Offshore Question-What is RACON please?
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Offshore Question-What is RACON please?
Can anyone tell me what RACON stands for and if it's not immediately obvious in the name, what it does-would be interested as I have not heard this expression before, thanks...
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Zaplead,
We don't use the term in Canada but I believe thats what we used to call in the Military, "Radar Control", I seem to remember the folks in Aberdeen using that term as well.
Cheers,
OffshoreIgor
We don't use the term in Canada but I believe thats what we used to call in the Military, "Radar Control", I seem to remember the folks in Aberdeen using that term as well.
Cheers,
OffshoreIgor
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Sounds good to me...
Thanks Igor,
That would seem to make sense to me. On an offshore Aerad chart I think they are marked as lit or unlit, therefore I am concluding they must be some form of guidance beacon but possibly distinct from a NDB or VOR.
The name you have assigned it sounds authentic enough, wonder if they are some form of beacon using RADAR waves as the signalling media rather than VHF radio waves?
All contributions welcome!!
That would seem to make sense to me. On an offshore Aerad chart I think they are marked as lit or unlit, therefore I am concluding they must be some form of guidance beacon but possibly distinct from a NDB or VOR.
The name you have assigned it sounds authentic enough, wonder if they are some form of beacon using RADAR waves as the signalling media rather than VHF radio waves?
All contributions welcome!!
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Does this explain?
They also appear on some airborne radar systems when beacon mode is selected.
Hope that helps.
Chopperman.
RACONs, also called radar responders, or radar transponder beacons, are receiver/transmitter transponder devices used as a navigation aid, identifying landmarks or buoys on a shipboard marine radar display. A racon responds to a received radar pulse by transmitting an identifiable mark back to the radar set. The displayed response has a length on the radar display corresponding to a few nautical miles, encoded as a Morse character beginning with a dash for identification. The inherent delay in the racon causes the displayed response to appear behind the echo from the structure on which the racon is mounted. Racons and their identifying marks are normally indicated on marine charts. Racons are used in the U.S. for the following purposes:
to identify aids to navigation, both seaborne (e.g. buoys) and land-based (e.g. lighthouses)
to identify landfall or positions on inconspicuous coastlines
to indicate navigable spans under bridges
to identify offshore oil platforms and similar structures
to identify and warn of environmentally-sensitive areas (such as coral reefs)
Outside the U.S., racons are also used:
to mark new and uncharted hazards (these should use the Morse identifier "D")
to identify center and turning points
as leading line racons
The U.S. Coast Guard operates approximately 80 racons. Several more are operated by states or private organizations, such as those marking oil rigs in the Gulf of Mexico, or bridges in California. The use of a racon for any purpose other than as a navigation aid is prohibited.
Racon Technical Characteristics
All racons used by the USCG are frequency agile type, designed to measure the frequency of every incoming radar pulse, and transmit an approximately 25 microsecond Morse-encoded response less than 700 nanoseconds later back to the radar on that frequency. The Morse-encoded response is encoded such that the length of one dash is equal to that of three dots, and the length of one dot equals that of one space. All racons operate over the frequency range 9300-9500 MHz marine radar band (X-band), and most additionally operate in the 2900-3100 MHz marine radar band (S-band). Racon range is approximately line-of-sight range, normally over 15 nautical miles, although actual range depends upon a number of factors, including mounting height, atmospheric conditions, and racon receiver sensitivity setting.
S-band racon antennas should be suitable for responding to radars using horizontal or vertical polarization. X-band racons should respond to radars using horizontal polarization. X-band antenna vertical divergence ranges from about 8 degrees for fixed installations, to 18 degrees for installation on buoys. S-band antenna vertical divergence is 22 degrees. Radiated power is 600 milliwatts. Receiver sensitivity is about -35 dbm.
Older racons, no longer used by the USCG but still used in other parts in the world, operate in a slow sweep mode. The transmitter on a slow sweep racon slowly sweeps every 1 to 2 minutes through the 9300-9500 MHz band, and when interrogated, responds back on the frequency the transmitter happens to be tuned to at the time. The response from most slow sweep racons is visible on a radar display for only about 5% of the time.
Ramarks are radar beacons which transmit independently, without having to be triggered by a ship radar. A ramark response on a radar display gives no indication of distance, but instead extends from the ship's position to the circumference of the display. Ramarks are not used in the U.S.
Display of a Racon Response
In order to conserve battery power, racons installed on buoys in the U.S. are programmed to operate 50% of the time. These racons are normally active for 20 seconds, and then off for the next 20 seconds. Racons installed on shore, where battery life is not a factor, are normally programmed to operate 75% of the time. Racons are usually not programmed with a duty cycle greater than 75%, in order to ensure that the response never completely masks an important radar target.
The anti-clutter rain control on a radar could mask a racon return, and may need to be shut off. The anti-clutter sea control on certain radars could also degrade a racon response in some situations. Clutter rejection circuitry on some radar equipment may also suppress a racon response. The detection range of a racon may also be reduced if the radar receiver is off-tuned. Tweaking the radar tuning control should correct that problem.
Under conditions of abnormal radio propagation, a spurious racon flash may be received at ranges considerably in excess of a racon's quoted range, regardless of the range to which the ship's radar is set; such a spurious flash may appear in any random position along the correct bearing on the display. Therefore, reliance should only be placed on a racon flash if its appearance is consistent and if the ship is believed to be within the racon's quoted range. (ALRS 2)
to identify aids to navigation, both seaborne (e.g. buoys) and land-based (e.g. lighthouses)
to identify landfall or positions on inconspicuous coastlines
to indicate navigable spans under bridges
to identify offshore oil platforms and similar structures
to identify and warn of environmentally-sensitive areas (such as coral reefs)
Outside the U.S., racons are also used:
to mark new and uncharted hazards (these should use the Morse identifier "D")
to identify center and turning points
as leading line racons
The U.S. Coast Guard operates approximately 80 racons. Several more are operated by states or private organizations, such as those marking oil rigs in the Gulf of Mexico, or bridges in California. The use of a racon for any purpose other than as a navigation aid is prohibited.
Racon Technical Characteristics
All racons used by the USCG are frequency agile type, designed to measure the frequency of every incoming radar pulse, and transmit an approximately 25 microsecond Morse-encoded response less than 700 nanoseconds later back to the radar on that frequency. The Morse-encoded response is encoded such that the length of one dash is equal to that of three dots, and the length of one dot equals that of one space. All racons operate over the frequency range 9300-9500 MHz marine radar band (X-band), and most additionally operate in the 2900-3100 MHz marine radar band (S-band). Racon range is approximately line-of-sight range, normally over 15 nautical miles, although actual range depends upon a number of factors, including mounting height, atmospheric conditions, and racon receiver sensitivity setting.
S-band racon antennas should be suitable for responding to radars using horizontal or vertical polarization. X-band racons should respond to radars using horizontal polarization. X-band antenna vertical divergence ranges from about 8 degrees for fixed installations, to 18 degrees for installation on buoys. S-band antenna vertical divergence is 22 degrees. Radiated power is 600 milliwatts. Receiver sensitivity is about -35 dbm.
Older racons, no longer used by the USCG but still used in other parts in the world, operate in a slow sweep mode. The transmitter on a slow sweep racon slowly sweeps every 1 to 2 minutes through the 9300-9500 MHz band, and when interrogated, responds back on the frequency the transmitter happens to be tuned to at the time. The response from most slow sweep racons is visible on a radar display for only about 5% of the time.
Ramarks are radar beacons which transmit independently, without having to be triggered by a ship radar. A ramark response on a radar display gives no indication of distance, but instead extends from the ship's position to the circumference of the display. Ramarks are not used in the U.S.
Display of a Racon Response
In order to conserve battery power, racons installed on buoys in the U.S. are programmed to operate 50% of the time. These racons are normally active for 20 seconds, and then off for the next 20 seconds. Racons installed on shore, where battery life is not a factor, are normally programmed to operate 75% of the time. Racons are usually not programmed with a duty cycle greater than 75%, in order to ensure that the response never completely masks an important radar target.
The anti-clutter rain control on a radar could mask a racon return, and may need to be shut off. The anti-clutter sea control on certain radars could also degrade a racon response in some situations. Clutter rejection circuitry on some radar equipment may also suppress a racon response. The detection range of a racon may also be reduced if the radar receiver is off-tuned. Tweaking the radar tuning control should correct that problem.
Under conditions of abnormal radio propagation, a spurious racon flash may be received at ranges considerably in excess of a racon's quoted range, regardless of the range to which the ship's radar is set; such a spurious flash may appear in any random position along the correct bearing on the display. Therefore, reliance should only be placed on a racon flash if its appearance is consistent and if the ship is believed to be within the racon's quoted range. (ALRS 2)
Hope that helps.
Chopperman.
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Thanks Chopperman...
Chopperman, thanks very much for that most comprehensive answer.
It is fantastic that we can share info on a forum such as this to help build a better understanding of systems and procedures out there, espp when they are safety related.
Thanks again for the considerable time you must have invested in making this post....Cheers, Zap
It is fantastic that we can share info on a forum such as this to help build a better understanding of systems and procedures out there, espp when they are safety related.
Thanks again for the considerable time you must have invested in making this post....Cheers, Zap
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Chopperman;
I have always thought of a radar transponder as a beacon, as that is how the Radars I use ar marked, usually Standby, TEST, Search 1,2 & 3 then WX, WX A (Alert) then BEACON or BEACON + SEARCH.
I would have never guessed that one. RACON must be one of those quaint British terms.
Cheers, OffshoreIgor
I have always thought of a radar transponder as a beacon, as that is how the Radars I use ar marked, usually Standby, TEST, Search 1,2 & 3 then WX, WX A (Alert) then BEACON or BEACON + SEARCH.
I would have never guessed that one. RACON must be one of those quaint British terms.
Cheers,
OffshoreIgor
