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Old 01-12-2018, 11:51   #1
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POSITION OF AIS UNIT

Any recommendations on positioning an AIS unit on a 14m fibreglass cruising yacht, e.g. underneath cabin top, under rear deck? It has been suggested a dedicated gps antenna is not necessary - discuss. Plans for coastal cruising in Australia. Should unit be located close to chart plotter? Position of antenna if advisable? All practical advice welcome.

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Old 01-12-2018, 11:56   #2
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Re: POSITION OF AIS UNIT

Place it where the rest of your electronics are. You can use an antenna splitter to share the VHF antenna. Some share the GPS input also.

Here is the install manual for the VESPER XB-8000: Vexper XB-8000 Install Manual
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Old 01-12-2018, 12:03   #3
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Re: POSITION OF AIS UNIT

I have just removed my AIS receiver that had a splitter using the same VHF aerial as the radio - worked well. I have now fitted a Raymarine AIS700 transceiver that has a built-in splitter and dedicated GPS. The reception and transmission was tested when I programmed the unit. All fine and I'm still using the same aerial with the VHF radio. I fitted the GPS unit inside the ceiling of the galley (fiberglass catamaran) and did not have to install it on the outside of the boat. Works 100%.
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Old 01-12-2018, 12:11   #4
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Re: POSITION OF AIS UNIT

Put it near vhf and chart plotter. And other electrics. You will be running cables to these devices. Or the same path those devices use.

It'll have its own gps antenna. No way around that. But the can be mounted underneith depending on overhead upstructions.

Vhf antenna can be split or have own.

This should not be in website help section.
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Old 01-12-2018, 12:20   #5
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Re: POSITION OF AIS UNIT

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Originally Posted by Nifty View Post
Any recommendations on positioning an AIS unit on a 14m fibreglass cruising yacht, e.g. underneath cabin top, under rear deck? It has been suggested a dedicated gps antenna is not necessary - discuss. Plans for coastal cruising in Australia. Should unit be located close to chart plotter? Position of antenna if advisable? All practical advice welcome.

Nifty
Hobart
Australia
It is very unclear what you are actually asking about here...

Are you asking about where to put an AIS display? If so the answer is pretty obvious: So you can see it clearly from where you normally pilot the boat. None of us know where that might be on your boat.

Are you asking where to put a "Black Box"? If so where ever makes the most sense from wiring and space concerns. There is no other concern. Only you can answer that.

If you are talking about a Class B (or Class A for that matter...) transmitting AIS, no matter what you have heard, most all of them DO actually require their own dedicated GPA antennae. Where to locate that has so many variables that it is impossible to answer for YOUR boat other than to say "a good view of the sky". Most modern GPS systems have enough sensitivity that a little cored FRP isn't a real issue. But better SNR will be be obtained with a mount out in the open.
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Old 01-12-2018, 12:21   #6
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Re: POSITION OF AIS UNIT

My AIS unit transmits and receives from the VHF antenna on top of my mast. I receive information from boats 20 miles distant, and I'm assuming they are getting mine. I have verified my transmissions at closer ranges--10 miles.

The AIS unit is located (velcroed) to the backside of the panel opening to the auxiliary DC circuits at the nav station. The splitter is 2 feet away--other side of the VHF radio. All these are located along the hull and under a teak deck.
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Old 01-12-2018, 13:24   #7
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Re: POSITION OF AIS UNIT

Thank you everybody for your prompt and practical advice. That I have the answer in less than 2 hours demonstrates the power that this forum harnesses. Safe sailing to all. - Nifty
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Old 01-12-2018, 14:40   #8
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Re: POSITION OF AIS UNIT

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If you are talking about a Class B (or Class A for that matter...) transmitting AIS, no matter what you have heard, most all of them DO actually require their own dedicated GPA antennae.
This is a bit unclear to me... The AIS units with which I am familiar all have built in GPS units with internal antennae. I believe that this is a requirement for FCC and other approval. Most have the option of adding an external antenna if the installation is below decks, especially on metal boats where signal attenuation in the decking is severe.

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Old 02-12-2018, 08:56   #9
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Re: POSITION OF AIS UNIT

suggest follow the installation instructions with the unit.
local country registration may dictate additional requirements.

as far as the antenna- a splitter should be a last resort on a transponder unit (vs receive only) . but that is your decision in "class b" unregulated units. required units must be stand alone antenna and gps.
as far as antenna locations, one is dealing with radio frequencies- ideally external clear view of the sky for the gps and a clear view of the horizon minimum three meters above the water for vhf antenna. The rest of your decision are based on the unit, interference, the display needs, power , etc.
The black box only needs to be someplace not to hot.

With all the rhetoric around, just remember a quality install is most efficient- and transmitting a 2 watt signal requires quality install.
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Old 02-12-2018, 09:48   #10
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Re: POSITION OF AIS UNIT

This past spring I installed a Vesper AIS 6000 unit on my boat. The installation was at the nav station behind the panel with the other electrical instruments. The AIS unit is mounted directly against the cabin house bulkhead.

I use a VHF splitter for the receive/transmit functions for the unit. I have a connection for an external gps antennae but I do not use it. The unit transmits and receives just fine where it is using the internal gps antennae.

Longest confirmed sighting of my unit to date is @ 15 miles from another boater we were cruising with.
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Old 02-12-2018, 09:51   #11
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Re: POSITION OF AIS UNIT

This is similar to another post whose AIS GPS input was not working properly due to the unit being located directly underneath the VFH radio that blocked GPS input. Make sure the AIS unit GPS is not obstructed.

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Old 02-12-2018, 11:06   #12
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Re: POSITION OF AIS UNIT

Where the black box and aerials go is far less important than being able to see the AIS output in the cockpit. Ideally overlaid on the chart plotter and, failing that, on a screen in sight from the helm.
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Old 02-12-2018, 11:16   #13
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Re: POSITION OF AIS UNIT

Quote:
Originally Posted by Jim Cate View Post
This is a bit unclear to me... The AIS units with which I am familiar all have built in GPS units with internal antennae. I believe that this is a requirement for FCC and other approval. Most have the option of adding an external antenna if the installation is below decks, especially on metal boats where signal attenuation in the decking is severe.

Jim
My el-cheapo Matsutec AIS gizmo has an external GPS antenna. Good and bad really. Bad, another antenna to locate in such a way that it won't get damaged and can actually SEE the satellites, good in that it allows a bit of flexibility in placing the device itself, which incorporates a smallish colour LCD display.

For the OP, assuming you are asking where to put a similar device with a display, I chose to put mine side by side with my plotter for three reasons:

1. It allowed easy comparison of the AIS "radar" with what I can see on the plotter. (Although the AIS data is also displayed on the plotter, see point 3, I do not like to assume this will always be the case.)

2. The plotter is in a convenient location to the helm, ipso facto, the AIS display becomes likewise.

3. Setting up a NMEA connection between the AIS unit and the plotter was made simpler by their proximity.

FWIW, my external GPS antenna works perfectly from INSIDE the fibreglass deckhouse. This was unexpected (to me), and made life a bit easier. GPS receivers have got a lot better in the last few years.

FWIW-2: I chose to use a separate antenna for the AIS, it's a contentious issue here on CF, but I don't like the idea of VHF splitters.
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Old 02-12-2018, 11:33   #14
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Re: POSITION OF AIS UNIT

Quote:
My el-cheapo Matsutec AIS gizmo has an external GPS antenna. Good and bad really. Bad, another antenna to locate in such a way that it won't get damaged and can actually SEE the satellites, good in that it allows a bit of flexibility in placing the device itself, which incorporates a smallish colour LCD display.
Hmm...

Upon rethinking things, perhaps the requirement is to have an internal gps receiver, but not that it's antenna is also internal. (Both refer to transceivers, not to rx only devices).

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Old 02-12-2018, 11:48   #15
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Re: POSITION OF AIS UNIT

Yes, an AIS unit must have its own GPS source (i.e. not take it from something else on the network). But that can be internal in its own box or wired. My XB8000 is deep down in the nav table and came with an external GPS aerial that's mounted on the pushpit.

Re: VHF aerials, yes the ideal situation is a separate aerial from the VHF, but it has to be a significant distance away so this is only really practical on a ketch. With a sloop, mounting the aerial on an arch or similar isn't going to give you the same range. A good quality splitter (such as the one made to go with the XB8000) will give you maximum range and let both work properly.

The display should obviously be wherever you helm the boat from. I chose the XB8000 because it integrates and transmits all data over Wifi, so I can see AIS and all other data on my ipad at the helm, and also see AIS data on the wired NMEA2000 chartplotter as a backup.
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