Seatalk Standard Horizon Interface

[KAM]

I am using a Raymarine NMEA converter box to connect my ST50 instruments to a CP300 plotter. When connected all the seatalk data appears on the plotter windspeed, depth etc but after a few minutes the plotter starts plotting random positions usually on the same bearing somewhere in the Noth Sea but it sometimes changes to somewhere in Spain. I thought it was because I had not used screened cables which I changed but it had no effect. Does it matter where I connect into the seatalk bus. I would have thought that the digital seatalk bus would be reasonably immune from noise and that the plotter would be unlikely to interpret noise as a position and wonder if there is an NMEA compatibility problem. I also have a Furno GPS connected to the seatalk providing SOG etc. Is it possible that the Furno NMEA data on the bus is causing a conflict with the CP300. I have tried disabling some NMEA sentences but no effect. Before I rip the wiring apart again I was wondering if anyone else has the Seatalk/Standard Horizon combination working.

 

[Guitarrich]

NMEA ports

Hi KAM, just browsing through quickly.
My first impression is that you may have a wiring issue. You can indeed connect to the Seatalk network more or less anywhere but......

You're using a plotter which needs NMEA 0183
You're using a GPS which employs NMEA 0183
You have Seatalk instruments and are converting their data with a (E80001?) converter box for the MFD.

This says to me you need to be using two different NMEA ports on your Standard Horizon MFD. I don't know much about this particular unit, but most units have more than one these days.
Is it possible that you've connected your Furuno GPS to the input port of the Raymarine converter box, rather than a bespoke port on the plotter? If so, this will be the cause of your misery!
Good luck...

 

[Simon054]

I have just connected my SH300 chartplotter to the autohelm units via a ST50 repeater unit. Everything seems to work fine except I have noticed that I need to power the chartplotter first before the instruments otherwise the CP will not identify any sats.

 

[KAM]

Guitarrich

Thanks for the comments. I think I will assume it's not noise. The Furuno is connected directly to the seatalk instruments rather than the plotter and does not use the interface box. The interface box is then connected between the seatalk and the plotter. I am only using the output side of the interface box. I only use the Furuno for speed data. The plotter has several ports. I have tried changing these with no effect. I suppose there may be an NMEA data conflict with the Furuno. I'll recheck at the weekend with the Furuno disconnected. I must have tried this already but I've only been dealing with the problem whilst sailing so not adopted a rigorous approach so far.

 

[Paul_R]

I had a similar problem using a CP180 in conjunction with Seatalk and the NMEA NMEA converter. I fed the CP180 NMEA out though the converter to make GPS info available (cross track error etc) to the autopilot and connected the CP180 NMEA in through the converter so I could use the CP180 as an additional repeater. The result were similar symptoms to yours. It worked OK if I disconnected the NMEA feed from the Seatalk converter to the CP180. The CP180 had an internal NMEA diagnostic trace, and when I looked at this it appeared OK with no corruption so I don't think noise is a problem.

The converter will publish GPS info to NMEA if it's available and I concluded that the CP180 was confused because it was receiving the same information from two sources - its own external GPS unit and reflected back from the Seatalk NMEA converter. I think you'll find its OK when you disconnect the Furuno GPS.

In the end I left the NMEA feed from Seatalk disconnected - may be not a suitable solution for you. If yours is the model with the external aerial, you could disconnect it. Your CP300 should be happy with the GPS info received via Seatalk from the Furuno GPS, but of course this means that you would need to have the Raymarine instruments on to get a fix displayed on the CP300.

 

[KAM]

Paul R

Thanks for the input. It sounds like the same problem. I use the Furuno to provide SOG data to the seatalk instruments with a permanent connection. The plotter gets moved from the cockpit to the chart table depending on what I am doing. The main reason for wanting the seatalk data on the plotter is so that I can keep an eye on the windspeed and depth from my bunk on wild nights in Scottish anchorages. Hopefully it should be as simple as using one or the other.