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A non-directional beacon (NDB) or non-directional radio beacon is a radio beacon which does not include inherent directional information. Radio beacons are radio transmitters at a known location, used as an aviation or marine navigational aid. NDB are in contrast to directional radio beacons and other navigational aids, such as low-frequency ...
The most basic radio-navigational aid used in aviation is the non-directional beacon or NDB. It is a simple low- and medium-frequency transmitter used to locate airway intersections and airports and to conduct instrument approaches, with the use of a radio direction finder located on the aircraft. The aviation NDBs, especially the ones marking ...
This also led to a revival in the operation of simple radio beacons for use with these RDF systems, now referred to as non-directional beacons (NDB). As the LF/MF signals used by NDBs can follow the curvature of earth, NDB has a much greater range than VOR which travels only in line of sight.
Low-frequency radio range audio signals: N stream, A stream and combined uniform tone (simulated sounds) The low-frequency radio range, also known as the four-course radio range, LF/MF four-course radio range, A-N radio range, Adcock radio range, or commonly "the range", was the main navigation system used by aircraft for instrument flying in the 1930s and 1940s, until the advent of the VHF ...
An amateur radio propagation beacon is a radio beacon, whose purpose is the investigation of the propagation of radio signals. Most radio propagation beacons use amateur radio frequencies. They can be found on LF, MF, HF, VHF, UHF, and microwave frequencies. Microwave beacons are also used as signal sources to test and calibrate antennas and ...
An automatic direction finder, which could be tuned to radio beacons called non-directional beacons or commercial AM radio broadcasters, was in the 20th century a feature of most aircraft, but is being phased out. [1] For the military, RDF is a key tool of signals intelligence.
A few aero navigation non-directional beacons also transmit single letter identification codes. They can be easily distinguished from letter beacons because they transmit in the allocated low frequency and medium frequency bands; most of them are listed in appropriate aviation handbooks and their transmission mode is A2A (full carrier with ...
Marker beacon. Locator Outer Marker (LOM), a High Frequency (HF) Non-Directional Beacon, co-located with an "outer marker" (OM) 75-MHz Marker Beacon. A marker beacon is a particular type of VHF radio beacon used in aviation, usually in conjunction with an instrument landing system (ILS), to give pilots a means to determine position along an ...