E3C: Auroral propagation; selective fading; radio-path horizon; take-off angle over flat or sloping terrain; earth effects on propagation; less common propagation modes
What effect does auroral activity have on radio communications?
CW signals have a fluttery tone
Signals experience long-delay echo
FM communications are clearer
CW signals have a clearer tone
What is the cause of auroral activity?
The emission of charged particles from the sun
Reflections in the solar wind
A low sunspot level
Meteor showers concentrated in the northern latitudes
Where in the ionosphere does auroral activity occur?
At E-region height
At F-region height
In the equatorial band
At D-region height
Which emission mode is best for auroral propagation?
What causes selective fading?
Phase differences in the received signal caused by different paths
Small changes in beam heading at the receiving station
Large changes in the height of the ionosphere
Time differences between the receiving and transmitting stations
How much farther 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 3-element, horizontally polarized beam antenna vary with 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?
What effect is usually responsible for propagating a VHF signal over 500 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 auroral propagation?
As the frequency of a signal is increased, how does its ground wave propagation change?
It stays the same
Radio waves don't propagate along the Earth's surface
What type of polarization does most ground-wave propagation have?
Why does the radio-path horizon distance exceed the geometric horizon?
Radio waves may be bent
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