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Old 12-11-2011, 06:22   #196
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Re: Radar or Not ?

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Originally Posted by barnakiel View Post
BTW I wonder what percentage of cruising radar owners know how to properly tune their units in various conditions. I also wonder how many of sailing boat installed units have arpa and, when not, how many radar owners would pass the test making radar plots (timed - the ship is making 20 Knots and coming your way).

I said 'I wonder' but indeed I mean 'many can't'.

Then, how efficient is a small radome, wide beam radar as a collision avoidance device?

So, to stay within the thread, I will say have radar is so dictated by your needs AND LEARN HOW TO USE IT. Understand the limitations, too.

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I haven't installed one in a few years but I can only guess they are the same or better..

out of dozens of small raymarine radars....maybe one or two had malfunctions and had to go back anyway..but the others straight out of the box left in the auto mode were almost as good as you could get a small radar to perform. They would pick up almost anything out there in piloting waters in reasonable conditions...perfect no...but VERY USEFUL to avaoid collisions and navigate. The most you had to do was select whether you were in the calmer waters of port or coast or more open sea.

That's why I always recommended raymarine...supposedly most other companies have radars that caught up in ease of use.
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Old 12-11-2011, 06:53   #197
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Re: Radar or Not ?

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Now with AIS transceivers, you have something that no radar can do. It's make YOU visible to AIS equipped ships. Again my experience is that few if any ships can see grp yachts on their radar, especially in a seaway.
Yes, we understand that AIS does things no radar can do. It also does things that no GPS, depthsounder, VHF etc. etc. can do, plus you can turn that around where every other tool does things that AIS can't do.

Now, if we look closely at the subject of electronic visibility, we see two main tools for this: radar and AIS. If you want better visibility on radar, buying an AIS transponder is silly... what you need is a better radar reflector, hence one of the active ones like the Sea-Me units that I posted about before. When you have that, every radar equipped vessel will see you on their radar and all their ARPA systems will automatically designate you a target and do their collision avoidance scheme.

Next AIS, I kinda agree that receivers are a bit silly too and indeed these aren't allowed on 300+ ton SOLAS ships. But we must not forget that yachts have no such requirements and can use whatever AIS unit they want or nothing at all. From that viewpoint, a receiver is better than nothing.

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These radars typically have beam widths of between 5 and 7 degrees. No such radar is going to detect seagulls. Even my own HD unit with 3 degree resolution struggles.
Oh my... now I see where the confusion originates. When your beam width is 7 degrees and your target is a tiny bird, any decent yacht radar will still detect that bird. The bird does NOT need to be as big as the beam width at all. The beam width has mostly to do with target discrimination, meaning that you can't see if there is one or two birds... both will present you a single echo.

So, receiver vs transponder for AIS is like having a good radar reflector of radar, both of these make you visible on the equipment of ships around you. As all ships have radar and not all ships have AIS, I think a Sea-Me or equivalent is more important than AIS... but alas, it isn't that exciting to discuss or own (it beeps at best).

cheers,
Nick.
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Old 12-11-2011, 06:58   #198
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Re: Radar or Not ?

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Originally Posted by psneeld View Post
(...) the others straight out of the box left in the auto mode were almost as good as you could get a small radar to perform (...)
How do we know how they could have performed, if they had been left in the auto mode?

That's the issue. Many owners never bother to learn about the radar, how to tune it, nor how to use radar plotting sheets. Many small radars lack arpa.

Why will officers and watchmen be trained to do such apparently unnecessary tasks even though they operate radars with arpa and much narrower scanning beams and from the decks that roll of much less?

Even if today's radars are better than yesterday's ones then with less interest in understanding how they work and how to use them the balance may very well be negative.

Gain, tuning, sea clutter, rain clutter - they are still there, surprisingly (to some).

?

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Old 12-11-2011, 07:04   #199
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Re: Radar or Not ?

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Power and cost. I have a nasa standalone which I know works down to under 11v and only draws 0.1a. Between that and an LED masthead I know I can still see and be seen, to an extent, even if the batteries die on me offshore.
The cost argument has weight, the power argument is weak. All transceivers I've seen can be put into silent mode if needed or desired, hence preserving power and consuming just a few watts in receive only mode. Do you lose power often?

The bottom line and point of this thread is newbies are being mislead into thinking that AIS is a 'good enough' collision avoidance system such that they don't need to invest in radar. For a very limited set of circumstances along with using ones eyes, that may work (daytime only, fair weather only boating). I would say that circumstances always change (or the boat never moves)!

I will never do a night passage without radar. Ever try to tiptoe thru 18 trawling shrimpers in a 5nm radius on a moonless night? You can't see their nav lights as their work lights are too blinding. Sails up, tight to a 15-20 wind, drastic course change requires waking crew. At 5nm out and using ARPA, I can get their COG and adjust mine a few degrees such to fall in behind them. Pre-ARPA, I was guessing and was right 90%, but that 10% where I cut in front of them justified ARPA for me. Even the admiral can interpret ARPA and change course accordingly! And none of these vessels are required to have AIS.
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Old 12-11-2011, 07:08   #200
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Re: Radar or Not ?

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Gain, tuning, sea clutter, rain clutter - they are still there, surprisingly (to some).
I completely agree that sailors should do a radar operators course regardless of how well the automatic modes of their radars function.

And (not but, as this doesn't contradict what I wrote above) modern radars like Furuno NavNet 3D have so much better automatic modes that one indeed doesn't need to do any manual tuning anymore. This doesn't mean that i'll operate at it's best; it just means that it'll operate good enough to not miss targets etc.

In the old days we were put on a little harbor tug or workboat with radar and the bridge windows were covered so that you were 100% dependent on the radar set (yes, smack in the middle of Rotterdam harbor with ships going everywhere). Even had to moor the boat like that. Today, computer simulations have replaced that and I even believe that you can get self-training software for this on your own PC. Get it !

cheers,
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Old 12-11-2011, 07:10   #201
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Re: Radar or Not ?

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So, receiver vs transponder for AIS is like having a good radar reflector of radar, both of these make you visible on the equipment of ships around you. As all ships have radar and not all ships have AIS, I think a Sea-Me or equivalent is more important than AIS... but alas, it isn't that exciting to discuss or own (it beeps at best).

cheers,
Nick.
I wonder how broadband radar will catch on.

Ocean Navigator | The magazine for long-distance offshore sailing and power voyaging

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Invisible targets. The different internal pulse characteristics have other consequences. Since the pulses are quite different, broadband radar does not detect conventional radar and vice versa, which means that the two systems do not interfere with each other. It also means that broadband will not trigger RACONs (radar beacons), SARTs (search and rescue transponders), active radar target enhancers such as the Sea-Me and EchoMax, and radar detectors such as the CARD (collision avoidance radar detector) system. Owners of broadband systems should be aware that they cannot detect many of the modern electronic navigation aids. In addition, captains who have mounted active radar target enhancers and CARD systems should be aware that they are not effective against broadband systems.
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Old 12-11-2011, 07:19   #202
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Re: Radar or Not ?

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I wonder how broadband radar will catch on
Exactly the reason that many incl. me will state that broadband radar is great for the 2nd "close range" radar set. Boats that only have one set should have a "regular" (modern, not the 1992 el cheapo model) yacht radar. This makes the broadband a good choice for the fishing/motor yachts and sailboats 70' and up or so, that all have two radar sets, but not for the majority of us simple cruisers who are better off with that Sea-Me.

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Old 12-11-2011, 07:20   #203
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Re: Radar or Not ?

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Do you lose power often?
Once was enough. Several days offshore coming up from Brazil. Batts wouldn't hold enough charge to keep radar working for long, AIS and LED masthead kept working to under 11v. Sailing solo using just ais to sleep isn't stressfree or clever, but it's miles better than nothing and as said before, it's a very rare occurance to come across a vessel out there not transmitting.

Hope for the best, plan for the worst.
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Old 12-11-2011, 07:23   #204
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Re: Radar or Not ?

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Exactly the reason that many incl. me will state that broadband radar is great for the 2nd "close range" radar set. Boats that only have one set should have a "regular" (modern, not the 1992 el cheapo model) yacht radar.
I'm just happy that I could scrape together enough pennies at the time to fit one

Wouldn't have the power, cash or room to fit another.
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Old 12-11-2011, 07:24   #205
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Re: Radar or Not ?

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And (not but, as this doesn't contradict what I wrote above) modern radars like Furuno NavNet 3D have so much better automatic modes that one indeed doesn't need to do any manual tuning anymore. This doesn't mean that i'll operate at it's best; it just means that it'll operate good enough to not miss targets etc.
+1

Mostly when I turn off automatic mode it's to check if it's actually working.
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Old 12-11-2011, 07:33   #206
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Re: Radar or Not ?

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Wouldn't have the power, cash or room to fit another.
you mean that there are no conventional yacht radars in the same price class as the new broadband sets? And that they are physically bigger? And that they use so much more energy?

Do understand that conventional radar send out very powerful but also very short duration pulses while the broadband radar uses a less powerful but constant beam. Try to imagine the graph for both... the energy consumption is the surface area of the graphs, not the height of the peaks of the conventional radar. The output in W of these units can not be compared for power consumption.

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Old 12-11-2011, 07:34   #207
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Re: Radar or Not ?

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Originally Posted by conachair View Post
Once was enough. Several days offshore coming up from Brazil. Batts wouldn't hold enough charge to keep radar working for long, AIS and LED masthead kept working to under 11v. Sailing solo using just ais to sleep isn't stressfree or clever, but it's miles better than nothing and as said before, it's a very rare occurance to come across a vessel out there not transmitting.

Hope for the best, plan for the worst.
OK, but my point is that an AIS transceiver would have served the same purpose, PLUS, if you had battery power, the other vessels could see you via AIS. The new Raymarine AIS650 transceiver works down to 9.6v and averages 3W draw, less in silent mode.

I go back to my earlier statement, AIS receivers are more toy than purpose. For proper collision avoidance, every vessel must have a transceiver.
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Old 12-11-2011, 07:48   #208
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Re: Radar or Not ?

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you mean that there are no conventional yacht radars in the same price class as the new broadband sets? And that they are physically bigger? And that they use so much more energy?
I meant I couldn't fit both, so I'll stick with the raymarine 2kW

Though a 4g looks so lovely.
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Old 12-11-2011, 07:53   #209
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Re: Radar or Not ?

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I go back to my earlier statement, AIS receivers are more toy than purpose. For proper collision avoidance, every vessel must have a transceiver.
You seem very sure that other vessels are watching. I know from experience that the big boys see me on radar, small stuff I don't trust anyway.

Do the big boys constantly watch for class b ais targets?

I really don't know what goes on on a bridge.

But for now will happily carry on looking after myself with a reciever, and not assume that I've been seen.
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Old 12-11-2011, 07:59   #210
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Re: Radar or Not ?

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The new Raymarine AIS650 transceiver works down to 9.6v and averages 3W draw, less in silent mode.

I go back to my earlier statement, AIS receivers are more toy than purpose. For proper collision avoidance, every vessel must have a transceiver.

That unit is class B.

Hope for the best, plan for the worst and don't assume anything

USCG Issues Safety Alert On Class B AIS
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