the Earth from solar coronal holes?

HF communications are disturbed

HF communications are improved

VHF/UHF ducting is improved

VHF/UHF ducting is disturbed



G3A15-2011: How long does it take charged particles from coronal mass ejections to affect radio-wave propagation on the Earth?

20 to 40 hours

28 days

14 days

4 to 8 minutes



G3A16-2011: What is a possible benefit to radio communications resulting from periods of high geomagnetic activity?

Aurora 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






G3B-2011: Maximum Usable Frequency; Lowest Usable Frequency; propagation

G3B01-2011: How might a sky-wave signal sound if it arrives at your receiver by both short path and long path propagation?

A well-defined echo might be heard

Periodic fading approximately every 10 seconds

Signal strength increased by 3 dB

The signal might be cancelled causing severe attenuation



G3B02-2011: 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



G3B03-2011: 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



G3B04-2011: What is a reliable way to determine if the Maximum Usable Frequency (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

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



G3B05-2011: What usually happens to radio waves with frequencies below the Maximum Usable Frequency (MUF) and above the Lowest Usable Frequency (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



G3B06-2011: What usually happens to radio waves with frequencies below the Lowest Usable Frequency (LUF)?

They are completely absorbed by the ionosphere

They are bent back to the Earth

They pass through the ionosphere

They are bent and trapped in the ionosphere to circle the Earth



G3B07-2011: 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



G3B08-2011: What does MUF stand for?

The Maximum Usable Frequency for communications between two points

The Minimum 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



G3B09-2011: What is the approximate maximum distance along the Earth's surface that is normally covered in one hop using the F2 region?

2,500 miles

180 miles

1,200 miles

12,000 miles



G3B10-2011: What is the approximate maximum distance along the Earth's surface that is normally covered in one hop using the E region?

1,200 miles

180 miles

2,500 miles

12,000 miles



G3B11-2011: What happens to HF propagation when the Lowest Usable Frequency (LUF) exceeds the Maximum Usable Frequency (MUF)?

No HF radio frequency will support ordinary skywave 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



G3B12-2011: What factors affect the Maximum Usable Frequency (MUF)?

All of these choices are correct

Path distance and location

Time of day and season

Solar radiation and ionospheric disturbances






G3C-2011: Ionospheric layers; critical angle and frequency; HF scatter; Near Vertical Incidence Sky waves

G3C01-2011: Which of the following ionospheric layers is closest to the surface of the Earth?

The D layer

The E layer

The F1 layer

The F2 layer



G3C02-2011: 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



G3C03-2011: Why is the F2 region mainly responsible for the longest distance radio wave propagation?

Because it is the highest ionospheric region

Because it is the densest ionospheric layer

Because it does not absorb radio waves as much as other ionospheric regions

All of these choices are correct



G3C04-2011: What does the term “critical angle” mean as used in radio wave propagation?

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

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



G3C05-2011: Why is long distance communication on the 40, 60, 80 and 160 meter bands more difficult during the day?

The D layer absorbs signals at these frequencies during daylight hours

The F layer absorbs signals at these frequencies during daylight hours

The F layer is unstable during daylight hours

The E layer is unstable during daylight hours



G3C06-2011: What is a characteristic of HF scatter signals?

They have a wavering sound

They have high intelligibility

They have very large swings in signal strength

All of these choices are correct



G3C07-2011: What makes HF scatter signals often sound distorted?

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

The ionospheric layer involved is unstable

Ground waves are absorbing much of the signal

The E-region is not present



G3C08-2011: 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



G3C09-2011: 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?

Scatter

Faraday rotation

Sporadic-E skip

Short-path skip



G3C10-2011: Which of the following might be an indication that signals heard on the HF bands are being received via scatter propagation?

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

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



G3C11-2011: Which of the following antenna types will be most effective for skip communications on 40 meters during the day?

Horizontal dipoles placed between 1/8 and 1/4 wavelength above the ground

Vertical antennas

Left-hand circularly polarized antennas

Right-hand circularly polarized antenna



G3C12-2011: Which ionospheric layer is the most absorbent of long skip signals during daylight hours on frequencies below 10 MHz?

The D layer

The F2 layer

The F1 layer

The E layer



G3C13-2011: What is Near Vertical Incidence Sky-wave (NVIS) propagation?

Short distance HF propagation using high elevation angles

Propagation near the MUF

Long path HF propagation at sunrise and sunset

Double hop propagation near the LUF





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