A
Racon is a type of
radarRadar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And...
transponderIn telecommunication, the term transponder has the following meanings:...
commonly used to mark maritime navigational hazards. The word is an acronym for RAdar beaCON.
When a racon receives a radar pulse, it responds with a signal on the same
frequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
which leaves an image on the radar display. This takes the form of a short line of dots and dashes forming a
MorseMorse code is a type of character encoding that transmits telegraphic information using rhythm. Morse code uses a standardized sequence of short and long elements to represent the letters, numerals, punctuation and special characters of a given message...
character radiating away from the location of the beacon on the normal
plan position indicatorThe plan position indicator , is the most common type of radar display. The radar antenna is usually represented in the center of the display, so the distance from it and height above ground can be drawn as concentric circles...
radar display.
A
Racon is a type of
radarRadar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And...
transponderIn telecommunication, the term transponder has the following meanings:...
commonly used to mark maritime navigational hazards. The word is an acronym for RAdar beaCON.
When a racon receives a radar pulse, it responds with a signal on the same
frequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
which leaves an image on the radar display. This takes the form of a short line of dots and dashes forming a
MorseMorse code is a type of character encoding that transmits telegraphic information using rhythm. Morse code uses a standardized sequence of short and long elements to represent the letters, numerals, punctuation and special characters of a given message...
character radiating away from the location of the beacon on the normal
plan position indicatorThe plan position indicator , is the most common type of radar display. The radar antenna is usually represented in the center of the display, so the distance from it and height above ground can be drawn as concentric circles...
radar display. The length of the line usually corresponds to the equivalent of a few nautical miles on the display.
Within the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the
United States Coast GuardThe United States Coast Guard is a branch of the United States Armed Forces and one of seven uniformed services. It is unique among the military branches in that it has a maritime law enforcement mission and a federal regulatory agency mission as part of its mission set...
operates about 80 racons, and other organisations also operate them, for example the owners of
oil platformAn offshore platform, often referred to as an oil platform or an oil rig, is a large structure used to house workers and machinery needed to drill wells in the ocean bed, extract oil and/or natural gas, process the produced fluids, and ship or pipe them to shore...
s. Their use for purposes other than aids to navigation is prohibited, and they are used to mark:
- lighthouse
A lighthouse is a tower, building, or framework designed to emit light from a system of lamps and lenses or, in older times, from a fire and used as an aid to navigation and to pilots at sea....
s and navigation buoyA buoy is a floating device that can have many different purposes. It can be anchored or allowed to drift. The word, of Old French or Middle Dutch origin, is now most commonly in UK English, although some orthoepists have traditionally prescribed the pronunciation...
s
- positions on inconspicuous coastlines
- navigable spans under bridge
A bridge is a structure built to span a valley, road, body of water, or other physical obstacle, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge and the nature of the terrain where the bridge is constructed.-History:The first...
s
- offshore oil platforms and other structures
- environmentally-sensitive areas such as coral reef
Coral reefs are aragonite structures produced by living organisms, found in marine waters containing few nutrients. In most reefs, the predominant organisms are stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate...
s
In other parts of the World they are also used to indicate:
- temporary, new and uncharted hazards (with a Morse character "D")
- to identify centre lines and turning points
- as leading line racons
Their characteristics are defined in the
ITU-RThe ITU Radiocommunication Sector is one of the three sectors of the International Telecommunication Union and is responsible for radio communication....
Recommendation M.824, Technical Parameters of Radar Beacons (RACONS). Racons usually operate on the 9320 MHz to 9500 MHz marine radar band (X-band), and most also operate on the 2920 MHz to 3100 MHz marine radar band (S-band). Modern racons are frequency-agile; they have a wide-band receiver that detects the incoming radar pulse, tunes the transmitter and responds with a 25 microsecond long signal within 700 nanoseconds.
Older racons operate in a slow sweep mode, in which the transponder sweeps across the X-band over 1 or 2 minutes. It only responds if it happens to be tuned to the frequency of an incoming radar signal at the moment it arrives, which in practice means it responds only around 5% of the time.
To avoid the response masking important radar targets behind the beacon, racons only operate for part of the time. In the
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
, a
duty cycleIn telecommunications and electronics, the duty cycle is the fraction of time that a system is in an "active" state. In particular, it is used in the following contexts:...
of about 30% is used — usually 20 seconds in which the racon will respond to radar signals is followed by 40 seconds when it will not, or sometimes 9 seconds on and 21 seconds off (as in the case of the Seven Stones Light Vessel). In the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
a longer
duty cycleIn telecommunications and electronics, the duty cycle is the fraction of time that a system is in an "active" state. In particular, it is used in the following contexts:...
is used, 50% for
batteryAn electrical battery is a combination of one or more electrochemical cells, used to convert stored chemical energy into electrical energy. Since the invention of the first Voltaic pile in 1800 by Alessandro Volta, the battery has become a common power source for many household and industrial...
-powered buoys (20 seconds on, 20 seconds off) and 75% for on-shore beacons.
RamarkA Ramark is a type of radar beacon occasionally used to mark maritime navigational hazards. The word is an acronym for RAdar MARKer.They are wide-band beacons which transmit either continuously or periodically on the radar bands...
s are wide-band beacons which transmit continuously on the radar bands without having to be triggered by an incoming radar signal. The transmission forms a line of Morse characters on the display radiating from the centre of the display to its edge. They are not used in the United States.