NMEA wiring

[FlyingSpud]

I want to connect a Garmin GPS, Simrad DSC radio and a set of ST60’s including a multi that acts as an NMEA interface.

The GPS seems to have NMEA out, the radio NMEA in and the ST60 Multi an in and out (shake it all about)

So it seems it must be GPS to Multi and then on to the radio.

My question is, given there seem to be two wires for each do you wire them up in parallel or series
(a) +ve goes from GPS to Multi to Radio and the radio then connects to the –ve of the GPS
or
(b) two GPS wires to Multi, then two wires on to Radio?


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[Oldhand]

I would wire them in series then the "senders" (the GPS and then the Multi) are only supplying one "receiver" each. Most NMEA equipment should be able to provide sufficient signal for up to three or four receivers but by only supplying 1 you will be sure of not overloading the senders.

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[LadyInBed]

I wouldn't go to the Radio via the multi, I would go from the GPS to the Radio then 'daisy chain' on to the multi. On the principle that if I need the radio to send out my position, I am probably in trouble, so don't want another bit of kit interfaceing as a repeater.

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[bedouin]

As I understand your set up:

(a) The Radio can only receive, and only needs position (From GPS)

(b) The GPS can only send.

In which case you need to connect the output from the GPS to the input on both the ST60 and the Radio - there is no need to connect the output of the ST60 since there is nothing that can use it.

So in effect you need to connect the +ve out of the GPS to the +ve in of the Radio and the ST60, and the -ve of the GPS to the -ve of the other two. This is a parallel connection of two receivers to the sender.

This ought to work but there is always a chance that the particular equipment you have won't work in that configuration.

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[tillergirl]

I thought that ST's did not put out NMEA but talked in SEATALK, Autohelm/Raymarine/Raytheon own language but They do an interface box which converts Seatalk in NMEA and allows GPS and Dsc to give/get their feeds. Works well. I don't think you will get NMEA out of ST instruments otherwise.

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[vyv_cox]

Mine is not the same equipment but just the same problem. NMEA output from my Garmin GPS goes to the RX of the B&G instruments (mainly for benefit of the on-deck repeater), TX from the B&G goes to the radar. This is all wired in series, + and - connections right through.

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[MartinGPerry]

The NMEA output on the ST60 multi only outputs a restricted set of NMEA sentences - check in the manual if you decide to go that route, though as others have said there will be no problem in paralleling 4 or 5 NMEA listeners to one NMEA talker
Just parallel the NMEA +/- data cables
Martin

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[philip_stevens]

I think you will find that the later models of the Autohelm ST models were the Plus version that had both NMEA and Seatalk in/out.



<hr width=100% size=1>regards,
Philip

 

[FlyingSpud]

Hmm.. Thanks for all of the advice but it seems as though I have 3 for doing it in series and 2 for doing it in parallel. At least it suggests it wasn’t as dumb a question as I thought it was.

So what to do? My suspicion is that both work, so perhaps I will just go for what seems the easiest to wire up, whichever I choose will, inevitably, not work.

Must admit I can see the attraction of having all Seatalk, but I suppose that is Raymarine’s big sales point.

Pat


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[vyv_cox]

The good thing with NMEA is that it won't do any harm if it's wrong. Just try whichever you think looks right and if it doesn't work, try another way. I understand that most GPS sets will support two or three outlets in parallel, so it should work however you like.

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