DSC/GPS Arrangement

[Guest]

after completing the VHF/dsc course in April I intend to buy a fixed radio with DSC capability.

I understand that you connect your GPS (in our case a Garmin45 hand held ) into the Radio, however I assuming that not only does the GPS send long and lat to the radio, the radion provides power via the same cable (5pin) to the GPS, is this correct?

I have also read in this months PBO that Silva do a fixed radio/DSC which has it's own GPS so doesn't need to be connected to a GPS or am I misunderstanding and that it is only a repeater for the GPS?

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[tr7v8]

Partially correct GPS send LAT/Long to radio but doesn't get power from GPS.A seperate tap into the 5 pin gives 12V.
Yes built in GPS means you don't need an external GPS.




<hr width=100% size=1>Jim

Draco 2500

 

[tome]

But you still need to wire a GPS antenna

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[snowleopard]

NMEA compatibility

i found that my gps was pushing out a version of nmea that the dsc didn't recognise. in my case it was a garmin 128 talking to an icom dsc. i solved the problem by telling the gps to send out nmea 0183 v2.0 (default was v1.5). you might want to ask the manufacturers whar version of nmea they work on before spending your beer vouchers.

incidentally my raytheon instruments also take nmea data from the gps but they only understand v1.5 so i'm stuffed!

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[poggy]

Hi,

I am pretty sure that the Silva is a repeater only with no internal GPS. It has a GPS interface for NMEA.

Love to know if I am wrong as otherwise it is a cheap unit.

Poggy


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[Oldhand]

As stated in other replies, the GPS will still require its own power source. The NMEA communication is one way, from the GPS to the DSC transceiver and as well as Lat & Lon, the transciever will also use UTC time. Depending on the type of transceiver, it may require your GPS output to be NMEA version 2 as opposed to 1.5.

I believe the Silva DSC VHF does not have a built in GPS but can be used to display GPS navigation information and also Navtex data from a suitable source. You would be much better off installing a fixed station GPS with both the advantage of reliable accuracy performance from a well sited fixed antenna and the reliability of a fixed NMEA output to the DSC VHF. If you wish to persist with a handheld GPS, have both a well sited fixed external antenna and a permanently wired in cradle to use ship's power and provide NMEA data output.

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[johna]

Re: NMEA compatibility

<incidentally my raytheon instruments also take nmea data from the gps but they only understand v1.5 so i'm stuffed!>

This is the sort of thing you would not think of when buying a dsc thank you for making me aware of the limitation. I have a Garmin 120 fixed talking to Raytheon radar and chart plotter. What do icon and Raymarine have to say about lack of compatibility?

johna

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[snowleopard]

Re: NMEA compatibility

what do you expect? they blame each other of course!!

the raytheon gets some of the data but confuses true and magnetic courses which is fun with 17 deg of variation in the caribbean!

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[coco]

There is one issue you might want to consider. Some DSC VHF systems require a symetrical signal for them to work. Garmin supplies only an asymetrical signal with their portable systems and most fixed systems. A way out of this, is to use an NMEA buffer / signal converter between the GPS and the DSC set (which you might want to have anyway to drive a long line or several NMEA receivers).

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