"Meindert Sprang" wrote in
:

No.

NMEA is laid out to prevent ground loops in the datalines. This is
achieved by having every input isolated. The outputs need not to be
isolated. And if everyone adhered to that spec, there would not be any
problem. In your case, youll be fine since that situation is almost
exactly to the NMEA spec.

Meindert

But, alas, he's hooking one side of his NMEA dataline to GROUND! It's not
isolated at all at that point. The whole databus is now negative ground,
not balanced pair. Any intersecting signal...HF from the SSB...AC hum from
the inverter or genset...VHF or any other transmitter signal...has a ground
reference, or several references if more than one listener or talker has
unbalanced output like Garmin. Instead of intersecting signals being
balanced out, phoneline style, now we have a great UNSHIELDED antenna to
ground.

Foil shielded cables help, but every time you come to an NMEA instrument
the damned fools have cheap open wires you're forced to connect your
shielded cabling to...making a big point of intrusion, anyway.



--
Larry

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