Passive Radar Reflectors - Not a Troll!

emsworthy

emsworthy

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Hopefully less contentious than asking a question about anchors!:)

Whilst the mast is down, we want to replace the old dihedral (?) rain catcher reflector, which is mounted on the backstay, with something a little more effective and modern.

As most of our sailing will be in the busy Solent I'd like the peace of mind that a decent passive reflector will bring without the expense and electrical drain of an active one. Am I right in saying all yachts should be fitted with one by law?

I've heard conflicting views on what seem to be the two most popular; the Blipper and the Echomax and have heard that the "tube" style one are pretty ineffective. Any suggestions from this august body?

Many thanks.
 
This months issue of Sailing Today has a test in which it concludes that passive reflectors work up to 7 miles. The best was the Echomax EM230 which just beat the Tri-Lens, the Blipper 210-7 and the Echomaster octahedral.
 
Thanks.

Thanks for that.

Having just scan read it I'm pretty sure this is where I got most of my information from before.

The one I forgot is the tri-lens type but IIRC they weigh about 5.5kg which I'm not sure I fancy wanging around above the spreaders on a yacht of only 26'. Would it make much difference to stability to have that weight a fair way up the mast?

Looking aside the technical stuff, I'm tempted to go for the Echomax. Any real world experience of this one?
 
One part of the SOLAS regs requires you to carry a radar reflector if its possible to do so.

Radar reflectors are like mirrors for radar - they cant reflect more radar waves back to the ship looking for you than hits the reflector in the first place so SIZE MATTERS! Radar reflector design is then about getting the reflector sending back even a decent part of the signal that hits it - after all, the reflector has to work through 360 deg horizontally and maybe 40 deg vertically so it cant just be a disch pointing towards the big ship.

The active radar reflectors only use 40ma or so on standby which is about the same as your GPS
 
emsworthy said:
Hopefully less contentious than asking a question about anchors!:)
As most of our sailing will be in the busy Solent I'd like the peace of mind that a decent passive reflector
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I dont want to put you off installing a good radar reflector, but please dont be fooled into thinking people in the Solent are looking at their radar screens! You'll be lucky if they are looking where they are going!
 
emsworthy said:
I'm tempted to go for the Echomax.
Click to expand...

Not many would try to dissuade you. However, as mentioned above, the QinetiQ report is a fairly useful guide. It is important to the 'peace of mind' you seek that you have a sound understanding of what is, and is not, happening when you rely on even the best passive reflector on a small vessel.

Firstly, the 'Equivalent Echoing Area' presented by such devices is very small, by any standards, and various reliable authorities consider that an 'EEA of at least 10sq.m.' is necessary. That's effectively impossible, on a small boat, using a passive reflector at its optimum orientation.

Next, that optimum orientation is very rarely presented to the ( sweeping ) radar transmissions of an approaching vessel, for your boat will be heeled, pitching, and yawing all the time. So only a little of the Radar Frequency energy hits your device and gets bounced back, and only a little of the time.

Further, if you are in lumpy seas or worse, your device may be effectively screened for part of the time, while you are down in the troughs - or the approaching vessel is. Or both.

Next, there is the issue of sea clutter. This is the display of RF returns from the steep faces of breaking seas. Such reflections can be/are quite large, masking your little reflector's return.

They are also intermittent, in that they don't persist in the same place. Many shipping radars' circuitry is designed to suppress returns that do not recur several times in the same place. That includes your weak return, bobbing and weaving and disappearing irregularly.

Next, in conditions of strong sea returns ( say, F5 and more ), many operators will deliberately suppress those strong returns so that they have more chance of spotting a small but regular return, such as a <30' vessel fishing, pilots' launches, and such. That 'suppression' is likely to include your weak, intermittent and irregular return just when you want it to be spotted.

Also, many ARPA sets will not even process and display your radar return if it is weaker than the threshold that set is configured for, or it isn't there on X number of consecutive sweeps.

Finally, it is an act of faith that someone on the approaching vessel will both see, note and do something helpful about your radar return. That's been shown, many times and tragically, to be misguided.

But certainly, one of the better passive devices is better than nothing. But do not believe, even for a moment, that its presence is justification for 'peace of mind'.

One of the other 'passive devices' that we need to consider is the 'third-world' bridge watchkeeper on a fast container vessel, with purchased Singaporean certificates and the 'sea clutter suppression' turned right up to avoid radar alarms and the need to do anything ( "I didn't see it" is one of the first excuses they learn ). Then there's the exhausted watchkeeper who has fallen asleep in his chair, while the autopilot gets on with the job ( all carefully discussed, and regularly, in the MAIB's Accident Reports )

Radar needs an active, responsible brain to interpret it. At each end of the process.

'Fear is natures' way of getting your attention'

But what do I know.....?

:)
 
Excellent replies and very useful.

Not quite what I was expecting but very enlightening (if not downright bl**dy scary) nonetheless.

Having worked in defence electronics many-many moons ago, all of Bilbo's words make absolute sense and serve as a reminder that it's probably best to assume the worst case scenario and if the technology works all the better! But nothing can beat a good pair of eyes.

I think I might spend the money on an enormous foghorn and some night vision goggles!:p
 
I'll concur with that - I can't see much point of AIS or Radar within the solent for "normal" sailing - whilst the ferries and commercial will operate radar, you still have to keep clear of the big stuff, and the ferries are easy to spot and keep clear of.

Unless you intend to sail at night and/or fog then IMHO a radar reflector isn't really much use within the confines of the solent.
 
I'll concur with that - I can't see much point of AIS or Radar within the solent for "normal" sailing - whilst the ferries and commercial will operate radar, you still have to keep clear of the big stuff, and the ferries are easy to spot and keep clear of.

Unless you intend to sail at night and/or fog then IMHO a radar reflector isn't really much use within the confines of the solent.
 
galadriel said:
I dont want to put you off installing a good radar reflector, but please dont be fooled into thinking people in the Solent are looking at their radar screens! You'll be lucky if they are looking where they are going!
Click to expand...

I agree, if I sailed exculsively in the solent I would hoist one after dark, but wouldn't fit one permanently as it's all done by eyeball there.
 
I have a Cyclops 1 fitted to Snark. Along with the tri-lens they are the only reflectors to give a consistent return, irrespective of attitude ( pitch, yaw, heel and direction). I know mine works at 7miles off Barfleur in poor conditions (Thanks Brittany Ferries).
 
As the Cyclops was concieved by DERA, and developed together with their Radar testing facility at Funtington (now ownerd and operated by QinetiQ), I don't know why it wasn't included in the Study.
 
emsworthy said:
... I'm tempted to go for the Echomax ...
Click to expand...

Current boat has a Firdel Blipper (on the boat when we bought it). Looking at the test results I struggle to see what it gains me over a decent octahedral reflector (I'm looking at the figures for 15-20° of heel). If I were to be buying new, I don't think I could justify the difference in cost (£100+).

As a aside: An active transponder is undoubtedly a powerful string to your bow, but IMHO it should be additional to a passive reflector, not a substitute.

Andy
 
recently I was looking at boats on radar in a fairly lumpy sea off the lizard and all were showing OK with the gain set to offshore to minimise sea clutter, my suspicion is that if you've got the reflector set properly you'll be visible .. and you probabably will in a boat anyway .. unless you're a rib or sumfink like that
 
Why replace the "rain catcher"? It meets the IMO legal requirement and in itself is not a bad piece of kit. Meantime save up for an active responder to which I personally would give high priority. Bilbobaggins is quite right: an ARPA radar needs consistent tracking to activate the auto detect facility and to achieve this you need a See Me or similar.
 
radar return

crossing Biscay last year, 40ft with passive reflector,called up container ship 4 miles off port bow.
Me : Vessel X,IN POSITION Y ,THIS IS YACHT Z, ARE YOU AWARE OF MY PRESENCE.
HIM: I THINK YOU MAKE MISTAKE,NO VESSEL IS WITHIN 7 MILES OF MY POSITION.
ME: PLEASE CHECK FROM YOUR STARBOARD BRIDGE WING
HIM: AHHH---- YES, I SEE YOU NOW,YOU ARE VER' SMALL!



Suspect radar was off( visibility WAS good) . To be fair he rsponded fairly quickly.
 
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