Originally Posted by night0wl
Thats what I needed to hear. Also, since the AIS is connected to the radio, do I need to have a separate set of wires to the VHF for emergency/distress DSC button?
Last question, I purchased a length of 28gauge wire (6 in the bundle)...so is it possible to plug in 2 wires each to the NMEA out of the seatalk/nmea junction box...2 for the AIS, 2 for the VHF for emergency distress/DSC? Meaning can I plug multiple "listeners" to the NMEA out of the seatalk/nmea box.
Lets make sure we are on the same page. I made the assumption that your radio and AIS both talk NMEA 0183 as most of the equipment around today does. If that is true:
1. The NMEA 0183 specification states that any NMEA "talker" can power up to four (4) "listeners." So you could take a "talker" wire off your junction box (which I presume has the GPS data as pretty much they all do.) You would be wiring the "listeners" in parallel - the NMEA + out from the talker goes to the NEMA + in on both listeners - same for the NMEA - out it goes to the NMEA - in on both devices. BTW if you have not yet purchased the junction box you can most likely get the same data from either your chart plotter or your autopilot computer (presuming you have one.)
2. Many older NMEA devices can daisy chain. That is you can feed NMEA into the device and it will repeat the NMEA sentences on the NMEA out of the device. Coupled with the 1 to 4 ratio this gives you lots of NMEA connections. Consider your chart plotter can power at least four devices, each device can power four devices, each of those can power four devices and so on. The limitation is that some manufacturers Insert WHY I HATE RAYMARINE HERE
violate the specification and don't repeat the input sentences (the technical name of a NMEA message) on the output side. There are several possible reasons for this. My explanation is that (unnamed marine electronics manufacturer that I hate) does this so that they can rip you off for more unnecessary "conversion" boxes.
3. Note that there is no real relationship between the AIS and the Radio. You are just trying to get the GPS sentences to both of them.
I don't understand why the AIS is connected to the radio unless you are feeding data through the AIS receiver into the radio. Can you please clarify?
4. In a pure NMEA 2000 world plugging the Radio and AIS into the NMEA 2000 bus would make this all happen auto-magically.