Looking for Advice on AIS Transmitters

[epoxyman]

Hello Boat Driver,
You raise several interesting issues:
My VHF antenna is at the top of my mast - 54 ft from water. If I were to add a second antenna dedicated to the ais, it would either go on the rail (~10ft off waterline) or on my Radar Mast ( about 16 ft from waterline). If I go with a Class B (1981 39' monohull cruiser), my normal cruising speed is about 6 kts/hr.

1) will class B Vs. Class A be a significant difference (Vespar XB8000 Vs. Em-Trak A100)?

2) Cruising primarily Northern New England, and primarily looking for the safety factor in FOG, proximity issues are mainly 1-2 miles. Large commercial vessels are typically not the issue (only some Lobster boats put out AIS signal). Some night cruising when the Lobster pot density allows but mostly day runs. May be taking the run to Nova Scotia but long distance cruising (Bahamas and out Islands) has been done and I no longer have the crew (kids are all grown and on their own). Will the antenna splitter still be a poor choice (figure with the additional above data - I have learned that defining the problem helps find the solution)?

[boat driver]

epoxyman,
AIS A is not needed for your conditions. best option for transmitting your position, but overkill. $$$$, functions not needed or in your capability
AIS B is fine, but ideally avoid the splitter. Provided with your info-assuming your navigation table midships. install a dedicated AIS tuned antenna on the radar mast- above the radar plane of transmission. This gives 360 degree line of sight with minimum interference. It is high enough to provide 4+ mile coverage "to a water surface receiver" or well beyond the capability of the PLB AIS transmitter if utilized. It gives the shortest run to the AIS receiver (approx 30'?) so minimal signal loss from line/connectors. Be sure to get an VHF antenna is tuned to AIS frequency.
Sidebar- VHF antenna are tuned to channel 16 (156.800mhz) and AIS are tuned to 161.975mhz. This is not critical but most efficient for transmitting, particularly at the 2watt power. Masthead antenna, unless upgraded, utilizing splitters add this loss of efficiency in addition to the long wire run, multiple connectors, and splitter losses.

The added benefits- this is a backup antenna for VHF radio in event of mast antenna damage, provides a duplicate vhf communication with other vessels AIS equipped, is the best install practice.
The splitter is an expensive piece of equipment and often sold as "plug and play" solution that does not require labor intense install. Out of pocket, a dedicated AIS antenna is cheaper, particularly if labor of running wire and installing AIS and antenna is DIY, vs purchasing the splitter and new masthead antenna.
The best info source is nosing around https://www.navcen.uscg.gov/?pageName=mtBoater This is a trove of easy to understand info supporting your education without a sales pitch.
To answer your question- Vesper makes a very good unit that gives great flexibility of technical wishes and can be a cornerstone to an existing electronics collection, particularly the capability to cross between NIMA 0183 and 2000. I do not know the EMtrak products to suggest preference.
Good luck.

[epoxyman]

Thank you Boat Driver for your excellent and concise response.
I have a spare VHF antenna in case of mast or otherwise antenna loss. This would probably be the best alternative Vs. a splitter. I greatly appreciate your knowledge sharing.
Thank you all that responded - this was a very worthwhile thread. Great info and always great to have multiple perspectives.
Respectfully Andy (epoxyman - yes there is a reason for this name)

[goboatingnow]

The Raymarine Ais700 is a good compromise , has an integrated splitter which makes installation easy and is the newer 5W SOTDMA system. Integrates very nicely with Seatalk system it’s the SRT platform , well proven.

I get contacts from about 10 -15 miles away more then adequate

[IslandHopper]

Some good information on AIS and Class B SOTDMA...

https://digitalyacht.net/wp-content/...aper-V1_01.pdf

3 – The New Class B+ Technology
The new Class B+, often referred to as “Class B SOTDMA” or “Class B 5W”, has been defined to bridge the gap between Class A and Class B transponders, offering some 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. For fast moving vessels this is important as a missed transmission can result in a vessel moving a long distance before it next manages to send a transmission.

Another feature that the new Class B+ technology it has taken from Class A, is the increased and automatic changing of transmission rates depending upon speed. Unlike Class A, the update rate is unaffected by whether the vessel is manoeuvring, but as the vessels speed increases, the number of transmissions increases so that other vessels get a clearer and more up to date view of where the boat is.

For slow moving vessels the increased update rates of Class B+ are not so important, but a fast power boat travelling at say 23 knots, will move 360 meters in 30 seconds, which is the update rate of a normal Class B transponder. On a Class B+ vessel travelling at 23 knots or more, the update rate is 5 seconds, so (using the above example) only 60 meters would be moved between updates.

Finally, Class B+ transponders have a higher power transmission 5 Watts instead of 2 Watts and this not only increases the range over which the vessel’s transmission will be received, assuming good antenna height and performance, but it also significantly improves the AIS Satellite reception, enabling global tracking.

[mickand]

I installed an em-trak A100 a few years ago and Class A is the way to go. Class B units only transmit your position around every 20-30 seconds and that's an undesirable delay if you're operating in confined quarters.
The Class A em-trak A100 transmits your position every few seconds, is fully programmable by you and gives many other benefits.

[Paul L]

Originally Posted by mickand

I installed an em-trak A100 a few years ago and Class A is the way to go. Class B units only transmit your position around every 20-30 seconds and that's an undesirable delay if you're operating in confined quarters.
The Class A em-trak A100 transmits your position every few seconds, is fully programmable by you and gives many other benefits.

The update rate for slow vessels, like a 6kt sailboat, is not very relevant. At 6kts you do 300ft in 30 seconds,
The increased power of the class B+ from 2 watt to 5 watt is far more important.

[pcmm]

Originally Posted by Paul L

The update rate for slow vessels, like a 6kt sailboat, is not very relevant. At 6kts you do 300ft in 30 seconds,
The increased power of the class B+ from 2 watt to 5 watt is far more important.

Class A transmits at 12watts which is a big difference even from class B+

Still class A is a bit overkill for recreational vessels

[Snore]

Broadcasting class B from my masthead, I have seen 'over the horizon' ships alter course to go around me. That range is more than adequate for me.

As to frequency of transmit- as PCMM stated, its a sailboat doing 6-7 knots! As to close quarters, one would hope that the bridge of the other vessels are looking out the window if things are that close.

Finally, unless you are fully NMEA2K, the advantage of the XB is it up-converts 0183 to 2K.

[Paul L]

Originally Posted by pcmm

Class A transmits at 12watts which is a big difference even from class B+

Still class A is a bit overkill for recreational vessels

Exactly, it is an overkill and not needed, so not much point in promoting the 12watts.

[Paul L]

Originally Posted by Snore

Broadcasting class B from my masthead, I have seen 'over the horizon' ships alter course to go around me. That range is more than adequate for me.

.......

Sure 2 watt class Bs work and have been the workhorse of small vesels for a long time. Any issues with age related coax, connectors, antenna problems, atmospheric conditions, etc, can easily cut that power in half. A 5 watt system is far better if you are buying new. But no reason to get rid of an existing 2 watt system,

The class B+ SOTDMA transmission protocol is also more likely to get your data packets through to other ships when you are in an area with excessive number of broadcasting class A ships - think Singapore Straits for example. The older class B CS-TDMA can at times not have a slot to transmit its data packets.

[Marathon1150]

We have two boats. I installed a Vesper XB-8000 on one of them prior to sailing from Mexico to French Polynesia. It uses a splitter to share the mast-top VHF antenna and feeds GPS position information to the SSB and VHF radios as well as to an ACR iPro EPIRB. As others have noted the technical support from Vesper is outstanding and being able to view AIS and other boat info on a phone or tablet is super handy. We did not use the boat's chartplotter for most of the 29 day voyage from San Jose del Cabo to Nuku Hiva - we had Navionics charts via iNavX on a tablet and used the XB-8000 data for everything else also via the tablet. We had a 10 mile radius AIS alarm set and whenever we contacted a deep sea that was within that range, they had already noted our position and in all cases they offered to change course so that we would not need to. I was impressed by and grateful for this courtesy.

Earlier this year I installed an Em-Trak B954 SOTMA Class B Transponder on our second boat. I chose this device rather than another XB-8000 because it has a built in GPS antenna (Em-Trak advises that it might not be suitable for all boats but it works on ours) and a built in splitter. Installation was super easy and it also provides a tablet/phone interface in addition to NMEA 2000 etc. It also cost less than a XB-8000 both for the base unit and because an external splitter is not required. However, I prefer the graphic display that the Vesper system uses over the Em-Trak approach but this might be a result of greater familiarity with the former.

[Nord Sal]

This has been a good thread. As someone who is looking into adding an AIS system, I really appreciate people sharing their expertise and experiences.

I have a question about splitters based on what I am reading. I see some people recommending to not use a splitter but instead use a separate antenna in order to gain a backup VHF antenna in case of antenna failure. This makes sense. I like redundancy and backup systems.

My question is this: Would it make sense to use two separate antennae as recommended by some in this thread, but also have an AIS unit with a integrated splitter or perhaps a separate inexpensive splitter for backup? My thinking is that in the event an antenna fails, both devices should still be able to function using the working antenna and bringing the splitter into use. Splitters don't seem to add much cost and it seems they could provide a backup to both systems if two antennae are used.

[Paul L]

Originally Posted by Nord Sal

This has been a good thread. As someone who is looking into adding an AIS system, I really appreciate people sharing their expertise and experiences.

I have a question about splitters based on what I am reading. I see some people recommending to not use a splitter but instead use a separate antenna in order to gain a backup VHF antenna in case of antenna failure. This makes sense. I like redundancy and backup systems.

My question is this: Would it make sense to use two separate antennae as recommended by some in this thread, but also have an AIS unit with a integrated splitter or perhaps a separate inexpensive splitter for backup? My thinking is that in the event an antenna fails, both devices should still be able to function using the working antenna and bringing the splitter into use. Splitters don't seem to add much cost and it seems they could provide a backup to both systems if two antennae are used.

Mounting is an issue if you use two antennas. The antennas need to be 1m a part (or so) to prevent one transmitter overpowering the others receiver. This is a pain on a sailboat and is usually handled by leaving the VHF antenna at the mast head and putting the AIS antenna on an arch or Bimini. The lower antenna height will limit the lower antenna range.

I had this setup on my previous class B AIS. For my upgrade to a class B+ unit I bought one with a built in splitter for the mast head antenna. In my installations the masthead with a splitter is superior performance,
I left the Bimini mounted antenna as backup, should I decide to have the mast fall down.

[epoxyman]

Again All, I am very thankful for all the input on my initial thread request.
West Marine has an Em-Trak A100 on sale for $399 (reg. $499). This seems to be a very good price for a Class A transceiver. Since it does not have an internal GPS antenna it requires the installation of the GNSS external antenna and the purchase of a splitter (very good feedback regarding the pros and cons of this - since when using the VHF radio it stops the AIS transmitting), or installation of a second VHF antenna. My question now to those that have the A-100 installed is, how compatible is this system with older Raymarine (E80) MFD systems? If you have done this installation, I would greatly appreciate your insight.
My potential alternative is to purchase a used Vesper XB6000 (Class B) with a splitter for about the same price. Any thoughts related to compatibility with the older Raymarine E80 would be appreciated.