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Old 13 January 2012, 08:10   #1
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NMEA 2K branch lengths?

Is there a maximum length of "branch" on an NMEA 2K network?

I will soon be wiring the plotter, and for simplicity and keeping as many of the connections undercover as possible, I am thinking of putting a single "T" near the head, and running a single branch to the A- frame for the GPS pod and eventually continue the backbone to the engine (part of a long term plan to instrument the engine).

Net result of this is going to be the best part of a 5m "branch" to the GPS pod. is that too long, or is the branch length inconsequential?
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Old 13 January 2012, 11:55   #2
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5m is nothing. NMEA network limits don't even come close to what you would have no matter how you wired a RIB network
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Old 13 January 2012, 12:17   #3
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Lowrance quote a NMEA 2000 network backbone maximum length of 100 metres, but also state that any device should not be more than approximately 6 metres from its 'T' connector.
Set up info here http://www.lowrance.com/upload/Lowra...173_112006.pdf
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Old 13 January 2012, 13:50   #4
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Maretron say that the sum total length of all drop lines should not exceed 256 feet so you should be ok
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Old 13 January 2012, 15:02   #5
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Would it not be neater to go to the outboard first and then up to the aerial, putting the terminator on T piece inside the cowling?
This is how I have done mine and at least the last connection is under cover out of the elements.
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Old 14 January 2012, 08:10   #6
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NMEA2000 on that engine. Its funny enough having it on the boat
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Old 14 January 2012, 08:38   #7
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I always thought it was 6m in any one drop. I install a fair new systems, and thats the rule I follow.
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Old 14 January 2012, 13:46   #8
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Quote:
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NMEA2000 on that engine. Its funny enough having it on the boat
Actually I only just noticed this, you don't get an interface for an engine that old anyway. The best you could get was the fuel flow sensor which could be mounted at the fuel tank. Assuming this is under the seat then the branch doesn't need to go to the rear.
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Old 14 January 2012, 14:16   #9
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Bruce, I may have dreamt this but I think you can get a box which will let you wire any sensor or alarm in and it will broadcast it onto your network, if you set it up right. Bet it is not cheap though.
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Old 14 January 2012, 14:26   #10
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Bruce, I may have dreamt this but I think you can get a box which will let you wire any sensor or alarm in and it will broadcast it onto your network, if you set it up right. Bet it is not cheap though.
Actisense are leaders in this field. I think you will find that most of the guidance on drop lengths and backbone lenghts are all realted to obtaining and complying with nmea certification. Out in the field you'll be suprised at how far you can push those supposed boundaries and still have a fully working system. An old article on Panbo.com illustrated this neatly.
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