<Milt wrote:.....AIS....Here's data for the first two ships....> We have been getting far better range on the ships we encounter here in the Caribbean since we changed to a COMAR CSB200 Class B transponder. Very often more than 40 miles and most often in the 32-35 mile range. These are the tankers and cargo ships generally either Panama bound or heading from Panama across the Atlantic. The tankers are usually bound for Trinidad and/or Venezuela. Cruise ships are also in this mid 30's range A few of the smaller mega yachts are typically in the 20 mile range. I think what this is showing is the effect of antenna height on the signal but there must be other factors here. A difference in say 50' on a cargo ship vs. a mega yacht wouldn't account for a 15 mile difference. Our SR161 from Milltech was giving just shorter ranges on an average. So if Milt and the others are getting such significant shorter range I would certainly look at both the units themselves first and then the installations. We of course still have the issue that most Class A unit can't see our name, course or speed. They all see out MMSI # and our lat/lon and that's it. This is a known software issue on the class A units as the class B units had not be finalized when the requirement for class a units were made mandatory. They forgot to make any requirement that they be upgraded on any kind of a schedule so the class B units are basically "dark" right now to the majority of shipping :-( Dave & Nancy Swan Song Roughwater 58 Caribbean Cruise '07

I've been told the same thing on AIS (mine is a Furuno FA150 Class  

Result is that I can routinely pick up targets 40+ miles away.  

Not sure if my unit can see Class B units or not... while some very  

How do you tell if a target is Class A or Class B from the data?

I've been told the same thing on AIS (mine is a Furuno FA150 Class A)... installation guidelines call for fairly low gain antennas to keep the number of targets down (reception beyond 20 miles doesn't make sense from a traffic avoidance perspective), but my installation uses the same high-gain antenna as our primary VHF. Top of antennas are nearly 40' off the water. Result is that I can routinely pick up targets 40+ miles away. Presumably, they can see me too. I like the range, although when the day comes when everyone has a unit, and I have to sort out 300 targets on my screen, I might think otherwise. Not sure if my unit can see Class B units or not... while some very distant targets only show MMSI, location and SOG/COG data (supplemental data is not transmitted as often, so presumably it takes a lot of packet retransmits to get through), I can't recall seeing a target under 10 miles range that didn't have a name. I'm in Puget Sound area . Either there are no Class B's around (doubtful given the huge number of AIS targets... often 20+ on screen) or my unit is recent enough (installed five months ago) that it has updated software. How do you tell if a target is Class A or Class B from the data? John Marshall N5520 - Serendipity On Jun 22, 2007, at 11:37 AM, Dave Cooper wrote: > <Milt wrote:.....AIS....Here's data for the > first two ships....> > > We have been getting far better range on the ships we encounter > here in the > Caribbean since we changed to a COMAR CSB200 Class B transponder. > Very often > more than 40 miles and most often in the 32-35 mile range. These > are the > tankers and cargo ships generally either Panama bound or heading > from Panama > across the Atlantic. The tankers are usually bound for Trinidad and/or > Venezuela. Cruise ships are also in this mid 30's range > > A few of the smaller mega yachts are typically in the 20 mile range. > > I think what this is showing is the effect of antenna height on the > signal > but there must be other factors here. A difference in say 50' on a > cargo > ship vs. a mega yacht wouldn't account for a 15 mile difference. > > Our SR161 from Milltech was giving just shorter ranges on an > average. So if > Milt and the others are getting such significant shorter range I would > certainly look at both the units themselves first and then the > installations. > > We of course still have the issue that most Class A unit can't see > our name, > course or speed. They all see out MMSI # and our lat/lon and that's > it. This > is a known software issue on the class A units as the class B units > had not > be finalized when the requirement for class a units were made > mandatory. > They forgot to make any requirement that they be upgraded on any > kind of a > schedule so the class B units are basically "dark" right now to the > majority > of shipping :-( > > Dave & Nancy > Swan Song > Roughwater 58 > Caribbean Cruise '07 > _______________________________________________ > http://lists.samurai.com/mailman/listinfo/passagemaking-under-power > > To unsubscribe send email to > passagemaking-under-power-request@lists.samurai.com with the word > UNSUBSCRIBE and nothing else in the subject or body of the message. > > Passagemaking Under Power and PUP are trademarks of Water World > Productions, formerly known as Trawler World Productions.