Not really. Your radar is sending out a signal that is rotating in a horizontal plane to the water and it's setup to detect return signals from the same direction as it is transmitting. Ditto for the other guy's radar. Occasionally, the rate of rotation of yours and his is such that they are pointed at each other but that doesn't happen too often. When it does, you typically see a line on the screen that's the vector between his boat and yours. When they are not in line, all you get is the reflection of your radar from his boat and vice versa.ssobol":2bvmtrk0 said:
Radar Reflector
- Thread starter bridma
- Start date
Any metal will give some echo--if you lined the interior with aluminum foil it would help. Roger gives a good explaination of the two Radars. The Radar sitting is very little area.
The reason that a radar reflector works well, is that it is designed to give far more surface area than presents to the radar beam as it first hits it. The Reflector is mounted in what is called the "Double Rain catch" position--that is with one of the "hollows", formed by the 3 pieces of metal directly up. This causes the radar beam which comes in from the side to bounce between the 3 pieces of metal and give a far larger echo than just the single sheet of foil or aluminum. There are some "Lens" type of reflectors--often encased in fiberglass which are more streamlined, less likely to be caught in the rigging and actually better reflectors.
On our largest boat we had a Firdell Blipper (now called Echo Master) about 45 feet off the water, and a research vessel could "see" us well at 13 miles.
See:
For the ferry's and commercial traffic, I would certainly equip my boat with AIS --a receiver at the least.
http://www.davisnet.com/product_documents/marine/manuals/00155-010_IM_00152_153_157.pdf
This is the manual for the Davis Echo master--lots of good information!
The reason that a radar reflector works well, is that it is designed to give far more surface area than presents to the radar beam as it first hits it. The Reflector is mounted in what is called the "Double Rain catch" position--that is with one of the "hollows", formed by the 3 pieces of metal directly up. This causes the radar beam which comes in from the side to bounce between the 3 pieces of metal and give a far larger echo than just the single sheet of foil or aluminum. There are some "Lens" type of reflectors--often encased in fiberglass which are more streamlined, less likely to be caught in the rigging and actually better reflectors.
On our largest boat we had a Firdell Blipper (now called Echo Master) about 45 feet off the water, and a research vessel could "see" us well at 13 miles.
See:
For the ferry's and commercial traffic, I would certainly equip my boat with AIS --a receiver at the least.
http://www.davisnet.com/product_documents/marine/manuals/00155-010_IM_00152_153_157.pdf
This is the manual for the Davis Echo master--lots of good information!
Actually, the radar reflector works by sending the radar signal back straight back to the receiver. Radar waves travel in straight lines (not 100% true, but close enough). By having 3 surfaces at right angles, no matter where the beam comes in, it will bounce between the surfaces and go back out 180 degrees from the input angle.
Since the radar signal is directed back to the receiver, more of the signal returns and you get better radar return than from a beam that is diffused in multiple random directions. It that case only a fraction of the outgoing wave is reflected back to the receiver.
Since the radar signal is directed back to the receiver, more of the signal returns and you get better radar return than from a beam that is diffused in multiple random directions. It that case only a fraction of the outgoing wave is reflected back to the receiver.
Hello, just a word on radar reflectors from Fan-C-Dory (C-Dory 25). We skipped the radar reflector for a radar transponder. The C-Dory has a very low profile, which makes it a real challenge to get the reflector any significant height above the water line. The advantage of the radar transponder (trade mark, SEA ME) is that it receives the x band radar energy and steps it up and sends it back out in the same direction it had received it. You appear much larger than your raw profile; you show up on ARPA sooner and stay longer. I have had commercial ships at night offshore do 30 degree right radar turns on my vessel 8 to 12 nautical miles away. The stand by mode and transmit mode only require milliamps dc power. The only draw back is the SEA ME retails for about $400 us. It is available thru the internet from an electronic company based in the U.K.
There is a product which is legal in the US (FCC approved), as about 3x the response of the See-Me and is available thru Defender: http://www.defender.com/product.jsp?pat ... id=2025484 @ $599.
and will probably be cheaper than the US See Me (which runs in the $650 currently, plus shipping).
There are issues with the in-expensive radar transponders. You should really have both X and S band--in this case the price steps up to close to $900. There is a saturation point and the transponder transmitter cannot respond fast enough if there are multiple radars in the same area. Panbo has reviewed these products in the past:
http://www.panbo.com/archives/2009/08/echomax_rte_looks_great_but_what_about_usa.html
S Band radar (much lower frequency) is used more in the rain and heavy fog by commercial ships, and does not trigger the X only transponders. Also the broad band radars we are seeing more of do not trigger either of these (X or S) band transponders.
You can now buy a Class B AIS transponder for less than $450! This gives you both the transmitter (some disadvantages of a Class B--but a Class A will run over $1000, and many on up from there), As well as a receiver.
If I was going to buy an Active transponder I would go with the EchoMax Active X/S, But I just seem to get by with an AIS receiver (part of my SR radio, which cost less than $300, including the loud hailer function).
Unfortunately many ships shut down their radar (and perhaps AIS) when at sea--but for the most part C Dorys don't go offshore to where this happens.
and will probably be cheaper than the US See Me (which runs in the $650 currently, plus shipping).
There are issues with the in-expensive radar transponders. You should really have both X and S band--in this case the price steps up to close to $900. There is a saturation point and the transponder transmitter cannot respond fast enough if there are multiple radars in the same area. Panbo has reviewed these products in the past:
http://www.panbo.com/archives/2009/08/echomax_rte_looks_great_but_what_about_usa.html
S Band radar (much lower frequency) is used more in the rain and heavy fog by commercial ships, and does not trigger the X only transponders. Also the broad band radars we are seeing more of do not trigger either of these (X or S) band transponders.
You can now buy a Class B AIS transponder for less than $450! This gives you both the transmitter (some disadvantages of a Class B--but a Class A will run over $1000, and many on up from there), As well as a receiver.
If I was going to buy an Active transponder I would go with the EchoMax Active X/S, But I just seem to get by with an AIS receiver (part of my SR radio, which cost less than $300, including the loud hailer function).
Unfortunately many ships shut down their radar (and perhaps AIS) when at sea--but for the most part C Dorys don't go offshore to where this happens.
colbysmith
Active member
Been thinking about this. Maybe for those of us that have radar, we don't need the radar reflectors or transponders. Just STAY OUT OF THE WAY, of targets we are picking up. I don't know about other radar units, but I've got an old black and white RayMarine that picks up a small flock of birds at about 1/2 mile. Also picks up fiberglass sailing vessels (small) and even local lake channel buoys that I don't think have any metal or reflectors on. Colby
Echomax looks like it's the KING of RTE's! I bought my first Sea Me in 2003 and my present Sea Me for my C-Dory several years ago. Perhaps if I did my homework I would of upgraded to the Echomax. All ships are required to have X band radar and operating, according to IMO rules. I think the S band is an option, however I am not 100 percent sure? We have the A mode AIS, along with HD radar, so the RTE is of limited use. If I were to replace the RTE I would go with the X/S model, it makes sense to be more visible to the S band set during heavy precipitation. The overload situation sounds interesting, however I am not sure if I have experienced it. The areas I operate at night and in low visibility has limited commercial traffic. When I talked to the commercial tugs on ch13, they say they have no problem seeing me on radar. Most of these operators do not have AIS, so the earlier detection on their radar is a nice advantage. However, I am always the one making the course corrections, which is fine by me!
When crossing oceans we ran the radar on standby or intermittent and would check it at least every 15 minutes. A ship traveling at 16 to 25 knots can come long way in 15 minutes! We would often plot the course of the ship. We also had a radar reflector--but it can be lost in sea clutter easily if the are any waves etc.
We find that AIS reception gives a lot of aid--especially with fast moving vessels. Don't count of large vessels giving you "Right of way"....
We once noted about 50 targets within 5 miles when we were sailing from Norfolk VA to Maine. It turned out that an enterprising lobster fisherman has made small radar reflectors and put them on the floats for his lobster pots. (We finally saw his running lights and contacted him on the VHF). That was a very old Raytheon radar..
We find that AIS reception gives a lot of aid--especially with fast moving vessels. Don't count of large vessels giving you "Right of way"....
We once noted about 50 targets within 5 miles when we were sailing from Norfolk VA to Maine. It turned out that an enterprising lobster fisherman has made small radar reflectors and put them on the floats for his lobster pots. (We finally saw his running lights and contacted him on the VHF). That was a very old Raytheon radar..
I mounted a Mobri reflector on my former 22 on the tall radar arch, and a BC Ferry told me it was bright and clear (about 2 nm distant.) Last fall, I got a sailboat version of a Mobri (meant to be tied to a shroud) for a song. The fit on my present 16 will not be as easy or as neat.
I have two questions: does a Mobri work if the tube is laid in the horizontal position? I am sure it will not be a 360 view, but is it even visible? Secondly, it might be easiest to mount inside in the horizontal; would that make a negative double-whammy on my visibility?
Thanks,
Rod
I have two questions: does a Mobri work if the tube is laid in the horizontal position? I am sure it will not be a 360 view, but is it even visible? Secondly, it might be easiest to mount inside in the horizontal; would that make a negative double-whammy on my visibility?
Thanks,
Rod
My opinion is that the Mobri radar reflector would not work well when laid on the horizontal. It is made to be used in a vertical position for there to be any reflection of the radar signal.
You also want it to be as high as possible--in the cabin, it may be below the visible horizon of the radar.
You also want it to be as high as possible--in the cabin, it may be below the visible horizon of the radar.
My impression, based on what the radar "sees" and what I see with my own eyes is that any boat with an outboard shows up pretty good. An outboard is a chunk of metal sitting off the waterline. However, most inboards don't show anything like it, unless they also have an outboard or reflector on board. An inboard engine is usually going to be at or below the waterline so I'm not surprised they don't give much of a target. What shows up the least are sailboats with no kicker; no surprise there. I wouldn't want a sailboat without a reflector. What I've always wondered about is would a Mylar "party" balloon work, even deflated (Mylar is metalized plastic film)? At least you'd look colorful.
Steve in Olympia
Steve in Olympia
For those who do not want a "radar reflector" there is a "Radar Flag":http://www.radarflagcompany.com/shop.cfm
A reflector is much better, but the radar flag does show a fairly good return on the tests-if it is at right angles to the radar beams...
We left Melaque Bay, just North of Barra de Navidad, Mexico at 3 AM (to arrive at our next harbor when the light was good). It was flat calm: I saw one small blip out of each 30 or so passes on the Radar screen ahead. I dropped the speed down to 3 knots and put Marie on the bow with a hand held search light. As we approached the possible target, I hit the air horn. Then the glow of a match in the dark was spotted by Marie. I am sure that the fisherman was napping in his 26 foot Panga--with a 70 hp outboard on the transom. Many years later EarthRace ran down a similar unlighted (?) Panga off Guatemala with the loss of the life of a fisherman.
I would not rely on a boat with Radar "seeing" a C Dory or any small boat nor visa versa. Slow down and use caution with poor visibility! What is a safe speed? That when you can stop before you hit an object when it comes into visual sight--be it fog, rain or darkness. Radar is just another tool, along with reflectors, detectors, transponders and AIS etc...
A reflector is much better, but the radar flag does show a fairly good return on the tests-if it is at right angles to the radar beams...
We left Melaque Bay, just North of Barra de Navidad, Mexico at 3 AM (to arrive at our next harbor when the light was good). It was flat calm: I saw one small blip out of each 30 or so passes on the Radar screen ahead. I dropped the speed down to 3 knots and put Marie on the bow with a hand held search light. As we approached the possible target, I hit the air horn. Then the glow of a match in the dark was spotted by Marie. I am sure that the fisherman was napping in his 26 foot Panga--with a 70 hp outboard on the transom. Many years later EarthRace ran down a similar unlighted (?) Panga off Guatemala with the loss of the life of a fisherman.
I would not rely on a boat with Radar "seeing" a C Dory or any small boat nor visa versa. Slow down and use caution with poor visibility! What is a safe speed? That when you can stop before you hit an object when it comes into visual sight--be it fog, rain or darkness. Radar is just another tool, along with reflectors, detectors, transponders and AIS etc...
thataway":3ieoa0p3 said:
Bringing this back for consideration.
I have had one of these in the home made version for a while. It is the 3 disks, cut so they fit together, but got it without anything to hold them in the 90 degree positions needed to be effective. I am looking for ideas to use to put them together, preferably so they can be disassembled, folded flat and stored in a drawer, to be brought out and assembled when the need arises since I do very little cruising in conditions that warrant returning someone else's radar signal.
What are you using, for either temporary or permanent holders and mounts? Any ideas would be helpful.
Thanks,
Harvey
SleepyC:moon
There are commercial (Davis) units which are foam with foil on both sides, and slits cut so that they hold in the 90 degree position.
You can use strings or wire ties to hold them in position. I also had a set of 3 rounds 24" in diameter painted black to make an anchor signal "ball". Same idea with the slits to hold them in the proper position.
You can use strings or wire ties to hold them in position. I also had a set of 3 rounds 24" in diameter painted black to make an anchor signal "ball". Same idea with the slits to hold them in the proper position.
That is what mine is supposed to look like when assembled properly. How ever, it is 2 round pieces and 2 halves of round pieces that when put together would make the 3rd round piece. Each is cut with a slit to slide together to make what looks like 3 round pieces all intersecting at 90 degrees, however they have some wobble or play and I need to find a way to fix them into position for functional use, ie clips, brackets, clamps etc and then I can get it into the "catch rain" position.
Painting it black and having it as a daylight anchor signal is a good idea. I think I saw where you mentioned that on another radar reflector thread. Thanks for another good idea.
Harvey
SleepyC:moon
_________________
Though in our sleep we are not conscious of our activity or surroundings, we should not, in our wakefulness, be unconscious of our sleep.
Painting it black and having it as a daylight anchor signal is a good idea. I think I saw where you mentioned that on another radar reflector thread. Thanks for another good idea.
Harvey
SleepyC:moon
_________________
Though in our sleep we are not conscious of our activity or surroundings, we should not, in our wakefulness, be unconscious of our sleep.
AstoriaDave
New member
Sleepy-C,
Cable ties, run through holes, might be quick and easy. Debur the holes with a countersink to minimize abrasion.
Cable ties, run through holes, might be quick and easy. Debur the holes with a countersink to minimize abrasion.