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Extra Class Exam Question Pool

effective 7/01/2016 thru 6/29/2020

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Topic 2016-E3: Radio Wave Propagation


2016-E3A: Electromagnetic waves; Earth-Moon-Earth communications; meteor scatter; microwave tropospheric and scatter propagation; aurora propagation

2016-E3A01: What is the approximate maximum separation measured along the surface of the Earth between two stations communicating by Moon bounce?

12,000 miles, if the Moon is visible by both stations

500 miles, if the Moon is at perigee

2000 miles, if the Moon is at apogee

5000 miles, if the Moon is at perigee



2016-E3A02: What characterizes libration fading of an EME signal?

A fluttery irregular fading

A slow change in the pitch of the CW signal

A gradual loss of signal as the Sun rises

The returning echo is several Hertz lower in frequency than the transmitted signal



2016-E3A03: When scheduling EME contacts, which of these conditions will generally result in the least path loss?

When the Moon is at perigee

When the Moon is full

When the Moon is at apogee

When the MUF is above 30 MHz



2016-E3A04: What do Hepburn maps predict?

Probability of tropospheric propagation

Sporadic E propagation

Locations of auroral reflecting zones

Likelihood of rain-scatter along cold or warm fronts



2016-E3A05: Tropospheric propagation of microwave signals often occurs along what weather related structure?

Warm and cold fronts

Gray-line

Lightning discharges

Sprites and jets



2016-E3A06: Which of the following is required for microwave propagation via rain scatter?

The rain must be within radio range of both stations

Rain droplets must be electrically charged

Rain droplets must be within the E layer

All of these choices are correct



2016-E3A07: Atmospheric ducts capable of propagating microwave signals often form over what geographic feature?

Bodies of water

Mountain ranges

Forests

Urban areas



2016-E3A08: When a meteor strikes the Earth's atmosphere, a cylindrical region of free electrons is formed at what layer of the ionosphere?

The E layer

The F1 layer

The F2 layer

The D layer



2016-E3A09: Which of the following frequency range is most suited for meteor scatter communications?

28 MHz - 148 MHz

1.8 MHz - 1.9 MHz

10 MHz - 14 MHz

220 MHz - 450 MHz



2016-E3A10: Which type of atmospheric structure can create a path for microwave propagation?

Temperature inversion

The jet stream

Wind shear

Dust devil



2016-E3A11: What is a typical range for tropospheric propagation of microwave signals?

100 miles to 300 miles

10 miles to 50 miles

1200 miles

2500 miles



2016-E3A12: What is the cause of auroral activity?

The interaction in the E layer of charged particles from the Sun with the Earth's magnetic field

The interaction in the F2 layer between the solar wind and the Van Allen belt

A low sunspot level combined with tropospheric ducting

Meteor showers concentrated in the extreme northern and southern latitudes



2016-E3A13: Which emission mode is best for aurora propagation?

CW

SSB

FM

RTTY



2016-E3A14: From the contiguous 48 states, in which approximate direction should an antenna be pointed to take maximum advantage of aurora propagation?

North

South

East

West



2016-E3A15: What is an electromagnetic wave?

A wave consisting of an electric field and a magnetic field oscillating at right angles to each other

A wave of alternating current, in the core of an electromagnet

A wave consisting of two electric fields at parallel right angles to each other

A wave consisting of two magnetic fields at right angles to each other



2016-E3A16: Which of the following best describes electromagnetic waves traveling in free space?

Changing electric and magnetic fields propagate the energy

Electric and magnetic fields become aligned as they travel

The energy propagates through a medium with a high refractive index

The waves are reflected by the ionosphere and return to their source



2016-E3A17: What is meant by circularly polarized electromagnetic waves?

Waves with a rotating electric field

Waves with an electric field bent into a circular shape

Waves that circle the Earth

Waves produced by a loop antenna






2016-E3B: Transequatorial propagation; long path; gray-line; multi-path; ordinary and extraordinary waves; chordal hop, sporadic E mechanisms

2016-E3B01: What is transequatorial propagation?

Propagation between two mid-latitude points at approximately the same distance north and south of the magnetic equator

Propagation between any two points located on the magnetic equator

Propagation between two continents by way of ducts along the magnetic equator

Propagation between two stations at the same latitude



2016-E3B02: What is the approximate maximum range for signals using transequatorial propagation?

5000 miles

1000 miles

2500 miles

7500 miles



2016-E3B03: What is the best time of day for transequatorial propagation?

Afternoon or early evening

Morning

Noon

Late at night



2016-E3B04: What is meant by the terms extraordinary and ordinary waves?

Independent waves created in the ionosphere that are elliptically polarized

Extraordinary waves describe rare long skip propagation compared to ordinary waves which travel shorter distances

Long path and short path waves

Refracted rays and reflected waves



2016-E3B05: Which amateur bands typically support long-path propagation?

160 meters to 10 meters

160 meters to 40 meters

30 meters to 10 meters

6 meters to 2 meters



2016-E3B06: Which of the following amateur bands most frequently provides long-path propagation?

20 meters

80 meters

10 meters

6 meters



2016-E3B07: Which of the following could account for hearing an echo on the received signal of a distant station?

Receipt of a signal by more than one path

High D layer absorption

Meteor scatter

Transmit frequency is higher than the MUF



2016-E3B08: What type of HF propagation is probably occurring if radio signals travel along the terminator between daylight and darkness?

Gray-line

Transequatorial

Sporadic-E

Long-path



2016-E3B09: At what time of year is Sporadic E propagation most likely to occur?

Around the solstices, especially the summer solstice

Around the solstices, especially the winter solstice

Around the equinoxes, especially the spring equinox

Around the equinoxes, especially the fall equinox



2016-E3B10: What is the cause of gray-line propagation?

At twilight and sunrise, D-layer absorption is low while E-layer and F-layer propagation remains high

At midday, the Sun super heats the ionosphere causing increased refraction of radio waves

In darkness, solar absorption drops greatly while atmospheric ionization remains steady

At mid-afternoon, the Sun heats the ionosphere decreasing radio wave refraction and the MUF



2016-E3B11: At what time of day is Sporadic-E propagation most likely to occur?

Any time

Around sunset

Around sunrise

Early evening



2016-E3B12: What is the primary characteristic of chordal hop propagation?

Successive ionospheric reflections without an intermediate reflection from the ground

Propagation away from the great circle bearing between stations

Propagation across the geomagnetic equator

Signals reflected back toward the transmitting station



2016-E3B13: Why is chordal hop propagation desirable?

The signal experiences less loss along the path compared to normal skip propagation

The MUF for chordal hop propagation is much lower than for normal skip propagation

Atmospheric noise is lower in the direction of chordal hop propagation

Signals travel faster along ionospheric chords



2016-E3B14: What happens to linearly polarized radio waves that split into ordinary and extraordinary waves in the ionosphere?

They become elliptically polarized

They are bent toward the magnetic poles

Their polarization is randomly modified

They become phase-locked






2016-E3C: Radio-path horizon; less common propagation modes; propagation prediction techniques and modeling; space weather parameters and amateur radio

2016-E3C01: What does the term ray tracing describe in regard to radio communications?

Modeling a radio wave's path through the ionosphere

The process in which an electronic display presents a pattern

Determining the radiation pattern from an array of antennas

Evaluating high voltage sources for X-Rays



2016-E3C02: What is indicated by a rising A or K index?

Increasing disruption of the geomagnetic field

Decreasing disruption of the geomagnetic field

Higher levels of solar UV radiation

An increase in the critical frequency



2016-E3C03: Which of the following signal paths is most likely to experience high levels of absorption when the A index or K index is elevated?

Polar paths

Transequatorial propagation

Sporadic-E

NVIS



2016-E3C04: What does the value of Bz (B sub Z) represent?

Direction and strength of the interplanetary magnetic field

Geomagnetic field stability

Critical frequency for vertical transmissions

Duration of long-delayed echoes



2016-E3C05: What orientation of Bz (B sub z) increases the likelihood that incoming particles from the Sun will cause disturbed conditions?

Southward

Northward

Eastward

Westward



2016-E3C06: By how much does the VHF/UHF radio horizon distance exceed the geometric horizon?

By approximately 15 percent of the distance

By approximately twice the distance

By approximately 50 percent of the distance

By approximately four times the distance



2016-E3C07: Which of the following descriptors indicates the greatest solar flare intensity?

Class X

Class A

Class B

Class M



2016-E3C08: What does the space weather term G5 mean?

An extreme geomagnetic storm

Very low solar activity

Moderate solar wind

Waning sunspot numbers



2016-E3C09: How does the intensity of an X3 flare compare to that of an X2 flare?

Twice as great

10 percent greater

50 percent greater

Four times as great



2016-E3C10: What does the 304A solar parameter measure?

UV emissions at 304 angstroms, correlated to solar flux index

The ratio of X-Ray flux to radio flux, correlated to sunspot number

The solar wind velocity at 304 degrees from the solar equator, correlated to solar activity

The solar emission at 304 GHz, correlated to X-Ray flare levels



2016-E3C11: What does VOACAP software model?

HF propagation

AC voltage and impedance

VHF radio propagation

AC current and impedance



2016-E3C12: How does the maximum distance of ground-wave propagation change when the signal frequency is increased?

It decreases

It stays the same

It increases

It peaks at roughly 14 MHz



2016-E3C13: What type of polarization is best for ground-wave propagation?

Vertical

Horizontal

Circular

Elliptical



2016-E3C14: Why does the radio-path horizon distance exceed the geometric horizon?

Downward bending due to density variations in the atmosphere

E-region skip

D-region skip

Downward bending due to aurora refraction



2016-E3C15: What might a sudden rise in radio background noise indicate?

A solar flare has occurred

A meteor ping

Increased transequatorial propagation likely

Long-path propagation is occurring





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