Adding AIS to current VHF network

[PaulRainbow]

It's not nonsense and quite the opposite - limiting the GPS location to where the unit has to be situated is an unnecessary & frankly pointless restriction.

It isn't limited, if a suitable place below decks cannot be found an external antenna can be fitted.

Struggling to find one? No Raymarine AIS units have ever had built-in GPS antennas.

One company, the only supplies a single model, the AIS700. They don't manufacturer it, it's made by SRT, the parent company of Emtrak, who make AIS units for several other companies, such as Raymarine.

Just because I advise not to use one with an internal GPS doesn't mean customers we install for don't think it's a good idea...

Who's "we" ?

I've had the same issues for MFDs with built-in GPS which is the reason they all have external connections available.

Very few with dedicated external GPS connections these days, most use N2K.

An external unobstructed GPS antenna is always going to offer more reliable performance -

Internal antennas work fine in most cases, if they don't just fit an external antenna, simple.

as is a dedicated antenna for AIS rather than using a splitter.

So, when you fit the Raymarine AIS700 you ignore the splitter and fit a second antenna ?

That is the advice I always give and surprised if you're a professional you think otherwise.

Virtually all manufacturers of AIS supply units with internal antennas, which almost always work with good accuracy. I've never had an issue with that, neither has any of my customers.

 

[PaulRainbow]

Who said anything about sailing at 1 - 10 knots? The boats we typically work with cruise at 25+

Again, who's "we ?

 

[Sandy]

Who said anything about sailing at 1 - 10 knots? The boats we typically work with cruise at 25+

Even at 4 - 6 knots If you're navigating a passage into or out of an unfamiliar or even familiar harbour at night then I would say ideally within the beam of your boat. It's very easy to wander out of a channel into low water using a chartplotter as an aid. Just claiming GPS doesn't need to be accurate so you can install things incorrectly isn't sound advice.

Even at >25 knots it is hardly fast.

I suspect if you entered any major harbour at that speed VTS would be barking down the radio. Longroom in Plymouth would certainly be doing so and I suspect a MOD Police RIB would be paying you a visit.

Entering a unfamiliar harbour at night my eyes are on stalks looking for buoys and lights. The last thing I look at is a chart plotter - that is like helming with a blindfold on.

 

[PaulRainbow]

The screen on the right, below, is a mirror of my the plotter on the flybridge of my own boat. The screen on the left is running stand alone, using the internal GPS of the tablet, it's mounted at the lower helm, beneath the flybridge.

Spot the difference ?

 

[andylipsberg]

The Garmin AIS600 is discontinued, dated, basic, expensive and only supports NMEA2000 (which adds even more cost).

A much, much better solution would be an Emtrak AIS. Available with a built in splitter, supports NMEA 0183 and 2000, multiplex's those. Also available with Wifi, if needed and SOTDMA or CSTDMA

thanks. cheapest transmitter would be €875 but with wifi it goes above 1 k. i will look in to it as well.

 

[PaulRainbow]

thanks. cheapest transmitter would be €875 but with wifi it goes above 1 k. i will look in to it as well.

Cheapest model with built in GPS and splitter is the B923 @ £650. (£920 with WIFI) This is a CSTDMA model

The SOTDMA version is the B953 @ £750 (£990 with WIFI)

There are cheaper ways of getting WIFI, by fitting an additional device.

 

[Refueler]

Part of the setup of the Em-Trak is that you must specify where on the boat your GPS antenna is as that is where the location of your boat is taken from.

Standard setup data for most AIS machines ... even my ONWA plotter with built in AIS Transceiver has this ... longitudinally and transverse ...

Nothing special about it.

 

[Refueler]

An external unobstructed GPS antenna is always going to offer more reliable performance - as is a dedicated antenna for AIS rather than using a splitter. That is the advice I always give and surprised if you're a professional you think otherwise.

More reliable - yes I can agree ... sometimes if I am moored up against a high wall that overshadows my boat - then my in-cabin GPS can be a bit iffy at times.

But .. I've highlighted a part of your comment that I think is an unnecessary comment on your part ??

Yes you can get a few more targets possibly by dedicated AIS antenna ... BUT it also depends where its mounted. It also depends on whether you use a passive or active splitter.

Tests when installing my ONWA AIS / Plotter gave following averaged results .... there is a thread dedicated on this forum if you search ...

In Ventspils Port and reasonable distance offshore - where an average of 15 to 20 targets ..
Dedicated antenna on pushpit rail - approx 2m above waterline. Average 6 - 9 targets being in the port, none from anchorage.
Passive ONWA splitter with VHF and Plotter both connected - also tested with VHF disconnected ... mast head at about 12m above waterline. Average of 15+ targets port and anchorage.
Without splitter and AIS only to masthead antenna. Average 15 - 20 targets .. yes marginally better than via splitter ...

I then checked another boat with ACTIVE splitter ... masthead antenna .. he had average nearer the 20 mark.

Given that the range of reception was the main reason target numbers increased - I suggest that splitter is more than adequate for our use .. the range at sea I get targets is more than enough to give me ample warning and to decide action.