Topic E3: Radio Wave Propagation
E3A-2012: Propagation and technique, Earth-Moon-Earth communications; meteor scatter
What is the approximate maximum separation measured along the surface of the Earth between two stations communicating by Moon bounce?
12,000 miles, as long as both can "see" the Moon
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 Earth-Moon-Earth 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 type of receiving system is desirable for EME communications?
Equipment with very low noise figures
Equipment with very wide bandwidth
Equipment with very low dynamic range
Equipment with very low gain
Which of the following describes a method of establishing EME contacts?
Time synchronous transmissions with each station alternating
Storing and forwarding digital messages
Judging optimum transmission times by monitoring beacons from the Moon
High speed CW identification to avoid fading
What frequency range would you normally tune to find EME signals in the 2 meter band?
144.000 - 144.100 MHz
144.000 - 144.001 MHz
144.100 - 144.300 MHz
145.000 - 145.100 MHz
What frequency range would you normally tune to find EME signals in the 70 cm band?
432.000 - 432.100 MHz
430.000 - 430.150 MHz
430.100 - 431.100 MHz
431.100 - 431.200 MHz
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 ranges is well suited for meteor-scatter communications?
28 - 148 MHz
1.8 - 1.9 MHz
10 - 14 MHz
220 - 450 MHz
Which of the following is a good technique for making meteor-scatter contacts?
All of these choices are correct
15 second timed transmission sequences with stations alternating based on location
Use of high speed CW or digital modes
Short transmission with rapidly repeated call signs and signal reports
E3B-2012: Propagation and technique, trans-equatorial; long path; gray-line; multi-path propagation
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 type of propagation is probably occurring if an HF beam antenna must be pointed in a direction 180 degrees away from a station to receive the strongest signals?
Which amateur bands typically support long-path propagation?
160 to 10 meters
160 to 40 meters
30 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 day is gray-line propagation most likely to occur?
At sunrise and sunset
When the Sun is directly above the location of the transmitting station
When the Sun is directly overhead at the middle of the communications path between the two stations
When the Sun is directly above the location of the receiving station
What is the cause of gray-line propagation?
At twilight, D-layer absorption drops while E-layer and F-layer propagation remain strong
At midday, the Sun being directly overhead superheats 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
Which of the following describes gray-line propagation?
Long distance communications at twilight on frequencies less than 15 MHz
Backscatter contacts on the 10 meter band
Over the horizon propagation on the 6 and 2 meter bands
Tropospheric propagation on the 2 meter and 70 centimeter bands
E3C-2012: Propagation and technique, Aurora propagation; selective fading; radio-path horizon; take-off angle over flat or sloping terrain; effects of ground on propagation; less common propagation modes
Which of the following effects does Aurora activity have on radio communications?
All of these choices are correct
SSB signals are raspy
Signals propagating through the Aurora are fluttery
CW signals appear to be modulated by white noise
What is the cause of Aurora activity?
The interaction of charged particles from the Sun with the Earth's magnetic field and the ionosphere
The interaction between the solar wind and the Van Allen belt
A low sunspot level combined with tropospheric ducting
Meteor showers concentrated in the northern latitudes
Where in the ionosphere does Aurora activity occur?
In the E-region
In the F1-region
In the F2-region
In the D-region
Which emission mode is best for Aurora propagation?
Which of the following describes selective fading?
Partial cancellation of some frequencies within the received pass band
Variability of signal strength with beam heading
Sideband inversion within the ionosphere
Degradation of signal strength due to backscatter
By how much does the VHF/UHF radio-path horizon distance exceed the geometric horizon?
By approximately 15% of the distance
By approximately twice the distance
By approximately one-half the distance
By approximately four times the distance
How does the radiation pattern of a horizontally polarized 3-element beam antenna vary with its height above ground?
The main lobe takeoff angle decreases with increasing height
The main lobe takeoff angle increases with increasing height
The horizontal beam width increases with height
The horizontal beam width decreases with height
What is the name of the high-angle wave in HF propagation that travels for some distance within the F2 region?
Which of the following is usually responsible for causing VHF signals to propagate for hundreds of miles?
How does the performance of a horizontally polarized antenna mounted on the side of a hill compare with the same antenna mounted on flat ground?
The main lobe takeoff angle decreases in the downhill direction
The main lobe takeoff angle increases in the downhill direction
The horizontal beam width decreases in the downhill direction
The horizontal beam width increases in the uphill direction
From the contiguous 48 states, in which approximate direction should an antenna be pointed to take maximum advantage of aurora propagation?
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
● = Unseen
● = Weak
● = Review
● = Learned
● = Incorrect answer