Larry, you bring up and interesting question that I am pondering. I am
going to be hooking my Garmin 176 up to my Simrad autopilot. The Simrad
nicely isolates the Nmea common from battery neg. Unfortunately, the Garmin
only has 4 connections, 12v+, Nmea in, Nmea out and common shared between
the Nmea and 12v -. If I connect this up, I'll be crossing the ships neg.
bus with Nmea common. This does not seem like a good idea to me. Do I need
to (or should I) be looking into some sort of optoisolator?

"Larry W4CSC" wrote in message
...
"William Andersen" wrote in
news:w3fve.406$HV1.345@fed1read07:

NMEA (+) to center of RCA connector; NMEA (-) to edge of RCA connector


Ah, yet another damned unbalanced connection to ground to insure any
transmitter keyed will trash all the data in the NMEA bus throughout the
boat....(sigh)

Maybe they should make the whole damned NMEA system COAX THAT'S SHIELDED!!

--
Larry

You know you've had a rough night when you wake up and you're outlined in
chalk.