T3C-2010: Propagation modes; line of sight, sporadic E, meteor, aurora scatter, tropospheric ducting, F layer skip, radio horizon
Why are "direct" (not via a repeater) UHF signals rarely heard from stations outside your local coverage area?
UHF signals are usually not reflected by the ionosphere
They are too weak to go very far
FCC regulations prohibit them from going more than 50 miles
They collide with trees and shrubbery and fade out
Which of the following might be happening when VHF signals are being received from long distances?
Signals are being refracted from a sporadic E layer
Signals are being reflected from outer space
Signals are arriving by sub-surface ducting
Signals are being reflected by lightning storms in your area
What is a characteristic of VHF signals received via auroral reflection?
The signals exhibit rapid fluctuations of strength and often sound distorted
Signals from distances of 10,000 or more miles are common
These types of signals occur only during winter nighttime hours
These types of signals are generally strongest when your antenna is aimed to the south (for stations in the Northern Hemisphere)
Which of the following propagation types is most commonly associated with occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?
D layer absorption
What is meant by the term "knife-edge" propagation?
Signals are partially refracted around solid objects exhibiting sharp edges
Signals are reflected back toward the originating station at acute angles
Signals are sliced into several discrete beams and arrive via different paths
Signals propagated close to the band edge exhibiting a sharp cutoff
What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?
D layer refraction
F2 layer refraction
What band is best suited to communicating via meteor scatter?
What causes "tropospheric ducting"?
Temperature inversions in the atmosphere
Discharges of lightning during electrical storms
Sunspots and solar flares
Updrafts from hurricanes and tornadoes
What is generally the best time for long-distance 10 meter band propagation?
During daylight hours
During nighttime hours
When there are coronal mass ejections
Whenever the solar flux is low
What is the radio horizon?
The distance at which radio signals between two points are effectively blocked by the curvature of the Earth
The distance from the ground to a horizontally mounted antenna
The farthest point you can see when standing at the base of your antenna tower
The shortest distance between two points on the Earth’s surface
Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations?
The Earth seems less curved to radio waves than to light
Radio signals move somewhat faster than the speed of light
Radio waves are not blocked by dust particles
Radio waves are blocked by dust particles
● = Unseen
● = Weak
● = Review
● = Learned
● = Incorrect answer