Using GPS data from a SeaTalkng/NMEA 2000 GPS source to supply a DSC VHF Radio

[Chuck - Raymarine - Moderator]

Using GPS data from a SeaTalkng/NMEA 2000 GPS data source to supply a DSC VHF Radio

Following the introduction of the Raystar 130 GPS Sensor and Raymarine's a6x and a7x a-Series MFDs, it was recognized that many customers had DSC VHF radios, single side band radios, etc. requiring 4800 BAUD NMEA 0183 GPS data sentences to support operation of these devices. Some of these customers did not have a 4800 BAUD source of GPS data to meet this requirement. In response, Raymarine introduced a feature within the v1.21 SeaTalk to SeaTalkng Converter software update permitting a SeaTalk to SeaTalkng Converter to transmit a limited set of 4800 BAUD NMEA 0183 GPS sentences. Raymarine has subsequently introduced the E70196 VHF NMEA 0183 to STng Converter Kit (shown below).

The SeaTalk to SeaTalkng Converter will output / transmit (tx) the following 4800 BAUD NMEA0183 v4.10 sentences:

- GGA - If L/L is present on STng, then GGA will Tx only populating data fields that are available, i.e. time/date etc.
- RMC - If L/L is present then RMC will Tx only populating data fields that are available, i.e. time/date etc.
- VTG - If SOG and/or COG valid in 129026 then VTG will Tx only populating data fields that are available, i.e. variation etc.

Following the software update, the SeaTalk to SeaTalkng Converter will be operate "Sense Mode" for the first twenty seconds. If first generation SeaTalk communications packets are detected while in Sense Mode, then the SeaTalk to SeaTalk Converter will operate as a SeaTalk to SeaTalkng Converter. However, if no first generation SeaTalk communications packets are detected while in Sense Mode, then the SeaTalk to SeaTalk Converter instead operate as a one way partial SeaTalkng/NMEA 2000 data bridge, transmitting the above listed NMEA 0183 GPS sentences featuring the $GP Talker ID at 4800 BAUD. While most manufacturers of marine communications products place no restrictions on the NMEA 0183 Talker ID that prefixes the above listed NMEA 0183 sentences, some (ex. Icom) product products which ignore NMEA 0183 sentences featuring NMEA 0183 Talkers IDs other than $GP.

The diagram below illustrates how a SeaTalk to SeaTalkng Converter may be used to supply GPS data from an a67 MFD to a DSC VHF radio requiring such data from a 4800 BAUD NMEA 0183 source. GPS data from a Raystar 130 or other SeaTalkng/NMEA 2000 data source may similarly be provided to the a DSC VHF radio using the SeaTalk to SeaTalkng Converter.



Note: Per international agreement, DSC VHF radios are intended to be interfaced to a source of GPS data whenever in use. In accordance with this agreement, DSC VHF radios will sound a NO FIX alarm at regular intervals whenever the VHF radio is not receiving GPS data via its NMEA 0183 or SeaTalkng/NMEA 2000 communications interface(s). DSC VHF radios have feature permitting one to manually enter the vessel's position. This feature is exclusively intended for emergency use should the VHF radio's source of GPS data have failed.

Note: The solution specified above applies to Axiom MFDs (not to be confused with Axiom Pro and Axiom XL MFDs) and Element displays as well. As the NMEA 0183 communications interface of Axiom MFDs and Element displays features a DeviceNet plug rather and a SeaTalkng socket, an A06075 39.4in (1.0m) DeviceNet (F) to SeaTalkng Spur Adapter may be used to interface an Axiom MFD to a SeaTalkng spur socket.

Many customers desire to monitor DSC VHF radio communications while at anchor, dockside, etc., but do no want to incur the additional power consumption a MFD. Such customers would be advised to
- install a Raystar 150 GPS Sensor as the vessel's primary GPS sensor and
- power the SeaTalkng/NMEA 2000 backbone and DSC VHF radio from dedicated power circuits.
In this way, only the SeaTalkng/NMEA 2000 backbone and VHF radio circuits need be switched ON while monitoring the DSC VHF radio.

RAYFAQ#