Active Radar reflector Sea-Me

[olivertwist]

Does anyone have experience with active radar reflectors like Sea-Me? How much more visible will they make you appear? Will anyone on a big ship notice?

[CapnK]

Very interesting product! If it works as claimed (and reading testimonials, it seems to), with that low power draw, I am definitely interested...

I'd like to see some more test results.

[AdriftAtSea]

The Sea-me should show up quite well, provided the ship in question is using the same radar band. The Sea-me only covers one range of radar frequencies, not all of them.  The Sea-me only covers the X-band of radar frequencies.  It will not be triggered by the S-band radars, which are longer reaching than the X-band frequencies IIRC.

[Captain Smollett]

How is this different from the C.A.R.D. system?  Isn't that much the same thing?

Either way, this is a Good Idea (tm).  It's how aircraft anti-collision and traffic control radar systems work (eg, the IFF system); very little in aircraft radar application these days works by actual return of the emitted energy.

It's pretty steep, though, at around 500 UK Pounds.  Seems I could build my transponder for FAR less than that.

[AdriftAtSea]

Capn Smollet-

The CARD is a radar detector...not an active radar reflector. The CARD will merely announce when it hears a radar signal.  The Sea-Me goes a step further.

The Sea-Me will basically take any X-band radar signal it "hears" and amplify it and re-broadcast it... to effectively create a huge radar return, instead of the somewhat spotty returns a normal radar reflector would normally create.

[BobW]

Where does AIS fit in the radar reflector range of products?

[Captain Smollett]

The CARD is a radar detector...not an active radar reflector. The CARD will merely announce when it hears a radar signal.  The Sea-Me goes a step further.

Ah, that's right.

The Sea-Me will basically take any X-band radar signal it "hears" and amplify it and re-broadcast it... to effectively create a huge radar return, instead of the somewhat spotty returns a normal radar reflector would normally create.

Yes, a transponder.  Got it.

[AdriftAtSea]

AIS isn't a Radar Reflector. 

IIRC, AIS is VHF-based and uses the MMSI and GPS info to broadcast a ship's location and heading over VHF Channel 70 (reserved now for DSC use).  The only reason it is related to RADAR or chartplotters is that most newer RADAR and chartplotter units can display AIS information, from an AIS receiver or transceiver, on their screen to give you a bit more information about what ships are around you.

The display of an AIS unit's output will look a bit like a RADAR screen, but does not require that any of the ship's have RADAR or RADAR reflectors. :)

Where does AIS fit in the radar reflector range of products?

[CapnK]

So, collating the data:

IIRC, the units/solutions ranked low to high price-wise would be the same as listing according to power draw and relative complexity, with the exception that Sea-Me and CARD are probably the same approx when it comes to complexity of install and the overall system:

• Reflector
• Sea-Me
• CARD
• AIS
• Radar

One cruiser I've met told me that CARD did not work so well, but since he was relating that to me in the third-person, and I have heard no other reports in the first-person either way, I consider this info highly anecdotal and suspect.

IIRC, AIS can be either more expensive than radar or cheaper, depending on which unit you use. The low end AIS is simply a receiver and is just now coming onto the market at the consumer level, the high end is a transceiver and is more or less a commercial product used primarily in large ships. I'm guessing that the high end might approach the same power draw as a radar, and if you add in the complexity and power usage of a laptop to display AIS data, it may be more than radar.

It seems to me that Sea-Me would be about the best small-boat solution going, then. Considering these:

• initial price
• power usage
• the ability to 'ping' back a boosted radar signal instead of just reflecting it back
• the fact that it can alert you both aurally and visually when such a signal is received
• it's non-reliance on a display unit of some sort

...it'd be the best of the solutions for ship alert/avoidance that I've seen.

[AdriftAtSea]

As I see it, the Sea-me is a better solution than the CARD, since it has most of the capabilities of the CARD system and adds the active radar transponder feature to them, for little additional cost or complexity of the installation. 

However, both CARD and Sea-me are dependent on the ships having and using their radar... and both IIRC work only with the X-band radars, not the longer ranged S-band. 

I'd second CapnK's suggestion that the Sea-Me is the best small sailboat alternative. 

[Bill NH]

For a good technical review of radar reflectors, both passive and active (like the Sea-Me) check out http://www.ybw.com/pbo/pdfs/radar_reflectors.pdf

Without going into all their conclusions, they found that "As expected the active Sea-Me outperforms all of its competitors, although at an elevation angle of 20˚ its stated performance level is exceeded by the POLARef." [a passive reflector]

The Sea-Me actually exibits an effective cross section that is an order of magnitude (10x) greater than several passive reflectors currently on the market.  Pretty impressive.

The report doesn't discuss power draw considerations...

[Bill NH]

As to AIS, it is important to remember that this system was designed for large commercial vessels and in that environment it fits seamlessly as part of an integrated bridge system.  Current large vessel systems combine ARPA (automatic radar plotting), ECDIS (electronic chart display & information system) and AIS information with the capability to overlay on a single large format display. 

Even with the new units proposed for smaller vessels, trying to use AIS on a small boat is going to be fragmented and inefficient at best.  The big advantage I see is that carrying an AIS transponder will cause you to show up on a large ships display even under conditions when you will be obscured in radar clutter, rain, longer distances, etc.

Here's an interesting example of a large-ship AIS application from gCaptain.com, a professional mariners board...

"It's the classic scenario from the Academy... You are the stand on vessel with no room to maneuver and a zero CPA contact is bearing down on you. You try the radio but no answer... what do you do next?

This post doesn't answer the question but gives you other options not available when you were at the academy.

Use your AIS & VHF DSC:

Head to the AIS and get the contact's MMSI number & name
Enter the number into your VHF DSC controller
Select a working frequency.

Hit send then start hailing on the working channel
What happens next is the GMDSS alarm will go off and his VHF will change to a working frequency. If [the mate] was away from the bridge he'll have to return to silence the alarm at which point he hears your hail.

What if the alarm doesn't wake him or he has it disabled?

CALL HIS BOSS [the captain]

Get his name from the AIS.
Look him up in your ITU pub.
Find his INMARSAT-B number and call him.

Why does this work? As it was explained to me "Most captains have an INMARSAT-B extension in their office, most captains spend most of their time in their office. Most of the time the captain will answer the phone and rectify the problem post-haste."

While we don't have GMDSS alarms or INMARSAT on small boats, the first part of the scenario is completely valid for sailors who have a DSC-enabled VHF and an AIS transponder! 

[Captain Smollett]

You are the stand on vessel with no room to maneuver and a zero CPA contact is bearing down on you. You try the radio but no answer... what do you do next?

What happened to five rapid blasts??

Does everything have to be an electronic, computerized, radio based solution?

[Zen]

exactly!

***** danger danger

[Bill NH]

Totally agree...  but I think the focus of the clip was on what's changed since the readers were in school, rather than a comprehensive "what to do" discussion.  I just included it because it illustrates the level of complexity and interconnectedness of these systems that we often see from a small boat perspective as isolated bits of gear. 

But get into an accident without trying the basics like sounding five and every mate knows the CG'll hang you out to dry.  I've caused more than one captain to fly out of his bunk with 5 blasts on the whistle during the midwatch.  On a large ship the frequency is so low that you feel it rumble throughout the entire house!

[AdriftAtSea]

IMHO, the problem with five rapid blasts is if the ship is large enough...the pilot house or bridge may be too far aft and too well insulated for them to hear you... If they've got AC and no open ports, plus the VHF, and various other electronics going... they're effectively deaf to the world outside them... especially to a horn a small sailboat will be equipped with.

You are the stand on vessel with no room to maneuver and a zero CPA contact is bearing down on you. You try the radio but no answer... what do you do next?

What happened to five rapid blasts??

Does everything have to be an electronic, computerized, radio based solution?

[Captain Smollett]

IMHO, the problem with five rapid blasts is if the ship is large enough...the pilot house or bridge may be too far aft and too well insulated for them to hear you... If they've got AC and no open ports, plus the VHF, and various other electronics going... they're effectively deaf to the world outside them... especially to a horn a small sailboat will be equipped with.

You need to read the stated problem.  THEY were in the ship that was limited in ability to maneuver (ie, a big honking vessel in a channel)  and THEY saw another on zero CPA ... for fun lets say this approaching boat is a sailfar boat.  THEY were the ones that were wondering "oh noes, how to we get 'em out of our way!"

I've been on a small boat tooted at by a big dog.  You have no trouble hearing it, believe me.