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Old 12-04-2013, 20:23   #121
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Re: Want the Best, Cheapest Easiest AIS solution:-)

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Originally Posted by Dennis.G View Post
You are much better radar operator than I am. I might see 90%+ of large ships on radar (who are required to have AIS anyway), but closer to 10% of small sailboats. They tend to just look like the rest of the sea clutter to me.

Of course the radar has to be on and i have to be sitting in front of the thing to see anybody on it.
An understanding of the technology and willingness to learn, hence knowledge on how to use it are a prerequisite.

I can tune my radar to see birds, I know/understand it's limitations and capabilities.

YMMV
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Old 13-04-2013, 00:40   #122
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Re: Want the Best, Cheapest Easiest AIS solution:-)

Yachties, often insist on keeping Radar and other instrumentation sets at the quint essential " Yacht NAv Station".

Me I have everything I need up where I can see it. My Pathfinder is mounted on my binnacle. It picks up most everything, and gets rid of sea clutter. As DD says, takes some time figuring out what you are looking at, when close to land. But when clear of land I have never missed identifying a vessel.

My path will take me 4000nm along 130Long mid ocean until F.Poly. Then mainly small vessels close in eyes and radar territory, when we eventually head to Thai waters, I will not be broadcasting my position! As every poster on here has a different boat, a different reason for having a boat and a different use for a boat it is not surprising such a divergence of opinion.

55m going on the Canadian Lottery tomorrow!! I will buy a ticket. my odds are 14 million to 1 to win:-) If I do Ill buy every poster on the thread a ruddy Vesper!
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Old 13-04-2013, 01:35   #123
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Re: Want the Best, Cheapest Easiest AIS solution:-)

Excellent - good luck PM me for me address to post the Vesper box to me!
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Old 13-04-2013, 01:56   #124
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Re: Want the Best, Cheapest Easiest AIS solution:-)

i will recopricate with a Vesper if i win next weeks 40m lotto.
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Old 13-04-2013, 02:29   #125
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Re: Want the Best, Cheapest Easiest AIS solution:-)

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55m going on the Canadian Lottery tomorrow!! I will buy a ticket. my odds are 14 million to 1 to win:-) If I do Ill buy every poster on the thread a ruddy Vesper!
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Old 13-04-2013, 03:07   #126
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Re: Want the Best, Cheapest Easiest AIS solution:-)

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How important for safety in the open ocean is the transmit facility with Ais?
From the point of view of a steel boat with a good radar echo....

Just to add to the mix .....

Offshore (off the shelf beyond the fishing boats) I found a nasa ais standalone receiver was plenty to be getting on with, I'd be picked up on radar and any avoidance by the big boys would happen usually before the ship even appeared over the horizon. Getting a good radar echo is well worth having a look at before casting off. If they ignore you then you have 5/10 miles at least to make a decision, radio up or course/speed change. Not many are over 15Kts so enough time to get sorted out. Offshore it certainly be nice to transmit but receive will be a very welcome little friend pulling 0.1A from the chart table. The nasa alarm is plenty loud enough as well to wake a single hander. (There's a nasa ais engine fitted now as well to opencpn which is great)

Closer to shore I don't really pay so much attention to the smaller vessels AIS, fantastic for shipping lanes but the little boats are usually assumed to be drunk, asleep or both until proven otherwise Just because they have a heading & speed one moment doesn't mean that it won't be completely different a minute later.

So transmit is great , but receive on it's own is a massive bang for the buck. As ever, your boat, your budget
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Old 13-04-2013, 03:26   #127
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Re: Want the Best, Cheapest Easiest AIS solution:-)

Great thread. I'm pre-planing a trip from New York to Bermuda and want a good AIS transceiver. My uneducated concern is that another small boat on a reciprical course may not have an AIS transmitter.

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Yes, I completely agree. That's why when people ask me for a recommendation and cost is the driving factor, I tell them an existing well functioning VHF antenna will work. But when performance is a factor, I recommend they consider an AIS-tuned antenna. If the existing masthead antenna is old, or of unknown origin, I recommend changing it, or at least professionally checking it.

So... if you are going to change it, then I recommend considering an AIS-tuned one. AIS-tuned antennas usually have around 6-7MHz of bandwidth so they will still work well with the VHF radio which has much higher power output. But they are optimized for 162MHz to be used with the much lower power output AIS.

Regards the signal loss due to splitters... that's quite true of most splitter designs. Most "designed for AIS" splitters have over 4dB of loss (that takes your 25W VHF and radiates 9W or less). We looked at this and designed a splitter that has virtually no loss on the VHF path and has 12dB of amplification on the AIS receive path. This results in an effective 6dB gain in sensitivity for our AIS units. It more than makes up for the longer cable run up the mast and combined with the antenna height results in significantly increased AIS receive range.
Jeff,

Since we are limited to line-of-sight with VHF frequencies, how much signal strength overall is needed to receive line-of-sight targets? (And how much transmit is really needed?)

Also, doesn't splitting and amplification each act to decrease sensitivity? It's really about signal to noise ratio, right? The splitting decreases signal no matter how you slice it. And amplifying increases noise.

How much signal loss do you get from a 2nd vhf antenna at the top of the mast, inches from the other VHF antenna? Let's say in the worst part of the antenna pattern.

Putting the above three thoughts together, a lot of the installation choices depend on what's needed to only hit line-of-sight. I guess I'm looking for a graphic showing the operational envelope from all these parameters. That and some feedback from real-world experiences.

(I'm a big believer in starting with the highest gain omnidirectional antenna that still has a beamwitdh in excess of your typical angle of heel. There's a lot more complexity, money, and effort needed to overcome a sub-optimal antenna. For example, using a higher gain antenna can overcome signal loss from using a splitter. So the best advice could be to both upgrade your masthead antenna and use a splitter.)

Regards,
Brad
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Old 13-04-2013, 10:32   #128
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Re: Want the Best, Cheapest Easiest AIS solution:-)

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Great thread. I'm pre-planing a trip from New York to Bermuda and want a good AIS transceiver. My uneducated concern is that another small boat on a reciprical course may not have an AIS transmitter.
A small boat? Most likely it won't be transmitting AIS. Assume this.

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Also, doesn't splitting and amplification each act to decrease sensitivity? It's really about signal to noise ratio, right? The splitting decreases signal no matter how you slice it. And amplifying increases noise.
An amplifier can reduce the system noise when it is placed close to the antenna. It should amplify the signal enough to compensate for the loss in the "downstream" coaxial cable or splitter. I've got a pretty tall mast and without an amplifier for my dedicated AIS antenna my range is just fine. Anyway, a splitter with a built-in amplifier should improve your signal/noise ratio if it is properly designed.

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(I'm a big believer in starting with the highest gain omnidirectional antenna that still has a beamwitdh in excess of your typical angle of heel.
I think you will find that the heel angle limits you to a short "3dB" (half-wave) vertical whip. Again, this works very well for me.
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Old 13-04-2013, 15:08   #129
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Re: Want the Best, Cheapest Easiest AIS solution:-)

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Originally Posted by conachair View Post
From the point of view of a steel boat with a good radar echo....

Just to add to the mix .....

Offshore (off the shelf beyond the fishing boats) I found a nasa ais standalone receiver was plenty to be getting on with, I'd be picked up on radar and any avoidance by the big boys would happen usually before the ship even appeared over the horizon. Getting a good radar echo is well worth having a look at before casting off. If they ignore you then you have 5/10 miles at least to make a decision, radio up or course/speed change. Not many are over 15Kts so enough time to get sorted out. Offshore it certainly be nice to transmit but receive will be a very welcome little friend pulling 0.1A from the chart table. The nasa alarm is plenty loud enough as well to wake a single hander. (There's a nasa ais engine fitted now as well to opencpn which is great)

Closer to shore I don't really pay so much attention to the smaller vessels AIS, fantastic for shipping lanes but the little boats are usually assumed to be drunk, asleep or both until proven otherwise Just because they have a heading & speed one moment doesn't mean that it won't be completely different a minute later.

So transmit is great , but receive on it's own is a massive bang for the buck. As ever, your boat, your budget
As a fellow metal boat owner, practically, I agree entirely. The OP's Dufour 35 isn't steel, however, and won't be seen easily by ships and in heavy weather, maybe not at all by similar sailboats.

Again, because I see AIS as the "bride of RADAR", offshore, I probably wouldn't turn the RADAR on much unless we were approaching squalls at night: I like RADAR's ability to find the heavy stuff and to locate "alleyways" of less rain and wind, if present. The AIS is like having someone in the crow's nest keeping a lookout; transponder AIS is like giving that lookout a megaphone and a flaming torch.

EPIRBs are pricy, too, and you aren't required to have one offshore. But since they been invented, only the truly eccentric or Luddite would decline to carry one.
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Old 13-04-2013, 16:07   #130
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Re: Want the Best, Cheapest Easiest AIS solution:-)

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As a fellow metal boat owner, practically, I agree entirely. The OP's Dufour 35 isn't steel, however, and won't be seen easily by ships and in heavy weather, maybe not at all by similar sailboats.

Again, because I see AIS as the "bride of RADAR", offshore, I probably wouldn't turn the RADAR on much unless we were approaching squalls at night: I like RADAR's ability to find the heavy stuff and to locate "alleyways" of less rain and wind, if present. The AIS is like having someone in the crow's nest keeping a lookout; transponder AIS is like giving that lookout a megaphone and a flaming torch.

EPIRBs are pricy, too, and you aren't required to have one offshore. But since they been invented, only the truly eccentric or Luddite would decline to carry one.
Well put and the gap in price between receive & transponder continues to narrow, if I was in the market today the decision wouldn't be as obvious.
Though I think, maybe partly to do with the internet and forums like this, people can get to be a bit black and white with boat tech, fit AIS then don't pay as much attention as might be wise getting as good a radar return as possible. All these bits do good and chances are when they do some good you'll never know, you don't tend to notice when nothing happens

As for radar, I found offshore the only thing it actually did was spot the squalls, plenty of time to get the shampoo ready
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Old 13-04-2013, 16:55   #131
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Re: Want the Best, Cheapest Easiest AIS solution:-)

Using NMEA 2000 to communicate between a black-box AIS and a different manufacturer's display may have problems with proprietary sentences. Check the documentation on www.panbo.com. Simrad just this month released some new MFD software that solves their problem on the NSE displays.
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Old 13-04-2013, 17:18   #132
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Re: Want the Best, Cheapest Easiest AIS solution:-)

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Originally Posted by S/V Alchemy View Post
As a fellow metal boat owner, practically, I agree entirely. The OP's Dufour 35 isn't steel, however, and won't be seen easily by ships and in heavy weather, maybe not at all by similar sailboats.

Again, because I see AIS as the "bride of RADAR", offshore, I probably wouldn't turn the RADAR on much unless we were approaching squalls at night: I like RADAR's ability to find the heavy stuff and to locate "alleyways" of less rain and wind, if present. The AIS is like having someone in the crow's nest keeping a lookout; transponder AIS is like giving that lookout a megaphone and a flaming torch.

EPIRBs are pricy, too, and you aren't required to have one offshore. But since they been invented, only the truly eccentric or Luddite would decline to carry one.

My Mam's name was Ludd!

I may be missing something here but my aging Pathfinder radar seems to pick up everything that it bounces a beam off. Logs, aircraft comming into land ( now the closing speed of that caused a instantaneous loosing of the bowels), high flying whales, big boats, rusting boats, small wroting boats, plastic boats. Must have it set up right and be able to use it.

Your comment about epirbs has has prompted me to start my next thread.

PS bought my ticket! draw in 4 hours Jeff hope you can come with a big order:-)e
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Old 13-04-2013, 17:35   #133
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Re: Want the Best, Cheapest Easiest AIS solution:-)

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I may be missing something here but my aging Pathfinder radar seems to pick up everything that it bounces a beam off. Logs, aircraft comming into land ( now the closing speed of that caused a instantaneous loosing of the bowels), high flying whales, big boats, rusting boats, small wroting boats, plastic boats. Must have it set up right and be able to use it.
Thread drift from AIS, but can anybody *really* see logs (via radar) when sailing on the open ocean? Sure, on a flat calm day I can tweak the radar to show logs, floating birds, etc, but when I am at sea with even a few feet of swell running, the sea-clutter is bad enough that I have to dial the sensitivity back to the point where a telephone-pole length log just isn't going to show up reliably. It seems that I'm often sailing in 6-8 ft seas with whitecaps starting, and at that point the radar is only going to show the big stuff.

Am I doing it wrong?
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Old 13-04-2013, 17:48   #134
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Re: Want the Best, Cheapest Easiest AIS solution:-)

Relax Paul! You are not loosing your grip. I was using a little bit of flamboyance in my reply to the steel boaters:-) Radar is great, but then so are your eyes, just another tool, to make Sailing easier. Like ais. I am definitely not a Luddite, but definitely not a jump on the "look at mine its bigger and better than yours wagon".
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Old 13-04-2013, 18:40   #135
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Thread drift from AIS, but can anybody *really* see logs (via radar) when sailing on the open ocean? Sure, on a flat calm day I can tweak the radar to show logs, floating birds, etc, but when I am at sea with even a few feet of swell running, the sea-clutter is bad enough that I have to dial the sensitivity back to the point where a telephone-pole length log just isn't going to show up reliably. It seems that I'm often sailing in 6-8 ft seas with whitecaps starting, and at that point the radar is only going to show the big stuff.

Am I doing it wrong?
I'm with you Paul. When the seas pick up my screen gets cluttered as well. It's a great tool, but certainly there are times when its usefulness is marginal (heavy seas, rain).
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