Follow-up on Seatalk Lighting Comms

[Steve]

Bill,Thanks for the reply. My job involves electronics controls, so I have some experience troubleshooting comms problems. As for the cables, I used Raymarine cables and interface blocks except where I had to extend the run between the GPS/Autopilot at the pedestal to the displays over the hatchway. I used shielded cable for the extensions, and the shields connected throughout.There is a PC/Seatalk interface box between the GPS/Autopilot and other displays. I tried removing it from the system at one point, but it didn’t help. I don’t have the software for the PC yet, so I haven’t tried any comms from a computer through the Seatalk bus. Christmas is coming, and it is on my list. I don’t know if that could help isolating the problem or not.The entire system is under warranty, and I will be sending everything expect the long cables and antennas back soon. I will make a cable diagram as well as a write-up of the problem part of the package. My concern is that the individual components will be checked out and found to work fine and everything sent back. I will then have a system that works but doesn’t talk properly like now.My suspect is the Autopilot or GPS, but that doesn’t have much to back it up. It may just be because the GPS won’t talk on the system unless it goes through the Autopilot. I guess at this point I am looking for anything that I can try while the system is still installed on the boat that might make it easier isolating the problem when you get the hardware.One final question: Is there any way to check the comms between the GPS and the VHF DSC without actually sending out a distress call? I would hate to send out a “test” and cause a panic, and also would not like to find out I have a problem at the point or a real distress call.Thanks for the help, and the forum is great. It is nice to have a single point of contact rather than bouncing from person to person and explaining the history every time. If you have specific information concerning my problem, I can be E-mailed at sestyles@yahoo.com.Steve

 

[Bill Boudreau]

NMEA on the Display

As suggested, the way to troubleshoot this is going to be disconnecting instruments from your series until the problem cures itself. If the instruments are sent to our repair center with this intermittent backlighting described as the problem, then they will be run together for an extended period and tested for this.There is not a good way of testing a VHF's DSC capabilities. Most of the displays will have some way of assuring you that you have position information available to the radio. Our Ray53 will say NMEA on the display when it has valid NMEA position information. You could bench the DSC function by loading the radio and testing reception by another DSC radio in the same room. This is how these communications are practiced during a GMDSS communication class. The radios around the room are programmed with different MMSI numbers and the participants can make phony DSC emergency calls. I DO NOT suggest you try this to test your radio. I would take your NMEA or Position indicator as a sign it is functioning properly. Raymarine or your radio’s manufacturer should be able to test this for you if you believe there is a problem.