VHF and AIS transceiver

[Rappey]

Onwa seems established as a good cheap brand backed up by official UK dealership.
I've just found this on aliexpress, dual channel ais tranciever, B+ and a whole £25 (plus £35 postage) . Could buy nearly 40 of them for the price of a older tech raymarine..

 

[Rappey]

I recently sold one of these units. It was really nice, superfast at gps location, could use it to plot a course.. would buy another if i needed another ais unit

 

[st599]

Onwa seems established as a good cheap brand backed up by official UK dealership.
I've just found this on aliexpress, dual channel ais tranciever, B+ and a whole £25 (plus £35 postage) . Could buy nearly 40 of them for the price of a older tech raymarine..

I think that's the price for the antenna - AliExpress has a habit of showing a picture of something expensive, then choosing only a component and the price for that.

 

[mrangry]

I am currently looking at the Navico unit as to buy a vhf, splitter and transceiver separately it is more expensive than the £830 the Simrad rs40 b currently selling for

 

[mrangry]

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

 

[lustyd]

Only for future proofing as the latest version, but standard B has been working just fine even in busy areas for most of us. I do acknowlege that some may have had issues but I'm inclined to think that's an installation specific issue rather than technology problem.

 

[KompetentKrew]

I think that's the price for the antenna - AliExpress has a habit of showing a picture of something expensive, then choosing only a component and the price for that.

It's a common trick on Amazon and eBay too these days,

 

[KompetentKrew]

Expensive option for a basic spec class B (not B+) transceiver.

I would fit a separate VHF and a decent AIS with built in splitter, such as an Emrak B9xx transceiver.

+1

For years, when I was a dreamer and learning to sail, I wanted a combined VHF and AIS transponder because I thought it was a logical and "right" way to arrange things.

When I bought my boat the B&G V100 fitted the bill because the existing VHF was also an ancient black box unit. However it was cheaper for me to buy the non-AIS version of the V100 and a separate em-trak B+ unit with splitter than to buy the AIS version of the V100, which was only class B and which would require a separate splitter or second antenna.

I thought B+ was much better value than having the two units combined.

 

[PaulRainbow]

Dunno why so many are making comments about Ethernet and how Garmin and Raymarine are so far behind. They have both been using Ethernet for at least 15 years.

One net is unlikely to replace N2K for many applications, N2K is perfectly capable for stuff like wind, depth, speed etc etc. If One net were to replace N2K completely you would all be complaining about the cost of the cables and other hardware (routers etc)

 

[PaulRainbow]

Thanks - it's ashame that unit seems to only put AIS out on the Wifi - NMEA sentences for all transducers would be useful too.

Would definitely prefer a B+ as Carrier Sense class B on Lake Solent is a bit hit and miss at times.

Emrak AIS has connections for NMEA 0183, NMEA 200 and USB, some models have wifi and Bluetooth. They also multiplex 0183 and N2K, most have built in splitters and they are very compact. Hard to see that a space saving worth having is there to be had.

Emtrak make the AIS units, or at least the major components, for most of the big names.

 

[PaulRainbow]

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

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

 

[lustyd]

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

 

[KompetentKrew]

B+ also does Space AIS, so your track is being recorded when you're mad offshore or mid-ocean. I assume it'll be picked up by Marine Traffic etc and available to the coastguard if your family call up to complain they haven't heard from you in 2 weeks.

 

[Refueler]

Onwa seems established as a good cheap brand backed up by official UK dealership.
I've just found this on aliexpress, dual channel ais tranciever, B+ and a whole £25 (plus £35 postage) . Could buy nearly 40 of them for the price of a older tech raymarine..

25 quid is only for the antenna .... click on the AIS unit and you will see real price !!

 

[st599]

B+ also does Space AIS, so your track is being recorded when you're mad offshore or mid-ocean. I assume it'll be picked up by Marine Traffic etc and available to the coastguard if your family call up to complain they haven't heard from you in 2 weeks.

The difference between B and B+ is the algorithm used to find a spare slot to tranmsit in and a slight increase in power. There's no new messages.

 

[Refueler]

B+ also does Space AIS, so your track is being recorded when you're mad offshore or mid-ocean. I assume it'll be picked up by Marine Traffic etc and available to the coastguard if your family call up to complain they haven't heard from you in 2 weeks.

Marine Traffic receives both B and B+ along with A of course ... its you - the user who decides what MT displays on your screen. As to the tracking Sats - I believe B is possibly rec'd.

 

[PaulRainbow]

The difference between B and B+ is the algorithm used to find a spare slot to tranmsit in and a slight increase in power. There's no new messages.

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

 

[KompetentKrew]

The difference between B and B+ is the algorithm used to find a spare slot to tranmsit in and a slight increase in power. There's no new messages.

A satellite 1000km above the earth's surface has a fairly big footprint - a message sent from a ship at the nearest edge of this footprint can arrive 9 milliseconds sooner than a message sent from the far edge of the satellite's footprint.

Therefore AIS message 27, which is indeed supported by AIS class-B+, is 9 milliseconds (87 bits of data) shorter, to ensure that message 27 can be received in space without packet collisions.

Example: ship A has the first transmission slot, ship B the second transmission slot. Using standard AIS messages, ship A will finish transmitting, ship B will immediately start. If ship A is further from the satellite in orbit then - using standard AIS message lengths - its message won't have finished arriving at the satellite when ship B starts transmitting. I.e. the beginning of a message from ship B can stomp on the end of ship A's message. Hence why message 27 is shorter, to ensure it completes in time even if it arrives at the satellite "late".

In order to make message 27 shorter the timestamp is omitted - "The receiving system is expected to provide the time stamp when this message is received."

This is complicated, so I hope my explanation is clear.

I wrote a longer explanation when I originally looked this up 2 years ago: AIS via Satellite

 

[KompetentKrew]

Marine Traffic receives both B and B+ along with A of course ... its you - the user who decides what MT displays on your screen. As to the tracking Sats - I believe B is possibly rec'd.

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.)

 

[KompetentKrew]

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

I think the increase is less significant when expressed in dB though?

And dB reflects the actual strength of sigma that can be received?

E.g. compare 1W vs 10W in the conversion table on this page: Watts to dBm Calculator - everything RF