Propagation Modes - T3C Flashcards
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
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
What is a characteristic of VHF signals received via auroral reflection?
The signals exhibit rapid fluctuations of strength and often sound distorted
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?
Sporadic E
What is meant by the term “knife-edge” propagation?
Signals are partially refracted around solid objects exhibiting sharp edges
What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?
Tropospheric scatter
What band is best suited to communicating via meteor scatter?
6 meters
What causes “tropospheric ducting”?
Temperature inversions in the atmosphere
What is generally the best time for long-distance 10 meter band propagation?
During daylight hours
What is the radio horizon?
The distance at which radio signals between two points are effectively blocked by the curvature of the Earth
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
