AIS recommendations

[Jabez]

Hi
i am looking to fit a AIS class b to my merry fisher 805
It has a raymarine hv element and a backbone already installed
also do i fit a separate aerial or use a splitter

Cheer upfront

 

[Momac]

I found a separate antenna cheaper than using a splitter. On yacht with a mast antenna perhaps a splitter would be the easier option.
I bought the raymarine ais and it was an easy fit but a friend bought em trak which was cheaper
B900 Class B AIS Transceiver - Work Boats, Fishing, Sailing, Motor, Tenders I em-trak.com

 

[Hurricane]

Hi
i am looking to fit a AIS class b to my merry fisher 805
It has a raymarine hv element and a backbone already installed
also do i fit a separate aerial or use a splitter

Cheer upfront

I suggest that you go for a B+ transceiver
Look up the difference - they will all be B+ in the future.

 

[Jamie Dundee]

I’ve fitted a separate antenna on both boats I fitted AIS to. I dislike splitters, the more connections between transmitter and antenna the more potential problems/weak spots.

Bear in mind that the AIS transponder must have a dedicated gps antenna, so make sure the one you buy comes with its own antenna or can be mounted in a suitable position if the gps is internal. They won’t work off a network gps antenna.

 

[richardbrennan]

I have a Digital Yacht AIT 2000 and being NMEA 2K it should be just plug and play on your system. I have found it a very good bit of kit. For what it's worth, the Digital Yacht guy on the SOTON Boat Show stand when I bought it recommended a sperate aerial rather than a splitter although they do manufacture both.

 

[aerofurb]

I have a Merry Fisher 725 and installed a Digital Yacht iAIS Tx Class B with wif-fi.

This kit plugs into the NMEA 2K system (Garmin GPS chartplotter) and wi-fi links to Navionics running on an iPad.

Used dedicated antennas, rather than a splitter. It all worked as advertised out of the box and no problems to date.

iAISTX - AIS Transponder with WiFi Interface - Digital Yacht

 

[Hurricane]

I have a Digital Yacht AIT 2000 and being NMEA 2K it should be just plug and play on your system. I have found it a very good bit of kit. For what it's worth, the Digital Yacht guy on the SOTON Boat Show stand when I bought it recommended a sperate aerial rather than a splitter although they do manufacture both.

I have a Merry Fisher 725 and installed a Digital Yacht iAIS Tx Class B with wif-fi.

This kit plugs into the NMEA 2K system (Garmin GPS chartplotter) and wi-fi links to Navionics running on an iPad.

Used dedicated antennas, rather than a splitter. It all worked as advertised out of the box and no problems to date.

iAISTX - AIS Transponder with WiFi Interface - Digital Yacht

It seems to me that both these are the old Class B not the new B+
IMHO, you should be buying a B+ these days - just look at the difference - it is huge.

 

[john_morris_uk]

It seems to me that both these are the old Class B not the new B+
IMHO, you should be buying a B+ these days - just look at the difference - it is huge.

B+ is only really an advantage for fast moving vessels so the ‘huge’ bit is entirely contextual.

( There’s a transmit power difference as well but it’s minimal advantage (3dB IIRC) and I completely confident my Class B that uses the VHF antenna at the top of my 17 metre mast has a greater range than any B+ from a lower down antenna on a planing boat.)

 

[Hurricane]

B+ is only really an advantage for fast moving vessels so the ‘huge’ bit is entirely contextual.

( There’s a transmit power difference as well but it’s minimal advantage (3dB IIRC) and I completely confident my Class B that uses the VHF antenna at the top of my 17 metre mast has a greater range than any B+ from a lower down antenna on a planing boat.)

I disagree entirely.
Unfortunately, I have a old Class B.
But if you are buying new I would ask this question.
Why are you installing an AIS transponder?
Presumable, you want to be seen.
It is significantly more expensive than a receive only so why not get the best.

For the record - here are the differences.

Function	Class A	Class B+	Class B
Transmit Power	12.5W	5W	2W
Transmit Rate	Up to every 2-3 secs	Up to every 5 secs	Every 30 secs

IMO, the extra power IS helpful.
We now have satellite receivers streaming AIS data onto the internet.
The extra power of Class B+ give and its faster transmission rate will definitely give a more likelihood that a station (satellite or other) will receive a complete AIS sentence.
If you are going to go to the effort of installing AIS, why not give it the best chance of working.

My experience over the last 12 years is that Class A systems appear on the system where Class B ones don't.
Just get the best - they will all be B+ systems in the future anyway.

 

[john_morris_uk]

I disagree entirely.
Unfortunately, I have a old Class B.
But if you are buying new I would ask this question.
Why are you installing an AIS transponder?
Presumable, you want to be seen.
It is significantly more expensive than a receive only so why not get the best.

For the record - here are the differences.

Function	Class A	Class B+	Class B
Transmit Power	12.5W	5W	2W
Transmit Rate	Up to every 2-3 secs	Up to every 5 secs	Every 30 secs

IMO, the extra power IS helpful.


We now have satellite receivers streaming AIS data onto the internet.
The extra power of Class B+ give and its faster transmission rate will definitely give a more likelihood that a station (satellite or other) will receive a complete AIS sentence.
If you are going to go to the effort of installing AIS, why not give it the best chance of working.

My experience over the last 12 years is that Class A systems appear on the system where Class B ones don't.
Just get the best - they will all be B+ systems in the future anyway.

With respect, you miss the point I was making. The suggestion was that B+ is a huge advantage. The advantage is definitely NOT huge. If the price was comparable, and I was installing one today, I would have no qualms about installing a B+ system, but the point I was making is that the advantage is definitely not as large as suggested. The power difference won't be noticeable with the difference in height of my antenna compared to a power boat. The transmit rate when I am doing 6 knots doesn't make any difference either.

If I was installing now and had the choice, and the money wasn't significantly different, I would install B+. Am I worried that I've got Class B in my displacement boat? A resounding no! The difference is only slightly significant when you are in a fast moving craft. It's not something to get one's underwear in a twist over. Ione certainly shouldn't over egg the advantage of B+. It's an improvement, but I suggest that it's marginal in practice.

I appreciate that this is the mobo forum, and for fast motor boats (and I do sometimes get to drive such craft) B+ will be a good thing. There's zero evidence that others craft are missing out on AIS transmissions at the moment, even in crowded areas. AIS can cope with 2,400 ships at a time IIRC.

 

[Hurricane]

With respect, you miss the point I was making. The suggestion was that B+ is a huge advantage. The advantage is definitely NOT huge. If the price was comparable, and I was installing one today, I would have no qualms about installing a B+ system, but the point I was making is that the advantage is definitely not as large as suggested. The power difference won't be noticeable with the difference in height of my antenna compared to a power boat. The transmit rate when I am doing 6 knots doesn't make any difference either.

If I was installing now and had the choice, and the money wasn't significantly different, I would install B+. Am I worried that I've got Class B in my displacement boat? A resounding no! The difference is only slightly significant when you are in a fast moving craft. It's not something to get one's underwear in a twist over. Ione certainly shouldn't over egg the advantage of B+. It's an improvement, but I suggest that it's marginal in practice.

I appreciate that this is the mobo forum, and for fast motor boats (and I do sometimes get to drive such craft) B+ will be a good thing. There's zero evidence that others craft are missing out on AIS transmissions at the moment, even in crowded areas. AIS can cope with 2,400 ships at a time IIRC.

The fact that your antenna is high up doesn't affect this discussion.
Of course, a higher up antenna will work better.
My point is that there is very little difference in cost between an older Class B and the new Class B+.
And I think the effectiveness is significant.
It isn't just the speed of the boat that counts.
It is the ability of the receiving station to pick up a transmission and the Class B+ is sending out 6 times the number of transmissions.
Have a look at the various websites (Vesselfinder and Marine traffic) and see their reports of the most recent AIS signal.
I'm not a particular Digital Yacht fan myself but here is a "like for like" comparison on eBay:-
The AIT 2000 - Class B
ait 2000 | eBay
And the AIT 2500 - Class B+
ait 2500 | eBay

As you can see, there is nothing in it so why not buy the better device.
Its a no-brainer

 

[Jamie Dundee]

The big difference between ‘B’ and ‘B+’ is detailed below, article from MBY. Useful in crowded waters but of little consequence where I boat.


However, the way different classes of transponder get their time slot varies. Class A transponders use a system called Self Organised Time Division Multiple Access (SOTDMA), which enables them to negotiate with other Class A transponders to reserve a time slot and book future ones. Class B transponders use a different technology called Carrier Sense Time Division Multiple Access (CSTDMA).

This allows Class B transponders to listen in to Class A transponders and grab an empty time slot to make their transmission. The system is designed so that Class A transponders always take priority over Class B ones, meaning that a Class A transponder will occasionally steal a time slot from a Class B one and force it to delay its transmission until another empty slot appears.

The number of transmissions that a transponder makes varies according to several different parameters, including Class (A or B), speed, navigation status and whether it is manoeuvring. The Class A transponder of a fast-moving ferry may output its position every couple of seconds while a Class B-equipped pleasure vessel will only transmit every 30 seconds.

A Class A transponder also transmits at 12.5W while a Class B transponder only transmits at 2W – a third of the power of a 6W handheld VHF. This restricts Class B transmissions to a maximum range of 8-10 nautical miles and means that traditional Class B transmissions are often not received by the AIS satellites that provide global vessel tracking.

AIS B+ explained
The new Class B+, otherwise known as Class B SOTDMA or Class B 5W, bridges the gap between Class A and Class B transponders, offering clear advantages for some types of vessels and applications.

Class B+ uses the same SOTDMA technology as Class A and therefore has the same priority when it comes to reserving a time slot, guaranteeing that it will always be able to transmit, even in busy AIS congested waters.

It also increases the transmission rate in line with your speed (but is unaffected by other manoeuvres), giving other vessels a clearer and more up to date view of where you are.

 

[Hurricane]

My point stands
Why buy an inferior product at the same price.