Considering AIS on a budget

[sanibel sailor]

Originally Posted by pcmm

I don't think being able to transmit wouldn't have really helped in this situation.

You're better to have a seperate antenna for AIS. Less expensive than adding a splitter and creates a redudancy in your antenna as AIS and VHF antennas are the same.

Author say other vessel but failed to identify tow. Adequate AIS receiver may have helped.

Yes you may have missed the original post. A separate antenna is my plan, at least initially.

[pcmm]

Originally Posted by sanibel sailor

Author say other vessel but failed to identify tow. Adequate AIS receiver may have helped.

Yes you may have missed the original post. A separate antenna is my plan, at least initially.

AIS won't tell you if the other vessel has a tow or not but it may tell you if its a commercial vessel ( by looking to see if its an A or B type transmitter)

[dougweibel]

It is often easy to identify a tug as a tug on AIS.

It is rare that a tug and its tow have separate AIS enabling you to see that something is under tow. If you just know there is a tug via AIS then you may act cautiously do to the potential for a tow, but the tug might also be pushing a barge or just underway on its own. You need to look at it, either visually or with radar, to see what is going on.

If the tug captain is trying to contact you to inform you that you are heading towards his cable he "may" have an easier time capturing your attention on VHF using your vessel's name but looking at an AIS transceiver as the silver bullet for such a situation is not consistent with our experience using both AIS receivers and AIS transceivers.

[AlanR]

I have an AIS receiver, mounted on my stern rail, about five feet above sea level. This gives me a range of about five miles, a bit more for a large (tall) ship.

Sailing out of Guernsey, the fastest ship around is Condor Liberation, a fast ferry, usually doing 38 Knots. At that speed I have about twelve minutes notice, which I consider to be plenty of time, especially as I can see the CPA and Time of CPA on both iNavX and OpenCPN, plotted on my chart.

Out of interest, I have occasionally connected it to my masthead aerial, and this can give me signals from the other side of the English Channel (sixty miles) on a good day, but reliably, about twenty miles. The Channel is very busy, of course, and seeing all that traffic is too much information.

I have Radar, too, and in bad viz it is either on four or eight miles range, where I can see what is important to me.

Another advantage of having the aerial on the stern rail is that it is an independant aerial, and can easily be switched over to the Maeine VHF, should the other aerial fail (dismasting?).

Enough information is enough, and any more is just distracting.

I hope this is the answer you are looking for.

Many, many boats do not have an AIS transmitter, so Radar is still more important, in my mind, than AIS. You could consider a Radar active transponder, such as the SeeMe as an alternative.

[sanibel sailor]

Here is my final (for now at least) decision.
Em-trak B100 transceiver with its own GPS antenna (included for $349 shipped), an old VHF whip antenna stern rail mounted on an extension, with enough VHF cable length to serve as a spare antenna for ship’s radio if masthead unit fails. GPS cable about 20 feet too long. PVC pipe antenna mount has a wood dowel inside so it is reasonably stiff. If the crew cannot resist using it as a handhold, I might revise it to stainless, but this version was about $5.

[SVHarmonie]

Originally Posted by pcmm

AIS won't tell you if the other vessel has a tow or not but it may tell you if its a commercial vessel ( by looking to see if its an A or B type transmitter)

Errr.... yes it certainly will.

"Towing" and "Long tow >200m" are vessel types that are broadcast by AIS transmitters. Certainly, sometimes the tugboat operator gets lazy and leaves his status as "tug" but that is usually enough for my to keep a closer eye out.

If your AIS receiver is not presenting you with this vessel type information, maybe it is time to upgrade, or learn how to use all its capabilities?

[Auspicious]

Originally Posted by sanibel sailor

If the crew cannot resist using it as a handhold, I might revise it to stainless, but this version was about $5.

A serious discussion with crew that includes the term "keel-hauling" may be in order. *grin*

Originally Posted by SVHarmonie

Certainly, sometimes the tugboat operator gets lazy and leaves his status as "tug" but that is usually enough for my to keep a closer eye out.

This is one of common shortfalls of Class A AIS, or indeed any repetitive task that depends on people. I've seen ships headed up the Chesapeake toward Baltimore with destinations shown as Ft Lauderdale, status "at anchor" while underway, and no end of other data entry "misses." Most ships get it right so the errors are mostly entertaining.

High end recreational running Class A have a pretty high error rate.

Class B doesn't get a free pass. Surprising number of boats running around reporting 3.5x their size because someone put dimensions in feet into fields that require meters. Bloody Americans.

https://www.youtube.com/watch?v=dstpxhIj52k