Electric beacon

In navigation, a radio beacon (rarely electromagnetic beacon) is a kind of beacon, a device which marks a fixed location and allows direction finding equipment to find relative bearing. Radio beacons transmit a radio signal which is picked up by radio direction finding systems on ships, aircraft and vehicles to determine the direction to the beacon. In navigation, a radio beacon (rarely electromagnetic beacon) is a kind of beacon, a device which marks a fixed location and allows direction finding equipment to find relative bearing. Radio beacons transmit a radio signal which is picked up by radio direction finding systems on ships, aircraft and vehicles to determine the direction to the beacon. A radio beacon is a transmitter at a known location, which transmits a continuous or periodic radio signal with limited information content (for example its identification or location), on a specified radio frequency. Occasionally the beacon function is combined with some other transmission, like telemetry data or meteorological information. Radio beacons have many applications, including air and sea navigation, propagation research, robotic mapping, radio-frequency identification (RFID) / Near Field Communication (NFC) and indoor guidance, as with real-time locating systems (RTLS) like Syledis or simultaneous localization and mapping (SLAM). A most basic aviation radio navigational aid is the NDB or Non-directional Beacon. These are simple low frequency and medium frequency transmitters and they are used to locate airways intersections, 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 airways intersections, are gradually decommissioned, as they are replaced with other navigational aids based on newer technologies. Due to relatively low purchase, maintenance and calibration cost, they are still used to mark locations of smaller aerodromes and important helicopter landing sites. There were also marine beacons, based on the same technology and installed at coastal areas, for use by ships at sea. Most of them, especially in the western world, are no longer in service, while some have been converted to telemetry transmitters for differential GPS. In addition to dedicated radio beacons, any AM, VHF, or UHF radio station at a known location can also be used as a beacon with direction finding equipment. A marker beacon is a specialized beacon used in aviation in conjunction with an instrument landing system (ILS), to give pilots a means to determine distance to the runway. Marker beacons transmit on the dedicated frequency of 75 MHz. This type of beacon is slowly being phased-out and most new ILS installations have no marker beacons. An amateur radio propagation beacon is specifically used to study the propagation of radio signals. Nearly all of them are part of the amateur radio service. A group of radio beacons with single-letter identifiers ('C', 'D', 'M', 'S', 'P', etc.) transmitting in morse code have been regularly reported on various HF frequencies. There is no official information available about these transmitters and they are not registered with the ITU. Some investigators suggest that some of these beacons (the so-called 'cluster beacons') are actually radio propagation beacons for naval use.