Of aerial navigation radio towers across the nation, along well-traveled air A simpler, clearer system was desired to ensure easy guidance for all aircraft - commercial, military and general aviation - using only a basic radio receiver.īy the mid-1930s, the U.S.
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But these were of limited usefulness, and required pilots to have DF equipment, and know how to use it correctly. Initial efforts focused on simple radio beacons, broadcasting a simple Morse Code signal that could be "homed in on" using direction-finding ("DF") antennas. Radio navigation technology emerged by the late 1920s, allowing fairly precise navigation without reference to the ground, nor the optimistic and daring trust in dead reckoning. Throughout the 1920s, commercial aviation was hampered by the need to fly only in fair weather, when aircraft could navigate by visual references on the ground (a technique called "pilotage"), or by risky assumptions based upon compass, airspeed and clock indications, and reported winds - combined, calculated and plotted on a map (a technique called "dead reckoning"). LF/MF Four-Course Radio Range - Avionics History by Richard Harris