simon_sluggett
Well-Known Member
Does a radar up the mast ,when switched on, act as a radar reflector to other vessels using radar ?
radar reflector- is it still needed if you have radar fitted.
- Thread starter simon_sluggett
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sarabande
Well-Known Member
It would be possible to build a radar reflector in or, more likely, onto to the framework / shroud of the radar scanner (the rotating bit).
AFAIK the reflecting area, orientation and rotation of the scanner means that the chance of 3rd party's beam being reflected from the scanner itself, are very small.
I can envisage a radome of twice the normal height, with the "upper storey" being a passive reflector.
AFAIK the reflecting area, orientation and rotation of the scanner means that the chance of 3rd party's beam being reflected from the scanner itself, are very small.
I can envisage a radome of twice the normal height, with the "upper storey" being a passive reflector.
Divemaster1
Well-Known Member
[ QUOTE ]
Does a radar up the mast ,when switched on, act as a radar reflector to other vessels using radar ?
[/ QUOTE ]
No!
At very rare occations the beams will meat each other and you'll gen an inteferrence, but not as a "norm" ... those times you get the inteferrance are the only indication that another vessel (somewhere) is operating a radar. Having a radar your self is not a replacement for a reflector. The rules still expect to see a radar reflector.... irrespective of Radar, AIS transmitter etc. You could argue that an AIS transmitter is better than a reflector, but IMO have not reached this conclusion yet ...
Does a radar up the mast ,when switched on, act as a radar reflector to other vessels using radar ?
[/ QUOTE ]
No!
At very rare occations the beams will meat each other and you'll gen an inteferrence, but not as a "norm" ... those times you get the inteferrance are the only indication that another vessel (somewhere) is operating a radar. Having a radar your self is not a replacement for a reflector. The rules still expect to see a radar reflector.... irrespective of Radar, AIS transmitter etc. You could argue that an AIS transmitter is better than a reflector, but IMO have not reached this conclusion yet ...
sheeplove
Active Member
I can't see what all the fuss is about with radar reflectors. I think they're unnecessary. My last boat had a "nothing special" Raytheon radar which picked up anything solid including small plastic mooring buoys etc. You just need to get practiced with tuning the thing...
macd
Well-Known Member
"You just need to get practiced with tuning the thing"
That would be hugely reassuring if everyone was -- and if they kept a fastidious radar watch.
That would be hugely reassuring if everyone was -- and if they kept a fastidious radar watch.
Barr Avel
Well-Known Member
Reflectors exist so that other can see you. That means that how good you are at tuning your own radar is irrelevant. Do you really think that ships in the Channel will be adjusting their radars to try to pick small signatures from yachts?
Marc.
Marc.
Divemaster1
Well-Known Member
I agree.... to acertain degree ....but the IMO apparently does not.... so to satify the regs., I have a £20 one fixed ...
Cheap, cheerful and meets the regs... and on top of it is a good performing reflector.
Sultans_Kapitein
RIP
If you are out in the channel, and there is a bulk carrier bearing down on you, you will think radar reflectors are an essential bit of kit.
sheeplove
Active Member
[ QUOTE ]
.That means that how good you are at tuning your own radar is irrelevant.
Marc.
[/ QUOTE ]
Not so sir! A reflector merely increases reflection. It is still necessary to tune clutter etc for radar to perform.
.That means that how good you are at tuning your own radar is irrelevant.
Marc.
[/ QUOTE ]
Not so sir! A reflector merely increases reflection. It is still necessary to tune clutter etc for radar to perform.
Barr Avel
Well-Known Member
Yes but the big ships' radar will be tuned to highlight other big ships. Therefore as a yacht you need to do everything you can to increase your own radar reflection. A reflector is therefore a vital piece of equipment.
Marc.
Marc.
G
Guest
Guest
[ QUOTE ]
Does a radar up the mast ,when switched on, act as a radar reflector to other vessels using radar ?
[/ QUOTE ]
Putting it simply .... No.
The only time YOUR Radar will indicate to another is if they have a Radar Watchman or similar.
Does a radar up the mast ,when switched on, act as a radar reflector to other vessels using radar ?
[/ QUOTE ]
Putting it simply .... No.
The only time YOUR Radar will indicate to another is if they have a Radar Watchman or similar.
Richard10002
Well-Known Member
[ QUOTE ]
Does a radar up the mast ,when switched on, act as a radar reflector to other vessels using radar ?
[/ QUOTE ]
1) No!
2) even if it did, who has their radar on 24/7?
Does a radar up the mast ,when switched on, act as a radar reflector to other vessels using radar ?
[/ QUOTE ]
1) No!
2) even if it did, who has their radar on 24/7?
G
Guest
Guest
[ QUOTE ]
I can't see what all the fuss is about with radar reflectors. I think they're unnecessary. My last boat had a "nothing special" Raytheon radar which picked up anything solid including small plastic mooring buoys etc. You just need to get practiced with tuning the thing...
[/ QUOTE ]
I disagree with you about being unnecessary. But I also consider that a lot of cr*p is spoken about how good they are.
The old metal rain-catcher has been around for yonks and IMHO is still a leading contender against all these new fangled clutter on mast.
As to another saying " rules" ......... apart from special rules such as specs for racing classes offshore / RORC etc. - where does it "Rule" that you must have one ?? It is reccommended - not compulsory.
I can't see what all the fuss is about with radar reflectors. I think they're unnecessary. My last boat had a "nothing special" Raytheon radar which picked up anything solid including small plastic mooring buoys etc. You just need to get practiced with tuning the thing...
[/ QUOTE ]
I disagree with you about being unnecessary. But I also consider that a lot of cr*p is spoken about how good they are.
The old metal rain-catcher has been around for yonks and IMHO is still a leading contender against all these new fangled clutter on mast.
As to another saying " rules" ......... apart from special rules such as specs for racing classes offshore / RORC etc. - where does it "Rule" that you must have one ?? It is reccommended - not compulsory.
srm
Well-Known Member
Two things:
1 A running radar will not act as a reflector - as said above you may get interference if both sets transmit on the identical frequency, but this does not give a range and bearing. However, most modern sets have interference rejection software to erase such returns from your display.
2 In response to Blowhorner: I have picked up seagulls and plastic buoys with my radar on a flat calm sea. I have also failed to pick up a number of yachts at less than 1 mile in a flat calm sea. (Given that I train MN officers in the use of radar I do have a basic understanding of correctly setting up a radar set). I can only assume Blowhorner's experience is based on a flat calm and he has yet to discover how sea reflections and rain can obliterate all but the strongest returns on his radar display.
Fortunately, we are still free to do as we like with our own (no commercial use) boats but given the well publicised cases of yachts disapearing without trace I would suggest a radar reflector is absolutely essential. Indeed SOLAS regulations now require a radar reflector on small vessels.
Personally, I carry two reflectors permanently mounted. A Firdel Blipper high on the front of the mast and the larger Firdell Pentland on the aft face of the radar mast. Each covers the areas that would otherwise be in shadow or blind sectors for the other reflector.
Do they work? Well the majority of ships in open water pass with a CPA of 1 mile which means they have plotted me and made a course adjustment at a range of three to five miles.
Hope these comments are of help.
1 A running radar will not act as a reflector - as said above you may get interference if both sets transmit on the identical frequency, but this does not give a range and bearing. However, most modern sets have interference rejection software to erase such returns from your display.
2 In response to Blowhorner: I have picked up seagulls and plastic buoys with my radar on a flat calm sea. I have also failed to pick up a number of yachts at less than 1 mile in a flat calm sea. (Given that I train MN officers in the use of radar I do have a basic understanding of correctly setting up a radar set). I can only assume Blowhorner's experience is based on a flat calm and he has yet to discover how sea reflections and rain can obliterate all but the strongest returns on his radar display.
Fortunately, we are still free to do as we like with our own (no commercial use) boats but given the well publicised cases of yachts disapearing without trace I would suggest a radar reflector is absolutely essential. Indeed SOLAS regulations now require a radar reflector on small vessels.
Personally, I carry two reflectors permanently mounted. A Firdel Blipper high on the front of the mast and the larger Firdell Pentland on the aft face of the radar mast. Each covers the areas that would otherwise be in shadow or blind sectors for the other reflector.
Do they work? Well the majority of ships in open water pass with a CPA of 1 mile which means they have plotted me and made a course adjustment at a range of three to five miles.
Hope these comments are of help.
bedouin
Well-Known Member
[ QUOTE ]
The old metal rain-catcher has been around for yonks and IMHO is still a leading contender against all these new fangled clutter on mast.
As to another saying " rules" ......... apart from special rules such as specs for racing classes offshore / RORC etc. - where does it "Rule" that you must have one ?? It is reccommended - not compulsory.
[/ QUOTE ]
They are now (pretty well) compulsory for new boats (as of SOLAS V - given the way it is interpreted in this country).
The principles of passive radar reflection are fairly straightforwards - indeed the old octohedral reflectors are good at certain angles - but have rather worryingly wide sectors of null or low reflection. The firdell/ echomax type are pretty well just an array of small octohedral types offset so that the highs of one counter the nulls of the other. However in both cases they are fundamentally limited by the size (cross sectional area).
Nothing that has a smaller physical cross sectional area than the conventional type can possibly work acceptably.
The old metal rain-catcher has been around for yonks and IMHO is still a leading contender against all these new fangled clutter on mast.
As to another saying " rules" ......... apart from special rules such as specs for racing classes offshore / RORC etc. - where does it "Rule" that you must have one ?? It is reccommended - not compulsory.
[/ QUOTE ]
They are now (pretty well) compulsory for new boats (as of SOLAS V - given the way it is interpreted in this country).
The principles of passive radar reflection are fairly straightforwards - indeed the old octohedral reflectors are good at certain angles - but have rather worryingly wide sectors of null or low reflection. The firdell/ echomax type are pretty well just an array of small octohedral types offset so that the highs of one counter the nulls of the other. However in both cases they are fundamentally limited by the size (cross sectional area).
Nothing that has a smaller physical cross sectional area than the conventional type can possibly work acceptably.
Bergman
Well-Known Member
I have never owned a car with a radar reflector fitted yet the police radar machines seem to manage to work perfectly well - and they have a lot less power than even a yacht radar.
Perhaps also worth a thought about how much time and effort and cash the Yanks put into making aeroplanes that didn't show up on radar.
Seems strange to me that some crumpled up bacofoil stuffed in an old fender is supposed to give a better radar reflection than a 40ft long aluminium mast, a 15 ft long aluminium boom and a couple of hundred meters of stainless wire rope.
Particularly if you consider the "reflector" is enclosed in a Faraday cage formed by aforementioned ss wire .
Perhaps also worth a thought about how much time and effort and cash the Yanks put into making aeroplanes that didn't show up on radar.
Seems strange to me that some crumpled up bacofoil stuffed in an old fender is supposed to give a better radar reflection than a 40ft long aluminium mast, a 15 ft long aluminium boom and a couple of hundred meters of stainless wire rope.
Particularly if you consider the "reflector" is enclosed in a Faraday cage formed by aforementioned ss wire .
srm
Well-Known Member
[ QUOTE ]
Yes but the big ships' radar will be tuned to highlight other big ships. Therefore as a yacht you need to do everything you can to increase your own radar reflection. A reflector is therefore a vital piece of equipment.
[/ QUOTE ]
The problem is "sea clutter". This is returns from the faces of waves.
On a big ship the radar will be mounted about 17 metres above the sea. This height is a compromise between range (a commercial radar will have range scales out to 46 miles) and the area around the ship which will be effected by sea clutter. The higher the radar scanner the further out sea clutter will extend.
In open water and a F4 wind sea clutter returns are likely to extend 1 to 2 miles out from the ship. The bigger the seas the further out sea clutter will extend and you will merge into the background noise.
Sea clutter can be reduced by a variable gain control, BUT it reduces all returns within this area. Basically, if you are within 2 miles of a ship you will probably be invisible on radar unless you have a radar transponder or a very good reflector.
Also, most ships use ARPA which requires a consistent return from your vessel for the radar to stay locked on - if they do detect you at all that is. The odd strong blip is not good enough.
There is nothing personal here guys - its just physics.
As far as small boats are concerned our only safe approach is to sail defensively, which is why I use two radar reflectors and keep a radar watch in anything other than very good visibility.
Have fun.
Yes but the big ships' radar will be tuned to highlight other big ships. Therefore as a yacht you need to do everything you can to increase your own radar reflection. A reflector is therefore a vital piece of equipment.
[/ QUOTE ]
The problem is "sea clutter". This is returns from the faces of waves.
On a big ship the radar will be mounted about 17 metres above the sea. This height is a compromise between range (a commercial radar will have range scales out to 46 miles) and the area around the ship which will be effected by sea clutter. The higher the radar scanner the further out sea clutter will extend.
In open water and a F4 wind sea clutter returns are likely to extend 1 to 2 miles out from the ship. The bigger the seas the further out sea clutter will extend and you will merge into the background noise.
Sea clutter can be reduced by a variable gain control, BUT it reduces all returns within this area. Basically, if you are within 2 miles of a ship you will probably be invisible on radar unless you have a radar transponder or a very good reflector.
Also, most ships use ARPA which requires a consistent return from your vessel for the radar to stay locked on - if they do detect you at all that is. The odd strong blip is not good enough.
There is nothing personal here guys - its just physics.
As far as small boats are concerned our only safe approach is to sail defensively, which is why I use two radar reflectors and keep a radar watch in anything other than very good visibility.
Have fun.
bedouin
Well-Known Member
[ QUOTE ]
Seems strange to me that some crumpled up bacofoil stuffed in an old fender is supposed to give a better radar reflection than a 40ft long aluminium mast, a 15 ft long aluminium boom and a couple of hundred meters of stainless wire rope.
[/ QUOTE ]
that's physics for you.
Radar reflectors are the radio equivalent of catseyes and the reflector on the back of your car. Have you never noticed how much brighter the reflector on the back of a car looks when illuminated from your position?
Seems strange to me that some crumpled up bacofoil stuffed in an old fender is supposed to give a better radar reflection than a 40ft long aluminium mast, a 15 ft long aluminium boom and a couple of hundred meters of stainless wire rope.
[/ QUOTE ]
that's physics for you.
Radar reflectors are the radio equivalent of catseyes and the reflector on the back of your car. Have you never noticed how much brighter the reflector on the back of a car looks when illuminated from your position?
srm
Well-Known Member
[ QUOTE ]
Particularly if you consider the "reflector" is enclosed in a Faraday cage formed by aforementioned ss wire .
[/ QUOTE ]
If your rigging wires are close enough to block 3 cm wavelength pulses they would make very good radar reflectors. Might capsize the boat in a light breeze though as the weight of SS wire will probably exceed that of the keel and hull. /forums/images/graemlins/smile.gif
Particularly if you consider the "reflector" is enclosed in a Faraday cage formed by aforementioned ss wire .
[/ QUOTE ]
If your rigging wires are close enough to block 3 cm wavelength pulses they would make very good radar reflectors. Might capsize the boat in a light breeze though as the weight of SS wire will probably exceed that of the keel and hull. /forums/images/graemlins/smile.gif
macd
Well-Known Member
"I have never owned a car with a radar reflector fitted"
Oh, but you have. Some years ago I did extensive research with police radar guns (in a partially successful attempt to devise a 'stealth' motorcycle). The headlights proved to be very capable radar reflectors.
Oh, but you have. Some years ago I did extensive research with police radar guns (in a partially successful attempt to devise a 'stealth' motorcycle). The headlights proved to be very capable radar reflectors.