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Old 06-10-2012, 06:53   #1
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AIS: two GPS antennas mandatory with Garmin?

Hi together,
can anybody help me with this question?

The Instructions for the active AIS Gramin 600 state on page 3

"The AIS 600 must be connected to the included GA 30 GPS antenna. The AIS 600 does not share GPS information with any other devices on the boat. If you have a chartplotter on your boat, it must receive GPS information from a separate antenna, ..."
( see http://static.garmincdn.com/pumac/AI...structions.pdf )

This seems to be quite strange.
I like to have as little antennas and installations as possible which is why I like the integrated VHF splitter of the AIS 600. But two GPS antennas???

What alternative AIS transmitter would you recommend. (good, non proprietary connectivity, integrated splitter)
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Old 06-10-2012, 07:05   #2
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Re: AIS: two GPS antennas mandatory with Garmin?

Seems typical. Our AIS transceiver is a Furuno, same way, dedicated GPS antenna.

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Old 06-10-2012, 07:13   #3
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Re: AIS: two GPS antennas mandatory with Garmin?

I think it's an AIS requirement for a dedicated GPS.
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Old 06-10-2012, 07:43   #4
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Re: AIS: two GPS antennas mandatory with Garmin?

It is an AIS requirement indeed; AIS needs a separate dedicated GPS antenna.
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Old 06-10-2012, 10:52   #5
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Re: AIS: two GPS antennas mandatory with Garmin?

I suspect it's only for a TRANSMITTING AIS system.
I have a Garmin 200 AIS VHF and Garmin 5208 Chartplotter GPS which share one VHF antenna with a splitter (also Garmin).
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Old 06-10-2012, 11:39   #6
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Re: AIS: two GPS antennas mandatory with Garmin?

Take a look at the Si-Tex Class B AIS Tranceiver. I just installed one on my boat. It has a built in GPS and will export NMEA 0183 GPS data. It can also use an external GPS if you have to but mine works from inside a cabinet in the pilothouse.

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Old 07-10-2012, 06:02   #7
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Re: AIS: two GPS antennas mandatory with Garmin?

AIS is actually governed by international treaties signed under the International Maritime Organization (IMO). Your home country also has rules about its use for instance the USCG information is here .

When AIS first came out it was required on certain ships over 300 gross tons. That has since been modified in the US, so that basically anything over 65 feet is required to carry AIS Class A, including recreational boats (There are exceptions)

The initial regulations governing AIS required a independent GPS antenna for the unit.

On a side note, using AIS Class A, one of the bits of information dispalyed is the location of the GPS antenna on the ship. That means if you are dealing with a 1200 foot long vessel and the GPS antenna is on the stern, there is over a 1000 feet of ship in front of the actual displayed position. On Class B units this information is not displayed normally.

Anyway the bottom line is your AIS has a second GPS antenna independent of the rest of your equipment, because it the law.

As far as AIS RECEIVERS, they do not need a GPS antenna to receive, only to transmit.
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Old 07-10-2012, 06:40   #8
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Re: AIS: two GPS antennas mandatory with Garmin?

Quote:
Originally Posted by Zanshin View Post
It is an AIS requirement indeed; AIS needs a separate dedicated GPS antenna.
And yet, some AIS devices accept GPS signal input and this signal can be split prior to entering the AIS unit and fed into other devices that use GPS signal.

Meanwhile, many AIS devices multiplex their GPS input and this can be later used by devices downstream from the AIS unit.

So, really, not a big issue, unless the GPS/AIS signal is a proprietary protocol that cannot be easily read by third party devices.

b.
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Old 07-10-2012, 08:17   #9
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Re: AIS: two GPS antennas mandatory with Garmin?

Barnakiel,
I never stated that it couldn't be done, just that it shouldn't be done.
All Class B or A AIS devices require GPS input from an antenna and then can output the GPS information via NMEA or other means to downstream systems. Note that those devices which accept NMEA input for GPS are not labelled or sold using the term "Class B" or "compliant".
While it is true that a signal splitter for GPS or VHF can be installed upstream, the specifications in AIS IEC 62287 don't allow it for Class A and most likely not for Class B (the online doc costs 280CHF and I can't find a free copy anywhere).
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Old 07-10-2012, 08:23   #10
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Re: AIS: two GPS antennas mandatory with Garmin?

Anyone know if these work "both ways" or just as receivers?

https://www.google.com/search?q=usb+...ient=firefox-a
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Old 07-10-2012, 10:12   #11
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Re: AIS: two GPS antennas mandatory with Garmin?

The AIS USB dongles are definitely receive-only.

As noted, Class-B AIS transponders by law require a dedicated GPS receiver. They will not accept a NMEA feed from an existing GPS.. The transponders actually incorporate the GPS receiver, and the external part is just an antenna / preamp. You will notice that the connector is (usually) a TNC coaxial plug/jack. This carries power to the preamp and the GPS radio signal from the antenna.

My transponder does include it's GPS data along with AIS data in the NMEA output. I could use this as my navsystem's primary GPS source if I wanted to.

Class-B transponder messages do contain the GPS receiver's location and vessel length / beam. Of course this static information may be mis-configured by the installer.
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Old 07-10-2012, 10:56   #12
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Re: AIS: two GPS antennas mandatory with Garmin?

The AMEC Camino 101 class B tranceiver will accept an external GPS signal. From personal experience, the Camino is very picky about the NMEA 0183 sentences from the external GPS. It requires 4 GPS sentences, RMC, GGA, GSA, and HDT. My Standard Horizon CPV-350 would not output GSA so, in my case, the Camino would not transmit. I ended up installing the companion GPS antenna for the Camino and all is good.
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Old 07-10-2012, 11:53   #13
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Re: AIS: two GPS antennas mandatory with Garmin?

Quote:
Originally Posted by Zanshin View Post
Barnakiel,
All Class B or A AIS devices require GPS input from an antenna and then can output the GPS information via NMEA or other means to downstream systems.
This sounds quite reasonable, but looking at the Garmin instructions for the active AIS Gramin 600, page 3, including the schematics, we see that the AIS 600 does NOT provide the GPS information for downstream systems.


"The AIS 600 must be connected to the included GA 30 GPS antenna. The AIS 600 does not share GPS information with any other devices on the boat. If you have a chartplotter on your boat, it must receive GPS information from a separate antenna, ..."
( see http://static.garmincdn.com/pumac/AI...structions.pdf )


Difficult to understand why. I can't imagine that they just want to sell more antennas.
But there seems to be little choice only. Which active AIS does actually provide the GPS information for downstream systems and which does not?
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Old 07-10-2012, 15:27   #14
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Re: AIS: two GPS antennas mandatory with Garmin?

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Originally Posted by myocean View Post
But there seems to be little choice only. Which active AIS does actually provide the GPS information for downstream systems and which does not?
If I remember them well, at least Simrad and Icom do.

b.
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Old 07-10-2012, 18:31   #15
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Your better off with multiple redundant GPS systems, rather then one doing everything


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