AIS Transponder: Yes or No

[SailFastTri]

Originally Posted by David M

Yes, the transponder needs a special transponder antenna. Regular VHF antennas do not work for transmitting. Why? I have no idea.

No - a standard VHF antenna works fine. If you don't have a separate antenna you need a splitter.

[CarlF]

Actually the West Marine transponder now lists for $499 so it doesn't take much effort to get it for $450. And this is an impressive piece of equipment. I could probably drive my car over the case without hurting it. It looks identical to a unit from Shine Micro -- a US company that mostly makes high end commercial and military AIS gear. Setup with my Garmin chartplotters was a snap.

WEST MARINE AIS 1000 Class B "Send and Receive" AIS Transponder at West Marine

Carl

[SailFastTri]

Originally Posted by CarlF

Actually the West Marine transponder now lists for $499 so it doesn't take much effort to get it for $450. And this is an impressive piece of equipment. I could probably drive my car over the case without hurting it. It looks identical to a unit from Shine Micro -- a US company that mostly makes high end commercial and military AIS gear. Setup with my Garmin chartplotters was a snap.

WEST MARINE AIS 1000 Class B "Send and Receive" AIS Transponder at West Marine

Carl

+1 on that. I've had mine for 2 years and it works flawlessly. It also feeds GPS information to my PC navigation software on the same serial interface as the AIS info. I wired the NMEA output to a 9-pin D-connector in my panel and make one connection via a Cables-to-Go serial/USB converter. Sweet

[Dragon Lady]

At under $500 it has to be a no brainer.

[svBeBe]

Here is a silly question for those who report that their transponder has worked "flawlessly" for XX amount of time. How do you know that?

It is obvious on the chartplotter when you are not receiving AIS. Is it also obvious when you are not sending out AIS signal?

We have an AIS receiver only. Have put off buying a transponder until these become more reliable. Many of the cruising boats we know who have transponders frequently don't send out AIS signals and it seems to be a common problem. Have the newer units finally been improved enough to be reliable?

Judy

[S/V Alchemy]

Originally Posted by svBeBe

Here is a silly question for those who report that their transponder has worked "flawlessly" for XX amount of time. How do you know that?

It is obvious on the chartplotter when you are not receiving AIS. Is it also obvious when you are not sending out AIS signal?

We have an AIS receiver only. Have put off buying a transponder until these become more reliable. Many of the cruising boats we know who have transponders frequently don't send out AIS signals and it seems to be a common problem. Have the newer units finally been improved enough to be reliable?

Judy

No, it is not obvious, but a rather simple bit of gear could show you whether you were transmitting from your AIS antenna just by reading the broadcast power from it. Secondly, if you are receiving, you can confirm with named ships whether you are "there" on their AIS units.

Like the bilge pump or many other bits of gear aboard, you should occasionally verify they are working as advertised.

I would add that as we have a steel boat, we return a stronger radar reflection than, say, a heeled FRP boat. Nonetheless, we consider it more important in terms of the physics of the situation to be seen rather than to see, as we have the means (eyes, ears, RADAR) to discover 800 foot cargo ships and to take appropriate action, whereas they may not see us, nor in certain conditions would they necessarily see us on radar.

AIS means they don't have to, and it gives them a bearing, our SOG, and a means to reach us if we have the radio on...which we should!

I consider AIS a more important advance than most plotters I've seen, because it does things that weren't possible prior to its introduction, whereas I can always use paper charts and obtain lat/lon via cheapo handheld GPSes or CN.

[svBeBe]

Originally Posted by S/V Alchemy

No, it is not obvious, but a rather simple bit of gear could show you whether you were transmitting from your AIS antenna just by reading the broadcast power from it. Secondly, if you are receiving, you can confirm with named ships whether you are "there" on their AIS units.
..............

That is what we have done for friends with AIS transponders. They frequently drop off our receiver. We confirm via VHF that their AIS is still turned on but yet they are not 'seen' by our receiver -- yet all ships in the vicinity remain displayed; so we know the problem lies with our friends' Class B transponders and not with our receiver. This has happened with numerous friends' boats. For this reason, we have been reluctant to purchase a transponder until the units have been improved to stop dropping signal output. Since several people in this thread report their transponders work 'flawlessly' I would like to know how they know this.

If these Class B units are improved now to be reliable then it might be time to buy one on our next trip home. If they are still dropping signal output then I don't want one yet.

Judy

[conachair]

Originally Posted by svBeBe

Here is a silly question for those who report that their transponder has worked "flawlessly" for XX amount of time. How do you know that?

I only have a reciever as well ( and love it deeply ) but this site might be of use to others

Live Ships Map - AIS - Vessel Traffic and Positions

[Auspicious]

Originally Posted by CarlF

+1 that a a ship can hail you by name in a passing situation. In crowded waters this is a huge safety factor. And if you hail them, they can see you by name too.

More importantly, you can call the big ship by name. In my experience the response rate when calling ships by description and location is down significantly. I attribute that to the widespread installation of AIS. The big guys simply aren't used to be called except by name.

Originally Posted by svBeBe

Here is a silly question for those who report that their transponder has worked "flawlessly" for XX amount of time. How do you know that?

In addition to calling a ship and asking or having a friend check on their AIS receiver one can--given Internet connectivity--see AIS information on web sites like MarineTraffic.com and APRS.fi as long as their is a contributing receiver in the region.

[S/V Alchemy]

Originally Posted by svBeBe

That is what we have done for friends with AIS transponders. They frequently drop off our receiver. We confirm via VHF that their AIS is still turned on but yet they are not 'seen' by our receiver -- yet all ships in the vicinity remain displayed; so we know the problem lies with our friends' Class B transponders and not with our receiver. This has happened with numerous friends' boats. For this reason, we have been reluctant to purchase a transponder until the units have been improved to stop dropping signal output. Since several people in this thread report their transponders work 'flawlessly' I would like to know how they know this.

If these Class B units are improved now to be reliable then it might be time to buy one on our next trip home. If they are still dropping signal output then I don't want one yet.

Judy

There could be several mitigating factors at play here, one being the height of the antenna, weather aspects, condition of the antenna lead, and so on. In other words, it might not be the transmitting half at all. I don't personally know the specs of the transponder, but the "cutting out" could be simply a signal strength cutoff point set too high. I know from general radio experience and personal experimentation that even a handheld VHF transmitting from a Zodiac can achieve, under the right conditions, some impressive ranges (well above the stated five miles) when conversing with a base station aboard a boat, and yet in other situations, you are lucky to raise someone a quarter-mile away.

So you have to figure out if it's an inherent flaw of the transponder's circuitry or a conditional flaw resulting from antennas, weather, low battery output, whatever.

[xymotic]

Originally Posted by S/V Alchemy

There could be several mitigating factors at play here, one being the height of the antenna, weather aspects, condition of the antenna lead, and so on. In other words, it might not be the transmitting half at all. I don't personally know the specs of the transponder, but the "cutting out" could be simply a signal strength cutoff point set too high. I know from general radio experience and personal experimentation that even a handheld VHF transmitting from a Zodiac can achieve, under the right conditions, some impressive ranges (well above the stated five miles) when conversing with a base station aboard a boat, and yet in other situations, you are lucky to raise someone a quarter-mile away.

So you have to figure out if it's an inherent flaw of the transponder's circuitry or a conditional flaw resulting from antennas, weather, low battery output, whatever.

And don't forget that class B transmits less often that all of the 'other' boats might be with Class A. So a single missed transmission might not be updated for a longer interval and then 'dropped' from the reciever's chartplotter. An occasional drop off at 5 miles would not bother me, if it consistently fails @ 1/4 mile then I'd be concerned about it.

Regardless, neither is a valid reason to have no AIS at all. Get one that works

[markpierce]

As of this moment, there are about a couple dozen pleasure boats transmitting AIS in San Francisco Bay. (The majority are docked/moored/anchored.) Appears to me there is definitely an increasing number of pleasure boats with AIS.

[David M]

Originally Posted by svBeBe

Since several people in this thread report their transponders work 'flawlessly' I would like to know how they know this.

Good question Judy.

I phoned home from the boat and my wife went on the internet to marinetraffic.com and checked to see if I showed up on the website. I have also checked iPads with 3G that people had brought onboard to check the same website.

[S/V Alchemy]

Originally Posted by xymotic

And don't forget that class B transmits less often that all of the 'other' boats might be with Class A. So a single missed transmission might not be updated for a longer interval and then 'dropped' from the reciever's chartplotter. An occasional drop off at 5 miles would not bother me, if it consistently fails @ 1/4 mile then I'd be concerned about it.

Regardless, neither is a valid reason to have no AIS at all. Get one that works

Good points. The "refresh" feature on Class B is a longer interval. I had forgotten that.

The suggestions to use web sites and smartphones to "see" your AIS updates is a good one. Like a SPOT Messenger going off twice a day in the ocean, a simple "OVER HERE" can convey a lot.

[captainKJ]

Personally I think AIS is a waste of money for a sailboat. I sailed supply and anchor boats in the gulf of Mexico. On a commercial vessel they are required. Spending many hours in the bridge most of the boats have 2 radar units. A good reflector is a must. I would rather have a very good reliable radar than an AIS unit. Just a new item for people to spend money on. Radar will tell you were the vessel is and it is easy to call them by giving them lat and long. I know this will start a debate but were are you sailing to and from. It is just another toy to buy. save the money and buy a better radar unit. the more toys you have on a boat the more they will break. Keep It Simple Stupid works wonders.