VHF and AIS transceiver

[PaulRainbow]

I can only assume that the question was whether those things are worthwhile, rather than what the technical difference is.

The question was

Can I also ask, is B+ really worth having in a displacement sailing boat over class B?

My reply was: It is if you value reserved slots to make sure your data gets sent on time and the 5w transmit power, rather than just 2w

I can only inform what he relevant differences are, i ignored the fact B+ transmits certain data at shorter intervals as the vessel reaches certain speeds, as the person asking the question appeared to be aware of this.

Whether it's worth having or not is up to the individual to decide.

Personally I don't think it makes a big difference in the real world because where the transmit power might make a difference (usually open water) it probably doesn't because there's less interference and horizon is still a thing so range won't dramatically increase. Sure, a few extra miles is nice and all else being equal more is better but B+ carries a premium and is not widely adopted so I may choose compatibility/interoperability/support over this especially given the current price premium. Where reserved slots might make a difference it probably doesn't because once you're over 1000 or so targets AIS becomes less usable anyway. with over 1000 targets in the area everyone will likely be looking out of the windows anyway and anything big may very well have exclusion zones - they certainly do in the Solent and will be ignoring AIS targets as they have no choice.

For fast boats...maybe. The ability to proactively increase transmissions when moving faster makes a lot of sense. As I said earlier though, the new version is usually a better option, if only for future proofing if it's not dramatically more expensive. With AIS though, it's unlikely class B will ever be deprecated in our lifetimes so it's not something I'd go out of my way to upgrade if a system is in place already.

Personally, if i had B i doubt i would change to B+ just for the sake of it.

 

[st599]

B+ reserves a slot, The "slight" increase in power is from 2w to 5w, is 2.5 times more powerful really "slight"

On a system that obeys the inverse square law, a power increase of 2.5 will give a slight increase in range.

I think B may be received, but message 27 and specific radio channels were added to B+ (and maybe to A?) to ensure satellite reception, see my previous reply (with citations).

Perhaps I could have expressed myself more clearly and concisely by saying the AIS-monitoring satellites are looking out for class B+ transponders; class B+ will ensure your position is reported when you're in the middle of the Atlantic or Pacific.

(I'm not certain that all B+ transponders support message 27, but em-track B+ models have a checkbox in the UI to enable it.)

Interesting as according to the ITU report:

• Satellite detection of the shipborne AIS should be limited to the AIS Class A (SOLAS Class) because the AIS Class B population is too large to be included.
• Separate operating frequencies in addition to AIS 1 and AIS 2 are needed that are not subject to terrestrial use.

But looking at the recommendation, it is allowed on B+, provided they've implemented the extra frequencies - however, it seems to be switched off within range of shore based station.

 

[KompetentKrew]

… however, it seems to be switched off within range of shore based station.

Yeah, I mentioned that in my 2022 comment that I linked before.

Message 27 is transmitted every 3 minutes, but the 3 minute countdown is reset every time a message of type 4 is received, and message 4 is reserved for base stations.

I'm surprised they didn't make B+ transmit message 27 less frequently - every 15, 30 or 60 minutes instead of every 3 minutes. Later firmware updates could allow it to be sent more frequently if that turned out to be unnecessarily conservative.

 

[Chiara’s slave]

On a system that obeys the inverse square law, a power increase of 2.5 will give a slight increase in range.

The range is most likely to be limited by the height of the antenna.

 

[Refueler]

The range is most likely to be limited by the height of the antenna.

Exactly .... but lets be honest - what range do you need ??

Lot of people - myself incl - tak about range we pick up other targets - but isn't it just as important - the range they see US ? The more power you can have in TX signal - surely the better that is - even if it only gets a couple of miles more ..

 

[Chiara’s slave]

Exactly .... but lets be honest - what range do you need ??

Lot of people - myself incl - tak about range we pick up other targets - but isn't it just as important - the range they see US ? The more power you can have in TX signal - surely the better that is - even if it only gets a couple of miles more ..

More can only be better, sure. It’s easier now that container ships have slowed down, but still, the sooner people know you are there….

 

[lustyd]

Are there reports of ships hitting people with AIS? My experience is shipping having plenty of time to turn and avoid me, presumably as they see my AIS but failing that their RADAR. I’ve never felt the need for more range. Not opposed to more, obviously!

 

[Irish Rover]

Are there reports of ships hitting people with AIS? My experience is shipping having plenty of time to turn and avoid me, presumably as they see my AIS but failing that their RADAR. I’ve never felt the need for more range. Not opposed to more, obviously!

That bridge might have been a bit happier if it was further away from the ship