E3C: Auroral propagation; selective fading; radio-path horizon; take-off angle over flat or sloping terrain; earth effects on propagation; less common propagation modes
E3C01:
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
E3C02:
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
E3C03:
Where in the ionosphere does auroral activity occur?
At E-region height
At F-region height
In the equatorial band
At D-region height
E3C04:
Which emission mode is best for auroral propagation?
CW
SSB
FM
RTTY
E3C05:
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
E3C06:
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
E3C07:
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
E3C08:
What is the name of the high-angle wave in HF propagation that travels for some distance within the F2 region?
Pedersen ray
Oblique-angle ray
Ordinary ray
Heaviside ray
E3C09:
What effect is usually responsible for propagating a VHF signal over 500 miles?
Tropospheric ducting
D-region absorption
Faraday rotation
Moonbounce
E3C10:
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
E3C11:
From the contiguous 48 states, in which approximate direction should an antenna be pointed to take maximum advantage of auroral propagation?
North
South
East
West
E3C12:
As the frequency of a signal is increased, how does its ground wave propagation change?
It decreases
It increases
It stays the same
Radio waves don't propagate along the Earth's surface
E3C13:
What type of polarization does most ground-wave propagation have?
Vertical
Horizontal
Circular
Elliptical
E3C14:
Why does the radio-path horizon distance exceed the geometric horizon?
Radio waves may be bent
E-region skip
D-region skip
Auroral skip
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