Topic 2016-E3: Radio Wave Propagation
2016-E3A: Electromagnetic waves; Earth-Moon-Earth communications; meteor scatter; microwave tropospheric and scatter propagation; aurora propagation
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
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
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
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
Tropospheric propagation of microwave signals often occurs along what weather related structure?
Warm and cold fronts
Sprites and jets
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
Atmospheric ducts capable of propagating microwave signals often form over what geographic feature?
Bodies of water
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
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
Which type of atmospheric structure can create a path for microwave propagation?
The jet stream
What is a typical range for tropospheric propagation of microwave signals?
100 miles to 300 miles
10 miles to 50 miles
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
Which emission mode is best for aurora propagation?
From the contiguous 48 states, in which approximate direction should an antenna be pointed to take maximum advantage of aurora propagation?
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
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
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
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
What is the approximate maximum range for signals using transequatorial propagation?
What is the best time of day for transequatorial propagation?
Afternoon or early evening
Late at night
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
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
Which of the following amateur bands most frequently provides long-path propagation?
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
Transmit frequency is higher than the MUF
What type of HF propagation is probably occurring if radio signals travel along the terminator between daylight and darkness?
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
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
At what time of day is Sporadic-E propagation most likely to occur?
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
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
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
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
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
Which of the following signal paths is most likely to experience high levels of absorption when the A index or K index is elevated?
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
What orientation of Bz (B sub z) increases the likelihood that incoming particles from the Sun will cause disturbed conditions?
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
Which of the following descriptors indicates the greatest solar flare intensity?
What does the space weather term G5 mean?
An extreme geomagnetic storm
Very low solar activity
Moderate solar wind
Waning sunspot numbers
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
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
What does VOACAP software model?
AC voltage and impedance
VHF radio propagation
AC current and impedance
How does the maximum distance of ground-wave propagation change when the signal frequency is increased?
It stays the same
It peaks at roughly 14 MHz
What type of polarization is best for ground-wave propagation?
Why does the radio-path horizon distance exceed the geometric horizon?
Downward bending due to density variations in the atmosphere
Downward bending due to aurora refraction
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
● = Unseen
● = Weak
● = Review
● = Learned
● = Incorrect answer