radio beacon

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radio beacon:

see radio rangeradio range,
geographically fixed radio transmitter that radiates coded signals in all directions to enable aircraft and ships to determine their bearings. An aircraft or ship can determine its line of position and drift if it knows its bearing relative to the radio transmitter
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Radio Beacon

 

a radio transmitting station that is located at a certain point on the earth’s surface or in a moving vehicle, such as a flying tanker, and that emits special radio signals whose parameters are associated with the direction of emission. When the signals transmitted by the radio beacon are received by a moving vehicle, such as a ship or an aircraft, the direction to the beacon—that is, the beacon’s bearing—can be determined. Radio beacons are examples of direction-finding radio navigation devices.

If the number of directions (courses, zones) in which a bearing can be established is unlimited, the beacon is omnidirectional; otherwise, it is directional. To find the bearing of a simple directional radio beacon, it is usually sufficient to have on board the aircraft or ship a standard radio receiver with a non-directional antenna. Depending on their purpose, radio beacons can be classified as marine beacons or aviation beacons; beacons designed to serve both ships and aircraft simultaneously also exist. Four principal classes of radio beacons are distinguished in accordance with the signal parameters on which they are based: amplitude, phase, frequency, and time. The amplitude class is the most widely used. Beacons of this type are subdivided into localizer (zone marker) beacons, direction-finding beacons, and marker beacons.

Localizer beacons are designed to establish definite courses in the horizontal or the vertical plane. In the first case, the radio beacon usually provides courses or zones that permit the ship or aircraft to orient itself either toward or away from the beacon —that is, to maintain a correct direction of motion. Localizer beacons that are designed to transmit to aircraft the direction of descent in the vertical plane are called glide-path beacons; they enable the aircraft to maintain a correct trajectory as it makes its approach glide.

Direction-finding beacons permit the bearing of the beacon to be found by a comparison of the position of the beacon’s rotating radiation pattern at the moment the bearing is taken with the known position of the pattern at some other time.

Marker beacons are used to mark points that are important for navigation—for example, control points for aircraft landing approaches or for ships, approaching a port and points where a route or waterway forms an angle. The antennas of such radio beacons usually have a narrow radiation pattern.

Radio beacons that make use of kilometric or longer waves have an operating range of up to 500 km. The bearings of such beacons can be determined from moving vehicles with an accuracy of ~1°–3°. Omnidirectional radio beacons that make use of decimetric or centrimetric waves have an operating range that is in practice limited to the line of sight. They provide a bearing accuracy of 0.1 °–0.25°.

Also regarded as navigational radio beacons are some radio transmitting stations with nondirectional radiation patterns and distinctive identification codes. Such stations are used solely for navigational purposes and are called nondirectional radio beacons. The bearing of a nondirectional radio beacon is established by means of a radio direction finder on board the moving vehicle. In aviation, such beacons are called homing stations. In addition, certain other radio stations with nondirectional radiation patterns are also classed as nondirectional radio beacons. Each such station has distinctive identifiable characteristics, such as a fixed radio frequency or a special call sign. Such stations are used for navigation as well as for their principal purpose. They include radio broadcast stations, radio sound beacons, radio buoys, radar beacons, and survival beacons.

M. M. RAICHEV

radio beacon

[′rād·ē·ō ′bē·kən]
(navigation)
A nondirectional radio transmitting station in a fixed geographic location, emitting a characteristic signal from which bearing information can be obtained by a radio direction finder on a ship or aircraft. Also known as aerophare; radiophare.

radio beacon

Fixed ground stations emitting RF (radio frequency) signals, especially those containing identification signals such as NDBs (nondirectional beacons), which enable aircraft to fix their position relative to them. These facilities normally operate in the frequency band of 190 to 535 kilohertz (kHz) and transmit a continuous carrier with either a 400 or a 1020 hertz (Hz) modulation. All radio beacons except the compass locators transmit a continuous three-letter identification in code, except during voice transmissions. When a radio beacon is used in conjunction with the instrument landing system markers, it is called a compass locator. Voice transmissions are made on radio beacons unless the letter W (without voice) is included in the class designator. Radio beacons are subject to disturbances that may result in erroneous bearing information. Such disturbances result from such factors as lightning, precipitation, static, etc. At night, radio beacons are vulnerable to interference from distant stations.