DSC Radios

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Dougie_the_Mate

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I recently bought a Silva DSC radio which came with a Navtex arial. When I went to fit it I found that our GPS system has no easy connector to effect the DSC facility without disabling the auto-pilot which is already wired into the GPS. I was told that I could use a handheld GPS which would operate the DSC distress facility if required.

Is this correct and is there a decent one which is not too expensive and which can be wired into the boats electrics to save on having to replace the batteries all the time?

Sorry if this sounds like a stupid question but I am not very technically literate.
 
Provided the cable for the handheld GPS is compatible with the socket for the DSC then the DSC will be aware of the GPS data usually. However, won't you have the same problem as now, i.e. connection problems ?

I would think it would make better sense to have a splitter to route the data signal from the fixed GPS to serve the DSC as well as the Autohelm- this shouldn't be difficult to arrange even if you feel you can't do it yourself.

This way your DSC positioning won't be dependent on the GPS onboard battery which you wouldn't want to flat at the crucial time
 
I have the data output lead from my Garmin 152 soldered to three wires, one going to the autopilot, one to the DSC and the third to an output plug which will take my hand held GPS. When set to NMEA it communicates with the Autopilot and DSC. To exchange data bwtween the GPSs, I set it to Garmin/Garmin. Garmin advised me that I could make upto three connections in that fashion. Although I am no techie, I assume that with moe than three, the signal gets too weak.
 
You should be able to split the signal from your current GPS to provide the NMEA signal for the Silva radio. It's just a question of identifying the wires. The Silva hanbook should help you ID the colour connections on the Silva, (probably just bare wires)
 
It is possible to buy a device which will allow one GPS to feed up to five devices. They cost about £200 but it could work out cheaper than buying a GPS for every device. Try Atkinson Marine in Lymington. ( I read about it in PBO and they were quoted)
 
Your GPS NMEA output is very unlikely to be upset about driving two devices. You should be able to just connect the DSC radio's NMEA input in parallel with the autopilot NMEA input. There's only two wires on the interface that you need to worry about. They'll be called something like NMEA 'live' and 'common', or + and - . If you accidently get the two connections round the wrong way it shouldn't do any harm except that the radio won't 'see' the NMEA signal (and the a/p may stop tracking the GPS as well) so just swap them over and you should be OK. I have my GPS driving three devices (DSC, A/P and PC) at times with no problems. The type of cable you use for the connection is unlikely to be critical either, unless it's very long or passes close to a source of interference. Twisted pair cable or telephone cable or even light mains flex would probably work OK.
 
I ended up buying one of those GPS "mice" off Ebay for about £40 and running it on 4 AA batteries. They're the ones that are just the GPS receiver and are designed to plug into palm tops running Sat-Nav software in cars. I think mine's a "Holux" but I'd have to go back to the boat to be sure!
 
Our Garmin 152 quite happily drives the DSC VHF, GPS Repeater & Laptop navigation by itself.

I would've thought there was a join in the cable between GPS & Autopilot somewhere - just T off there to the VHF - test it before finishing the installation though.

Tell us what GPS & AP you have and we might be able to help with the connections!
 
Ours feeds the Radio and Yeoman. I used a couple of small junction boxes from Index Marine and telephone cable to join them so that the GPS is in the cockpit and the Yeoman at the nav station
 
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