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Old 20-05-2013, 06:57   #376
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Re: Please turn your AIS off when docked/moored/anchored

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DSC can get seriously annoying on a summer weekend in a busy area due to periodic false alarms, to the point we occasionally turn off the VHF when in the past we would leave it on. As far as I can tell, there is no way to prevent hearing the piercing alarm tone. Like AIS alarms, I wonder if we are suffering from too many devices crying wolf too often, so we end up muting or turning them off, or putting on filters that eliminate both the annoying alarms and some we should be paying attention to.
False alarms are a different thing than using DSC to communicate, etc. Routine communications, position polling and all the other functionality does not go out to anyone other than the specific mmsi chosen and would never become annoying, or even noticeable, to the general area.

The alarm or notice functionality has to either be specifically chosen, or someone is lifting the little cover and pushing the red button.

I suspect if this is happening, it is because the radio being used has poor engineering and user interface. That isn't a problem with DSC itself.

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Old 20-05-2013, 07:08   #377
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Re: Please turn your AIS off when docked/moored/anchored

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I suspect if this is happening, it is because the radio being used has poor engineering and user interface. That isn't a problem with DSC itself.
But, it's happening in the real world. I have heard numerous distress alerts on DSC and not a single one has been real. Apparently, too, the vast majority of DSC radios are not connected to GPS so the Coast Guard can't so easily track down the false alarms, so instead they have to go on Channel 16 and endlessly broadcast for everyone to check their radios and make sure they haven't triggered a false DSC alert. Sometimes this goes on for hours.
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Old 20-05-2013, 07:19   #378
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Originally Posted by Kettlewell View Post

But, it's happening in the real world. I have heard numerous distress alerts on DSC and not a single one has been real. Apparently, too, the vast majority of DSC radios are not connected to GPS so the Coast Guard can't so easily track down the false alarms, so instead they have to go on Channel 16 and endlessly broadcast for everyone to check their radios and make sure they haven't triggered a false DSC alert. Sometimes this goes on for hours.
dSC in the US is really suffering from lack of user training and points up the problem , when you have a license free environment. Else where the licensing is primarily about education and training.

In Europe , which has DSC now for nearly 20 years the experience was that at first there was a lot of false distress alarms, but the number has tailed off and settled down to a manageable figure.

Given that I only ever fit SH radios and I often turn off the DSC scanning. !!

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Old 20-05-2013, 07:21   #379
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It is wonderful to have hailing channels quiet, call someone without all the Aunt Bea's following the conversation around and quietly and quickly poll your friends positions to see where they are in a cruising ground.
My standard SH config is to scan all ship to shore and ship to ship channels , hence ill always follow your conversation DSC initiated or not !!!!

And I never allow auto polling !!!

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Old 20-05-2013, 07:51   #380
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Re: Please turn your AIS off when docked/moored/anchored

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My standard SH config is to scan all ship to shore and ship to ship channels , hence ill always follow your conversation DSC initiated or not !!!!

And I never allow auto polling !!!

Dave
But I suspect you would become very bored with my conversations and soon stop following me! But there are a certain type of people who do seem enthralled listening to me set up a time to go fishing or asking if I could borrow a crimp from a friend...

Yes, auto polling is a choice with good reasons both ways. Having it set on our HH is a safety procedure for us in case one of us is stranded. Makes it easy to know just where to go - particularly since I am often miles offshore in it.

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Old 20-05-2013, 07:54   #381
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Re: Please turn your AIS off when docked/moored/anchored

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dSC in the US is really suffering from lack of user training and points up the problem , when you have a license free environment.
I think user training is only partly the problem and would go away completely if the radios were engineered better. I cannot believe how complicated and unfriendly many of the current units are. And there is absolutely no reason for it - it is simply software and intelligent use of buttons/knobs, no different than a telephone for the most part.

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Old 20-05-2013, 07:55   #382
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Re: Please turn your AIS off when docked/moored/anchored

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AIS is no where near its technical limits in the situation Evans described.

I have described TWO situations (within a couple of days). One was sailing by NYC (at about midnight) where my AIS was only able to transmit about half of its scheduled messages - that would seem very clearly to imply that class B IS near its technical limits in some particularly crowded areas.

How do you explain that event otherwise? I am honestly interested to hear a technical explanation. I have already discussed this with Vesper (there was nothing wrong with my unit, and they consider this a common event in high traffic areas) but would be delighted to hear your explanation.

I would be interested in a technical perspective on this also . . . . My sense from the AIS message slot specs is that there might/must have been (about order of magnitude) 1000 AIS (A & B) turned on in the greater NYC area at mid-night (on a weekday) to account for my 50% drop-our rate. Do you technical experts agree?

Nick has (I think) agreed that class B can in fact be near its technical limits in some crowded areas, but just thinks B is a crap solution and that we should have class A units. I have not given this much thought but my immediate personal reaction is that having many pleasure vessel switch to class A would cause more problems (it is higher power, and more frequent message transmit, and would be more difficult for commercial ships to filter).

Note: one linguistic point. When I refer to 'the AIS system" I mean from end user eye ball to end user eye ball, including the user interfaces, so for example I include filtering when I refer to 'the AIS system'. Jedi (I think) only refers to the 'machine to machine communications' when he says 'AIS system'.

Evans problem is the state of art for AIS in leisure vessels isn't good enough

Related to my second situation (Newport), which we have discussed more, and I think already beaten to death, I think we most all agree:

Specifically, I completely agree that the filtering commonly available is not 'good enough' yet. I have one other suggestion on that . . . a 'marine/mooring field filter'. I can look at the screen and pick out marinas and mooring fields by seeing clusters of very tightly packed very slow moving boats. I am guessing there is more enough CPA power in these units to also identify these clusters, and say filter out any that has more than 10 boats in it. Each specific boat would then perhaps be 'woken up' if it starts moving or you get within 100m of it. This filter would then leave unfiltered the isolated single very slow moving vessels (pot picking and waiting for Warf time) that I like to have alarms for.

I also agree that black box installations should have on/off switches, and if some installers and not putting such in then their 'state of the art' is not good enough.
.............
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Old 20-05-2013, 07:58   #383
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Re: Please turn your AIS off when docked/moored/anchored

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But, it's happening in the real world. I have heard numerous distress alerts on DSC and not a single one has been real. Apparently, too, the vast majority of DSC radios are not connected to GPS so the Coast Guard can't so easily track down the false alarms, so instead they have to go on Channel 16 and endlessly broadcast for everyone to check their radios and make sure they haven't triggered a false DSC alert. Sometimes this goes on for hours.
Yes, I agree it is happening - didn't express myself well. I meant to say "I suspect this is happening because the radio has poor engineering and user interface". I don't think the people triggering it are doing it intentionally - just trying to push through the Sanskrit to make a simple call.

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Old 20-05-2013, 08:11   #384
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Re: Please turn your AIS off when docked/moored/anchored

Coastwise cruising within the USA we don't see a need for private DSC calling as we all have cell phones and the system works well almost everywhere--and you can get people when ashore, etc. It is much more pleasant carrying a cell phone around than a handheld radio, and again the phone is much more useful for other things. The regular VHF party line is useful out on the water to stay in touch with emergencies, weather, people you run into you don't know calling, communicating with small craft, etc. DSC, not so much. Even the CG routinely asks people to switch to a cell phone if available.
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Old 20-05-2013, 08:14   #385
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Re: Please turn your AIS off when docked/moored/anchored

Not installing a transponder was a conscious decision for us, coupled with the fact that they were all >$1000 when we were at that decision point.

My thinking was:

1. There would be no way I would rely my class B signal to help a commercial ship navigate around me - therefore whether I had a transponder or not was not an issue. I can always see that commercial ship and take full responsibility for staying well away from it no matter its intentions. For the very few times when the situation of what action I should take is unclear to me, I call the ship and ask it what action it would like me to take. If I had a transponder, that would not change my situation at all. If my transponder was "overloaded" and only transmitting half of the time, it would not change my situation at all.

2. Class B transmission rates are slow enough to only give "approximate" information. While this may be the same as "accurate" information for a slow boat, it is not the same for a higher speed power boat. So I don't rely on that in close quarters beyond noticing that the target is present and navigating, like we did before AIS. For longer distances and quarters, I believe class B has limited transmission ranges (I may be wrong here) and I have often seen boats visually before I get them as AIS targets. Therefore, I reason that having a class B AIS transponder is of limited use to me.

Having said that, it is conceivable that we will get a transponder sometime in the future. The prices have rapidly approached those of receiver only units.

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Old 20-05-2013, 08:22   #386
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Re: Please turn your AIS off when docked/moored/anchored

One point - and this is not an accusation, just a point - I regularly watch ships on radar with the AIS overlaid on it. The radar return will move forward outside the target icon, then the target icon will "jump" up to the return after a while. This, of course, is the delay between transmission rates. Class B power boats doing 20 kts have an even longer distance between their actual and reported positions and speeds.

My purpose in making this observation is to point out that AIS should only be used as a tool for situational awareness and decision making and not for maneuvering and navigating/helming.

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Old 20-05-2013, 08:31   #387
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Re: Please turn your AIS off when docked/moored/anchored

@Evans (sorry I cant't quote your post because it's one big quote...)

You described two situations but those were not situations where the AIS system has become overloaded.

But I now see that you define the AIS system as including the human operators who configure their equipment for settings and alarms. This means that errors like wrong destination or navstate would also be system errors, as well as inadequate filtering or too much filtering. This may be your point of view but it is not that of the industry.

I believe you reported that your unit skipped transmissions due to high noise level? High noise might have been caused by many things, incl. cross-modulation, your alternator or fridge, atmospheric conditions and a thousand other things. Or it might have been your unit's CPU being overloaded trying to keep track of time slots that are in use or not. Because that is how class-B works: by listening it tries to find empty timeslots. A high noise level just might make it think that the timeslot is in use.

I also never stated that class-B is crap. I wish you would stop polarizing the issue. Class-B uses the scraps left-overs from class-A is what I said. This means something very different.
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Old 20-05-2013, 08:41   #388
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Re: Please turn your AIS off when docked/moored/anchored

Re Icom DSC/VHF:

I have used Icom ham gear for many years with success and pleasure, so when I needed to buy a new VHF I went with them without much research. The radio functions in its normal capacities quite well... no complaints there. But when I encountered the DSC section of the owners manual (and I do RTFM as a rule) I was defeated. Approximately one half of all the pages in the book were related to using DSC to make a call (distress or otherwise), and as said, it is written in an incomprehensible fashion.

Considering that my background includes many years of using complicated electronics, my difficulty in usefully understanding the manual indicates that it is hopeless for the non-techo. No wonder that the DSC features are not used by many.

Shame on Icom! Surely they could do better.

Cheers,

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Old 20-05-2013, 08:50   #389
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Re: Please turn your AIS off when docked/moored/anchored

I know we are OT on this DSC stuff, but my radio lost its MMSI programming, and the only way to reprogram it is to send it back to the factory. Since the units have to be hardwired in that is a huge pain too. They really need a standard plug-and-play connector for all radios and GPS units so that any idiot, including myself, can install or replace without hassle. Maybe NMEA 2000 connectors do the job if you are replacing everything at once.
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Old 20-05-2013, 09:07   #390
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Re: Please turn your AIS off when docked/moored/anchored

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I think it has to do with the radio engineering (well, programming), and there is hope there. We have a new Standard Horizon DSC radio and using the DSC functions (all of them) are as simple as using a telephone. None of them take more than 2-3 pushes of a single button labeled "call". Many friends of ours have Icom radios, and the DSC functions on those radios may as well be in Sanskrit. They have most of the same functionality as we do, but using it is beyond those without MIT engineering degrees.

I always attempt to help people set up and use their DSC functionality and everyone is immediately hooked.

It is wonderful to have hailing channels quiet, call someone without all the Aunt Bea's following the conversation around and quietly and quickly poll your friends positions to see where they are in a cruising ground.

When I am out in the dinghy spearfishing (with our HH DSC), Michele can push a button and my location shows up on our chart plotter. Similarly, when I find a good fishing reef or mount offshore, I can push a button and the position of it gets plotted back on the boat.

So yes, there are countless DSC sets out there with the owner having never figured out how to use them. Everyone with newer Standard Horizon sets seem to know how to use it, so I can only hope that the implementation of this functionality gets better engineered over time. There seems to be no real learning curve or hurdle to using it - just implementation of its functions.

Mark
Position polling is a fantastic function. Our handheld is a SH H851, and it's great being able to see where the dinghy is with the push of a button. Will be great for cruising in company (haven't tried that yet myself).

Our fixed set is Icom and I really don't think the DSC functions are so hard to use. I will admit, however, to having inadvertently sent All Ships calls by mistake on two separate occasions when I was first finding my way around it. . The Coast Guard didn't love that too much

My old plotter wouldn't plot received position reports (and position of distress calls) -- I'm hoping the new one will. I've got to get NMEA0183 into the plotter somehow for that and I'm afraid that will require a multiplexer since the port is already occupied by speed data from my DST-2
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