"GeoffSchultz" wrote in message
ups.com...
AIS cable run from the patch panel to the C80 which is at the wheel;

Ah, I don't know how your wiring is setup, but the C80 had an gavanically
isolated NMEA input. To maximize surpression of interference, make sure you
have one single cable with a twisted pair between the RS-232 plug of the AIS
receiver and the NMEA input of the C80. Do not combine the signal return
with the power ground of the AIS receiver or any other device. This ensures
the currents in both wires are equal and thus maximum surpression of
radiation is achieved. Eventually you could use screened cable, use a
twisted pair for the data and return and connect the screen to ground at the
C80 side only. The C80 is an IEC945 approved device so it is safe to assume
that it's signal ground is clean.

Meindert