Everything about Radio Beacons totally explained
Electric beacons are a kind of
beacon used with direction finding equipment to find ones relative
bearing to a known
location (the
beacon).
The term
electric beacon includes radio,
infrared and
sonar beacons.
Radio beacons
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 (
radio-frequency identification, RFID) and indoor guidance as with
real time locating systems (RTLS).
Radio navigation beacons
A most basic aviation radio navigational aid is a the
NDB or Non-directional Beacon. These are simple low frequency and medium frequency transmitters and they're 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're replaced with other navigational aids based on newer technologies. Due to relatively low purchase, maintenance and calibration cost, they're still used to mark locations of smaller aerodromes and important helicopter landing sites.
There are also marine beacons, based on the same techonlogy 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. Chains of radio navigation beacons for marine use are still active around the Russian and Ukranian coastline.
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.
ILS marker beacons
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 phased-out and most new ILS installations have no marker beacons.
Radio propagation beacons
A
radio propagation beacon is specifically used to study the propagation of radio signals. Nearly all of them are part of the
amateur radio service.
Single letter HF beacons
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're 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.
Space and satellite radio beacons
Beacons are also used in both
geostationary and inclined orbit satellites. Any satellite will emit one or more beacons (normally on a fixed frequency) whose purpose is twofold; as well as containing
modulated station keeping information (telemetry), the beacon is also used to locate the satellite (determine its azimuth and elevation) in the sky.
A beacon was left on the moon by the
last Apollo mission, transmitting FSK telemetry on 2276.0 MHz
Driftnet buoy radio beacons
Distress radiobeacons
distress beacons,
emergency beacons, or simply,
beacons, are those
tracking transmitters that operate as part of the international
Cospas-Sarsat Search and Rescue satellite system. When activated, these beacons send out a
distress signal that, when detected by
non-geostationary satellites, can be located by
triangulation. In the case of 406 MHz beacons which transmit digital signals, the beacons can be uniquely identified almost instantly (via
GEOSAR), and furthermore, a
GPS position can be
encoded into the signal (thus providing both instantaneous identification & position.)
distress signals from the beacons are
homed by
Search and Rescue (SAR) aircraft and ground search parties who can in turn come to the aid of the concerned
boat,
aircraft, and/or persons.
There are three kinds of distress radiobeacons:
- EPIRBs (Emergency Position Indicating Radio Beacons) signal maritime distress,
- ELTs (Emergency Locator Transmitters) signal aircraft distress
- PLBs (Personal Locator Beacons) are for personal use and are intended to indicate a person in distress who is away from normal emergency response capabilities (for example 911)
The basic purpose of distress radiobeacons is to get people rescued within the so-called "golden day"
(External Link
) (the first 24 hours following a traumatic event) when the majority of survivors can still be saved.
IEEE 802.11 Wi-Fi beacons
In the field of
Wi-Fi (wireless local area networks using the IEEE 802.11b and 802.11g specification), the term
beacon signifies a specific data transmission from the
wireless access point (AP), which carries the
SSID, the channel number and security protocols such as
WEP (Wired Equivalent Protection) or
WPA (Wi-Fi Protected Access). This transmission doesn't contain the link layer address of another Wi-Fi device, therefore it can be received by any LAN client.
AX.25 packet radio beacons
Stations participating in packet radio networks based on the
AX.25 link layer protocol also use beacon transmissions to identify themselves and broadcast brief information about operational status. The beacon transmissions use special
UI or
Unconnected Information frames, which are not part of a connection and can be displayed by any station. Beacons in traditional packet radio networks contain simple information text, readable by the human operator.
This mode of AX.25 operation, using a formal machine-readable beacon text specification developed by Bob Bruninga, WB4APR, became the basis of the
APRS networks.
Infrared beacon
Infrared beacons are the key infrastructure for the Universal Traffic Management Ssystem (UTMS) in Japan. They perform two-way communication with travelling vehicles based on highly directional infrared communication technology and have a vehicle detecting capability to provide more accurate traffic information.
A contemporary military use of an Infrared beacon is reported in
Operation Acid Gambit.
Sonar beacon
Further Information
Get more info on 'Radio Beacons'.
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