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Old 31-08-2016, 20:11   #16
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Re: AIS, Receiver or Transmitter

I'll just throw this out there after all, if I can't stir the pot here..

Anyway, I have read that in busy shipping lanes large boats will tune filtering to exclude smaller boats...I have no idea if this is true or even possible. I am just string the CF pot.

Any way, our boat came with an AIS receiver. The equipment still works and it's better than nothing so we will use it until it's good and dead. But when we do replace it my preference would be a transmitter / receiver.
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Old 31-08-2016, 20:26   #17
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Re: AIS, Receiver or Transmitter

No, Sea Dreaming ships do not.

I should point out that most AIS units have a card reader of some type recording every digital AIS signal received from every ship... This includes shore stations and satellites.

So if a ship decides to turn their transmit off and has a collision every ship on the ocean will have a notion becuse the struck ship will have the record, as will every other ship in range plus big brother in space.

And the offending captain goes to jail for a decade or so. Just not worth it, eh?


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Old 31-08-2016, 21:48   #18
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Re: AIS, Receiver or Transmitter

Quote:
Originally Posted by skipmac View Post
Wrong argument.

Manufacturers will make anything they can legally sell. Doesn't matter whether it makes sense, whether it is ethical or moral. Just because someone makes it and sells it doesn't mean it's the correct solution.

There might be other reasons or arguments against an AIS transceiver vs a receiver but that one isn't valid.

Personally the only reason I can think of is to save a few bucks. I can think of no other advantage at all.
The difference between RX & TX AIS is more than a few bucks, the smallest price differential I saw was $300. Even an RX only machine is a serious chunk of change once you add in antenea splitter, cabling, something on the order of $600 or more if you need a display. For a few people that is the difference between going and staying.

For a larger group of folks the push for every little piece of safety equipement sinks cruising plans in budgetary scope creep.

The tone of your statement "Manufacturers will make anything they can legally sell." implies you don't think they should be offering RX only models. The inference I make is you believe that not only shouldn't they be making them, carriage of the TX models should be mandatory. But then where would that stop, pretty soon all conceivable pieces of safety equipment would be mandatory.

If it really were such a "No Brainer" it would be Coast Guard mandatory.

If the only reason you can think of for an RX AIS is cost savings then I doubt you put much thought into it. There are 2 additional reasons I can think of right off the bat.

First would be the space occupied by the hardware. That's actually a pretty limited reason, only very small crusing boats would find the space for a TX or RX unit plus the antenea splitter. As it happens I have such a boat so this is something I have considered, I could find space for the unit and splitter if I really tried but not the battery and solar panel needed to support them (see the next paragraph for a discussion of this issue). The only reason I will be having any AIS on my boat is because I can get it as a feature of the VHF radio I am going to install and it is only offered in RX.

Second is the power used. For an RX unit the power draw is about 1/3amp for unit and splitter, with a display requiring more. There is an Icom unit with display that uses 0.7amp for RX. That's about 17 amp-hr/day. In TX mode the Icom draws 1.5amps or 36amp-hr/day. That means an extra 72 amp-hr of battery capacity and an extra 144w of solar panels to buy, find space for and mount. On boats up to 30' I can see problems finding space for the extra battery and solar panels in order to support the unit's power needs.

If you use the all in one VHF/AIS I intend to install as the basis for comparison, then I will pay an extra $250 for the AIS and use extra 0.2amps (4.8 amp-hr/day) compared to a similar VHF radio. I can find a place for an extra 20w of solar and the installed battery capacity will have to do.

A TX unit with built in dispay is about $900. Antennea splitter about $250. Let's say $50 for the cabling. Extra battery is onging to be $160. Solar panel $220 and wiring another $50. That's $1630 installing yourself. It's also a $1380 price difference from the the RX unit I am going to install.

The difference between a TX and RX system is more than "a few bucks" (depending on your definition of a few bucks) and there are space and power issues that must be considered.
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Old 31-08-2016, 22:23   #19
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Re: AIS, Receiver or Transmitter

I have a receive only unit I recently installed and use it with OpenCPN on a dedicated nav computer. I am so impressed with the information provided that I now intend to buy a transmit/receive unit.
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Old 31-08-2016, 23:39   #20
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Re: AIS, Receiver or Transmitter

everyone I know that has bought and used extensively a receive unit has said that they should have bought a transmitter. There are several places in the world now that you have to have an AIS transmitter. (Singapore, Thailand and probably others. They do add considerably to your peace of mind, especially in busy areas or poor visibility. But I'd still have a radar 1st.
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Old 31-08-2016, 23:42   #21
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Re: AIS, Receiver or Transmitter

I just got back online, am surprised that I sparked a bit of vitriol with my answer.

Let me give a little bit of background about me first. I'm a commercial captain, with 25 years experience in the Bering Sea and North Pacific fisheries. When I'm not doing that, I'm sailing generally long distances.

This isn't to brag, but just to illustrate that I know of what I speak, and have the somewhat rare opportunity to be on both sides of the AIS equation, commercial and pleasure.

First, on the commercial side. The stories that you have heard are generally true. AIS has become the primary tool for risk of collision detection and avoidance. Sure, guys are looking at their radar too, but AIS is so widespread now, that it's really the primary device these days.

Also, when there's a sea running, small boats simply do not show up worth a damn on radar, regardless of what kind of a reflector you've installed. Big vessels often tune their clutters so that rain and sea don't muck up their screen, and with that, most of us are tuned out.

On the recreational side, something really remarkable happens. Ships will actually follow COLREGS (generally) when you are transmitting AIS. Each vessel has been identified, and with that comes accountability. This matters to the guy on the ship. A small blip with no signal will more often be ignored.

I've personally (while outside coastal shipping lanes where rule 9 applies) had most ships take appropriate give-way action since installing a transmitter. This did not happen before with nearly the same regularity.

I started with a RX only unit. The difference in ship behavior is quite dramatic since we've started transmitting.

So, yes, with all this in mind (I could go on about this at more length), I am so arrogant to say the following.

No brainer. Transmit AIS. End of story.

Should it be mandatory? Of course not. Nor should any other gizmo. This is about personal choice. I happen to think that it's the wrong choice to not fit AIS for cruising where shipping is present (everywhere), but it's up to the user, and should stay that way.

It's the most significant contribution to maritime safety since GPS.


To each their own, but this is not a place to save a few hundred bucks.
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Old 01-09-2016, 01:52   #22
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Re: AIS, Receiver or Transmitter

I truly understand why everybody wants the TX. But, if you're totally used to avoiding hazards, actually, Receiver only is far more restful and less distracting. We used to have RX, now both. I think (and I know some of y'all will try and shoot me down) that if money is an issue, your RX only unit will give you so much more info than you had before.

That said, after buying RX only, Jim, too decided he wanted TX. I have not seen much difference, myself, other than being distracted. Pls let me explain. On watch at night, I do not want to be overloaded by data. I want to keep my night vision. I haven't yet watched a big ship avoid us, because he made a 2 degree adjustment miles back. So, probably TX isgood, but, and that is the data overload dimension. NOW, having written that, the seas we travel are relatively uncrowded. If you're traveling the English Channel, yes, RX/TX helps the ships stay out of your way, and that is a very good deal with the shipping lanes to cross and so on.

Fwiw, I've become used to it, now, but I did like it better when it was RX.

Ann-- possibly the only dissenter, whose input should be ignored!
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Old 01-09-2016, 02:00   #23
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Re: AIS, Receiver or Transmitter

+1 TJ

To a few other replies:

I believe the power used for transmit with Class B AIS is just for a split second every 30 seconds. It would have no visible impact on your 24 hour power consumption.

A black box transciever like the Vesper doesn't require any panel space. It can be tucked away anywhere and be connected to your chartplotter (or wifi to a tablet or phone)

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Old 01-09-2016, 02:09   #24
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Re: AIS, Receiver or Transmitter

Quote:
Originally Posted by Ann T. Cate View Post
I truly understand why everybody wants the TX. But, if you're totally used to avoiding hazards, actually, Receiver only is far more restful and less distracting. We used to have RX, now both. I think (and I know some of y'all will try and shoot me down) that if money is an issue, your RX only unit will give you so much more info than you had before.

That said, after buying RX only, Jim, too decided he wanted TX. I have not seen much difference, myself, other than being distracted. Pls let me explain. On watch at night, I do not want to be overloaded by data. I want to keep my night vision. I haven't yet watched a big ship avoid us, because he made a 2 degree adjustment miles back. So, probably TX isgood, but, and that is the data overload dimension. NOW, having written that, the seas we travel are relatively uncrowded. If you're traveling the English Channel, yes, RX/TX helps the ships stay out of your way, and that is a very good deal with the shipping lanes to cross and so on.

Fwiw, I've become used to it, now, but I did like it better when it was RX.

Ann-- possibly the only dissenter, whose input should be ignored!


Ann, I'm not clear how transmitting changes your situation while on watch?

Transmitting happens in the background, and the information that you see is only derived from the receive function anyway, so the act of transmitting should not change anything.

Did you put in a new unit with a different display? This would seem to be about the only thing that could have happened. Transmitting shouldn't matter a bit.

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Old 01-09-2016, 02:24   #25
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Re: AIS, Receiver or Transmitter

A huge advantage of an AIS transceiver in the crowded waters I frequent is that it allows more intelligent VHF contact with commercial ships in crossing situations. Hailing "this is the white sailboat on your port bow" is rarely successful.

Since installing a transciever, I find that VHF hails are usually answered -- presumably because my boat's name is displayed on their plotter. And not infrequently, a ship will hail me first to confirm my intentions.

This put to an end those stressful moments when I would ask my wife "does it look like he's turning to port?"


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Old 01-09-2016, 02:46   #26
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Re: AIS, Receiver or Transmitter

This decision should be informed by where you sail and what amount of commercial traffic frequents those waters. Clearly some places it would not buy you all that much and others it would be very useful. In LIS southern NE where there is commercial shipping it may not merit the expenditure. A receiver should give you ample time to avoid a mishap and you will receive CPA and so on. It's a prudent approach to just steer clear of large and fast vessels... which is possible I would think. Data overload is a real issue and may distract rather than make you safer.

Maybe.
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Old 01-09-2016, 03:17   #27
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Re: AIS, Receiver or Transmitter

FROM Adelie

The difference between RX & TX AIS is more than a few bucks, the smallest price differential I saw was $300. Even an RX only machine is a serious chunk of change once you add in antenea splitter, cabling, something on the order of $600 or more if you need a display. For a few people that is the difference between going and staying.

True the meaning of a few bucks is relative. I would wager that most cruisers have at least low to mid six figures invested in their boat and most boaters with boats costing a lot less than that are not really in need of AIS. Note I said "most' and that means absolutely not all. So for most cruisers considering what's invested in their boats an additional $300 would be a few bucks.

For a larger group of folks the push for every little piece of safety equipement sinks cruising plans in budgetary scope creep.

I am not and have not pushed for everyone to have AIS or any other gear. I sailed for years with nothing more than a depth sounder and a VHF and still believe it is perfectly safe and sane for someone to do so today. All these expensive gadgets can make cruising easier and perhaps less stressful and probably improve safety but they are NOT necessary to have before leaving the dock. And believe me, I own a boat and understand budgetary creep down to the depths of my wallet.

The tone of your statement "Manufacturers will make anything they can legally sell." implies you don't think they should be offering RX only models. The inference I make is you believe that not only shouldn't they be making them, carriage of the TX models should be mandatory. But then where would that stop, pretty soon all conceivable pieces of safety equipment would be mandatory.

You are reading into my statement things that were not said, meant nor I think even implied. I was only pointing out that a statement by rwidman saying if receive only AIS units were made then that demonstrated there must be a valid reason for them. There may be a valid reason for manufacturers to make certain products but the reverse is not true IE just because a manufacturer makes something does not mean there is a good reason for doing so (other than to make money for that manufacturer). It very well might be a good thing but just because someone makes or sells something is not proof that it is good.

If it really were such a "No Brainer" it would be Coast Guard mandatory.

I would call in a no brainer only in the context of transceiver is inarguably better in function and safety than receive only. If for some reason one cannot buy, use or install a transceiver then a receive only is better than none at all.

If the only reason you can think of for an RX AIS is cost savings then I doubt you put much thought into it. There are 2 additional reasons I can think of right off the bat.

I confess I did not spend a lot of time thinking about other possible reasons. I guess I should have specified that again I was considering the majority or, if there is such a thing, the typical cruiser. Like 99.9999% of any generalized statements there will be exceptions to the rule and those reasons you state below are perfectly valid. My point was that some of the reasons for receive only stated by some others were not valid.

First would be the space occupied by the hardware. That's actually a pretty limited reason, only very small crusing boats would find the space for a TX or RX unit plus the antenea splitter. As it happens I have such a boat so this is something I have considered, I could find space for the unit and splitter if I really tried but not the battery and solar panel needed to support them (see the next paragraph for a discussion of this issue). The only reason I will be having any AIS on my boat is because I can get it as a feature of the VHF radio I am going to install and it is only offered in RX.

Second is the power used. For an RX unit the power draw is about 1/3amp for unit and splitter, with a display requiring more. There is an Icom unit with display that uses 0.7amp for RX. That's about 17 amp-hr/day. In TX mode the Icom draws 1.5amps or 36amp-hr/day. That means an extra 72 amp-hr of battery capacity and an extra 144w of solar panels to buy, find space for and mount. On boats up to 30' I can see problems finding space for the extra battery and solar panels in order to support the unit's power needs.

If you use the all in one VHF/AIS I intend to install as the basis for comparison, then I will pay an extra $250 for the AIS and use extra 0.2amps (4.8 amp-hr/day) compared to a similar VHF radio. I can find a place for an extra 20w of solar and the installed battery capacity will have to do.

A TX unit with built in dispay is about $900. Antennea splitter about $250. Let's say $50 for the cabling. Extra battery is onging to be $160. Solar panel $220 and wiring another $50. That's $1630 installing yourself. It's also a $1380 price difference from the the RX unit I am going to install.

The difference between a TX and RX system is more than "a few bucks" (depending on your definition of a few bucks) and there are space and power issues that must be considered.

It's good to point out to potential buyers some of the "hidden" costs of AIS. Like most stuff on a boat, just buying the basic kit is only the beginning.
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Old 01-09-2016, 04:40   #28
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Re: AIS, Receiver or Transmitter

The only thing I will add is where are you going to cruise? If you are sailing the Chesapeake Bay maybe not or spend time anchored in Fla or really not moving a lot.

We have transmit but then again we are in the Med/Black Sea and there are a number of shipping lanes we have to cross and we have more than once had conversations with big boats on passing or crossing ect --

So think about where you are sailing and why you need it.
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Old 01-09-2016, 05:07   #29
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Re: AIS, Receiver or Transmitter

Quote:
Originally Posted by Adelie View Post
Second is the power used. For an RX unit the power draw is about 1/3amp for unit and splitter, with a display requiring more. There is an Icom unit with display that uses 0.7amp for RX. That's about 17 amp-hr/day. In TX mode the Icom draws 1.5amps or 36amp-hr/day. That means an extra 72 amp-hr of battery capacity and an extra 144w of solar panels to buy, find space for and mount. On boats up to 30' I can see problems finding space for the extra battery and solar panels in order to support the unit's power needs.
I received the following email from Jeff Robbins of Vesper Marine, when I was considering AIS options a couple years ago:
Quote:
Thanks for your email and questions. Actually, the power consumption is about the same whether silent mode is enabled or not. That's because the transmit duty cycle is very low. Transmissions are 26ms every 30 seconds so the effect is only .08%. As a result, silent mode isn't really designed to save power - rather it's for those times where you want to keep your XB-8000 running (eg. you are using the GPS as your primary positioning device for other devices or want to continue to view other vessels nearby) but don't want to transmit for privacy or other reasons. You can control silent mode wirelessly via apps, using our PC/Mac utility, or by connecting a simple switch.

Yes, you can turn the WiFi off and that will reduce power. This is done using our PC and Mac utility software. You connect to the unit via USB and tell it to switch off the WiFi. In that case, it will draw around 250mA (3W) or less.
Does not seem like power consumption is a big factor in making the transmit/receive-only decision.
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Old 01-09-2016, 05:08   #30
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Re: AIS, Receiver or Transmitter

Many years ago, I used to ride motorcycles. Bell Helmets had a great ad that they used to put in the motorcycle magazines. It said: If you have a $10 brain, buy someone else's $10 helmet. (Of course, this was in the day when you actually could go down to K-Mart and buy a helmet for $10. Yes, it was that long ago.)

For some reason--I can't imagine why--the discussion about whether or not an AIS transmitter is worth the money made me think of that advertisement.
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