Connecting DSC VHF to RAYMARINE chartplotter

[CAN DRAC]

Did any of you hook up the VHF that came with the boat (in our case the Icom M422) with a Raymarine chartplotter in order to be able to broadcast the vessel's position in a Distress call via DSC?

Ours seems to be properly wired through the NMEA 0183 output (via the AIS) but the VHF still says NO POSITION even when we get a satellite fix on the plotter.

Wondering if there is something else that needs to be configured differently on the plotter or the VHF...

Anyone gone through that?

Thanks!

-franc
s/v Can Drac

[Mike Brown]

Franc, funny you ask since I just mentioned that I want to do that. I installed an ICOM 5000 AIS in the fall but never checked to see if it impacted the DSC on the VHF. How do you test it without alerting the Coast Guard?

[CAN DRAC]

Yeah, it's a requirement here in Spain so I must find a solution.

In our ICOM VHF there is no need to press the Distress button to test the GPS feature. You just press the DSC button for a second and it displays your position (if received, of course).

In your case, it looks like the PC Data out on your AIS should be connected to the VHF GPS input, since the chartplotter NMEA 0183 output is likely to be taken by connecting to the AIS data in/out. Same as mine.

The issue is that despite all the wiring being as indicated in the manual, the VHF continues to say NO POSITION.

??

[Mike Brown]

Franc, the AIS data out runs to the E120 not the VHF. I'll likely have to run a jumper from the AIS data out to the VHF to get the DSC to provide a fix. I'm going over to work on the boat tomorrow. If I have the time I'll connect and test it and let you know what happens.

[Ricardo Negrini]

That won't work. Due to frequent data change and safety reasons, the chartplotter must receive AIS data quickly in order to be effective in calculating any threat to your vessel or alarming under your triggers. So, AIS>Plotter runs NMEA data at 38,400 bps (not that fast, but sufficient in this case). ICOM uses standard NMEA baud rate at 4,800, wich is more than enough to handle lat/long. In case of ICOM AIS MXA-5000, either data out (to PC or to Chartplotter) runs at same baudrate, thus I had to pickup the NME 4800 from the autopilot core-pack in a separated cable. On E120/E80 34,800 is the std for the data input, thus although your proAIS software can configure such baudrate on AIS500, it is not recommended. Make sure you pick the YELOW cable that provide 4,800 bps, and ground. Note: ICOM VHF uses a different kind of interface, it is not current-balanced RS-422, neither a full RS-232 implementation, so input signal must be from DATA+ (yellow cable at your AIS500) and GROUD. Hope this helps ....

[CAN DRAC]

Thanks Negrini,

But I´m following the instructions on the Raymarine AIS250 which has a 4,800 baud output precisely for DSC VHF. It reads:

NMEA 4.8 OUT:
This port allows devices requiring NMEA 0183 data running at 4.8 kbaud as their input to integrate into the NMEA network. Typically a DSC radio’s or a 3rd party non-Raymarine Autopilot’s NMEA input would connect to this port.

(http://www.raymarine.com/GetFile.aspx?fileId=735&categoryId=3)

I'm using a Raymarine cable with several colored wires inside and connecting the RED and the ground.

Still NO POSITION...

:(

[Mike Brown]

Franc sorry but I didn't get a chance to connect the PC to VHF today. I'll keep it in mind and let you know what I find. Good luck in the mean time.

[CAN DRAC]

Thanks, Mike. Still a mystery to me...

[Ricardo Negrini]

So, are you connecting like this ?

AIS250 . . . . . . . . . . . . . . . .M422
NMEA 4.9 OUT + _____ NMEA IN (RED)
NMEA 4.8 OUT - _____ DC GROUND (BLACK) or another VHF GND ref.

if so, check your cable continuity with a multimeter. It
should work, otherwise it might be a faulty unity. Also, if
you have the chance, plug your laptop on this lead NMEA OUT +/-
on AIS250, set baudrate, open the terminal application, and try
to read the sentences transmitted. Look inside

Another point for verification is, how your GPS is connected to
this system ? is it possible the AIS250 not receiving GPS position
sentences ?

[CAN DRAC]

Thanks for the update. AIS is working fine, showing on screen, etc so I guess GPS is going in properly. I also checked for continuity and it was fine but I will double check or try a different wire. Will any wire do or is there a specific type for this?

[Ricardo Negrini]

only reason for a good shielded cable would be routing through electromagnetic noise sources, or long distance, wich is not the case. I asked you about how the GPS is hooked because since your AIS is a receiver only, it doesn't require GPS input to work. So, if your GPS is hooked on plotter (like mine) you don't have this information sent to your AIS (like mine), thus not able to repeat such sentence .... Are you sure your AIS does receive lat/long information ?

[Andrea]

Very good point. Yep my GPS is connected to the plotter. How do we get it to send position data to the AIS? According to the manual the 4.8 baud output on the AIS appears to be designed to connect DSC VHF, after all, no?

[Ricardo Negrini]

Icom-5000 does not have a 38,400 INPUT, only OUTPUT, so I had to run a NMEA cable from the closest 4,800 available (AP corepack in my case) up to VHF. In your case, the 250 has a 38,400 INPUT and OUTPUT. Your plotter does carry position sentences (as per pg 15 of manual), make sure you have NMEA 38,400 IN and OUT correctly plugged to the PLOTTER <> AIS. I mean you should have 4 wires interconnecting your AIS and PLOTTER. As per your description, the only wire functioning is the NMEA 38,400 OUT from your 250.