Help!! VHF needs GPS.

[PuffTheMagicDragon]

My new DSC VHF (Cobra MR F75 EU) came with a twin cable that is meant to interface with my GPS. One wire is red and the other is black. The instructions say that I should:
"2. Bond the NMEA out negative wire to the black wire of the GPS interface cable.
3. Bond the NMEA out positive wire to the red wire of the GPS interface cable."
Now the data/power cable of my GPS (Garmin GPSMAP 176) has 4 wires:
A RED one and a BLACK one that go straight to the battery via a switch, and
A BROWN called 'Data Out' and a BLUE called 'Data In'.
Question:- How do I connect them? Which wire goes where?
I thought that I could understand plain english but this has me really stumped. It being about electronics does not help me as my background was mechanical / production engineering. Things one could see, touch and figure out.
I know that there are some people who are extremely knowledgeable in the field of electronics in this forum and I look forward to getting some sound advice as I'd love to start playing with my new toy....
Thanks in anticipation for any help - especially if it works!
Fair Winds!


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[chriscallender]

My vote is

Black (DSC) to Black (Garmin)
Red (DSC) to Brown (Garmin)


Quite often the GPS also has some menu option to enable the NMEA so its worth checking the manual, because its quite possible to have it wired correctly but if the menu on the Garmin isn't set to spit out any NMEA or its in the wrong format, then the DSC won't get anything from the GPS.

hope that helps.

Chris

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[oldharry]

Negative NMEA out is the same as the negative battery feed in Garmins. Connect the brown NMEA 'Data out' from the GPS to the 'NMEA out positive' wire of your VHF

The Garmin red and black are the power supply, Brown is the NMEA output from the GPS unit; Blue provides NMEA data back in to the GPS so is not needed fro the VHF

The DSC set allows for a GPS where the Data negative is not connected to the negative 12v supply. The NMEA input to the DSC is labelled as 'output' because it needs to be connected to the 'output' line of the GPS.


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[Talbot]

would make more sense to me for the nmea out on one machine to be linked to nmea in on the other. Connect them up and see if they work, provided you are only linking nmea lines it wont matter. If it works - great, if not reverse the connection.

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[PuffTheMagicDragon]

Perhaps I wasn\'t clear..

The wires on the VHF set are not labelled as 'NMEA out' or anything NMEA. They are simply referred to as "the red wire of the GPS interface cable" and "the black wire of the GPS interface cable". These two wires (forming the 'GPS interface cable') are coming out of the VHF and have bare ends that need to be connected to the GPS.
It is the Garmin wires that are labelled as Brown Data Out, and White Data In (and not blue as I wrote in my original). To me this means 'data coming out of Garmin' and 'data going into Garmin'.
It is also making me feel thicker by the minute! I'm sorry if I am sounding stupid. (It's probably because I am, but don't tell anyone!)
My sincere thanks for all your efforts.
Fair Winds!

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[Prospero]

Re: Perhaps I wasn\'t clear..

Chriscalender is quite correct, I've recently carried out the same excercise with a Garmine 128. Connect the NMEA out from the Garmin ( Brown) to the NMEA DSC red and theGarmin negative ( black) to the DSC negative. As Chris callender says Garmin uses the battery negative. The next complication is persuading the two to talk to each other you need to enable theGarmin to talk to theDSC and then to make sure you are using the correct version of NMEA 0183. I solved it by setting the Garminto use the latest version it could support and the two then communicated. I still have to be certain that this is not causing a problem with my wind instrument which will no longer showtrue wind speeds. That however is for another day. Good luck it reallydoes work.

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[PuffTheMagicDragon]

Re: VHF needs GPS - The Finale!.

IT WORKS ! ! !
It was a classic case of acute RTFM. All I had to do was to instruct the Garmin to send out instructions as was indicated on pages 58-62 of the manual!
Unfortunately, the latest version of the software that I had downloaded for the GPSmap 176, version 4.01 October 2004, has removed a tag from the main menu called COMM (for COMMunication) and the functions are now combined in another heading. I had not noticed the implication.
The sequence from the main menu is now : SETUP > INTERFACE > SERIAL DATA FORMAT > NMEA IN / NMEA OUT.
Having done that I immediately got the correct date, time and position on the VHF display. The only niggle is that the VHF drops the leading 0 in the Longitude; thus it shows '14E' instead of the more correct '014E'.
For the benefit of whoever might be interested, the RED wire from the Cobra goes to the Garmin BROWN (Data out) wire. The other wire from the Cobra, i.e. the BLACK one, can go either to the negative bus of the boat or to the Garmin WHITE (Data in). Both of them work.
The conclusion is - two super pieces of equipment and a very pleased sailor.
Thank you to Prospero, Talbot, Oldharry and Chriscallender who offered suggestions and explanations, as well as to those who tried but couldn't.
Special thanks must, however, go to Sigurd who dared to ask the obvious question! I always had a soft spot for Norway!
Fair Winds!

35° 53.732' N 014° 29.51 E


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