11 radar reflectors tested : Not all models are really easy to see
Alexander Worms
· 14.05.2023
This is how we tested
11 radar reflectors in the test: the results, how radar reflectors work, radar technology: broadband or magnetron radar.
Who needs a passive radar reflector in the age of AIS? Thanks to modern electronics, you are highly visible on the screens, certainly on those of commercial shipping. Well, the question seems justified at first glance. On closer inspection, however, the answer is clear: everyone who is on the water with commercial shipping needs such a device. This is because AIS technology is dependent on a power supply - if this fails, the yacht is no longer visible. Passive radar reflectors work at all times. What's more, there are some areas, such as the Waddenzee in the Netherlands, where a radar reflector is simply mandatory.
Not much has changed in terms of products in recent years. On the market, the Tin cube which Tubes and the Echomax . There was also a device called Trilens. This reflector is now sold under the name 3Lenzz offered again.
But how good is the performance of the reflectors in practice and when it is not a question of being seen by large devices on the bridge of a commercial vessel, but by a less powerful yacht radar? First of all, it is difficult to make generalisations and the conclusions must be formulated precisely.
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The problem is explained using an example: the 3Lenzz consists of three spheres that are mounted at an angle of 120 degrees to each other. A test by the British coastguard had already shown that it has a blind spot every 120 degrees. If radar signals hit this blind spot, the echo on the screen disappears. All reflectors have such blind spots, to a greater or lesser extent. During our test, we recognised the 3Lenzz by the fact that the echo was clearly visible, disappeared for a few orbits and then reappeared. The test boat was obviously close to a blind spot on the reflector. In practice, this would be the case when approaching with an exact bearing, for example when a ship is travelling towards an anchor berth that is not swinging. However, if the angle between the two changes by just a few degrees, there is an echo.
The conclusion that it doesn't work well because it was sometimes poorly visible in the test would not be the whole truth. The echoes were clear when measured from a different position. The conclusion is therefore that the 3Lenzz delivers good results with changing courses of approach and only shows weaknesses at three points on the full circle.
To simulate the situation on a sailing boat, we measured each reflector vertically and at an angle of 30 degrees. Here, too, some models showed weaknesses. In particular, the models with an already small reflective surface sometimes collapsed significantly. However, even the weakest reflector ensured that our test pontoon appeared on the radar screen.
The echo of each reflector was measured a total of eight times - from a distance of 0.5 and 1.5 nautical miles, vertically and at an angle of 30 degrees, using a modern broadband radar and a conventional magnetron radar. The displays of the broadband radars are shown in the individual test images. Measurements were taken from a motorboat on which both antennas were installed. The reflectors were installed at a height of around three metres on a pontoon on a wooden mast, which could also be tilted. The results were then saved using a screenshot on the Garmin devices used; these were radars commonly used on yachts. We optimised the settings of the radar unit for the medium-sized sheet metal reflector and did not change them in the further course of the test in order to ensure the same conditions for all reflectors. We only tested the two inflatable reflectors in an upright position, as these are usually suspended.
Plastimo sheet metal small
At close range, it is always easily recognisable on both devices. At greater distances, it is not visible in a vertical position; echoes only became visible when the mast was tilted. For an optimum echo, the reflector must be mounted in the rain catcher position, but this can only be the case either in an upright or tilted (in the test) position. Mounting is difficult, the metal sheets are sharp-edged.
- Weight: 0.45 kg
- Reflective surface, total: 3.0 m²
- Price: 33,92 €
- Distribution: Bukh Bremen
- Dimensions: 215 x 215 x 280 mm
- Rating: ***
Plastimo sheet metal RORC
The big brother is consistently easier to recognise on both devices at close range. From a greater distance, the solid-state radar struggles with reproduction. On the radar, the reflector cannot be seen in an upright position; when the boat is heeled over, it blends in with the tug echo. The reflector is very large. There is no opening on the inside to feed a stage through; the installation of the reflector on a sailing boat is unclear.
- Weight: 1.0 kg
- Reflective surface, total: 7.0 m²
- Price: 52,48 €
- Dimensions: 340 x 340 x 470 mm
Echomax EM 12
Good visibility at both distances. A rather weak echo when measured upright on the magnetron radar. At the greater distance, the reflector also clearly stands out from the echo of the tug. Mounting is easy, a foot helps with mounting on the spreader, for example. A spherical cut-out in the centre makes mounting on the stay easier as it can be threaded through. The plates are not sharp-edged.
- Weight: 0.73 kg
- Reflective surface, total: 5.5 m²
- Price: 80,50 €
- Distribution: Lindemann KG
- Dimensions: 360 mm
The rod is only visible as an echo from a short distance, but it is always equally good, regardless of whether it is vertical or inclined. At greater distances, it is invisible on the semiconductor radar. Only the magnetron radar can detect an echo in a vertical position. The reflector is lightweight and easy to install. However, it is more expensive than the similarly performing Plastimo tube. A base for mounting on deck is available.
- Weight: 0.38 kg
- Reflective surface, total: 2.0 m²
- Price: 49 € (as of 8/2022)
- Distribution: Lankhorst Hohorst
- Dimensions: 50 x 570 mm
Plastimo pipe small
At close range, the Plastimo tube is reasonably visible, but the echoes are visibly weaker compared to the Mobri tube. At greater distances, an echo is only recognisable in a vertical position and on the semiconductor radar. The tube therefore reacts sensitively to heeling. Some of the aluminium plates inside are severely bent and not aligned at right angles. Lightest reflector in the test field.
- Weight: 0.25 kg
- Reflective surface, total. 2,0 m²
- Price. 36,53 €
- Dimensions: 50 x 580 mm
Same picture as its little brother: no visibility at a distance of 1.5 nautical miles. Only the magnetron radar in vertical position shows a slight echo. However, the Mobri is clearly visible at close range. The twice as large reflective surface compared to the smaller version does not result in a better echo. The extra weight and price are therefore not worth it. Also available with base.
- Weight: 0.88 kg
- Reflective surface, total: 4.0 m²
- Price: € 95 (as of 8/2022)
- Dimensions: 100 x 590 mm
Plastimo pipe large
The same picture as with the competitors in tube form: At short distances, the image is usually good, although very small echoes occur with magnetron radar; at greater distances, they are almost completely invisible. Here too, the larger reflective surface does not result in a better echo. The aluminium plates inside are also bent and not mounted at right angles. The workmanship does not look very high quality due to the burrs on the plastic.
- Weight: 0.90 kg
- Price: 62,83 €
Echomax 230 BR
The very large device is the only reflector that produces an echo under all conditions and regardless of the radar technology. However, these are sometimes rather weak, especially if the reflector is tilted. If the reflector is upright, very good echoes are consistently displayed. The Echomax is very large and heavy, the required mounting bracket costs extra, but is very solid. Rather for large ships.
- Weight: 2.5 kg
- Reflective surface, total: 24 m²
- Price: 301,07 €
- Dimensions: 245 x 610 mm
- Evaluation: ****
The 3Lenzz shows consistently good echoes at short distances. At greater distances, reliable echoes are only visible when the device is mounted vertically. If the device is tilted, a strong echo is only visible about every third round, but it is reliably visible in the same place. This is probably a consequence of the three-part design, see running text. The 3Lenzz is the most expensive and heaviest reflector in the test.
- Price: 389 €
- Distribution: Northwest radio
- Dimensions: 300 x 300 x 150 mm
Echomax EM230i
Very good and clear echoes throughout thanks to the large projection surface. Due to the suspended mounting, the reflector is always aligned vertically, so no curved values were measured. Due to its low weight, it is the ideal addition for small cruisers who only want to use the reflector when necessary. As with the ball, we recommend replacing the reflector after five years. However, it is very expensive in comparison.
- Weight: 0.42 kg
- Reflective surface, total: 17 m²
- Price: 296 €
- Dimensions: 300 x 750 mm
Plastimo inflatable
Good visibility at short distances, barely visible at greater distances. As the ball always hangs vertically when it is hoisted on a flag halyard, for example, there were no measurements when tilted. Rather poor echoes despite the comparatively large reflective surface. Unfortunately, the ball was leaking, so that constant re-inflation was necessary. The reflector is very large and light when inflated. Expensive.
- Weight: 0.6 kg
- Reflective surface: 10 m²
- Price: 268,94 €
- Dimensions: 615 mm
It used to be like this: after the radar unit was switched on, it took quite a while for the first image to be taken. This was because the electron beam tube, the magnetron, had to heat up first. This took time and required a lot of energy. Operating the devices also swallowed up a lot of electricity. So, on long patrols in areas with little traffic, it was only allowed to carry out a sweep every few minutes. If nothing was seen, the device switched back to stand-by mode and only used the energy required to keep the tube at the right temperature.
Modern radar devices solve this differently. There, it is not tubes that generate the signal, but semiconductors. They can also generate signals of different wavelengths. As a result, the radar is available as soon as it is switched on and requires much less power. In addition, the radiation is significantly lower, which is good for the health of the people on board. A broadband or semiconductor radar generates roughly the same radiation as a smartphone. Due to the different wavelengths, the radar can generate even more information from the reflected signals. So-called Doppler radars quickly recognise whether an echo is approaching or moving away and in which direction it is doing so without the need for complex plotting. This makes it possible to calculate the point of closest approach and the time until then.
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Radar reflector performance
Because sailboats are notoriously poor radar targets, many sailors purchase a passive radar target enhancer (RTE), or radar reflector, to improve the vessel’s signature. How effective are these devices? For my recent book Radar Reflectors for Cruising Sailboats, I developed a method for describing and comparing RTEs. We’ll use it here to compare a few of the common passive radar reflectors on the market.
The strength of the radar signal reflected by a target is related to the radar cross section, or RCS. A larger RCS means the target will be detected at greater range, by lower power radar sets, in poorer weather conditions and more consistently. Consistent detection is especially desirable for collision avoidance because your vessel may be missed by a human operator and it may be ignored by automatic radar plotting aid software.
Radar reflectors cannot be completely described by a single RCS value. Rather, the RCS depends on the orientation of the radar reflector relative to the radar that is painting it. The orientation, or aspect, is simply the relative bearing of the radar from your vessel and the elevation angle of the line of sight to the radar relative to your deck. For a radar dead abeam, the elevation angle is your vessel’s angle of heel; for a radar dead ahead or astern, the elevation angle is your vessel’s pitch angle. A complete characterization of a radar reflector includes the RCS at all bearing angles, or azimuths from 0° to 360° and all elevations angles from -90° to +90° – although a smaller range of elevation usually is adequate.
Polar diagram
Radar cross section is commonly presented in a polar diagram. To obtain polar diagram data, the target is mounted on a rotating platform in an indoor radar range (radar anechoic chamber). A carefully calibrated radar system records the strength of the reflected signal as the platform rotates through 360° and graphs RCS against azimuth.
A polar diagram describes the RTE as long as it is vertical (elevation is zero). It does not represent performance if the RTE is tilted away from the vertical, as would be the case if the RTE is mounted on a vessel that is rolling or pitching in a seaway or simply sailing at a constant angle of heel. Consequently, single polar diagrams do not provide enough information to compare radar reflectors that are to be used on sailboats. Manufacturers sometimes provide several polar diagrams for different tilt angles, but this is not common practice and, even when the data are available, it is not easy to visualize performance given multiple polar diagrams.
Analytic RCS diagram The data visualization problem may be overcome by a single quantized, color-coded RCS diagram showing the data from many polar plots. Such a diagram is easier to interpret than multiple individual polar plots, but obtaining enough anechoic chamber data to produce a detailed diagram is costly and time consuming. My solution was to develop analytic models of all common RTE, calculate RCS over the entire range of aspect, and present the results in a color-coded analytic RCS diagram. An analytic approach is possible because all RTE are made of a few basic elements that have been analyzed and described thoroughly in the technical literature. Basic elements can be combined analytically to represent any RTE if the physical structure is known. The color-coded diagram allows one to visualize RCS over a large range of aspect and compare RTE with a common display. Included here is the analytic RCS diagram for a Davis EchoMaster 121/2-inch octahedral, mounted in the normal orientation. RCS magnitude is quantized so only six colors are needed. I have used green to indicate an RCS greater than 10 m2, yellow between 5 and 10, dark blue between 2.5 and 5, light blue between 1.25 and 2.5, purple between 0.625 and 1.25, and red less than 0.625 m2. The 2:1 spacing of contours allows six colors to cover a large range of RCS. Essentially, green is good. RCS decreases progressing from yellow to purple, and red means you probably won’t be detected. Examining the diagram, the major feature is the eight circular areas of green, yellow and dark blue centered at about 35� elevation. These correspond to the eight corner cube pockets that are the main element of the octahedral. The narrow vertical and horizontal green areas come into play at certain aspects. This diagram is interpreted as follows. The main response consists of eight cones oriented about 35� above and below horizontal. There is good response at very small elevation angles, roughly �4�, but even at zero elevation, there are small ranges of azimuth for which the response is red. Consequently, this RTE would be marginally useful as long as the vessel on which it is mounted does not heel more than 4�, or heels about 35�. For heel angles between a few degrees and about 20� there is a lot of red. You would present a very small RCS to the radar, and you probably would not be detected at most azimuth angles. There is more red than green or blue over the range of aspect encountered by monohull sailboats, so the octahedral, in normal orientation, may not be the best choice. On the other hand, there is a lot of green and blue for elevation angles less than 4� so this would not be a bad choice for a vessel that does not tilt much. RCS is not the only criterion for selecting an RTE. Cost, mounting, weight and windage aloft, power consumption, and reliability also are important, as is the application, i.e., collision avoidance, search and rescue, fixed navigation aids. Even the type of vessel and expected sailing conditions are important for collision avoidance because of different ranges of heel angle. However, the analytic RCS diagram succinctly summarizes the variation of RCS with aspect and enables one to compare RTE on a common basis.
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Tri-Lens Radar Reflector
In the September 1995 issue, we reported results of radar reflector testing done at the Stanford Research Institute in Palo Alto, California. This was made possible thanks to Dick Honey, then a semi-retired senior principal scientist at SRI, uncle to former SRI research engineer, well-known navigator and sailor Stan Honey (also the guy who puts the yellow first-down band across the screen of your TV during pro football games). Stan also assisted, as did West Marines Chuck Hawley and a third member of this Bay Area brain trust, Jim Corenman.
Two Types Marine radar is of two types: X-band and S-band. The former is the type commonly carried aboard small boats. It operates at a frequency of about 9.4 GHz (9400 MHz) and has a wavelength of 3.2 centimeters (cm). S-band radar is used aboard large ships and operates at 3 GHz with a wavelength of 10 cm.
Ship operators generally use their X-band radar near shore because it has better resolution and can pick up smaller targets better than S-band, which is commonly preferred offshore due to its longer range and superior resistance to sea clutter.
Terms Radar reflectors are described in terms of their Radar Cross Selection (RCS) and their performance is measured in decibels (dB) relative to some reference, usually a 1m2 sphere (profile).
Tri-Lens Radar Reflector In our 1995 test, a recommended minimum average RCS of 2.5 m2 was adopted at the suggestion of GEC Marconi, maker of the Firdell Blipper reflector.
Radar reflector performance is a direct function of size, proportional to the fourth power of its linear size. Doubling a reflector’s size increases its effective area 16 times. In the 1995 report, we wrote: “As the smallest dimension of a reflector gets down to a few wavelengths of the radar signal, it quits acting as a reflector and starts to act as a lump of metal. Remember that a wavelength is 3.2 cm (1-1/4″) for X-band, and 10 cm (4″) for S-band. So, small reflectors must be looked at with a great deal of suspicion, as there really is no substitute for size.”
Besides strength of return, consistency also is critical. Many radar units are not continually monitored but set to automatically sound an alarm if a target registers three consecutive “hits.” One big hit wont alert the ship’s crew that a smaller vessel is in the vicinity.
Reflectors tested in the 1995 report included the octahedral Davis Echomaster and Emergency; the trihedral and dihedral-based Holland Yacht Equipment, Firdell Blipper, Mobri, High Gain Rotation and Cyclops; and the Luneburg lens-type Lensref. We also tested the Radar Flag, which was practically invisible.
1995 Results The top-performing reflector six years ago was the Davis Echomaster in the vertex up position with 0 heel, which registered 63% of returns above 2.5 m2. In the double-catch rain position and 20 heel, just 43% of returns were above 2.5 m2.
The Lensref has virtually no nulls; its polar plot is a virtual circle. Had the minimum average RCS been just 2.0 m2, the Lensref would have easily won with 100% of returns greater than the threshold. At 2.5 m2, however, just 30% of the returns exceeded the threshold. And this was at less than 18 heel, over which its performance fell off dramatically. A gimbaled mount was recommended.
The Tri-Lens Last year, we were contacted by Tim Rozendal of Rozendal Associates in Santee, California, asking us to test his new reflector. Tim said he has supplied more than 20,000 Luneburg lenses to the US Navy, Army, Air Force and Coast Guard. When he became interested in developing a product suitable for the recreational boating industry, he studied our 1995 SRI report and came up with two sizes of the Tri-Lens Radar Reflector. Due to computer problems at SRI, we were unable to have Rozendals Tri-Lens tested in the same anechoic chamber as the others. Instead, we directed Rozendal to Ohio State Universitys Electro Science Laboratory Compact Range. A copy of the 1995 report was supplied to OSU so that the same test protocol could be followed, and a Davis Echomaster was also tested as a control.
The Tri-Lens has a novel configuration of three modified Luneburg lens reflectors oriented about a vertical axis. It was measured only at X-band.
We asked Dick Honey to review the OSU report and interpret the data. In his summation to PS, he said the Tri-Lens shows “the uniform azimuthal response expected of Luneburg lenses, as well as the excellent tilt (heel) response expected from the design, i.e., each lens looks only into its 120 azimuthal sector so that the spherical reflector on the back of each lens can be quite large, with no aperture blocking as occurs with most single Luneburgs designed for 360 coverage. In other words there are very few narrow angular gaps in the coverage between each lens.”
At 0 heel, 90% of returns exceeded the 2.5 m2 threshold; at 20 heel 70% exceeded the threshold and at 25 heel 69%. The Tri-Lens easily outperformed all other reflectors in the 1995 test.
Honey nevertheless had criticism of the Tri-Lens.
“Our reservations,” he wrote, “are not with the angular coverage, but with the magnitude of the reflection. (This same reservation applies to virtually all passive radar reflectors on the market today!) The Rozendal reflectors use 5.25-inch diameter spheres inside a somewhat larger radome, the spheres being approximately 4.2 wavelengths across at X-band, but only 1.4 wavelengths across at S-band. This means that they may not be much better at scattering S-band radar signals back towards the radar than the average winch, and S-band may be the only radar in use on the high seas (if any).
“As mentioned in our earlier test, the radar cross-section (RCS) of similar reflectors increases as the fourth power of the size, so it would take a relatively small increase in the size of the Luneburg lens to bring the X-band RCS up to 10 square meters (m2) the minimum echoing area requirement in the latest International Standard (ISO 8729, Marine radar reflectors, sec. 5.1.1). That is, a perfect Luneburg lens 5.25 inches in diameter should have an RCS of about 2 m2 at X-band, but a lens only 40% larger or 7 inches in diameter should have an RCS of 10 m2. In addition, it would have a 2-wavelength diameter at S-band, where it might begin to reflect better than a winch. Unfortunately, this would add significantly to the weight of a Lens-based reflector, and weight is already a concern with these reflectors, relative to an octahedral reflector like a Davis Echomaster.
“Rozendal also offers a Mini-Lens reflector, which as expected given its small size, cannot compete with any reflector on the market except for the Mobri.
“Wouldnt it be great if a radar reflector could achieve an RCS of at least 10 m2 at X-band over 360 of azimuth with trivial nulls and wide tolerance for heel? Of course, it should be less than a foot in diameter, weigh little, and be ‘almost free,’ as they say in Mexico.”
In response to these criticisms, Rozendal agrees that the Mini Tri-Lens “does not perform well using the 2.5 m2 threshold.” The Mini Tri-Lens, he says, was “intended for small boats and coastal sailing. It should be mounted as high as possible, preferably on top of the mast. The mini Tri-Lens does not have a large RCS but gives a consistent return. It has three narrow dead spots. The Mobri has 16 dead spots and any octahedral will have eight dead spots. A premium must not only be put on RCS but on the consistency of the return as well. Anything that will help improve a vessel’s radar visibility is worthwhile, particularly shorthanded vessels and those without radar.”
The International Standard for Marine Radar Reflectors (ISO 8729) was revised in 1997 and came two years after our 1995 test. In addition to the section 5.1.1 noted above, there are other relevant sections. 5.1.2 requires that a reflector’s azimuthal polar diagram “shall be such that its response over a total of 240 is not less than 2.5 m2. The response shall not remain below this level over any single angle of more than 10.”
And section 5.2 states, “The performance of the reflector up to at least +/- 15 from the horizontal (the degree of heel) shall be such that its response at any inclination remains above .625 m2 over a total angle of 240.”
Rozendal asserts that “This specification was written around the performance spec of the largest Cyclops unit (it weighs approx. 22 lbs.). They claim their unit is the only passive reflector that meets ISO 8729. No aluminum octahedral reflector is technically able to meet this specification. The Tri-Lens exceeds this specification.”
The standard Tri-Lens measures about 12″ across, is 6″ high, and weighs about 5.5 lbs. It sells for $219 and the Mini version for $129. West Marine now carries them. Price includes a Mast Mount Bracket and a coupler that can be adapted to any marine antenna mount.
As for Honey’s wish for a 10 m2 RCS/360 reflector, Rozendal said he does make a large Tri-Lens using 8″ diameter lenses. It has a RCS of 10 m2 for 300 and minimal degradation when in elevation. It weighs around 15 lbs. and sells for $699.
While bigger is better when it comes to radar reflectors, there are practical limits aboard small boats. Installing a radar unit may be a skipper’s best defense against collision at sea-the idea being that the best safeguard is for you to see the other guy rather than hoping he sees you-but not everyone wants or can afford a radar set. And even then, hanging a relatively inexpensive passive reflector certainly doesn’t hurt.
Compared to the high cost of the Lensref (about $425), the Tri-Lens is a bargain. It costs more than the Davis Echomaster ($60), but outperforms it. If you’re in the market for a passive radar reflector, we recommend the Tri-Lens ( www.tri-lens.com ).
Contact- Rozendal Associates, Inc., 9530 Pathway St., Santee, CA 92071; 619/562-5596
Also With This Article Click here to view “Ranking of Reflectors.”
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Radar returns, active, passive and no reflector comparison
- Thread starter FairweatherDave
- Start date 18 Dec 2019
- 18 Dec 2019
FairweatherDave
Well-known member.
Bit of a spontaneous question prompted by the Snowflakery thread and losing power leaving Bristol docks. I have no experience of radar beyond Second World War films and I have read up a tiny amount about passive radar reflectors ie if you can deploy one you should. But I understand radar can also detect buoys. So surely a yacht will show up on a radar return without the passive radar reflector in a moderate sea state. It can get awfully technical and since I am a Solent pootler in daylight I can get away being a radar ignoramus. But on a scale of 1 to 10 if 7 was the return score for a passive radar reflector and 10 for an active radar See me device where would you put a boat without a passive radar reflector? PS I do have a passive reflector (not the octagonal rain catcher type) that I can hoist but have never seen the need to use it.
Bear in mind that many buoys have radar reflectors on them. A sailing yacht with a decent sized mast on it is a pretty good target when the mast is upright. But in a poor seastate, a reflector is generally better. A lot of variables, including the human in front of the radar screen.
But on a scale of 1 to 10 if 7 was the return score for a passive radar reflector and 10 for an active radar See me device where would you put a boat without a passive radar reflector? Click to expand...
I have read up a tiny amount about passive radar reflectors ie if you can deploy one you should. Click to expand...
GHA said: maybe 8 More seriously after the Ouzo there were tests done showing how next to useless most passive radar reflectors are. Will be on google somewhere. From the very occasional big ship people posting on sailing forums, they seem generally very happy to see yachts transmit AIS, transmit isn't such a budget killer anymore. (must get one ) Legal requirement under SOLAS v isn't it? One of the very few. Solas Chapter V - Annex 15 - Radar Reflectors Click to expand...
Serious point taken. Inevitably AIS comes up and I have AIS receive. This is already beyond my needs but is fun to have. Active radar (See Me) and AIS transmit future possibilities but overkill for what I do. The reason for posting is that for a hypothetical channel crossing I would use AIS and then radio a ship if I was concerned. At that point I would hope they could see me on their radar. In good visibility and good sailing conditions I'm not sure I would want to hoist the passive radar reflector. This is a on the sofa pipe dream scenario for me, real world practicalities of sailing far away .
Ever since the Ouzo it has seemed to me a bit rash to rely on every bl**dy big ship being enough on the ball to spot you and (assuming you are sailing and therefore stand on vessel) avoid running you down. Hence my vote for AIS receiver in the first instance - fairly cheap, easy to use and pretty obvious whether it is working or has failed. Gives you a sporting chance of keeping well out of trouble. After a dreadful crossing of the North Sea in big seas AND fog, when we were juggling with up to four ships in very close proximity, I decided it would be worth adding AIS transmitter. We never learnt how to operate the radar effectively, so it has remained switched off for several years.
Resolution said: Ever since the Ouzo it has seemed to me a bit rash to rely on every bl**dy big ship being enough on the ball to spot you and (assuming you are sailing and therefore stand on vessel) avoid running you down. Hence my vote for AIS receiver in the first instance - fairly cheap, easy to use and pretty obvious whether it is working or has failed. Gives you a sporting chance of keeping well out of trouble. After a dreadful crossing of the North Sea in big seas AND fog, when we were juggling with up to four ships in very close proximity, I decided it would be worth adding AIS transmitter. We never learnt how to operate the radar effectively, so it has remained switched off for several years. Click to expand...
I answer to the original, I would venture an answer of five. I would normally pick up yachts at around three miles on normal settings, but rain could skew the answer in favour of the reflector.
Elessar said: octohedrals correctly rigged in the “catch rain” position are better than a poke in the eye. I have a triball which is one of the better passives that can stay rigged even on a sailing boat and they work when heeled. the tube types are only better than useless when exactly upright. When of course a mast is also better than useless as a radar reflector....... Both are useless when heeled. Click to expand...
From the report, it can be seen that, although any radar reflector is better than none, the type of reflector fitted to Ouzo can theoretically produce a reasonable peak increase in the RCS but, in practice, its overall performance is poor, and it is now evident that at best there was only a 50% probability that the ship would have been able to detect Ouzo on the radar at close range. This type of radar reflector gives optimal performance when deployed in what is termed the “catch rain” orientation (Figure 12). However, if the unit is tilted even a few degrees from this orientation, the reflected energy drops very significantly, thus reducing the RCS. This type of radar reflector, although popular and widely sold, is of little benefit on board a yacht which is frequently heeled. Furthermore manufacturers are not required to supply instructions on the optimum method of deploying the unit, and most do not do so. The problem is further compounded because many of the reflectors come supplied with holes drilled for connecting to a halyard (Figure 13), which encourages the units to be hung in the incorrect orientation, 45° removed from the optimum “catch rain” position. QinetiQ Funtington’s report (Annex 4) concluded that, bearing the above factors in mind, it was unlikely that deployment of the radar reflector on Ouzo would have made very much difference to the RCS of the yacht. Click to expand...
GHA said: Not much better than a poke in the eye in any, according to the report , quite scary reading >> https://assets.publishing.service.gov.uk/media/547c7053ed915d4c10000083/OuzoReport.pdf Click to expand...
lw395 said: Funny how ships can see all those buoys with simple corner reflectors fixed on them. If you actually read and understand the whole Ouzo report, the salient point is that because the radar on a big ship is high up, it faces a challenge in seeing small, fairly close targets which are well below the horizon, in rough sea conditions. Especially when the operator is not primarily looking for said targets. It's often been said that radar works a lot better when the radar's mounted on the small boat and the big metal thing is the target. Click to expand...
matt1 said: Well, yes, isn't that the point. Radar see's Buoys because they are metal, despite being small. Not a lot of metal mass visible on a yacht....unless it's upside down ;-) Isn't GRP pretty much invisible to radar? Click to expand...
Well I have found an advert for my passive reflector. "Radar reflector for boat or yacht. Pains Wessex Marine Radar Reflector, Reflecta SC42. Very good condition. The casing is white plastic. This is a rigid spherical marine radar reflector, diameter 395mm. No brackets, there is a fixing eye top and bottom that also allows a halyard to be used. Originally described as: Robust design with tough outer casing, unique octahedral design ensure angular accuracy and smooth radar reflectivity to give guaranteed high performance. " Anyone care to share the secret or make an intelligent guess of how you hoist it to its optimal position? I've hoisted it once and it swung around like a wrecking ball despite some down haul.
This is a convoluted topic, with no straightforward and simple answers. There's a lot of 'Yes, but..... no, but'.... I'm one of the 'not very many' who had the benefit of a deeply-professional training in radar - both theory and practice - and used it daily in my day job. I believe I know enough about its strengths and limitations to make choices FOR MY PURPOSES. Thus, in daylight and/or good visibility, I rely on lookout. .... as all the professional bodies urge. In restricted visibility, I treat that as a 'hazard situation' and change my course, location and practices to address the hazard as far as I can. That doesn't include continuing as if all was well..... It isn't. AIS is a 'fit'. It adds some warning, and the possibility of avoidance action by the others. Radar is not a 'fit', for every single time I have shipped on board a sailboat with radar, no-one but myself had the faintest notion about how to make effective use of it, or even apply the relevant Colregs..... and I was long out of practice. I carry passive reflectors for use in reduced visibility. The 'teensy-weensy' octahedral jobs are no better than 'emotional support' toys. They support a deluded notion of safety, which simply makes matters even more unsafe. The SOLAS requirement is very difficult to achieve in a small boat, in a permanent installation. It is largely impracticable. Clearly, the best way to achieve a likely-sufficient Radar Cross-Sectional Area ( RCS ) - or 'reflective size' - is the fitting and use of an active radar transponder, of the SeeMe or Echomax type. The next best thing - and by a long way the best of the 'passive' devices - is the Echomax inflatable radar reflector..... which does satisfy the SOLAS requirement for RCS. I have two of these. Yes, they're a modest pain in the jaxey to inflate and string up on a signal halyard, but no more so than running up a Breton or Irish courtesy ensign. Having drifted along in dense fog, dark, and no wind in mid-Channel more than once, I know the fear of hearing big diesel engines 'somewhere nearby out there' and having no idea whether they were aware of us, or oblivious. Short of a SeeMe, my blow-ups are a damn sight better than an aluminium 'raincatcher' which I know to be bluddy useless.
To answer my own question I found this " The octohedral UPRIGHT has a higher return over a wider range of angles, than catch rain. The ARPA and clutter reduction in most radars makes consistency of return more useful than peak rcs. The 4inch tube type is v good when exactly upright. All these devices are 'not to be relied on 100%'. Do not rely on them for your survival! They are just one sensible precaution. I am a little sceptical about kinuseless's graph implying that the radr is utterly blind at a range of 4nm, perhaps a ship radar user will confirm this? It has been pointed out before that while yachts make crap radar targets, the ships that try to run us down make very good ones. So fitting the radar to the yacht might be the better option. In radar speak, a seeme is only a few dB cheaper than a radar nowadays. I think the best approach is often an AIS receiver, which puts the onus on the yacht to do the avoiding. The vessels not transmitting AIS probably won't be looking too hard at radar either. To return to the point, suspending an octo on the kite halyard, with a downhaul to corner of the transom for me. If it ends up touching the main leach, move it to the other side. " Courtesy of lw395 circa 2007. That'll do me. Thanks
I had a very tense run-in with an unidentified return in deep fog well off to the west of Cadiz. Which turned out to be a pot-mark. I've seen really quite large ships that look pretty much the same as well. I accept that I'm clearly pretty crap with it, but it does take a bit of skill to drive a radar.
johnalison said: I doubt if buoys represent a good target without a reflector. Many are rounded objects that are a bit like fishing boats like the French ones that show up no better than much smaller yachts, at least on my set. Click to expand...
- 19 Dec 2019
One of my early experiences in using my now old JRC RADAR is that it works well if it's on the correct range and tuned correctly. Back in about 2002 I came back into Poole harbour solo on a dark foggy night. At that time I didn't know the buoyage layout well and it was pre Chart Plotter so I had the RADAR on on short range and the chart to hand. I could pick up boats on their moorings, the channel buoys and markers for the small ships channel which I could follow without a problem. I have an octahedral reflector at the top of the mizzen and for peace of mind in my early days with this boat I have called up the ferry on X channel passages to ask if I was visible on their RADAR, I was, but I'm still not sure if it's the reflector or the fact that I have two aluminium pole pointing skyward and two laying horizontal! I wouldn't give you tuppence for those so called reflectors that look like a neon tube and I am suspicious of some of the ones that look like fenders, you just don't know what is inside them. Maybe I'm just an old cynic.
FairweatherDave said: To answer my own question I found this " The octohedral UPRIGHT has a higher return over a wider range of angles, than catch rain. The ARPA and clutter reduction in most radars makes consistency of return more useful than peak rcs. The 4inch tube type is v good when exactly upright. All these devices are 'not to be relied on 100%'. Do not rely on them for your survival! They are just one sensible precaution. I am a little sceptical about kinuseless's graph implying that the radr is utterly blind at a range of 4nm, perhaps a ship radar user will confirm this? It has been pointed out before that while yachts make crap radar targets, the ships that try to run us down make very good ones. So fitting the radar to the yacht might be the better option. In radar speak, a seeme is only a few dB cheaper than a radar nowadays. I think the best approach is often an AIS receiver, which puts the onus on the yacht to do the avoiding. The vessels not transmitting AIS probably won't be looking too hard at radar either. To return to the point, suspending an octo on the kite halyard, with a downhaul to corner of the transom for me. If it ends up touching the main leach, move it to the other side. " Courtesy of lw395 circa 2007. That'll do me. Thanks Click to expand...
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Installing a new radar reflector
Keep your family safe while sailing with this guide on installing a radar reflector for your boat.
Installing a New Radar Reflector
As you embark on your sailing adventure with your family, safety should always be a top priority. One essential piece of safety equipment that you should consider upgrading or installing on your boat is a radar reflector. In this comprehensive guide, we will discuss the importance of radar reflectors, the different types available, and how to properly install one on your boat.
Table of Contents
Why you need a radar reflector, passive reflectors, active reflectors, choosing the right radar reflector for your boat, mounting options, installation tips, testing your radar reflector.
A radar reflector is a device that helps make your boat more visible to other vessels’ radar systems. This is particularly important in situations where visibility is poor, such as during fog, heavy rain, or at night. By increasing your boat’s radar signature, you can significantly reduce the risk of collisions with other vessels.
In many countries, radar reflectors are required by law for certain types of boats, especially those under a specific size or those that are not made of metal. Even if it’s not a legal requirement for your boat, it’s still a wise investment to ensure the safety of your family and your vessel.
Types of Radar Reflectors
There are two main types of radar reflectors: passive and active. Each type has its own advantages and disadvantages, so it’s essential to understand the differences before making a decision.
Passive radar reflectors are the most common type and work by reflecting the radar signals emitted by other vessels back to their radar systems. They do not require any power source and are generally low maintenance. There are several different designs of passive reflectors, including:
Octahedral reflectors: These are made of metal plates arranged in an octahedral shape, which provides a strong radar reflection from all angles. They are often collapsible for easy storage when not in use.
Luneburg lens reflectors: These are spherical devices made of materials with varying refractive indices, which focus the incoming radar signals and reflect them back to their source. They are less common than octahedral reflectors but can provide a stronger reflection.
Cylindrical reflectors: These are made of metal tubes arranged in a cylindrical shape, which can provide a strong radar reflection when oriented correctly. However, their performance can be significantly reduced if they are not aligned with the incoming radar signals.
Active radar reflectors, also known as radar target enhancers (RTEs), work by receiving the incoming radar signals and then transmitting a stronger signal back to the source. This can result in a much larger radar signature than passive reflectors, making your boat more visible to other vessels.
Active reflectors require a power source, usually your boat’s 12-volt electrical system, and may also require periodic maintenance. They are generally more expensive than passive reflectors but can provide a higher level of safety due to their increased visibility.
When selecting a radar reflector for your boat, there are several factors to consider:
Size and weight: The size and weight of the reflector should be appropriate for your boat. Larger reflectors generally provide a stronger radar reflection, but they can also be more challenging to install and may create additional wind resistance.
Performance: The performance of a radar reflector is measured in square meters of radar cross-section (RCS). A higher RCS value indicates a stronger radar reflection. Look for a reflector with an RCS value that is appropriate for your boat’s size and the conditions in which you will be sailing.
Mounting options: Consider how and where you will mount the reflector on your boat. Some reflectors come with mounting brackets or can be easily attached to existing structures, while others may require additional hardware or modifications to your boat.
Budget: Radar reflectors are available at various price points, so consider your budget when making a decision. Keep in mind that investing in a high-quality reflector can provide increased safety and peace of mind during your sailing adventures.
Installing Your Radar Reflector
Once you have chosen the right radar reflector for your boat, it’s time to install it. Proper installation is crucial to ensure the reflector’s effectiveness and your safety on the water.
There are several mounting options for radar reflectors, including:
Mast mount: Mounting the reflector on your boat’s mast is a popular option, as it provides a high and central location for optimal radar reflection. This can be done using brackets or clamps designed for your specific reflector.
Shroud mount: Another option is to mount the reflector on your boat’s shrouds (the cables that support the mast). This can be done using special shroud clamps or by attaching the reflector directly to the shrouds with cable ties or other fasteners.
Radar arch mount: If your boat has a radar arch, you can mount the reflector on the arch using brackets or clamps. This provides a high and unobstructed location for the reflector.
Pole mount: If none of the above options are suitable for your boat, you can mount the reflector on a dedicated pole. This can be a fixed or removable pole, depending on your preferences and your boat’s layout.
When installing your radar reflector, keep the following tips in mind:
Height: The higher the reflector is mounted, the more effective it will be. Aim to mount the reflector as high as possible while still being accessible for maintenance and inspection.
Clearance: Ensure there is adequate clearance around the reflector so that it is not obstructed by other structures or equipment on your boat. This is particularly important for passive reflectors, which rely on a clear line of sight to incoming radar signals.
Orientation: Make sure the reflector is oriented correctly according to the manufacturer’s instructions. This is especially important for cylindrical reflectors, which need to be aligned with the incoming radar signals for optimal performance.
Secure mounting: Ensure the reflector is securely mounted to your boat using appropriate hardware and fasteners. Regularly inspect the mounting points for signs of wear or corrosion and replace any damaged components as needed.
After installing your radar reflector, it’s essential to test its performance to ensure it is providing adequate radar reflection. This can be done by asking a nearby vessel with radar to check your boat’s radar signature or by using a radar reflector tester, which is a specialized device that measures the strength of your reflector’s radar reflection.
Regularly testing your radar reflector is a good practice to ensure it is functioning correctly and providing the necessary safety benefits.
Installing a radar reflector on your boat is an essential safety measure that can significantly reduce the risk of collisions with other vessels. By understanding the different types of reflectors available, choosing the right one for your boat, and properly installing and maintaining it, you can ensure the safety of your family and your vessel during your sailing adventures.
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This is how we tested. The echo of each reflector was measured a total of eight times - from a distance of 0.5 and 1.5 nautical miles, vertically and at an angle of 30 degrees, using a modern broadband radar and a conventional magnetron radar. The displays of the broadband radars are shown in the individual test images.
Dennis O'Neill. August 23, 2012. 0 shares. Yachting Monthly finds out. We looked at 10 radar reflectors - from £15 and £499 - testing them in a lab and at sea. The results, as Toby Hodges discovered, were startling. Click here to download the article.
By The Rigging Company July 7, 2015. A radar reflector is used to help make your vessel more identifiable by other boats and ships that use radar to scan for vessels as well as other obstructions. In the world of radar reflectors there are many, many options. For sailboats the options are narrowed down a bit, but there is still much controversy ...
1995 Tests. West Marine tested radar reflectors in 1995, lead by Chuck Hawley along with experts Stan Honey, Dick Honey and Jim Corenman. Although 1995 was a long time ago, the tests are still relevant and interesting, because just about all of the products and technology are unchanged. Download the 1995 Radar Reflectors Test.
We tried it out as a comparison with a traditional reflector using a boat with radar on board and found that the flag was just as good (and doubles as a flag too!). We first tried it on a pole off the stern and it "painted" well. ... I have also seen numerous reviews which consistently placed the Davis among the best of the reflectors. Carl and ...
Whereas he had not been visible on my radar up to that point, as soon as the reflector was on deck his boat showed a strong return blip. This was on a 33 foot sloop. This was on a 33 foot sloop. I do believe the testing that shows that a typical sail boat has a very unreliable return.
IStream. 545 posts · Joined 2013. #2 · Apr 7, 2014. The effective range of your reflector to another radar is the analogous to the range you'd get from your own radar antenna looking for returns from a target: range (nautical miles) = 1.25 * sqrt (height in feet) Not to be glib, but the higher the better.
For a radar dead abeam, the elevation angle is your vessel's angle of heel; for a radar dead ahead or astern, the elevation angle is your vessel's pitch angle. A complete characterization of a radar reflector includes the RCS at all bearing angles, or azimuths from 0° to 360° and all elevations angles from -90° to +90° - although a ...
Tri-Lens Radar Reflector In our 1995 test, a recommended minimum average RCS of 2.5 m2 was adopted at the suggestion of GEC Marconi, maker of the Firdell Blipper reflector. ... Latest Sailboat Review. Sailboat Reviews. The PDQ 32 Cruising Cat Used Boat Review. September 25, 2024.
Radar reflectors can be mounted to the masts of boat cabins as well. To start to make sense of this, we need to delve into a bit of radar history, and have a rudimentary understanding of how it works. In 1904 a patent for "an obstacle detector and ship navigation device," was issued - this device used radio echoes to determine the approximate bearing of objects
3971 posts · Joined 2000. #9 · Apr 26, 2012. I use radar quite often here in the PNW and sailboats without reflectors invariably are weak targets. It's counter intuitive that with a big tall aluminum mast and all the SS rigging that it wouldn't make for a good reflector but the fact is that they don't show up very well.
41,951. Visit site. Bear in mind that many buoys have radar reflectors on them. A sailing yacht with a decent sized mast on it is a pretty good target when the mast is upright. But in a poor seastate, a reflector is generally better. A lot of variables, including the human in front of the radar screen. 18 Dec 2019.
Installing a radar reflector on your boat is an essential safety measure that can significantly reduce the risk of collisions with other vessels. By understanding the different types of reflectors available, choosing the right one for your boat, and properly installing and maintaining it, you can ensure the safety of your family and your vessel ...
I'll jump in. A radar reflector is a dirt-cheap way to increase your chances of being seen. I have a Davis one fixed at the masthead where it can't be shielded by sails, and whenever I radio a ship to ensure we're not going to exchange hull paints, they've already seen me. It is not a substitute for careful and constant vigilance, but it is a big help and enormous peace of mind.
As far as I know, all the radar reflectors you can buy for a yacht are somewhere between poor and better than nothing. But it's only as far as I know. The last major test I can think of was done ...
Radar is more expensive than AIS, but you may wish you'd taken the plunge when the visibility closes in amid busy waters. TAGS: electronics gear Instruments knowledge radar. All of us are keen to avoid collisions and to be aware of what other vessels might be in the vicinity. We all try to maintain a good watch, but looking out on a drizzly ...
paulk. 5664 posts · Joined 2000. #4 · Jul 28, 2008. US Sailing and the RORC have both performed tests on radar reflectors. Both sets of tests seem to indicate that the Davis type, (round interlocking panels that create "pockets") mounted in a "catch rain" position is among the most effective passive reflectors available.
Two weeks ago, in broad daylight, I had a Catalina 38 motor past me with its Davis radar reflector up above its spreaders, in plain unobstructed view of my radar. You can see the boat, less than 1/4 mile away, on my port bow as the yellow blob. By contrast, you can see a buoy with its own reflectors (admittedly more than the Davis) in the upper ...
For radar reflectors with an RCS of 2m2 and above the probability of being tracked inside 2nm increases significantly. With a radar reflector of RCS of at least 4m2 50% probability of detection is achieved beyond 10nm from 4.5nm. Probabilty of detection by a X-Band 25kW radar of various RCS target sizes. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% ...
The Maritime and Coastguard Agency has updated its guidance and is urging all owners of boats under 15m/49.2ft to fit a radar reflector. All boats less than 15m/49.2ft and under 150 gross tonnage should permanently carry a radar reflector. according to the Maritime and Coastguard Agency. Credit: Graham Snook/Yachting Monthly. The Maritime and ...
July 2006, Block Island Sound is enveloped in patchy fog, two radar-equipped sailboats pass within 20 feet after failing to detect each other despite calm waters. Neither vessel had a radar reflector hoisted. July 2009, chaos on Block Island Sound as fog descends on hundreds of recreational boaters, skippers constantly calling out on VHF 9 & 16 in attempts to avoid collision. A ferry and a ...
Previous work established fundamental bounds on subwavelength resolution for the radar range resolution problem, called superradar [Phys. Rev. Appl. 20, 064046 (2023)]. In this work, we identify the optimal waveforms for distinguishing the range resolution between two reflectors of identical strength, leveraging results in quantum metrology. We discuss both the unnormalized optimal waveform as ...