"Steve Zweigart" wrote in message
...
To take this thread a step further, in my "junkbox" are two Delorme
Earthmate GPS receivers formerly used with laptop computers. For some
reason, the output from these units does not convey location information
to my radio. (I have not yet tried it with the autotiller.) My guess
is that there's a baud rate problem. I'm not aware of adjustable
settings on the units, which are said to be NMEA compliant, but it seems
that there MUST be a way to switch from RS-232 to RS-422 in order to
utilize the NMEA output feature.

This could indeed be caused by incompatibility between RS-232 and RS-422
levels, not to mention the fact that RS-232 is 'single ended' and RS-422 is
differential. If you want an explanation about connecting differential and
single ended devices, download a manual of my NMEA multiplexers. It contains
a page with drawings about how to connect devices with eachother. You can
find it on
http://www.shipmodul.com/datasheets/man_mpx-41_en.pdf
Look at page 3.

Meindert