Racon
Encyclopedia
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
transponder
Transponder
In telecommunication, the term transponder has the following meanings:...
commonly used to mark maritime navigational hazards. The word is a portmanteau of RAdar and beaCON.
When a racon receives a radar pulse, it responds with a signal on the same frequency which puts an image on the radar display. This takes the form of a short line of dots and dashes forming a Morse
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
character radiating away from the location of the beacon on the normal plan position indicator
Plan position indicator
The 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 States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the United States Coast Guard
United States Coast Guard
The United States Coast Guard is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the military branches for having a maritime law enforcement mission and a federal regulatory agency...
operates about 80 racons, and other organisations also operate them, for example the owners of oil platform
Oil platform
An oil platform, also referred to as an offshore platform or, somewhat incorrectly, oil rig, is a lаrge structure with facilities to drill wells, to extract and process oil and natural gas, and to temporarily store product until it can be brought to shore for refining and marketing...
s. Their use for purposes other than aids to navigation is prohibited, and they are used to mark:
- lighthouseLighthouseA lighthouse is a tower, building, or other type of structure 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 for maritime pilots at sea or on inland waterways....
s and navigation buoyBuoyA 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- by far the majority are on buoys rather than lighthouses. For example, at Boston HarborBoston HarborBoston Harbor is a natural harbor and estuary of Massachusetts Bay, and is located adjacent to the city of Boston, Massachusetts. It is home to the Port of Boston, a major shipping facility in the northeast.-History:...
, only the Boston Lighted Whistle Buoy B and the North Channel Entrance Lighted Whistle Buoy NC have racons (showing "B" and "N", respectively)
- by far the majority are on buoys rather than lighthouses. For example, at Boston Harbor
- navigable spans under bridgeBridgeA bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...
s such as- Arthur Ravenel Bridge
- Golden Gate BridgeGolden Gate BridgeThe Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to...
- San Francisco – Oakland Bay Bridge (three racons)
- to identify centre lines and turning points
- offshore oil platforms and other structures
- including approximately 35 in the Gulf of Mexico
- environmentally-sensitive areas such as coral reefCoral reefCoral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s
In other parts of the World they are also used to indicate:
- temporary, new and uncharted hazards (with a Morse character "D")
- as leading line racons
ITU-R
The 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
Microsecond
A microsecond is an SI unit of time equal to one millionth of a second. Its symbol is µs.A microsecond is equal to 1000 nanoseconds or 1/1000 millisecond...
long signal within 700 nanosecond
Nanosecond
A nanosecond is one billionth of a second . One nanosecond is to one second as one second is to 31.7 years.The word nanosecond is formed by the prefix nano and the unit second. Its symbol is ns....
s.
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 Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, a duty cycle
Duty cycle
In engineering, the duty cycle of a machine or system is the time that it spends in an active state as a fraction of the total time under consideration....
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 Sevenstones Lightship
Sevenstones Lightship
The Sevenstones Lightship is moored off the Seven Stones reef approximately 10 miles North East of the Isles of Scilly.-External links:**...
). In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
a longer duty cycle
Duty cycle
In engineering, the duty cycle of a machine or system is the time that it spends in an active state as a fraction of the total time under consideration....
is used, 50% for battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
-powered buoys (20 seconds on, 20 seconds off) and 75% for on-shore beacons.
Ramark
Ramark
A 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.