Ouzo - radar reflector report published
- Thread starter misterg
- Start date
Captain Haddock
Member
Very interesting, looks like I'll be ordering a Sea-Me for my next boat.
Kylora
Member
Cheers. Is there a requirement for a gimballed reflector do you think?
Ash
Ash
Oldhand
New member
Funtington used to produce circular polar plots in the old Admiralty/Plessey days, much quicker to decipher than the linear one's in this report, I guess that's called progress!
I don't think they went far enough with only 20 degrees elevation change, which I suspect was a limitation of the anechoic chamber size. I wonder how much more the SeaMe falls off at 30 degrees, a more typical angle for a yacht beating to windward.
I don't think they went far enough with only 20 degrees elevation change, which I suspect was a limitation of the anechoic chamber size. I wonder how much more the SeaMe falls off at 30 degrees, a more typical angle for a yacht beating to windward.
Talbot
Active member
sea me is no good at all if they are looking at the other frequency radar.
fluffc
Member
Seems the best 'budget' solution is to mount two octaheadral reflectors, one above the other, and 45 degrees out of alignment with each other to compensate for the (very worrying) nulls.
Surprising to see the varying plots of the Echomax and Blipper types.
Also confirmed my suspicions that the Plastimo Tube reflectors are of little use. This is particularly worrying considering the number of the 2" varieties that are appearing on (racing) yachts. ('Thou shalt carry a radar reflector')
Surprising to see the varying plots of the Echomax and Blipper types.
Also confirmed my suspicions that the Plastimo Tube reflectors are of little use. This is particularly worrying considering the number of the 2" varieties that are appearing on (racing) yachts. ('Thou shalt carry a radar reflector')
Sinbad2222
New member
One can conclude from the report that, discarding the small tube reflector and the very expensive specialist units, the average radar cross section of the yachtsman's reflectors is between 2 and 8 metres.. The report does not quantify the average RCS of a yacht without a reflector or the RCS of the hole in the water made by the yacht. Until we have some idea of the magnitude of these RCSs as compared with 2-8 square metres no conclusions can be drawn about the efficacy of reflectors and we must, unfortunately, still rely on anecdotal evidence.
Twister_Ken
Well-known member
>I wonder how much more the SeaMe falls off at 30 degrees, a more typical angle for a yacht beating to windward.<
30 degrees! You should reef earlier!
30 degrees! You should reef earlier!
Greenwichman
Member
Sorry, but I don't agree. As a professional seafarer I have gained more than anecdotal evidence: a yacht - with or without a passive reflector - is a very poor radar target in anything other than ideal conditions.
As said in previous forum posts, save your money, the weight aloft and the windage, a passive reflector will gain you nothing.
The "Sea-Me" active transponder product is a start, but as someone else has said, it operates on one band only. It is also expensive to fit and consumes a whack of power when replying to a radar 'interrogation', which in The Channel would be virtually continuously.
The surprise is that only one company is in this market at present, so there are no downward pressures on price. This is despite the fact that the similar 'Racon' technology is now at least 40 years old.
What is needed is customer resistance to buying any more of these useless passive things, and a clamour from us as yacht users and from the yachting press for an affordable, workable active transponder system to complement AIS and active radar.
Meanwhile, there continues to be no substitute for a very good lookout, bright lights, avoiding fog and mist, and keeping clear of the ahead-sector of anything large and fast.
As said in previous forum posts, save your money, the weight aloft and the windage, a passive reflector will gain you nothing.
The "Sea-Me" active transponder product is a start, but as someone else has said, it operates on one band only. It is also expensive to fit and consumes a whack of power when replying to a radar 'interrogation', which in The Channel would be virtually continuously.
The surprise is that only one company is in this market at present, so there are no downward pressures on price. This is despite the fact that the similar 'Racon' technology is now at least 40 years old.
What is needed is customer resistance to buying any more of these useless passive things, and a clamour from us as yacht users and from the yachting press for an affordable, workable active transponder system to complement AIS and active radar.
Meanwhile, there continues to be no substitute for a very good lookout, bright lights, avoiding fog and mist, and keeping clear of the ahead-sector of anything large and fast.
Bilgediver
Well-known member
I suspect you are missing the point with the SeaMee.
It is not an inefficient box of nails in a plastic case. It is a radio device and gives a very healthy signal to the ships radar so a bit of falling of due to antenna tilt would be minimal.
John
It is not an inefficient box of nails in a plastic case. It is a radio device and gives a very healthy signal to the ships radar so a bit of falling of due to antenna tilt would be minimal.
John
Marsupial
New member
Greenwinchman I agree, but the power drain is not significant,
Sinbad,
I would suggest you go out to sea on a clear calm day on a boat equipped with radar, have a look at the screen then have a look at what your eyes can see. I bet your eyes see more than the radar, at least that has been my experience over a fair few years. Playing around with the controls, range, tuning, gain, clutter etc may get a better return from some targets but others may be distorted such that you wont be able to determine their bearing. What will you do in fog? However, the biggest lesson I have learned is that, for most of the time, boats with passive reflectors don’t show up any better than boats with no reflector, and most of the time they don’t show up at all.
We now have a set of test results that is consistent with what many of us already knew - passive reflectors are of dubious benefit. The message is clear don't wast money on passives and lobby for better active systems - let's say that not fitting a passive reflector is a £130 discount on the active offering.
Sinbad,
I would suggest you go out to sea on a clear calm day on a boat equipped with radar, have a look at the screen then have a look at what your eyes can see. I bet your eyes see more than the radar, at least that has been my experience over a fair few years. Playing around with the controls, range, tuning, gain, clutter etc may get a better return from some targets but others may be distorted such that you wont be able to determine their bearing. What will you do in fog? However, the biggest lesson I have learned is that, for most of the time, boats with passive reflectors don’t show up any better than boats with no reflector, and most of the time they don’t show up at all.
We now have a set of test results that is consistent with what many of us already knew - passive reflectors are of dubious benefit. The message is clear don't wast money on passives and lobby for better active systems - let's say that not fitting a passive reflector is a £130 discount on the active offering.
misterg
Active member
Interesting. Seems if you're not prepared to spend >£300, there's not much point spending >£30.
The "See-Me" is the clear winner, but if it stops working, you've got nothing. Other than the big, heavy, expensive tri-lens, a simple corner cube works as well as anything. Two decent sized octahedrals (mounted as far apart as possible, and at slightly different orientations ca. 30-45 deg) seem to have the potential to perform very well, but isn't this what's inside the Blipper & the Echomax?
It's worrying that all apart from the See-Me don't meet the current standard, let alone the proposed improved standard.
Worst of all, is the very hit and miss performance in the less than ca 1.5 miles, which is arguably the most critical range for busy coastal waters in darkness or poor visibility - even with the best reflector, you've not got much better than a 50/50 chance of being detected. Anything less, and it's odds-on that you won't be detected.
Glad I sail in shallow water where big ships don't usually venture.
Andy
The "See-Me" is the clear winner, but if it stops working, you've got nothing. Other than the big, heavy, expensive tri-lens, a simple corner cube works as well as anything. Two decent sized octahedrals (mounted as far apart as possible, and at slightly different orientations ca. 30-45 deg) seem to have the potential to perform very well, but isn't this what's inside the Blipper & the Echomax?
It's worrying that all apart from the See-Me don't meet the current standard, let alone the proposed improved standard.
Worst of all, is the very hit and miss performance in the less than ca 1.5 miles, which is arguably the most critical range for busy coastal waters in darkness or poor visibility - even with the best reflector, you've not got much better than a 50/50 chance of being detected. Anything less, and it's odds-on that you won't be detected.
Glad I sail in shallow water where big ships don't usually venture.
Andy
Oldhand
New member
Why?
hornblower
Member
You'll go faster for one thing
Bergman
New member
Fairly predictable outcome.
It would have been of greater interest to see some measurements using real boats with and without reflectors.
It would have been of greater interest to see some measurements using real boats with and without reflectors.
BrendanS
Well-known member
The logistics and reproducibility of trying this in real life conditions would make any test almost worthless in comparison terms.
tome
New member
[ QUOTE ]
Fairly predictable outcome.
It would have been of greater interest to see some measurements using real boats with and without reflectors.
[/ QUOTE ]
Are you sure you fully understand the report?
Fairly predictable outcome.
It would have been of greater interest to see some measurements using real boats with and without reflectors.
[/ QUOTE ]
Are you sure you fully understand the report?
Allan
Well-known member
The report does make interesting reading. I remember a report in PBO some years ago that when they did tests on the water they found that fitting a reflecter could reduce the radar reflection of a yacht. If I remember correctly it was something to do with phasing or something. Sorry not to add anything positive to the thread.
Allan
Allan
DJE
Well-known member
[ QUOTE ]
.....passive reflectors are of dubious benefit.....
[/ QUOTE ]
But the POLARef 11 reflector did very well. It's currently a "Made to order" £2,000 item. Surely mass production could bring that technology within the budget of cruising yachtsmen.
.....passive reflectors are of dubious benefit.....
[/ QUOTE ]
But the POLARef 11 reflector did very well. It's currently a "Made to order" £2,000 item. Surely mass production could bring that technology within the budget of cruising yachtsmen.
Bergman
New member
Thinking about your comment, the answer must of course be no.
No-one can know what it is that they don't know.
My thoughts such as they are, are that the report compares a number of devices with each other and against a standard 10 sq metre RCS. and does this under tightly controlled conditions
However in the reports own words:
"While this gives a very good comparison, it is not a
comprehensive set of measurements, in that it cannot take into account
different radar parameters, clutter, target RCS/range/aspect etc"
It is limited in its scope.
What it does not say is what the RCS of a typical 30ft GRP yacht is. What for example is the RCS of a typical mast and rigging - I do not know but would like to see someone measure it.
It does not indicate to what extent any of these devices would solve the issue of the yacht being lost in clutter - which is said to be one of the major causes of the incident.
I would have liked to see some attempt to relate these "laboratory" results to what they mean in the real world of a small sailing boat beating to weather in a F5 in the dark.
No-one can know what it is that they don't know.
My thoughts such as they are, are that the report compares a number of devices with each other and against a standard 10 sq metre RCS. and does this under tightly controlled conditions
However in the reports own words:
"While this gives a very good comparison, it is not a
comprehensive set of measurements, in that it cannot take into account
different radar parameters, clutter, target RCS/range/aspect etc"
It is limited in its scope.
What it does not say is what the RCS of a typical 30ft GRP yacht is. What for example is the RCS of a typical mast and rigging - I do not know but would like to see someone measure it.
It does not indicate to what extent any of these devices would solve the issue of the yacht being lost in clutter - which is said to be one of the major causes of the incident.
I would have liked to see some attempt to relate these "laboratory" results to what they mean in the real world of a small sailing boat beating to weather in a F5 in the dark.