NMEA connection of ICOM M421

[Jimbob]

Hi all

Just some helpful info if you are fitting the ICOM DSC M421 to a GSP/ chart plotter

I’m sure this may seem straight forward, but it took me a couple of hrs reading the books

1) Firstly depending on the GSP check that the data speed rate is set at 4800, and the NMEA is 0183 v2.0 3.02. If there are no settings and its fairly new then this should be the output anyway, as example my Raymarine 420 is about 3 years old and has no facility to change.
2) The connections are (switch power off before starting)

a) NMEA data out (Yellow in my case) of the GSP or plotter goes to the NMEA + of the radio, the inner core (White). Do not use the NMEA + from the GPS or plotter
b) The Data out common (brown wire in my case) of the GSP or Plotter Goes to the outer copper cable (seems like the shield). Do not use the NMEA – from the GPS or plotter. There is only one core so again you cannot go wrong.

That’s it, I hope it helps

[Rupert Bear]

I had to use both + and - to get the 421 to accept the NMEA output from my Garmin plotter. One wire was fine when I had the Silva but the Icom just didn't like only one wire although in theory it shouldn't matter!