AIS class B transponder

[Libations Too]

Does anyone have experience with AIS transponders? I have a NASA "Radar" AIS receiver that I really like, partly because of its low power requirement and because it is a stand alone unit. How much more power does a transponder require? Do ships and other commercial vessels monitor AIS? My use would be primarily for coastal cruises and offshore passages....not in enclosed waters such as SF Bay.

[selene]

I'd also be interested in people's opinions.  I am tempted by the Standard Horizon VHF with AIS (http://www.standardhorizon.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=83&encProdID=A2C2F4EB2A092075389DC4199A79B6C1&DivisionID=3&isArchived=0), just as an additional safety measure.  I don't have a radar, and so being in the fog in SF Bay would scare the heck out of me!

[Libations Too]

The VHF with combined AIS display is an interesting approach. While an improvement over no AIS, the tiny screen, lack of an alarm function, inability to determine closest point of approach or time to closest point of approach seem like disqualifying limitations to me. (EDIT...AS ED POINTS OUT BELOW, THE SH2150 RADIO IS CAPABLE OF DETERMINING AND ALARMING CPA AND TCPA. MY PREVIOUS STATEMENT HERE IS NOT CORRECT.) But, as I said, it is better than nothing and if one needs a radio upgrade ,why not choose one with an AIS display. I have a stand alone AIS receiver which similarly lacks the ability to determine CPA or TCPA, but it does have an alarm function that interupts my other activities if a vessel is within target range.

I have found the AIS receiver (with alarm) somewhat annoying within SF Bay...just too many targets. Sailing in the fog is always a challenge but shipping lanes and even ferry routes are well established and, when one needs to cross, studying the AIS and trying to determine CPA or TCPA manually is just too much of a distraction from watchkeeping for me (most of the time sailing alone). Offshore my impression is exactly the opposite...the AIS receiver is a wonderful tool and the alarm function, with a range set at 8 or 16 nm, gives me plenty of time to monitor targets and take action if necessary.

Having said all of that, I am increasingly tempted by the class B transponder since it sends my course, speed, etc. to any other vessel with an AIS receiver. So instead of just me watching out for others, I give others the data needed to watch out for me. The Vesper WatchMate display and an Em-trak transponder seems like a good, low power drain combination. But I am just beginning to gather data and power drain is a big factor for me.

[Dolce_Vita]

The VHF with combined AIS display is an interesting approach. While an improvement over no AIS, the tiny screen, lack of an alarm function, inability to determine closest point of approach or time to closest point of approach seem like disqualifying limitations to me. But, as I said, it is better than nothing and if one needs a radio upgrade ,why not choose one with an AIS display.

I took this approach two seasons ago, and I've been really happy with it.  The secret is to interface it's NMEA outputs to the chartplotter.  My Garmin GPSMAP 545 shows all the details buried in the AIS data, including CPA & TCPA. And with the AIS receiver integrated into the VHF radio, I don't need either an antenna splitter or a second antenna (which would have to be located far away from the radio's antenna.

I have found the AIS receiver (with alarm) somewhat annoying within SF Bay...just to many targets.

Same issue in the Chesapeake.

Sailing in the fog is always a challenge but shipping lanes and even ferry routes are well established and, when one needs to cross, studying the AIS and trying to determine CPA or TCPA manually is just too much of a distraction from watchkeeping for me (most of the time sailing alone). Offshore my impression is exactly the opposite...the AIS receiver is a wonderful tool and the alarm function, with a range set at 8 or 16 nm, gives me plenty of time to monitor targets and take action if necessary.

That was exactly what motivated me too.  Last spring we did a circumnavigation of the DelMarVa penninsula, and crossing the mouth of the Delaware bay offshore involves crossing five separate shipping lanes.  The previous time I did this trip, we crossed those lanes in a dense fog. I did not want to repeat that experience!

[rbrtfeld]

I put in a Garmin 740S chartplotter and radar along with a Garmin AIS 300 VHF radio that picks up and shows all AIS targets on the Chartplotter screen this past year. It works great but the alarm feature as mentioned is annoying in a busy harbor. Good news is that you can turn off the alarm if needed.  If I had to do it over again, I would have purchased the Garmin AIS 600 AIS VHF radio that not only receives AIS targets but also transmits your position as well.  I had a cheap attack when I was doing all the electronics at one time.  I am consdiering selling my AIS 300 and buying the Garmin AIS 600 this next year. It would be a easy conversion with the system I have. I would feel more comfortable in Fog or for that fact all the time that other large ships can see me as well as me seeing them.       

[Libations Too]

My Garmin GPSMAP 545 shows all the details buried in the AIS data, including CPA & TCPA.

Ed, unless I am terribly mistaken the information regarding CPA and TCPA is not "buried in the AIS data" that are received on your boat. CPA and TCPA are determined via algorithms employed by instruments that are installed on your boat....primarily your GPS, AIS receiver, or your chart plotter. Your GPS provides speed and course for your boat and your radio (or the AIS receiver part of it) provides speed and course data for target vessels. Then another instrument (chart plotter or AIS receiver/display combines the two sets of data to determine the CPA and TCPA.

I mention this as a clarification because, as I noted in my earlier post, I don't think the referenced Standard Horizon radio (and certainly not my NASA "Radar" receiver) has the capability to generate CPA or TCPA information. In your situation you did not mention the make/model of your VHF/AIS. Does it, by itself, generate and display the CPA and TCPA info? Or is this something the chart plotter does?

[Dolce_Vita]

Ed, unless I am terribly mistaken the information regarding CPA and TCPA is not "buried in the AIS data" that are received on your boat. CPA and TCPA are determined via algorithms employed by instruments that are installed on your boat....primarily your GPS, AIS receiver, or your chart plotter. Your GPS provides speed and course for your boat and your radio (or the AIS receiver part of it) provides speed and course data for target vessels. Then another instrument (chart plotter or AIS receiver/display combines the two sets of data to determine the CPA and TCPA.

I mention this as a clarification because, as I noted in my earlier post, I don't think the referenced Standard Horizon radio (and certainly not my NASA "Radar" receiver) has the capability to generate CPA or TCPA information. In your situation you did not mention the make/model of your VHF/AIS. Does it, by itself, generate and display the CPA and TCPA info? Or is this something the chart plotter does?

Doh!! You're absolutely right, as I would have realized if I thought about it for a second. My appologies for the sloppy thinking.  (It was 2 in the morning! )

Anyway, I have the Standard Horizon Matrix Series GX2100.  Both it AND the Garmin Chartplotter do CPA/TCPA alarms.  The radio will display distance & bearing to a selected AIS target, but I don't see any display page for the CPA/TCPA. (I never use the radio's display anyway. Too tiny!)  The chartplotter will display basic info if you hover the cursor over the target, and will display just about everything, if asked via a menu.  During an alarm, the target enlarges, turns red, and displays the CPA/TCPA info.  It also plots a little red icon at the projected place where your courses intersect that looks like a sinking sailboat!    Since I have the chartplotter mounted right at the helm, this is perfect for me, as I just have to glance down instead of going below to the nav station.

As for the GX2100, It was replaced with the GX2150, which is the one I should have gotten.  There was an issue with the number of NMEA connections needed to the chartplotter in the 2100 that was fixed in the 2150.

[Libations Too]

Thanks Ed...I completely missed this CPA/TCPA capability when I looked at the SH web link earlier. Seems like the only limitation with the SH2150 is the screen size. I am going to edit my earlier comment to reflect this.