ASI 650 Multiplexer & DSC Messages

[rsqunit]

I understand the AIS 650 has a built-in NMEA multiplexer to be able to take the messages received from the E80 Chartplotter at 38400 baud and repeat them at 4800 for the VHF radio to get GPS info for DSC.

Question: Does the multiplexer also send messages back from the VHF to the E80 so that DSC info can be displayed on the E80/E120?

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum rsqunit,

Q. Does the multiplexer also send messages back from the VHF to the E80 so that DSC info can be displayed on the E80/E120?
A. Yes.

[rsqunit]

Thank you! One more question about the setup.

I have a iCOM M424 VHF Radio, and I want to get GPS data to it for DSC. The manual and some forum threads say that to prevent the GPS data conflicts the AIS should be configured to not send out GPS data via NMEA.

I also understand that the iCOM does not accept GPS data from the Chart Plotter that is preceded with the Talker ID (EC).

I completely get that there could be conflicts if two devices were sending out GPS data on a network. However, if the 4800 NMEA port is only attached to the VHF, would this still be an issue? Can I safely send GPD data from the AIS to the 4800 NMEA port to the VHF?

I rather not have to install yet another SeaTalk to NMEA converter just to attach the VHF.

Thanks!

Wil

[Chuck - Raymarine - Moderator]

Wil,

Please click here to view a FAQ addressing this subject. Your suggested solution is not valid for Icom VHF radios, Icom SSBs, and any other products requiring 4800 BAUD NMEA 0183 GPS sentences featuring the "GP" NMEA 0183 Talker ID as the MFD is not the originating source of GPS data within the system. Accordingly, should the system already feature a SeaTalk to SeaTalkng Converter, then an E70196 VHF NMEA 0183 to STng Converter Kit simple be daisy chained via an appropriate length of SeaTalkng Backbone Cable to the currently installed SeaTalk to SeaTalkng Converter. The NMEA 0183 output of the VHF radio may be interfaced to the 4800 BAUD NMEA 0183 input leads of the AIS650.

[rsqunit]

Thanks Chuck. I don't think I explained it very well.

1. Yes, I understand that the iCOM does not accept GPS data that has an EC Talker ID. My understanding it is that it just ignores it instead of processing it, but it does not cause any issues.

2. If I enable the "Output of GNSS Sentences" on the AIS 650 using the ProASI2 software, I have confirmed that "GP" sentences are sent out by the AIS via NMEA. I assume this means the iCOM would process these properly, but I won't be able to actually connect it this way to fully test until next week as I am not on the boat right now.

The follow-up questions are:

a) The manual of the ASI 650 says not to enable "Output of GNSS Sentences" other than for troubleshooting, because of potential "GPS Data Conflicts and/or performance issues" I imagine the potential data conflicts would occur if multiple GPS devices were reporting "GP" data sentences in the network. This part makes sense to me. However, what I do not know is whether in the configuration where the VHF is the only device attached to the AIS via NEMA at 4800 and the E80 is the only device attached to the AIS at 38400, would this still cause the potential conflict? Does the E80 take the GP sentences and repeat them into the SeaTalk network so other devices on the network would get conflicting data with other GPS data sources?

b) Is there a way to have the AIS send out the "Output of GNSS Sentences" only via the 4800 NMEA output port (attached to the VHF only) and not on the 38400 output port (attached to the E80). If it is, then it seems to be this would be the optimal/simplest solution in my configuration.

c) What are the "performance issues" mentioned in the manual related to having "Output of GNSS Sentences" enabled? This does not make much sense to me either.

Thanks again for the help!

Wil

[Chuck - Raymarine - Moderator]

Wil,

Q1) What I do not know is whether in the configuration where the VHF is the only device attached to the AIS via NEMA at 4800 and the E80 is the only device attached to the AIS at 38400, would this still cause the potential conflict? Does the E80 take the GP sentences and repeat them into the SeaTalk network so other devices on the network would get conflicting data with other GPS data sources?
A1) E-Series Classic MFDs doe not support multiple data sources. Enabling the GNSS output of the AIS650 would cause it to transmit GPS data sentences in addition to AIS data sentences to the MFD. Should the MFD presently be interfaced to a source of GPS data, then enabling the GNSS output of the AIS650 would introduce a second source of GPS data, resulting in a conflict. The E-Series Classic MFDs will indeed bridge GPS data received via its NMEA 0183 port to SeaTalk.

Q2) Is there a way to have the AIS send out the "Output of GNSS Sentences" only via the 4800 NMEA output port (attached to the VHF only) and not on the 38400 output port (attached to the E80). If it is, then it seems to be this would be the optimal/simplest solution in my configuration.
A2. No.

Q3) What are the "performance issues" mentioned in the manual related to having "Output of GNSS Sentences" enabled? This does not make much sense to me either.
A3) The AIS650 outputs only a subset of the data items produced by a GPS sensor, hence the reason for not using it as the system's primary source of GPS data.

Should it not be desirable to install an E70196 VHF NMEA 0183 to STng Converter Kit, then the alternative would be to install a dedicated NMEA 0183 GPS Sensor to support the GPS data requirements of the VHF radio.

[rsqunit]

Thanks for the detailed information Chuck!

Wil

[Chuck - Raymarine - Moderator]

You're welcome.