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Old 24-01-2013, 15:30   #46
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Originally Posted by denverd0n View Post
Even most of the power boat guys that I know prefer to leave before sunrise, so that the light is right when they are navigating the many shoals and reefs of the Bahamas.
Agreed
But before sunrise is not what I call a night crossing
:-)
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Old 27-01-2013, 22:41   #47
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I too think AIS is relatively useless. However a few days ago while being slowly overtaken by a large cargo ship I used the AIS and OpenCPN to advantage. It was advantageous if I could cross his bow but in the rough fast conditions I found it difficult to estimate the safety of such a bold move. The OpenCPN plot said "Go for it!" It would have been pathetic to slow this girl down and take the indignity of his stern. Heh.

And I figured he had probably computed my crossing as well and would consider me a fool to not take his bow. Eat my wake suckkkah!
Why did you not contact the vessel concerned? Trying to cross the bow of any ship is not all that smart. He should know your intentions and you his.



Let's take a situation I was in recently coming back from Mexico on the "bash" to California . It was a windy, wavy night and visibility was poor, radar was working but only at a fairly short range of a few miles due to the rolling and pitching of our 38 foot Hans Christian, lots of sea scatter and false echoes. On our AIS screen a large cruise ship showed up at about 18 miles, The CPA (closest point of approach) showed as less than 1 mile, I waited a while and then followed the correct radio procedure and asked the officer of the watch what were his intentions. He replied that they had out AIS signal for quite a while and were altering course to give a 2 mile CPA. No sweat and no surprise. If we were not keeping a good watch the cruise ship would have made the course alteration anyway, very reassuring.
I recently asked the skippers of the last Clipper Round the world race what was their most valuable piece of equipment, and they all agreed to a man it was the AIS transponder.
My experience described above was typical of many situations that we encountered both sailing to Mexico and back. AIS properly installed is increadably valuable.

I don't see why any commercial vessel using class A would filter out class B signals. No commercial captain wants to run the risk of loosing their license running down any size vessel. I leave the AiS transponder on at all times except when on our slip.

In the event of a sinking the USCG keeps a track of all AIS within its range, and that extends well beyond line of site, I don't know how they manage to do this, but they do, so they will have a accurate position of all transponders in US costal waters. Big Brother? You bet, but I love it!!!
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Old 28-01-2013, 03:05   #48
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Why did you not contact the vessel concerned? Trying to cross the bow of any ship is not all that smart. He should know your intentions and you his.
I did not contact him because there was no safety issue at all. And he would know my intentions when I changed course. I knew his intentions were to go to Manila.

Your opinion about crossing the bow of a ship is too general. Surely there is some distance parameter for my being "stupid", no?

We were close. Under a mile and only a few hundred meters abreast. But on the AIS the intersection was over 10 minutes away as I am fast and he was overtaking slowly. No big deal.

When I fell off the wind a few degrees to take his bow my speed, and our separation, increased dramatically. I crossed his bow in under a minute. A few minutes later he passed safely a mile behind.

My point was AIS is not just an aid to run and hide from the 18 ships 18 miles away (nearly useless), it's a tactical tool too.
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Old 28-01-2013, 04:12   #49
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Re: New Inexpensive Ais Transponder

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Originally Posted by skipmac View Post
I did get closer than a mile twice. Once because the guy on watch (I won't mention any names) didn't think to turn around and look behind us. I happened to come on deck and saw a giant freighter about 1/4 mile behind and overtaking. The second time I was on watch and was a bit tired and didn't go aft to look behind the genoa for a while (center cockpit boat so healed over the gennie blocked a large area). Finally occurred to me that a look see was overdue and I discovered the Exumas mailboat was about 1/4 mile to port. Hello!

One thing that I would like from AIS is to know the name of the boats around you. I tight quarters or bad viz I'll call other boats but always something like "sailboat calling tug pushing barges westbound." It would be very cool to call them by name.
Skipmac:

Just installed an AIS transponder last year and find it very useful. Yeah not every boat has it. But, the BIG guys do. I too have at times been surprised to discover a tug and barge coming up behind me in places like New York harbor. Even though I do look around the tendency is to look forward most of the time. I like the "heads up" warning the AIS transponder gives me and the other ship way before "where the hell did he come from" comes from my lips. I've also noticed that with AIS the other ships often do make slight course corrections (as I do too) well in advance of our getting too close to each other. You can see this in real time.

Ship identity is kind of neat too. Sailing back to my home port rushing to beat Hurricane Sandy's arrival last fall I spied a tall ship a few miles south of me. AIS told me it was the Mystic Whaler doing the same.

My AIS transponder also has a button to send out a distress message on the AIS stream (with ship idenity GPS coords etc...) when I activate it. Which I hope I never have to do. But, a nice thing to have on board for safety.
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Old 28-01-2013, 06:56   #50
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Onestep,

I've had the opportunity to test a unit from an early batch and can share some of my first hand information from my two weeks of use.

First I'd like to start by saying it's a great idea and in my opinion designed correctly it would be an excellent addition to an AIS receiver.
However, there are 4 reasons why I wouldn't recommend it to you right now.

1. The interval on which it transmits is longer than most receivers accept so you'll show up and disappear from others AIS displays.
This also causes fast vehicles to not see you. I had a .5mile encounter with the Victoria Clipper in the fog. The never saw us until we passes them. (I was in radio contact with them)
This can be adjusted but will affect battery life.

2. The range is VERY limited due to the low tx power. I tried to mitigate this by raising it up to the first spreader and that increased the range some but it was still very limited.

3. It can't be charged and used at the same time.
It's charged via a 5v custom connector in the bottom.

4. Some receivers can't fully handle having a separate transmitter onboard. Standard Horizon Matrix 2100 is one example of such receiver. If used as a standalone unit it can be fixed with an update but if used together with a separate display, such as a chart plotter then you're in for some trouble.

I hope that was the information you were looking for.
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Old 28-01-2013, 10:54   #51
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Re: New Inexpensive Ais Transponder

thanks sv inspirare. i'm not much of an electronics guy but i seem to sense a good use for an ais transmitter. now, i'm talking a very limited situation here. just crossing the gulf stream between florida and the bahamas. many sailors on the board have much broader use and so probably need much better equipment. so i'm still looking...
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Old 19-02-2013, 14:57   #52
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Re: New Inexpensive Ais Transponder

The "myth" of being able to filter out Class B targets has been thoroughly debunked on www.panbo.com. Part of the confusion is the difference between "decluttering" the display versus not tracking certain classes of targets. Decluttering simply means not displaying targets. The AIS still tracks them internally. According to everything that I've read, any target that presents a risk of collision will set off the appropriate alarms, whether or not the target was visible on the display.
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Old 03-05-2013, 16:01   #53
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Originally Posted by SV_Inspirare View Post
4. Some receivers can't fully handle having a separate transmitter onboard. Standard Horizon Matrix 2100 is one example of such receiver. If used as a standalone unit it can be fixed with an update but if used together with a separate display, such as a chart plotter then you're in for some trouble.
Can you elaborate on this, or post a link to this issue?

Thanks!
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Old 03-05-2013, 16:24   #54
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Re: New Inexpensive Ais Transponder

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Can you elaborate on this, or post a link to this issue?

Thanks!
It'll probably sound the alarms for collision with yourself.
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Old 03-05-2013, 16:38   #55
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Once I saw a tech buffing a dark shadow on a hull hours later he was still buffing. Turned out he was buffing his shadow. Sort of similar
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Old 03-05-2013, 18:06   #56
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Yet another totally pointless "discussion"!!!
It is irrelevant whether they are looking for you on AIS. YOU are responsible for YOUR safety and YOUR vessel!! No discussion.
Yes you are and part of that obligation is to use any means available to you to ensure you are visible to others including AIS transmit

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Old 03-05-2013, 18:18   #57
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The people playing down AIS have
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Old 03-05-2013, 18:20   #58
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The people playing down AIS have obviously not sailed in high density shopping areas. With my AIS transponder I see ships changing course to avoid me over the visible horizon ! That's an advantage.

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Old 03-05-2013, 18:30   #59
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Re: New Inexpensive Ais Transponder

Going past Singapore is highly amusing with AIS my screen just turns black and sounds collision warnings constantly.. I turn the alarm off and go dodge the big boys... Its a busy part of the world LOL Anyway wasn't the original post about a certain product ? Looks like a fleet management system to me .
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Old 03-05-2013, 18:35   #60
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Re: New Inexpensive Ais Transponder

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Going past Singapore is highly amusing with AIS my screen just turns black and sounds collision warnings constantly.. I turn the alarm off and go dodge the big boys... Its a busy part of the world LOL Anyway wasn't the original post about a certain product ? Looks like a fleet management system to me .
Does your manual describe that behaviour as normal for high traffic areas? If so, you need to know that it isn't normal. I am at the Panama Canal and see 175-250 targets without a problem... on an old 1st generation black box transponder.
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