Well, I guess I’d come down on the side of connecting the VHF to the other, existing, instruments
(MFD, GNSS, and AIS) in an NMEA 2000
network. Two benefits:
- · Position of incoming DSC calls would be plotted on the chartplotter (assuming the MFD supports it), facilitating navigation to the reported position, and
- · Able to conveniently initiate DSC calls to AIS targets (assuming the VHF supports it).
The first benefit requires connecting the VHF to the network (or at least to the MFD); the second benefit simply requires the VHF to have an internal AIS receiver (or to be connected to an AIS receiver or transceiver on the network).
But if your network already has a GPS receiver and an AIS device, an inexpensive VHF such as the SH GX2000 can provide these benefits without paying for a redundant internal GPS and AIS. And the NMEA 2000
network cabling and infrastructure is pretty robust and bulletproof, assuming a decent installation--which mitigates the reliability
concern. Certainly much more so than NMEA 0183
“…(could multiple GPS data sources create confusion in the VHF’s or the plotter’s mind…?)…”.
”…My mfd , vhf, AiS all have independent gps functionality even though all are networked together….”
Most modern networks have multiple GPS sources, typically with varying accuracy. Devices in your network should have some method of manually prioritizing these different sources so that the preferred, most accurate instrument data is used by other instruments
and displays that receive the data (typically of the same manufacturer). For example, in my B&G MFD is a “Settings-->
Position” dialog that is used to select the preferred GNSS data source where multiple sources exist.
“…would somebody create an app that will allow your MFD to use more data from your VHF someday using NMEA2000? For example, automatically plot DSC coordinates from a call or relay?...”
No app needed—provided your make & model of MFD supports receiving DSC call data from the VHF—either as NMEA 0183
DSC/DSE messages or as NMEA
2000 PGN 129808-DSC Call Info.
For example, my venerable SH GX2150 VHF sends a DSC/DSE message pair upon receipt of a DSC call (e.g. a DSC Position report) from another vessel. The VHF is connected to my B&G MFD and to a PC running OpenCPN
, and both devices plot the position of the calling vessel on their chart. The DSC call info also appears in the AIS target list on the MFD and in OCPN.
“….Originally I was looking for connecting VHF and plotter for potentially being able to call an AIS target directly from the plotter…”
This appears possible only by using a proprietary PGN supported by an MFD and VHF from the same vendor. AFAIK there is no standard, vendor-independent PGN that would provide multi-vendor interoperability, unfortunately.
That said, if the VHF has a built-in AIS receiver, or can connect to an external AIS like the SH GX2000, then you can quickly initiate a call to an AIS target using the radio’s interface with no need to enter the MMSI number of the target. Not as simple, perhaps, as poking a finger at your MFD’s touchscreen, but since you’ve got to have to get the VHF mike in your hand anyway to talk to your target, not that much more inconvenient.