Join Date: Feb 2011
Location: San Francisco Bay area
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Re: NMEA Frustration
"nly two connections needed are the NMEA In +/- on the VHF to the Data out +/- on the GPS, however the VHF instructions say to connect the bare ground wire to the bare ground on the GPS... Is the ground the same as NMEA In -? "
No it is not the same. The confusion arises from the fact that sometimes signal - refers to the one side of a bipolar output / input, and sometimes to an inverted version of the signal. In the latter case, connecting it to ground at the other end will result in no signal, as the circuit is not complete. Connecting + to + and - to - won't work either, without the ground circuit complete.
Went through all this connecting my Lowrance plotter to my Standard Horizon GX2150 radio.
In that case I connected + out to + in, and ground to ground. The - input is left floating, as is the - output. Ground might be a separate wire, or cable sheath.
If you could provide links to the wiring diagrams for the two devices, I could be more specific.
Bristol 31.1, San Francisco Bay