DSC VHF Question

[Robin]

We have just installed a NASA DSC VHF and so far have not got the LAT/Long from the GPS to the VHF. I may have connected the NMEA the wrong way but before I take to the wiring diagrams again have a question:-

Since I have only just installed the set I haven't yet aplied for the MMSI number to program into it. Will it actually work as a DSC set until this is entered? I am wondering if this is why the GPS position is not being displayed on the VHF. Probably my wiring but it just occured to me as I drove home that it might be a clever built in feature to DSC programs to prevent the set transmitting an unidentified DSC message, ie no MMSI no DSC???

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[Strathglass]

Robin
Can only speak for the combination which I have.

A Garmin 128, an XM DSC and a NASA GPS repeater.

Prior to installing them in my yacht I connected them together on the dining room table, with the GPS aerial out the window. I did not even have to refer to any of the instruction manuels.

I do not yet have a MMSI number so I could not install one.

All three worked and displayed correctly,with the Lat and Long coordinates showing up both on the DSC and repeater displays.

I suspect that the NASA DSC VHF will work just the same. Someone else may be able to confirm this.

Iain


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[discovery2]

I think you may be correct in assuming No MMSI no DSC!

I have a Simrad RD68 set and the manual states that the 9 digit MMSI number must be permanently entered into the set otherwise the DSC functions cannot be accessed. Whether that also applies to the Lat/Long coordinates, I don't know.

David

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[Joe_Cole]

Does your GPS need to be set up to send the NMEA data?

I spent ages trying to get my Yeoman plotter working, before I worked out that the GPS needed to be set up correctly!

Joe

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[Robin]

Thanks, so unless it is a NASA specific thing I must have cocked up the wiring!

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[Robin]

Thanks, though Ian got his working without the MMSI so it looks like it is me.

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[Robin]

Actually that was my first thought too but I have turned 'on' all the NMEA sentences on the GPS and also tried changing between 2 places and 3 places of decimals. The same set (Shipmate 5800) is connected to our Yeoman and that is working OK. Must be me!

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[Birdseye]

more likely to be the settings either on the gps or on the receiver. the gps (going on my garmin sets) has to be instructed to output the lat / long in nmea form, which is likely what the radio wants. as for the radio, it might also need some setting input though this is less likely. refer to the manual.
the wiring in my case was no more than a simple twinflex carrying a basic 5v (if i remember correctly) signal.

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[Robin]

I did check the GPS (Shipmate 5800) settings and all seems OK especially as it is running our Yeoman plotter OK ( the Yeoman is displaying LAT/Long correctly). I also looked at the NASA menu setup and the Lat/Long function was 'on' as it should be. Ours too is just a 2 lead NMEA connection, I must have connected either to NMEA 'in' to the GPS instead of 'out' or maybe the ground lead wasn't correct. I ran out of time to do any real checks so I brought all the manuals home to study. Yet another 10 minute job that takes several hours!

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[Gunfleet]

Robin I had ths problem on a navico/simrad 1400 which I fitted the dsc controller add on to. I had a brown nmea and a black something or other. It's nothing to do with powering the device, the controller gets its power from the main set. But I eventually discoverd that the brown nmea out from the gps would connect fine to the dsc brown and work as long as the dsc black went battery earth, presuming a neg earth system. Then it worked just fine.


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[Robin]

Thanks for that, according to the manual one of the connection options on the DSC NMEA 'ground' lead is to connect to the battery -ve, so that might work in this case too so definitely something to try.

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[[3889]]

Not sure if this is what John is saying but you must have the dsc and gps either powered off the same battery or else connect the two batteries negative terminals to allow the return signal to the dsc.You do not need an mmsi to get gps output from the dsc.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by HiAndDri on 08/12/2003 07:45 (server time).</FONT></P>

 

[Robin]

Thanks, that is a good point as we do have 3 separate battery banks, though in this case both the Shipmate GPS and the VHF are on the same one. The negatives from all 3 banks are all connected. I studied again the manuals last night and I'm pretty sure I did connect the NASA to the correct NMEA out from the GPS. The NASA NMEA ground was connected to the GPS NMEA output 'return' -ve as per instructions but I didn't try connecting it to the battery negative (which was an option according to the NASA instructions). Fingers crossed this will be the solution, but I'll call NASA today too in case they know the combination I have.

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[Plum]

Just to confirm what others have said, the NASA DSC will (should!) display the Lat/Long without the MMSI being entered.

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[Robin]

Ta for that, just hoped it was something simple for once!

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