Disappearing AIS targets

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Robert,

Onboard your vessel, is it normal for the AIS250 to be interfaced to both your PC and to the MFD's NMEA 0183 input port? If so, and it has been interfaced as specified within your thread, then please note that paralleling the 38400 BAUD output of the AIS250 may indeed be responsible for the NMEA 0183 signal supplied to the MFD dropping below that which the MFD can support. With regard to the AIS250 and AIS500 products, Raymarine has historically recommended that the 38400 BAUD NMEA 0183 output from these products not be paralleled. In the case of the AIS500, it was further stated that simultaneous use of the product's 38400 BAUD NMEA 0183 output leads and its DB-9 Serial Plug were prohibited. Accordingly, it is recommended that the AIS250 be disconnected from the "MiniPlex Lite" and that the AIS250's 38400 BAUD output port only be interfaced to the MFD's NMEA 0183 input port alone.

Alternatively should AIS data from the equipment specified additionally need to be interface to a PC, then it would typically be recommended that the AIS250 instead be interfaced to a powered and properly terminated SeaTalkng / NMEA 2000 backbone to which the a/c/e/eS/gS-Series MFD had also been interfaced. A NMEA 0183 to NMEA 2000 data bridging device supporting AIS sentences (ex. Actisense NGW-1-ISO-AIS) would be used for such purposes. Any other NMEA 0183 devices would similarly be interfaced to the SeaTalkng / NMEA 2000 backbone. The PC would then be interfaced to the system via a NMEA 2000 to USB gateway (ex. Actisense NGT-1, etc.)