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Old 18-10-2014, 07:03   #121
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Re: Class B AIS

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Originally Posted by a64pilot View Post
I see your point, and I may wait, just I'm waiting for a lot of things and darnit, I want some toys Plus honestly from a financial perspective it's sometime easier to spread things out a little
Crazy to put off for years an essential piece of nav equipment when you can buy it now and sail with it on every time you go out and use it, learn it, become expert with it whilst making sure its nicely integrated into your system.

Also its a fun bit of kit to use. Instead of passing a big ship and saying "Theres a Big Ship" you can look at AIS and say its a oil tanker heading for Dubai and will arrive in 3 weeks time. You can see the ports the fishing boats hail from (you can learn that fishing boats only turn off AIS when theres an internet forum around).
You can plot routes from the way AIS users: when I was in the Bahamas where the water is shallow I could see the draught on the local supply ships was 2 meters, same as me, so if they would nip through a reef, or between two islands I would plot a route along their track for future use. Stealing? Bad or lazy nav? No! Its using modern tech in modern ways.

Also you can check up on your boat when you are home or at work by dialing it up on Marinetraffic.com if you are in a reception area. When I was in Australia every day I could see if my boat is still afloat in the Caribbean!

All that and more for less that a Boat Dollar. Thats not bad

And sure as hell when you buy the damn thing you don't have to worry about mumbo jumbo like 'forward correction of error in digital data' because in the real world of you and your boat your horizons have just been expanded in reality.


Go buy one!
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Old 18-10-2014, 10:06   #122
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Re: Class B AIS

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Originally Posted by colemj View Post
But you did have a valid point about the digital aspect of AIS - no doubt there is signal processing and filtering going on in the receiving end that increases the S/N more so than is done on the voice end.

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Spot on.

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Old 19-10-2014, 07:01   #123
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Re: Class B AIS

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Originally Posted by colemj View Post
...about the digital aspect of AIS - no doubt there is signal processing and filtering going on in the receiving end that increases the S/N more so than is done on the voice end.
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Originally Posted by svlamorocha View Post
Spot on.
You and others seems to assume that there is some mechanism or method or technique in sending AIS digital data that will cause a receiver of those signals to perform better than the receiver manufacturer specifies it will perform. I see no basis for this. I assume that the receiver manufacturer's specifications about the performance of his AIS receiver represent the best performance it can deliver. It is not reasonable to assume that there exists some unexplained phenomenon that will cause all AIS receivers to work better than their manufacturers say they will.
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Old 19-10-2014, 07:56   #124
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Re: Class B AIS

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Originally Posted by continuouswave View Post
You and others seems to assume that there is some mechanism or method or technique in sending AIS digital data that will cause a receiver of those signals to perform better than the receiver manufacturer specifies it will perform. I see no basis for this. I assume that the receiver manufacturer's specifications about the performance of his AIS receiver represent the best performance it can deliver. It is not reasonable to assume that there exists some unexplained phenomenon that will cause all AIS receivers to work better than their manufacturers say they will.
That is not what I meant. I meant that with defined digital signals, a receiver can apply signal processing - not error correction - that is not available with voice signals.

I believe the manufacturer's specs and do not think the sets are magically exceeding them. I think the similar performance of AIS and voice have more to do with the power each is using to transmit.

For example, listen to the AIS bands and you will not hear the signal itself, while the receiver will catch it as a very strong, clear signal.

BTW, We were recently in Colon Panama (Caribbean Sea) receiving good (class A) AIS signals from the Perlas Islands, which are not only 60-90nm away, they are on the other side of the continent in the Pacific Ocean. We not only received these signals continually for weeks, we have also received them the last 3 times we were there in the past 3 years.

We have NEVER received a voice transmission from the other side of the canal (~35nm), even though there are dedicated frequencies for that which are in use continually. I don't think that was necessarily atmospheric conditions for the AIS.

On the other hand, I generally agree with your point that AIS and voice should be considered similar in range.

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Old 19-10-2014, 08:15   #125
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Re: Class B AIS

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....For example, listen to the AIS bands and you will not hear the signal itself, while the receiver will catch it as a very strong, clear signal.
I completely agree that a human ear listening to an AIS channel will not be able to recognize and demodulate the data in the AIS transmission. But, conversely, an AIS receiver cannot recognize spoken word. So in that regard a human ear is quite remarkable as a demodulator, as much as as any AIS receiver.
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Old 19-10-2014, 11:51   #126
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Re: Class B AIS

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Originally Posted by continuouswave View Post
I completely agree that a human ear listening to an AIS channel will not be able to recognize and demodulate the data in the AIS transmission. But, conversely, an AIS receiver cannot recognize spoken word. So in that regard a human ear is quite remarkable as a demodulator, as much as as any AIS receiver.
I wasn't talking about demodulating - I can't hear any signal at all. While over on the ham bands, I can hear and recognize PSK, RTTY, etc just fine, although I can't demodulate it.

The AIS signal may be beyond my hearing frequencies, or so fast that I cannot recognize it above white noise, but I suspect it is just a low signal that dedicated DSP's can pick out easily.

Any comments on why I can receive AIS signals regularly, for long periods of time over several years, in places where the voice signals from the same vessel cannot be received?

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Old 19-10-2014, 13:39   #127
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Re: Class B AIS

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Originally Posted by colemj View Post
I wasn't talking about demodulating - I can't hear any signal at all. While over on the ham bands, I can hear and recognize PSK, RTTY, etc just fine, although I can't demodulate it.

The AIS signal may be beyond my hearing frequencies, or so fast that I cannot recognize it above white noise, but I suspect it is just a low signal that dedicated DSP's can pick out easily.

Any comments on why I can receive AIS signals regularly, for long periods of time over several years, in places where the voice signals from the same vessel cannot be received?

Mark
I thought my previous comments were germane to this topic: Class B AIS

As for listening to AIS signals, you need to turn your squelch off. The message bursts are 20 milliseconds long, and that's not usually long enough to open the squelch. Also, the data sounds like very short noise bursts, or typically, reductions in the idle-channel noise.

Regarding the OP's question, AIS is not something you just plug in and instantly use like an expert. Sure, it is handy right out of the box, but it takes some time to learn how to set the alarms, and how to interpret what your system is showing you. I suggest that you find a transponder that you can make fit into the rest of your gear (or one that is stand-alone), and start using it. We are pretty far up on the learning curve these days, so any well-reviewed transponder with the interfaces you need should serve you well.
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Old 19-10-2014, 15:35   #128
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Re: Class B AIS

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Originally Posted by colemj View Post
I wasn't talking about demodulating - I can't hear any signal at all. While over on the ham bands, I can hear and recognize PSK, RTTY, etc just fine, although I can't demodulate it.

The AIS signal may be beyond my hearing frequencies, or so fast that I cannot recognize it above white noise, but I suspect it is just a low signal that dedicated DSP's can pick out easily.
When you are tuning around with your amateur radio communication receiver, you are probably listening with a rather narrow bandwidth and a product detector, receiving amplitude modulated signals. That is why you hear a narrow-shift FSK RTTY signal. Plus, an amateur RTTY signal has its carrier on for many minutes at a time--RTTY is really one of the most demanding modes for operating duty cycle, it is 100-percent key down full carrier all the time. It is not hard to hear a signal like that.

If you were to employ the same sort of communication grade receiver, a narrow bandwidth, and a product detector, I think you could hear AIS signals, too. The reason you do not hear them when you tune for them with your VHF Marind Band radio is the receiver has a much wider bandwidth, an FM detector looking for voice modulation, and a SQUELCH circuit that is probably too slow to un-mute.

Your problem in not hearing AIS transmissions is not related to the signal level. They are coming down the antenna feedline probably louder than some of the voice signals you can copy. You are just listening for them by ear to the audio output of a receiver that is not very good at detecting them. Then you make a rather incorrect leap in concluding that because you do not hear them in the recovered audio output of an FM voice receiver that their signal level must be very weak.
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Old 31-10-2014, 21:26   #129
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Re: Class B AIS

Okay. This thread seems to have calmed down a bit.
Now, if I'm starting with nothing. No computer, no
VHF, no plotter, nothing. What do I need for a basic
AIS transceiver?

Please try to stay out of the technical outer limits. (funny emoticon here)
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Old 31-10-2014, 21:49   #130
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Re: Class B AIS

Currently the core of my shopping list is the XB-8000.

XB-8000 AIS transponder with built-in WiFi and NMEA 2000 Gateway

includes GPS and antenna. Has free software (MarineMate) for tablet and as I am a current iPad user this makes sense for me.

Also advertise a more capable software (NavPlay) that looks interesting.

For me this is a pretty convenient way to get AIS transceive added to the boat. On the surface its' $800 and my current iPad and I am good to go.

If you want to get a dedicated display unit plus the ability to share out to a computer or tablet this is also an interesting basic choice.

http://www.vespermarine.com/transpon...chmate-tx.html

And finally if you want a color dedicated display here is the cadillac version.

http://www.vespermarine.com/transpon...te-vision.html

I have an old VHF - Soon I will be replacing and am waiting for someone to add AIS trasponder but so far no one is doing that. So my VHF choice will be DSC but not AIS - couple hundred bucks and the XB8000 or Watchmante 850.

So for $11 or $12 boat bucks I have gotten a latest gen DSC/VHF + AIS transponder, plotter, nmea 01183/2000 and WiFi.

I really think someone needs to put it all in one box at around $1,000, but even if a full AIS transponder, DSC VHF, WiFi, NMEA unit existed the strategy in this post eliminates the sinlge point failure issue a combined box would have.
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Old 01-11-2014, 05:37   #131
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Re: Class B AIS

I'm pretty much in the same place as Ex-Calif - starting from scratch. I was also leaning
towards the XB-8000, but I see the Garmin AIS 600 has the antenna splitter built in
for less than the XB-8000 and a separate splitter. The Vesper has a few other little nice
features like FM from the splitter and wireless, but I'm not sure if the wireless would be
much use for me.

As for a new VHF, there doesn't seem to be any reason to pay for one with AIS as I plan to
have the AIS transceiver feed 2 chartplotters. I really like the Standard Horizon radios, but I
can't bring myself to purchase new electronics that are not NEMA 2000. I'm
leaning towards an iCOM VHF, but they are expensive...

Thoughts?
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Old 01-11-2014, 05:53   #132
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Re: Class B AIS

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Originally Posted by Ex-Calif View Post
I have an old VHF - Soon I will be replacing and am waiting for someone to add AIS trasponder but so far no one is doing that. So my VHF choice will be DSC but not AIS - couple hundred bucks and the XB8000 or Watchmante 850.
The latest firmware on the XB8000 added the ability to talk to selected VHF radios and make direct DSC calls to AIS targets. I don't know which exact radios those are, but they are probably listed on Vesper's website.

This pretty much gives you a VHF/AIS combo. Having the ability to highlight a ship on the AIS display and push "call" to ring them directly on VHF is a very convenient feature - one of my favorite features on our Standard Horizon VHF/AIS combo.

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Old 01-11-2014, 05:59   #133
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Re: Class B AIS

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Originally Posted by MooGroc View Post
I'm pretty much in the same place as Ex-Calif - starting from scratch. I was also leaning
towards the XB-8000, but I see the Garmin AIS 600 has the antenna splitter built in
for less than the XB-8000 and a separate splitter. The Vesper has a few other little nice
features like FM from the splitter and wireless, but I'm not sure if the wireless would be
much use for me.
The Vesper w/splitter and Garmin are the same price once you look past the MSRP.

Don't discount wireless functionality so quickly. It can be used to setup the unit from tablet, phone or computer without having to plug in with cables, get wireless nav data on tablets and phones and computers, act as a general router for the ship, among other things. It is actually more useful than I thought, but we specifically use it for sending Nav data to computers and tablets.

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Old 01-11-2014, 06:07   #134
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Re: Class B AIS

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Originally Posted by colemj View Post
The Vesper w/splitter and Garmin are the same price once you look past the MSRP.

Don't discount wireless functionality so quickly. It can be used to setup the unit from tablet, phone or computer without having to plug in with cables, get wireless nav data on tablets and phones and computers, act as a general router for the ship, among other things. It is actually more useful than I thought, but we specifically use it for sending Nav data to computers and tablets.

Mark
I did check the street price and thought the Garmin was still cheaper, but you make a good point about the wireless. In any case, the price difference isn't significant and I should ignore it and just pick the better unit.
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Old 01-11-2014, 18:21   #135
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Re: Class B AIS

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Originally Posted by colemj View Post
The Vesper w/splitter and Garmin are the same price once you look past the MSRP.

Don't discount wireless functionality so quickly. It can be used to setup the unit from tablet, phone or computer without having to plug in with cables, get wireless nav data on tablets and phones and computers, act as a general router for the ship, among other things. It is actually more useful than I thought, but we specifically use it for sending Nav data to computers and tablets.

Mark
These things are developing all the time. WiFi is here and it's going to get more pervasive. Now, it could be a little "scary" relying on a router rather than cables for your data but waddya gonna do.

The marble keeps turning...

Vespers color unit say's it will take boat instrument data and send it over WiFi to a tablet with their upgraded software integrating iNavx, AIS and boat instruments onto an iPad.

Wasn't that long ago we were talking $7,000-$10,000 full blown chartplotters to get that functionality and integration.

Then of course the Irridium Go is WiFi.

They are still figuring all this out but I am pretty sure there gonna figure out all kinds of ways to integrate this stuff. I am no longer a fanatical early adopter (wasted enough money on Palm Pilots, Betamax, Laserdisk, JAZ drives etc.) but a year in with good reviews and I'll dive in.
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