Another Ais question

[Storyline]

Am thinking of getting a budget two channel receiver and I see that some can also accept a GPS position. As I am going to connect the Ais to a plotter with its own GPS am I right in thinking the AIS receiver does not need to know it's own GPS position ?

 

[chanelyacht]

Am thinking of getting a budget two channel receiver and I see that some can also accept a GPS position. As I am going to connect the Ais to a plotter with its own GPS am I right in thinking the AIS receiver does not need to know it's own GPS position ?

Depends on the AIS receiver and how you'll use the information, but to purely receive an AIS signal, no it doesn't.

 

[Storyline]

Depends on the AIS receiver and how you'll use the information, but to purely receive an AIS signal, no it doesn't.

The one I am thinking of is the Digital Yacht AIS100 and I just want to connect it to my plotter with 0183 and just see the position (and info about) of targets on the plotter relative to our position.

 

[prv]

The one I am thinking of is the Digital Yacht AIS100 and I just want to connect it to my plotter with 0183 and just see the position (and info about) of targets on the plotter relative to our position.

In that case I'm fairly sure it doesn't need a GPS connection. I fitted a Digital Yacht AIS in our previous boat (though not that exact model) and the reason for the GPS input was so that you could feed both position and AIS data to a plotter without taking up more than one NMEA port, or having to set ports to two different speeds which some plotters have limitations on. If your plotter already has a GPS feed (internal or external) and there's a spare port for the AIS, then you don't need this.

Pete

 

[Storyline]

Thanks all - understand now

 

[wooslehunter]

Not sure about the capabilities of NMEA multiplexers, but AIS is transmitted on the NMEA bus at a far faster rate than standard: 38400 baud vs 4800 baud. So,if you do need to multiplex both sources onto the same port, then the multiplexer must be capable of changing the standard 4800 port up to 38400. Then you can connect the output into a single ports on the plotter. This is why AIS receivers sometimes have the facility to take in a standard 4800 signal & multiplex it together with its own 38400 AIS output.

Consider the situation where you have auxiliary data from other instruments into your plotter & you want to control an auto-pilot. The simple way is to connect one port on the plotter to the auto pilot & a second port to the aux data Both would be set to 4800 baud. Now add an AIS to system. You either need a 3rd port or you have to take the aux data into the AIS receiver which then multiplexes it with its own data & outputs that at 38400 baud. You connect that to the second plotter port & set the speed.