Passive radar reflector - anything better than Echomax?

RobbieW said:
186000 is one of those numbers that sticks in my mind, a bit like 3.142, as an approximation (in miles/sec) of the speed of light. Google tells me the number you were looking for is 62,400 :)
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Thanks. I Was wrong by a factor of a bit less than 3. Only 5dB...
Normally, it's not 186 that sticks in my mind, but 168, the number of hours in a week.

but 186xxx sounds like the sail number of a Laser worth about £1200 to me...

I tend to think of the speed of light as about a foot per nanosecond.
But I think some radar people used to define a 'radar foot' as c/1ns?
 
TernVI said:
Thanks. I Was wrong by a factor of a bit less than 3. Only 5dB...
Normally, it's not 186 that sticks in my mind, but 168, the number of hours in a week.

but 186xxx sounds like the sail number of a Laser worth about £1200 to me...

I tend to think of the speed of light as about a foot per nanosecond.
But I think some radar people used to define a 'radar foot' as c/1ns?
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I usually think of it as metres per microsecond, and I remember the velocity in ice as well as air (300 m/μS in air, 164 m/μS in ice). Both were everyday numbers when I dealt with ice-sounding radar.
 
jamie N said:
... Passive reflector's are less good, but still give a better feeling than nothing.
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One of the points being made in the reports linked in this thread, are that passive reflectors are not good (except for a couple that also have huge reflective null points). The rest are not worth it.

Risk taking is known to increase when an individual thinks they have some form of enhanced safety, in our case a passive radar reflector that we believe will increase us being seen, despite the fact that the reports suggest they are useless. This risk taking effect was famously trialed between Volvos (perceived safe cars) and other models (perceived less safe cars). The test was to accelerate to 30mph and then brake hard to stop as close as possible to a polystyrene wall without hitting it. Every Volvo driver hit the wall, none of the other unsafe car drivers hit the wall. The effect has also been measured in offshore workers where the increase in personal safety and safety controls before performing work, has both failed to reduce incidents and in some cases has lead to an increase in incidents (there is more to it than just just that, especially around repetition and familiarity). Our unfamiliarity with fog, may be the brown trowser factor that cancels out any thoughts of improved safety by using an ineffective passive radar reflector.
 
BlowingOldBoots said:
One of the points being made in the reports linked in this thread, are that passive reflectors are not good (except for a couple that also have huge reflective null points). The rest are not worth it.

Risk taking is known to increase when an individual thinks they have some form of enhanced safety, in our case a passive radar reflector that we believe will increase us being seen, despite the fact that the reports suggest they are useless. ....
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The report does not actually say they are useless.
Anyone who works with radar will be familiar with 'corner reflectors'. They are useful and have been greatly used for over 50 years.

The problem is the 'finger in the air' nominal 10sqm 'requirement' has been taken not as a minimum average but as a minimum of minimums (minima?).
A radar does not typically need anything like 10 sqm of RCS to 'see' a target from 'quite a long way away'.
As an example, a typical aircraft has a fairly small, very specular RCS, and they are tracked over very much greater distances.

There is of course a limitation that the return from the yacht must be discernable amid the 'clutter' returned from the sea.
Which is why all the 'my boat was seen from miles away' tales are of limited value.
 
I question the statement : "Which is why all the 'my boat was seen from miles away' tales are of limited value."

I agree that if the tale has no supporting evidence - then its supposition at best. But as in my case already posted a number of times - the OOW stated clearly the over 10nm and that it was the Auto ACAS that tracked me ...

I would be wary of comparing ATC Radar to Marine based ... ATC radar is as I understand tighter beam width and needs two sets to ascertain height / direction. Plus ATC concentrate on set direction spread ... (Military of course is different ball game).
 
Civil ATC radar relies totally on SSR - ie transponders which additionally return an altitude signal - civvy radar operates in azimuth only and has no capability whatsoever in elevation. That is purely a military application. Primary radar is simply not reliable enough in returning a useful signal at realistic ranges and is surprisingly ineffective against low level targets at even short ranges due to the old enemy, ground clutter, hence the problems we have with seaborne surface radar - weeding a small signal (a mast and bits of wire as opposed to a 300ft long wall of steel) that is right in amongst the noise (sea clutter) is not at all easy, let alone reliable.
If you want to rely on being seen you have to go active, either AIS or a radar transponder like SeaMe.


Here's a piece from queue-ineti-queue that contains their analysis of the performance of a wide selection of passive and active yacht reflectors so that's about as gospel as you can get...

https://www.ussailing.org/wp-content/uploads/2018/03/2007-Radar-Reflector-Test.pdf
 
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Slowboat35 said:
Civil ATC radar relies totally on SSR - ie transponders which additionally return an altitude signal - civvy radar operates in azimuth only and has no capability whatsoever in elevation. That is purely a military application. Primary radar is simply not reliable enough in returning a useful signal at realistic ranges and is surprisingly ineffective against low level targets at even short ranges due to the old enemy, ground clutter, hence the problems we have with seaborne surface radar - weeding a small signal (a mast and bits of wire as opposed to a 300ft long wall of steel) that is right in amongst the noise (sea clutter) is not at all easy, let alone reliable.
If you want to rely on being seen you have to go active, either AIS or a radar transponder like SeaMe.


Here's a piece from queue-ineti-queue that contains their analysis of the performance of a wide selection of passive and active yacht reflectors so that's about as gospel as you can get...

https://www.ussailing.org/wp-content/uploads/2018/03/2007-Radar-Reflector-Test.pdf
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Sorry but have to disagree with the highlighted red ....

There was a famous mid-air collision between an Indian and a Ukrainian aircraft some years back where the Ukrainian co-pilot mistook the flight level instruction from ATC. The aircraft changed flight level and the two collided. The investigation highlighted the fact that the VERTICAL / ALTITUDE radar planned to be installed at the airport had been delayed and was a contributory factor. If the radar had been installed - they believed ATC could have detected the error and advised the two aircraft.
There was a documentary on it in fact ... and the ATC operator involved suffered breakdown and was unable to work again for many years after.

If you go to airports and look - many especially major airports have not only horizontal sweep antennas - but a separate vertical oscillating antenna - that vertical antenna is the altitude detecting radar. Many are approach radars and lined up with runways - but there are many that have further reach.

Transponders with flight data are additional....

I grew up with my Father who was Chief Flight Operations CAA (DTi) ... who was also part of of the Air Accident Investigation Bureau ... I know that was not ME ... but I don't think my memory has been destroyed just yet ...
 
Humm. The big radar antenna rotating at the northern entrance of LHR is an L-Band medium range primary radar. It has a main beam and a pencil beam, used to suppress ground clutter. I reaches out about 350 km. IIRC.
Most large airports have smaller primary radars (60 km range IIRC) to deal with aircraft with failed or no secondary radar transponders. These primary radars use a lot of Moving Target Aquisition techniques to suppress ground clutter.
ATC mainly relies on secondary radar and aircraft transponders, which actually have a data link capability. This is also used by the transponders to form the TCAS system (Tactical Collision Avoidance System) between aircraft.

Civil Ships S and X band radars are comparatively simple. The military seem to use a lot of C-Band radar these days.
 
Doesn't change the fact of the documented collision and findings of that mid-air ..............

Todays ships radars 3 + 10cm are a lot different than even just a few years ago. Most now have digital processing to daylight viewable TV screens. The target acquisition and clutter reduction not only sorted by user - but digitally as well .. this has had a huge effect in improving the displayed data ...

Unfortunately it has had a part to play in the increasing habit of OOW not using Mk1 eyeball as much now ...
 
Refueler said:
Sorry but have to disagree with the highlighted red ....

There was a famous mid-air collision between an Indian and a Ukrainian aircraft some years back where the Ukrainian co-pilot mistook the flight level instruction from ATC. The aircraft changed flight level and the two collided. The investigation highlighted the fact that the VERTICAL / ALTITUDE radar planned to be installed at the airport had been delayed and was a contributory factor. If the radar had been installed - they believed ATC could have detected the error and advised the two aircraft.
There was a documentary on it in fact ... and the ATC operator involved suffered breakdown and was unable to work again for many years after.

If you go to airports and look - many especially major airports have not only horizontal sweep antennas - but a separate vertical oscillating antenna - that vertical antenna is the altitude detecting radar. Many are approach radars and lined up with runways - but there are many that have further reach.

Transponders with flight data are additional....

I grew up with my Father who was Chief Flight Operations CAA (DTi) ... who was also part of of the Air Accident Investigation Bureau ... I know that was not ME ... but I don't think my memory has been destroyed just yet ...
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You need to go back and reread the Uberlingen report. Ground radar had little or nothing to do with it.
 
Refueler said:
Doesn't change the fact of the documented collision and findings of that mid-air ..............

Todays ships radars 3 + 10cm are a lot different than even just a few years ago. Most now have digital processing to daylight viewable TV screens. The target acquisition and clutter reduction not only sorted by user - but digitally as well .. this has had a huge effect in improving the displayed data ...

Unfortunately it has had a part to play in the increasing habit of OOW not using Mk1 eyeball as much now ...
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It's that automation of functions that makes it important to get to 10 m2 RCS on a yacht. ARPA needs highly observable targets. The skill of a trained radar operator to extract targets from clutter is being lost and anyway, there are so few on a bridge these days. GMDSS was designed to reduce the cost of bridge crew. AIS is now integrated with the ECDIS so is even better than primary radar, when both are working.
 
I once attended a talk given by the boss of Echomax. His view was that the small tube ones were worse than useless and you'd be better off hoisting a frying pan up your mast. The larger ones, his included, were sorta, kinda ok, but not great, and that if you really wanted to be seen, you should use an active reflector. Ok, he was on a bit of a sales kick for his active kit, but I saw no reason to doubt what he was saying.
 
RAI said:
Still very relevant to this discussion though. TCAS was ignored by the Russian when he obeyed the Swiss ATCO, who was later stabbed to death by an irate Russian father.
Primary radar could not have helped
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Am I right in thinking that the system (at the time) that could have prevented the Indian midair couldn't actually see or calculate altitude, but obtained it from the aircraft's transponder?
 
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