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Old 02-26-2012
svzephyr44 svzephyr44 is offline
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Quote:
Originally Posted by BarryL View Post
You can't connect multiple devices NMEA 0183 device together unless you add additional gear (multiplexor). NMEA is SLOW (2400 baud typically) and requires you to connect little tiny wires.
Barry
Barry's information is mostly correct. NMEA 0183 was defined in 1983 (wow.) It operates at 4800 baud, eight bits, one stop bit, no parity. Except for high speed NMEA which is used only for AIS connections.

A NMEA Talker can power 4 NMEA listeners. A NMEA listener can only listen to one talker.

The big problem with 0183 is that people like Raymarine decided to violate the standard that says anything a listener hears needs to be repeated on the talker side of the instrument. They did this so they could sell expensive and unnecessary "conversion" boxes.

As pointed out above NMEA 2000 is the new standard. Usually manufacturers don't repeat NMEA 2000 data onto NMEA 0183 outputs. What does this mean. Well, lets say you purchase a NMEA 2000 wind instrument but have a NMEA 0183 multi-function display. Guess what, the NMEA 2000 wind data will not show up on the NMEA 0183 multi-function display. They do, however, usually repeat NMEA 0183 data on the NMEA 2000 bus. So if you buy a NMEA 0183 wind instrument and a NMEA 2000 multi-function display the wind data might show up on the the multi-function display. Confused yet?

Simple rule. If you have old instruments that communicate on NMEA 0183 you probably want to get new instruments that will talk NMEA 0183. If you are getting new instruments then go with NMEA 2000.

BTW most chart plotters talk both, but again the rub is what the rest of your instruments will display. The good news is that the tech support people at Garmin etc. are pretty good about telling you what will happen if you call them up and say "I have these specific instruments wired together like this."

Last comment to make it even more confusing: Back in the dark ages (yesterday) all of the manufacturers had proprietary communication protocols - Raymarine had SeaTalk, SeaTalk2, HSI, and a couple of others. None of these talk to NMEA 0183 or NMEA 2000 without a converter box.

You may start drinking heavily now.

Fair winds and following seas.
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