Wiring icom ic-m604a vhf, mxa-5000 ais, Garmin 740s

[Lyric]

I am trying to wire, via nmea 0183, an Icom m604a vhf with DSC, Icom AIS receiver and a Garmin 740s chartplotter together. The chartplotter is using the internal GPS antenna. I would like to use the chartplotter’s GPS for the VHF and AIS. The chartplotter has two 0183 ports. I would like to be able to receive and plot the DSC and AIS information from the VHF and MXA-5000 (respectively) using only one 0183 chartplotter port if possible so that I would have a free chartplotter 0183 port for a future planned device.

Has anyone here made a similar connection or have a recommendation?

Thank you,
Matt

I linked the guides for each product below.
MXA-5000 link: http://www.icomamerica.com/en/products/marine/ais/mxa5000/default.aspx
IC-M604A link: http://www.icomamerica.com/en/products/marine/mountedvhf/m604a/default.aspx
740s link: https://buy.garmin.com/shop/store/manual.jsp?product=010-00835-02&cID=148&pID=37721&ra=true

[Lyric]

I have attached a wiring diagram. Perhaps one of you talented NMEA experts could help me with the best wiring connection scheme. The Garmin chartplotter shares a common ground for all NMEA 0183 ports.


I'm probably making a mountain ouf of a mole hill but this is my first time working with NMEA. How should i proceed to allow the VHF and AIS to receive GPS data from the chartplotter, allow the AIS to talk back to the chartplotter and allow the VHF to talk back to chartplotter? Thank you.

[DotDun]

1) You should be able to split/connect the NMEA0183 output from the Garmin to both the AIS and VHF with no problem, hence supplying GPS to both VHF and AIS. I would guess the VHF will limit the speed to 4800.

2) NMEA0183 is a 'single-talker' network, so you will need a multiplexer to get both DSC and AIS into a single port to the Garmin. Also the multiplexer will need to support a 38400 input and a 4800 input, as I believe the AIS will be 38400 and the VHF 4800. Obviously, the output of the multiplexer will be 38400 into the Garmin. Since the port speed in #1 will need to be 4800 for the VHF, I don't know if Garmin can accept 38400 on the same port as transmitting 4800. This may be a show stopper for only consuming a single port on the Garmin.

3) Although having DSC connected to your Garmin is useful, you will probably only see 1 or 2 messages a year on average. There is not much DSC traffic unless you buddy boat and use the position request/response mechanism.

[Lyric]

So it sounds like I would need a multiplexer to achieve single port use. If I decided to connect the second port now and deal with getting a multiplexer once the need arises would my wiring scheme look like the following image? Also how does the 740s communicate with the other devices (Do i need to tell the chartplotter which NMEA sentences to send out of each port?)?

[DotDun]

If you are forced to use both ports on the Garmin, connect one port to the AIS and the other to the VHF. That way you won't have any speed issues. Your drawing shows the AIS input to the Garmin on the same port as the GPS output to the VHF. AIS runs at 38400 (NMEA HS) and my guess is once you set that Garmin port to HS, it's output will also be set to HS and the VHF won't accept it. So, use the two ports on the Garmin and dedicate one to low speed (VHF) and the other to HS (AIS).

I personally wouldn't invest in a NMEA0183 multiplexer. I would opt for a NMEA0183 to NMEA2000 gateway (like the Actisense NGW-1). Leave the VHF on NMEA0183 and put the AIS thru the gateway to NMEA2000 then to the Garmin. That will free up a NMEA0183 port on the Garmin.

NMEA2000 is current technology, NMEA0183 is ancient technology.

[Lyric]

Thank you for your help.

[Lyric]

Update for anyone attempting this project: Garmin 740s, Icom IC-M604A and Icom MXA-5000 are all connected and work perfectly. I used both NMEA 0183 ports on the Garmin and have full fuctionality of all devices.

[EnduroSailing]

Hi,
Thank you for this thread, I am also new to NMEA. The wiring diagram posted and compatibility comments with Garmin devices has been useful to me, but I cannot get AIS targets to show up on the plotter...

I now have a Garmin Echomap 62UHD connected to a second hand MXA-5000 with the blue cable (TX) from the garmin power cable connected to the AIS data-in (+) and the brown (RX) wire to AIS data-out (+) and all - grounded with the chartplotter. On the Garmin, I have also selected Serial Port to "NMEA High Speed". I am using default settings for the NMEA 0183. Is this correct? (XTE precision = 3, Sounder etc...)
Under NMEA 0183 diagnostics under "VDM = ----"
Any ideas on what have I missed?
(edit: antennae is working well for transmitting and receiving vhf separately)