I want to operate the TRX with a Raymarine C60 multi-function-display. For that I want to use the NMEA interface at which the GPS datas are supplied at the moment. (easyTRX in use with an chartplotter, which has only one NMEA input (most of the Raymarine devices).
This is why the devices are only different in the design, the graphical user-interface for programming the MMSI and the basic applications for displaying AIS. Different are mostly the flexible factors like the detail grade of the manual, the completeness of the connection cables, and necessary accessory and also the availability of useful accessory devices splitters with class B capability and combined VHF/GPS antennas. Also the service of the manufacturer which ours is the best one! All class B transceiver have in common, that they need an own GPS. This is necessary because the normally existing GPS antennas deliver NMEA GPS data. This NMEA data are generally not exactly enough in reference to their time-base. A typical class B AIS telegram takes 25ms. Within 1 ms the class B transceiver hast o deliver his „beam“. In order that sent telegrams are not overlapping, every sender has to keep an exact for sending. The date for sending has to be more accurate as the telegram. The date of sending is determined at ca. 100µs by the class B sender. This is only possible, when the sender gets the raw data from the GPS antenna and not NMEA data, which are only accurate to 1/10 s. This is the reason.
You cannot put both, the easyTRX with a data rate of 38400 Baud and the GPS NMEA data with 4800 Baud, to one interface of the C70. In your case of usage you will need a multiplexer, which increases the 4800 Baud of the NMEA GPS data to 38400 Baud.