AIS Transmitter Suggestions

[Homer Shannon]

Several years ago I added a McMurdo Smartfind AIS receiver to my boat's electronics. The AIS receiver is tied in with my Uniden UM525 VHF radio and my Garmin 540s chart plotter. This arrangement works very well. I can see all AIS targets within about a ten mile range and I'm prepared for emergency DSC broadcasts in the event of some dire situation.

I have noticed that the number of vessels using AIS transmitters has increased dramatically in the past two years. Since these vessels must also have AIS receivers, it can be assumed that the number of vessels with receivers has also increased. Perhaps it is time to consider adding a transmitter to my own configuration.

Given my current configuration, which I am very happy with, what would be the most efficient and economical way to add an AIS transmitter?

[billknny]

You have to replace your existing receiver, or keep it as a backup. Nobody sells a "transmit only" Class B AIS.

If you are connected to your radio and MFD via NMEA2K you can probably leave the existing receiver in place and tell the displays to ignore it, although that will require a separate antenna.

If you are connected via NMEA0183 you'll have to disable the existing receiver. In a simple system there is not (usually) a way to have two NMEA0183 talkers saying the same thing because the sentences don't come with a source ID.

[Homer Shannon]

It wouldn't be a big deal to remove the existing AIS receiver - and it wasn't a big investment. I am using NEMA2000 communications and receiving on the standard VHF antenna, a basic Shakespeare job. Any recommendations on a good AIS transceiver?

[DeepFrz]

Are you looking for AIS-B or B+? I like Vesper Marine because of the service they give on CF. They seem to monitor CF and join in when they are able to help out.

[Homer Shannon]

OK, I had to do a little reading to give you a good answer. I think for my needs a standard AIS-B would be sufficient. I don't move very fast (sailboat) and I don't normally travel in highly congested areas.

[continuouswave]

I suggest you look closely at em-trak. em-trak is the house brand of SRT Marine Systems. SRT is more or less the gold standard in AIS devices. They design the actual silocon chips used in AIS, and they are the original equipment manufacturer (OEM) for many products sold under private label brands.

The em-trak Class-B model B100 used to retail for about $550, but the price has recently been reduced. You can find this Class-B AIS tranceiver for under $350. It may be headed for end-of-life and replacement with a newer model, but it represents a best-buy at this moment. See:

https://us.binnacle.com/p10043/em-tr...duct_info.html
[No affiliation with this vendor]

There is a more recently introduced model, the B300, which sells for about $480.

https://www.milltechmarine.com/em-tr...der_p_423.html
[No affiliation with the vendor]

At one time I was trying to keep abreast of Class-B transponders, and I wrote and updated an article on them. The article is a bit out of date now, but it may be useful for you. See

AIS Class B Transceiver Round Up
continuousWave: Whaler: Reference: AIS Class-B Transceiver Round Up

If you do get a Class-B transceiver (or transponder), I suggest using a dedicated antenna for it, rather than using an automatic antenna switching device to share an antenna. The AIS frequencies are at the very high end of the VHF Marine Band at 162-MHz. Most ship station antennas are tuned for the very low end of the band at 156-MHz, where all ship transmitters operate, and their VSWR bandwidth is usually not very broad.

AIS transmitters often will object to operating into a transmission line with a VSWR above about 2:1, and may not work very well trying to feed an antenna tuned for the wrong end of the band.

Also, the transmission interval of Class-B is rather infrequent, and it would be a shame to miss an opportunity to transmit when scheduled due to the shared antenna being in use by the other transmitter. The whole point of AIS is to transmit your position, and impeding that by sharing an antenna seems to be at odds with the point of having an AIS transmitter. A Class-B transmitter is just operating at a few Watts of power. You ought to provide the transmitter with a low-loss, low-VSWR transmission line to a well-tuned antenna.

The better antenna sharing automatic switching devices cost more than a second antenna will cost. They also add complexity to the system. Adding a second antenna for AIS will add redundancy to the system; you could is the AIS antenna for the voice transmitter in an emergency.

For those reasons, I suggest having a dedicated AIS antenna that is tuned specifically for 162-MHz.

If you must use a shared antenna, it would be best to replace the current antenna with a new antenna that is designed to have a wide VSWR bandwidth and is useful on both voice and AIS. Those antennas usually are made with larger diameter radiating elements to produce a broader VSWR bandwidth. Of course, they cost more than single-purpose antennas. Again, the dedicated AIS antenna seems like a good choice.

[DefinitelyMe]

We did what you want to do recently - indonesia required it - and it didn't require any messing around with the existing setup.

We bought a matsutec standalone AIS transponder from aliexpress for something like $350. You program it yourself with your MMSI (very, very easy. US or EU retailers won't let you do this. They want to program it for you before delivery I believe) and connect it to an antenna either via a splitter or a second antenna (we went with a second, deck-mounted antenna. That way if we lose our mast it can double as a backup).

Having two receivers running at the same time isn't an issue. Your existing setup stays the same and the Matsutec displays on it's own screen. Your existing unit should recognise the signal from the transponder as 'self' (because both units are programmed with the same MMSI no.) automatically and require no action on your part.

[Nicholson58]

Given that your current set up works and you like it I would add a second totally independent backup. We really like our Watchmate 850. It uses less than 10 watts and also performs as an excellent anchor watch. It can be networked but we leave it independent. On the hook, everything else is off and the Watchmate alarms if we exit the circle. Nearly all cruising boats in the Caribbean operate class B

Our VHS is also an AIS. Having a backup is nice. We consider AIS essential, second only to depth.

[hjohnson]

I installed a Vesper Marine XB-8000, and have been quite happy with it. We navigate using iNavX on our iPad, and this unit (combined with an NMEA multiplexer) puts all our data onto our iPads via Wifi.

[mjadczyk]

Thanks for helpful comment - I am looking for installation of the AIS unit myself and I was considering various producers, but most of them are really expensive with no apparent advantages. Therefore I may be going with Em-Trak.
I would agree with the installation of the separate antennas for many reasons, but at the same time - do you have any suggestions as where this antenna should be installed (I would like to have it on the mast) to not to interfere with VHF antenna?

[DefinitelyMe]

Originally Posted by mjadczyk

I would agree with the installation of the separate antennas for many reasons, but at the same time - do you have any suggestions as where this antenna should be installed (I would like to have it on the mast) to not to interfere with VHF antenna?

People often put a second antenna on a spreader, inboard near the mast. We put ours on the aft rail and it works well enough.

[Tillsbury]

If you're going to install a second antenna, there's an argument that it would be best on a separate pole such that you could use it for your vhf in case of dismasting.

[Pete7]

Originally Posted by mjadczyk

Therefore I may be going with Em-Trak.

We installed the Em Tack B100 last weekend and fired it up. 10 minutes work adding the MMSI number and details (you are allowed to do your own in the UK) and it started to transmit without any problems, showing up on Vessel Finder later that day.

I really didn't want to drill more holes than necessary to run the external GPS antenna outside, so mounted it inside next to the chart table. Works perfectly and the AIS software shows a good signal as expected.

The VHF antenna is a high quality Shakespeare 5400 recommended by Nick (SV Jedi). This is mounted on a 2m pole on the stern with the cable routed through to the chart table and will reach the VHF, if the masthead antenna were to develop a fault. We used this previously with a RX only AIS and it gives a good range of about 7 miles, often more.

Please Recommend a Quality VHF Masthead Antenna

The Vesper series get good reviews on CF, but I don't need AIS wifi and the cheaper price £300 for Em Trak against £500 for the Vesper 6000 clinched the decision.

Pete

[continuouswave]

Originally Posted by mjadczyk

do you have any suggestions as where this antenna should be installed...to not to interfere with VHF antenna?

The best separation for two vertically polarized monopole antennas is to separate them vertically while keeping them in line, i.e., one above the other, but some distance between them.

More about mounting two antennas on a boat at

Mounting Two VHF Marine Band Antennas on a Small Boat - CONTINUOUSWAVE