On Sat, 20 Sep 2003 14:40:37 -0500, "Keith"
wrote:


Well, I finally took out the expander and hooked up a terminal strip with
the NMEA data coming in and hooked up to all four items NMEA IN wires, and
their four (-) wired jumped together, but not hooked to ship's ground at the
terminal strip, and it works fine, drives all four items, and no noise any
longer.

Things that make you go HMmmmmmmmmmmm...

NMEA will not tolerate, and is too stupid to handle, more than ONE
talker on a circuit. That's the whole reason you needed a
multiplexer. If there are 4 talkers, all talking at once because they
are all too stupid to LISTEN to the circuit before sending data (like
SeaTalk does for instance) the output data stream is a useless
addition voltage with no data on it. That's the multiplexer's job.
Hooking two NMEA outputs together can also damage the NMEA talker
circuits because one device is pulling the line low when the other
device is pulling it high, resulting in a BIG current through both
devices....not good!



Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?