What does your Class B AIS transponder do for you?

[Chotu]

And another follow on question. Do they make AIS class B transponders that can switch over to just receivers when needed?

[Anders]

Originally Posted by Chotu

And another follow on question. Do they make AIS class B transponders that can switch over to just receivers when needed?

I think all of them can be set to receive only. Some can also switch of message 27 but that would not make much of a difference in costal waters.

[sailingharry]

Originally Posted by Sailer_Med

It's not required so do what you want!



I am unsympathetic to people that break the rules. If they get busted based on their AIS data more power to it! It's alot more efficient using your datastream to enforce anchorage laws etc than chasing around in a big expensive powerboat.

I generally follow rules, regardless of big brother. But I have received camera speed tickets for 40 in a 25 zone (yes, I wasn't paying attention), I have run red lights that were way past red (WTF -- was that red???!!!!). If license plates were something I could avoid for free, or pay for and get tickets, I would turn it in tomorrow. My behavior wouldn't change, but my tickets would.

This would be even worse. Enforcement that is exclusively focused on boaters with an interest in safety sends the wrong message. And if a reckless speedster has an AIS and is motivated turn it off to avoid tickets -- that doesn't sound like a desired outcome.

All this said, I don't have any worries that this is going to happen. And my ezpass won't be used to calculate speeding tickets.

[KWF]

Originally Posted by rslifkin

In my mind, AIS and radar go together nicely, but neither can replace the other. Depending on the situation, each one can potentially give you information the other one can't.

Agree.

[HeywoodJ]

Originally Posted by Chotu

Is the standard length VHF masthead whip antenna correct for AIS?

They do make shorter and longer ones for the mast head.

What’s correct for the AIS class B wavelength?

All AIS (class A, B, B+) transmit on the same two frequencies: 161.975 and 162.025MHz. That is within the overall marine VHF band, but most of the voice channels we generally use are in the 156-157MHz range. The only voice channels that get up near the AIS frequencies are shore side of the duplex channels. Most antennas at the store are built around that 156.5MHz number, so are not perfect for AIS, but they do pretty well and probably the vast majority of Class B AIS installations use a standard VHF antenna. There are specialty antennas available if you run a separate AIS antenna or have giant concerns about the performance.

For the other question, I can only answer for ours, yes, there is a "run silent" switch that allows us to listen only.

[Tsuru]

Originally Posted by Chotu

Is the standard length VHF masthead whip antenna correct for AIS?

They do make shorter and longer ones for the mast head.

What’s correct for the AIS class B wavelength?

Chotu, I can’t give you a technical answer, but I’ve owned 2 boats with AIS transponders. 1st used an active splitter on the masthead VHF antenna. I currently use a dedicated AIS antenna mounted above our spreaders. There was no practical difference in operation. I routinely pick up targets 20 to 30 miles out. The wavelength on the dedicated antenna is slightly different, but I’d have no problem using a splitter off the main VHF antenna. That said, there has been some instances of the AIS interfering with LED nav lights. This is why our AIS antenna is not at masthead.

[carlosproa]

You could consider a transom mounted alternative. Since you have a Cat and severe rolling is out of the equation, and from the pictures I guess your transom height to the waterline looks to be high, you can still get pretty good radius coverage with a 10 to 15 ft pole and a dedicated made for AIS antenna.

I am sure someone here can give you calculations but my guess is you can safely cover about 6 nm vs 10 or 11 on a split mast antenna. I am not sure what the delta in minutes are for corrective actions for say a container ship going cruising speed of 20 to 22 knots straight at you? Say you are going like 5 knots, container ship 20 knots, so (check my math I am in the middle of battling the flu and might be delirious [emoji23]) so at transom height you have 16 min to react vs 27 min on a mast based?

[carlosproa]

Originally Posted by singlespeed

Not a lot in the undeveloped third world countries. Many vessels that are supposed to have them, simply can't afford them. Don't rely on them, especially in known drug running or smuggling corridors or waters known to have piracy issues.

Or illegal fishing crews

[Slovak]

Originally Posted by bcboomer

From what I see that is not "plug and play". I don't know what percentage could, even if they wanted to, build that unit.

Huh? Based on the installation manual and my own experience, it's a matter of inserting antenna into the housing, apply a couple of heat shrinks, and plug it in. You can make it more complex if desired, but the hardest part on our boat was running the CAT5 cable.

[chubby]

years ago my 1st impression was that class B AIS transponder was a toy at best and a waste of money at worse...


big ships only show class B when there is room..

with most simply not want to see any class B at all...anywhere.


these days..

i still think it is a waste of money...

(a properly set up solid state radar makes AIS redundant for a small sailboat)



but i'll probably purchase/set up a AIS eventually....one day.

more for me easily identify/name vessels for hailing when needed...rather than some imagined safety benefit of sending transmissions that will intentionally filtered out by my intended target.

[wholybee]

Originally Posted by chubby

years ago my 1st impression was that class B AIS transponder was a toy at best and a waste of money at worse...


big ships only show class B when there is room..

with most simply not want to see any class B at all...anywhere.


these days..

i still think it is a waste of money...

(a properly set up solid state radar makes AIS redundant for a small sailboat)



but i'll probably purchase/set up a AIS eventually....one day.

more for me easily identify/name vessels for hailing when needed...rather than some imagined safety benefit of sending transmissions that will intentionally filtered out by my intended target.

I really depends on where you sail. If you cross oceans, or are in a very crowded port, AIS is very important, if not essential. I have has 100's of encounters with cargo ships and oil tankers in the middle of the ocean, and I would not want to do that without AIS. Usually, I see them on AIS turn to avoid me before I have visual contact. A few times, they hailed me several miles out to let me know they see me or to ask for something not "normal".

I have had times when up to 7 ships were on a collision course with me at the same time. AIS was essential to coordinate the actions all 7 ships needed to take, to not only avoid me but each other as they were all turning.

I have had multiple times when coming into port I had to wait for outgoing traffic to be clear before my entering. Because of topography, seawalls, etc. This can only be seen with AIS.

But, if you are a causal sailor, coastwise from a not too crowded bay, in an area without heavy shipping traffic, then and AIS transponder is a waste of money.

[nrx500]

My Class B AIS transponder is my insurance policy. I sail the east coast in the vicinity of the Chesapeake Bay Bridge Tunnel, The Delaware River, and New York Harbor. There is a great deal of commercial traffic in these waters, and there can also be thunderstorms and fog. In the past, before AIS, I broadcast Securitay messages on channel 16 in reduced visibility. I also listened to channel 13 to hear position reports for commercial vessels. Now that has changed.

I have a Si-TEX MDA-5 Class B SOTDMA AIS receiver/transmitter connected to the NMEA 2000 backbone. It has a zero loss antenna splitter built in. The masthead VHF antenna plugs directly into the SI-TEX and the VHF radio antenna cable plugs into the SI-TEX. The SI-TEX also needs a ground wire which can be as simple as a wire connected to the negative bus on the DC panel. It also needs a GLONASS satellite antenna (included with the unit) connected to the back panel. Mine sits in a donut hole drilled into a a piece of 2x4 on a shelf near the SI-TEX. The range is comparable to all VHF transmissions. The higher the sending and receiving antennae, the further the signal reaches. Line of sight transmission is typically 20 nautical miles.

The advantages of the Class B AIS transponder are:
1. It puts my boat and identification info on the chartplotters of every boat in my vicinity with an AIS receiver.
2. It also puts their positions and contact information on my chartplotter screen.
3. My chartplotter shows time and distance to vessels on intersecting courses with my boat. That gives me the option to call a vessel to arrange for safe navigation maneuvers.
4. There is also a free phone ap called Marine Traffic. My wife uses it to see where my boat is. It also sends email messages giving my noon position, when I stop, and when I get underway.

If you sail in the vicinity of large, fast moving vessels and you are out in fog, storms, or darkness; Class B SOTDMA AIS will make your travels safer. The installation is also something you can do yourself.

[hjohnson]

Originally Posted by W32

I was thinking of an AIS transponder purchase but on further inspection I am not certain of how good of a use of money it is, because it isn't cheap. The reason for my hesitance is that these things put out less than 4 watts of transmit power which doesn't seem very much to me. A ship traveling at 20 knots isn't going to be able to do much by the time it picks up your 4 watt transmission. I'm thinking of how limited a typical 5 watt hand held VHF is and even though there is a height advantage it still won't be impressive. Come to think of it, I haven't heard of even one instance where a Class B transmission has effectively alerted the crew of a fast moving MV that made any difference. I'd like to hear your experience with your transponder. Does it give you any peace of mind?

So two stories as to why I think it’s worthwhile.

THis past summer, I was lazilly tacking my way southward in Trincomali Channel in the Canadian Gulf Islands, and this deep sea merchant was heading north to one of the reserve anchorages. A long ways off, the pilot (I presume) was able to call me directly on the radio to make sure I saw him and otherwise coordinate. Rather than calling “The sailboat in Trincomali Channel” he was able to call “Sailing Vessel Sagres” which immediately got my attention. I felt good that they were watching out, and I let him know that I intended to short tack and let him go by.

Similar, December 23rd 2020, I had just delivered Christmas Presents to my 2 y/o nephew after dark in my nicely decorated boat (doing my own little parade of lights) and was heading home through First Narrows back into Burrard Inlet. A merchant ship was heading into the pass at the same time, in the mists, and was able to coordinate with me that I stick to the south shore. I could barely see him, in the mist that came up he could mostly see the glow from me being literally lit up like a christmas tree.

So yes, I now view having a full AIS transponder as an important safety device.

[hjohnson]

Originally Posted by HeywoodJ

For the other question, I can only answer for ours, yes, there is a "run silent" switch that allows us to listen only.

I’ve got a Vesper splitter splitting my masthead antenna between my VHF and the Vesper transponder. I routinely pull in contacts from 30-40 miles. It’s a 27’ boat so my masthead is roughly 40 feet above the water.

[SunnySpray]

I am sailing long distance since 1981. The first big game changer was GPS. what a difference! The second big game changer is AIS, both transponder and receiver. If I had to chose only one piece of navigation equipment to take along on a voyage, my vote would go to the AIS system!! It works without fail, and you really see ships altering course to avoid a close CPA. Also, it allows you to call them by name, which is essential when you want to receive a reply. Anyone doubting the value of AIS should not be out there.