Simrad NAIS 400 sentences

I think the MUX is only between the three NMEA 0183 ports (1 x USB, 2 x serial).

The N2K port doesn't even carry all GPS data that the builtin GPS produces and that is sent out over NMEA0183.

Haven't tested that it doesn't output any converted 0183 data. Maybe I should do that for something simple like depth or speed data.

As I understand the NAIS-400 it has it's own DSC receiver built-in, so no need for passing DSC alerts from the GX2000 VHF to the plotter.

I Should get my own within a week or two, so the above information is only based on what I have been able to look up in the manual.

Mikkel, I think that all AIS transponders have DSC receivers so that authorized ground stations can make local changes in transmission rates and even shut down frequencies or certain classes of transmissions. But I don't think that your AIS will receive DSC alerts, direct calls or polling information.

I don't think any AIS transponder has a DSC receiver. DSC is transmitted on channel 70. AIS is on 87B and 88B. Having a receiver for 3 channels would increase the complexity significantly.

It is true that AIS ground stations can send out instructions to AIS transponders, but that is done over the regular AIS frequencies using the same kind of AIS datagrams., in particular using message types 16, 22 and 23. Only so-called "competent authorities" can do this.

See http://www.navcen.uscg.gov/?pageName=AISMessages

I am probably wrong (wouldn't be the first time)..

But if you look at the AIS specifications http://www.bandg.com/Documents/products/operator-manuals/NAIS-400_UM_EN_988-10373-001_w.pdf?epslanguage=en-GB

on page 29 is written: AIS Receiver x 2 (One receiver time shared between AIS and DSC)

So I just assumed this was for DSC alerts.... If this isn't the case the above question is very relevant for me too... :)

Hm, good catch Mikkel. As you can see my assumption about a 3 channel decoder is still true: it is time-shared.

No idea what that means and what the functionality is -- now and possible in later firmware.

You are right that there are only so many uses a DSC receiver could have though.

To the first point on Muxing.. I called Simrad and they told me that the NMEA0183-4800 input was also Muxed onto the NMEA2000 output, so that gave me some hope.

But when I asked what sentences were supported, the Tech didn't know offhand and told me he would have to do some homework and get back to me. That was last week and he hasn't called me yet, so I thought I'd ping the forum to see if others know.

Good questions you others raise above. When I get to the bottom of this, I will post answers for all. I appreciate anyone chiming in. thanks

Just an update regarding the DSC receiver in the NAIS-400 AIS transponder.

Asked simrad in DK what the possibilities with the DSC receiver is, and it took them quite some time before they could answer, but the answer they came up with was actually the exact same as you Ben. It is only for ground station communication.

Simrad confirmed that Kees is right that the muxing internal to NAIS-400 is only for NMEA 0183 and it doesn't mux it onto NMEA-2K output.

Regarding DSC.. Simrad replied to me:
[quote - simrad] -
2 – What is the DSC capability of the NAIS-400?

All Class B AIS equipment is required to ‘listen’ to channel 70 for DSC channel management messages on a fixed schedule. At certain times of day the NAIS-400 will tune one AIS receiver to DSC for a few minutes to receive DSC channel management commands from an AIS base station. These may be used by the local authority to move AIS traffic onto alternate VHF channels, or return to the default channels. This is the only function of DSC reception in AIS & it does not replace DSC functionality in a VHF radio. This information is relevant only to the internal operation of the AIS and therefore not output to any data port.
[unquote - simrad]

I am still waiting for a response on exactly what 0183 sentences can be received/muxed/transmited. This information should be in the manual.