Identifying a Radar Reflector

[srm]

The original Firdell reflector, dating from the 1970's (that I still have) is a large lump that had to be suspended away from the mast and was not very popular. A couple of years later they brought out the much smaller and lower performance Blipper with mast mounting brackets so almost everyone fitted one on the front of the mast.
The big Firdell worked; on two occasions I was illuminated by search light at night. The light was switched on directly on my bearing so assume we were on radar but our lights not seen.
Depending on the size of the mast and reflector a mast mounted reflector will have a big dead patch astern and over the quarters where the curvature of the mast scatters incoming and outgoing pulses so they do not provide returns at the scanner.
Also, passive reflectors suitable for small vessels are only effective on the 3cm wave length, they would have to be 3x the size to be seen on a 10cm radar. Big ships often rely on the more powerful 10 cm radar.
Merchant ships require a consistent radar return at a minimum of 5 mile range to have time to assess risk of collision and take appropriate action. Irregular returns are filtered out along with sea clutter by the processing software so a passive reflector will be less effective offshore than in a flat calm; come to think of it I have picked up radar returns from seagulls on a flat calm sea.
All this supports the conclusion that active reflectors are best, provided that they are mounted correctly. If you are fitting one go for a dual channel system. Yes, they are more expensive but you are more likely to be seen if you provide returns on both radar bands.

 

[Refueler]

It concluded that only the most expensive and heaviest passive reflector met the relevant standards, and that was marginal. The reflector in question (TriLens, I think) would be inappropriate for most leisure craft, being both heavy and bulky. Active reflectors (e.g. SeaMe) met the relevant standards.

There were also serious issues with passive reflectors at angles of heel typical of sailing craft.

I have experience of passive reflectors, and can also, from my own knowledge (I was involved in a specialized form of radar for many years), state that they are dependent on very precise orientation of the reflecting surfaces. The Qinetiq report used new reflectors in factory condition for testing, and only obliquely considered the effect of age on them. But you can be sure that the figures Qinetiq give are for a reflector that is in ideal condition, mounted in the ideal manner. A reflector that has been exposed to weather and the violent motion at a masthead will behave considerably worse.

I came to the conclusion that passive reflectors were only of use under ideal conditions long before the Qinetiq report came out; I have read it from end to end and it confirmed my previous estimation.

Many years ago - I was Mate on Seismic Vessels ... we used to tow 3 mile cables with a buoy on the end.

That buoy had a 'rain catcher' reflector mounted on a short mast for us to be able to get an echo on the radar ... it worked. OK - if sea was getting a bit lively - then no way ... but as long as clutter was not so bad - we got an echo, of course we knew it was there which helped.

The hardest bit was not radar echo - but the Tech's used to ask us 'Mariners' to do an angle check of the cable buoy to the vessel ... and that was horizontal sextant angle stuff ... I hated doing that - the sextants they had on board were usually Davis Mates .... with very low power scopes for sun use ....

 

[Refueler]

Collisions between ships and yachts (whether in fog or not) are almost one in a generation events which might mean that either ships generally have no difficulty in "seeing" and avoiding yachts, or yachts manage to find ways of keeping clear of ships. If the former, and most yachts fit passive reflectors then they must work!

My 25ft motor sailer was tracked for near 10nm on a ships radar when I was in the Baltic crossing from Gotland to Latvia. Weather at time had waves / swell that must have hid major part of boat at times ... F3 - 4 ....

I know about the 10nm as I called them up when I did a 360 as the bearing change was not enough and I felt he was not going to give Port to Port enough room ... my 360 was bold and clear to him so no fear of his misunderstanding ... once he was passing ahead of me - I called him to ask if he had seen me ... he replied yes at 10nm on radar and that he had a passing CPA of 1 cable !! I politely told him that 1 cable to me is impossible to determine and why when we have all the Baltic does he want to swamp me with his 14kt wash ??

At that time - I had no reflector - only mast and sails ... but sails were damp from previous nights rain ...

 

[AntarcticPilot]

Many years ago - I was Mate on Seismic Vessels ... we used to tow 3 mile cables with a buoy on the end.

That buoy had a 'rain catcher' reflector mounted on a short mast for us to be able to get an echo on the radar ... it worked. OK - if sea was getting a bit lively - then no way ... but as long as clutter was not so bad - we got an echo, of course we knew it was there which helped.

The hardest bit was not radar echo - but the Tech's used to ask us 'Mariners' to do an angle check of the cable buoy to the vessel ... and that was horizontal sextant angle stuff ... I hated doing that - the sextants they had on board were usually Davis Mates .... with very low power scopes for sun use ....

I was on the technical crew for a couple of North Sea surveys in about 1975 - Oil Hunter was the vessel; converted stern trawler. I have two abiding memories - being as sick as a dog because the instrument room was at the centre of every possible motion, with no ports of any kind, and fighting the cable in on a deck that was regularly flooded by waves coming up the stern ramp. Of course, the cable only came in when the weather was getting a bit too wild! Fortunately we were issued decent waterproof kit, so we stayed dry, but it was still a bit too exciting!

 

[Refueler]

I was on the technical crew for a couple of North Sea surveys in about 1975 - Oil Hunter was the vessel; converted stern trawler. I have two abiding memories - being as sick as a dog because the instrument room was at the centre of every possible motion, with no ports of any kind, and fighting the cable in on a deck that was regularly flooded by waves coming up the stern ramp. Of course, the cable only came in when the weather was getting a bit too wild! Fortunately we were issued decent waterproof kit, so we stayed dry, but it was still a bit too exciting!

Compagnie Generale de Geophysique ..... (CGG) ....

One job was deliver a converted Stern Trawler of theirs from Galveston to Falmouth. By time we arrived - everything was wet .. bunks ... bedding ... clothes ... you name it ... they'd sold the vessel to a fledgling UK outfit who wanted it in UK before spring ... we had to brave N Atlantic in it ...

Vessel name : Orion Arctic. We'd completed our assignment in Gulf of Mexico ... previous assignment I had on her to that we'd shot the California coast ....

 

[pandos]

This isn't much to do with Stemar's situation, but it does seem ridiculous to me seeing modern 33'-45' AWB's, with all the trimmings & toys in them, 'proudly' sporting a '2 bob' reflector, when the best reflector in our world costs HALF the price of a Musto jacket, which he's bought for each of his family.
Form over function doesn't look so clever in fog.

An xs active reflector would be better...

 

[AntarcticPilot]

Compagnie Generale de Geophysique ..... (CGG) ....

One job was deliver a converted Stern Trawler of theirs from Galveston to Falmouth. By time we arrived - everything was wet .. bunks ... bedding ... clothes ... you name it ... they'd sold the vessel to a fledgling UK outfit who wanted it in UK before spring ... we had to brave N Atlantic in it ...

Vessel name : Orion Arctic. We'd completed our assignment in Gulf of Mexico ... previous assignment I had on her to that we'd shot the California coast ....

My main job was interpretation, as a very junior geologist. I spent time doing processing and acquisition to gain experience. Company was S&A Geophysical, which became Horizon Exploration. Best but was my first year or so, working at an office on the corner of Bond Street and Oxford Street! Of course, in both this job and my next (storage and cataloguing seismic data) I came across all the major players, including CGG. I've probably handled data you helped to acquire!

 

[Tranona]

Not so; you are assuming that radar is a factor in all collisions, which is unlikely.

This was in response to zoidberg's post on confirmation bias and (only very slightly) tongue in cheek. You could say the same if you hung one of those plastic owls in the rigging instead - the chance of being run down in fog would be very little different because it is such a rare event.

You are right, radar detection or lack of plays only a very small part in the risks associated with sailing, and like many "safety" issues has assumed an importance in debate way out of proportion to the actual size of the problem.

 

[jamie N]

You are right, radar detection or lack of plays only a very small part in the risks associated with sailing, and like many "safety" issues has assumed an importance in debate way out of proportion to the actual size of the problem.

I entirely agree, and will happily admit that I only bought my Echomax active because of my wife, who being a non-yottie, insisted that as I intended on sailing all over and around Scotland solo, that I had everything reasonable to ensure safety, thus I've the reflector and an AIS transceiver also.
I was sailing in fog from Orkney to Fair Isle and quite relaxed being as visible as I was able to be, and was able to see what was what around me (precious little), and know that they'd be able to see me also. The only thing that might've given me a problem would be something long, thin, low in the water, coloured black and with a conning tower on it!

 

[Refueler]

My main job was interpretation, as a very junior geologist. I spent time doing processing and acquisition to gain experience. Company was S&A Geophysical, which became Horizon Exploration. Best but was my first year or so, working at an office on the corner of Bond Street and Oxford Street! Of course, in both this job and my next (storage and cataloguing seismic data) I came across all the major players, including CGG. I've probably handled data you helped to acquire!

Maybe .. with CGG ... I shot North Sea (seismic grids and the single shot for well determination) .... Gulf of Mexico ... West Africa ... California Coast ...

Most of our 'tapes' were packed of to Massy, Paris but quite possible .. I know we sent odd tapes from Norwegian Fjords to Military as we were 'sub hunting' occasionally. Dem pesky Ruskies !

I also worked Western Geo in N.Sea but didn't like the work system they had ... so I trundled back to normal ships !

 

[srm]

and fighting the cable in on a deck that was regularly flooded by waves coming up the stern ramp.

Brings back memories. I did two summers with SSL, '69 and '70 when a student. They had two Norwegian stern trawlers on charter. The stern deck got waist deep in sea at times while recovering the cable, but was probably much safer than some of the ex-Gulf of Mexico boats that were around in the early days and had very little freeboard aft. At the job interview I was told that I would be the lowest form of life on the ship, but being a temp I got moved around all the departments which made it interesting. I discovered who stayed warm and dry all the time, so after graduating got a job as a trainee hydrographic surveyor with a NERC research unit.

 

[Ian_Rob]

A lot of small commercial fishing vessels only have Simrad 4G (or the equivalent). If I am reading the tech info correctly (and I may not be) the RTE trigger threshold for an Active X ‘painted’ by a Simrad 4G radar is only 183.5 metres. Setting aside that the chances of collision are very small, the protection afforded by active reflectors in some situations doesn’t seem that great?

 

[Stemar]

Well, I never expected this to blow up like that, though after close to 20 years on the forums, I don't know why I'm surprised! May I offer a new collective noun: an argument of forumites?

For the kind of sailing I do, I'm more interested in meeting the letter of the law on this, so the reflector will be reassembled and refitted. On a cat, even a vertical mast will have a decent radar reflection, and the reflector will add a bit more, but I'd rather rely on knowing where the big boys are and keeping out of their way than relying on being seen by them - IF they're looking

I have a limited budget and, as I can get an AIS receiver gizmo for much the same price as an active radar reflector, I know where I'd rather spend my money.

 

[Refueler]

I plumped for AIS equipped Plotter .... Onwa at far less money than a non AIS job from more well known brands ... not only receive - but transmit as well.

It may not be all in as a radar reflector echo on a screen - but it certainly helps.

 

[zoidberg]

People interested in 'See and Be Seen' might care to re-read this excellent article from Yachting Monthly passim.....

Echomax 230i foldable

The article is halfway down the link-page.

Me? I have two of them. I'm a bug* for a bargain, and they're each encased in a thin netting mesh, rather like those Italian salamis hung up in delis. Takes the load off the internals....