Class B AIS transponders - any use ?

[PembrokeshirePromise]

With all the discussion on Ouzo and radar reflectors I just wondered if people thought fitting an Class B transponder might have a place.

I see that these can have the transmit bit disabled - and just use them as a normal AIS reciever - perhaps switching on in fog / night / miles out at sea ? Seem to cost c. £500 - so a fair bit more that the NASA AIS engine - but only double a dual channel receiver ?

Do/will big ships monitor class B as well - or will they switch it off if many people take it up ?

Obviously not a total solution - much better to get out the way yourself - but curious as to what peoples opinions are ....

 

[pennycar9]

I would rather spend my money on an active radar reflector,or at least a firdell or echo max. Nasas AIS radar will not show you to any other radar and dont forget that the display will only show ais equipped shipping.The next thing that comes along could be a fifty foot motor yacht and he wont know your there and you wont see him either. My advice is to equip yourself with the best reflector you can. Steer well clear of those silly little tubular things though.

 

[Channel Ribs]

I am normally a huge fan of anything gadgety and or electronic, certianlu I feel like I should be getting quite excitied at the idea... But alas I am not. /forums/images/graemlins/frown.gif

As far as I can tell, there are a limited number of 'slots' available to class B, so in busy waterways where it would be needed most it will be hit and miss. /forums/images/graemlins/blush.gif

I think that a different system is needed, perhaps a transponder which would be triggered by commercial shipping's radar and then giving AIS type data. That way it is the comercial boys that have to spend the money and we can keep the gin budget intact. /forums/images/graemlins/wink.gif

 

[peterb]

[ QUOTE ]
a transponder which would be triggered by commercial shipping's radar and then giving AIS type data.

[/ QUOTE ]

Isn't that a Class B AIS?

 

[Channel Ribs]

I was more thinking of something that doesn't tie up radio frequencies, but in any case I do not have a well rounded/researched plan. /forums/images/graemlins/wink.gif

More an active radar reflector, with gps and mmsi data overlaid in the response.

 

[Stork_III]

You mention Firdell as a "Good" (implied) reflector. Have you seen the comparison of Firdell/Echomax performance, admittedly on the Echomax website, which absolutely slates the inadequate performance of the Firdell, doesn't meet the BS EN ISO 8729 for Radar reflectors. Echomax may be biased but what they say, and how they say it, would have been prevented by now if Marconi (Firdell makers) had any contrary evidence to force a retraction. Firdell was also slated by US Sailing report in 1999.

I have a Firdell, don't know if it really works, and am considering junking it in favour of the Echomax, they make one with same fixings so can reuse Firdell mast brackets.

I am awaiting the MAIB Radar Reflector Report with interest, supposed to be issued 1 May, as stated in Ouzo Report, but now delayed. I wonder if someone doesn't like the conclusions on one of the Reflectors tested?

 

[Amphitrite]

AIS Class B is quite efficient as far as use of the available (and limited) slots is concerned. This has been discussed at great length by the technical steering committees and they did quite some testing and where satisfied with the results. In case of a very large number of boats with Class B, a competent shore station (CoastGuard) can slow down update rates. However, as these Class B transponders transmit with 2 Watt, the range is limited to what is actually needed for collision avoidance (around 5-7 nm) and thus slot cluttering is further reduced.

As far as displaying of Class B data on ships bridges is concerned, an increasing number has AIS integrated into the radar screens (mandatory for all new buildings after 2008) and a good number has AIS as an ECDIS overlay. Class B filtering is not a standard feature (they are normally quite happy to see as yotties).

Holger

 

[jb2006]

I know firdell have been slated by Echomax and other testers, however, we had a firdell on the old boat and it was fine as far as we could tell, vessels with AIS transmitters took avoiding action before we could see them - we could see them on the AIS radar display.

That said I have bought an Echomax for the new boat !