VHF to GPS to DSC
- Thread starter jibes138
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When in doubt, read the instructions. The GPS manual will tell which two pins (or terminals on larger units) are the signal out and the radio will tell you which two pins or pair of the bare wires coming out of one of the cables are the signal in. Just connect them up properly and you'll be in business.How do you connect the GPS to the VHF for the DSC to show current position? Why don't they just build the GPS right into the radio?
If you have a handheld Garmin GPS, you can buy a kit to make a plug and cable from these folks:
http://www.pfranc.com/
or you can pay an outrageous amount to buy a cable with the same plug and cut the other end of the cable to find the proper wires. Use a straightened paper clip with a multimeter to find which cable goes to which pin.
Why no GPS on VHF
Well in fact there are units available. However most of us already have a GPS installed on the boat so why buy a new one and have to re wire it to the system.
Also you would have to have the VHF on to get the GPS to function. I'm thinking anchor watch and such where you don't need the radio on.
The general idea on wires is:
data in (out) to the unit (from the rest of the world)
data out (in) of the unit (to the rest of the world)
OR
data in
ground
OR
data A in
data A out
data b in
data b out
So you have 3 wire, 2 wire or 4 wire possibilities. And of course the GPS is 3 wire and the VHF will be 4 so you HAVE to make a splice.
One units data out is the other units data in. You have to keep those straight. The data out wires are really circuit grounds so a 4 wire is really a 3 wire and both are really 2 wire circuits. Circuit grounds ARE NOT chassis grounds or 12V grounds but that is what they call them in some books. Don't sweat what it is called just don't use something other than a connection wire from (to) the unit to ground it. ie don't tie the grounds to a convenient metal surface or the ground buss of the panel. It will most likely work but you get lots of noise. Also the metal sheath around the cable is also a ground which may or may not be the one you want.
As Roger L said, gota read the instructions.
Well in fact there are units available. However most of us already have a GPS installed on the boat so why buy a new one and have to re wire it to the system.
Also you would have to have the VHF on to get the GPS to function. I'm thinking anchor watch and such where you don't need the radio on.
The general idea on wires is:
data in (out) to the unit (from the rest of the world)
data out (in) of the unit (to the rest of the world)
OR
data in
ground
OR
data A in
data A out
data b in
data b out
So you have 3 wire, 2 wire or 4 wire possibilities. And of course the GPS is 3 wire and the VHF will be 4 so you HAVE to make a splice.
One units data out is the other units data in. You have to keep those straight. The data out wires are really circuit grounds so a 4 wire is really a 3 wire and both are really 2 wire circuits. Circuit grounds ARE NOT chassis grounds or 12V grounds but that is what they call them in some books. Don't sweat what it is called just don't use something other than a connection wire from (to) the unit to ground it. ie don't tie the grounds to a convenient metal surface or the ground buss of the panel. It will most likely work but you get lots of noise. Also the metal sheath around the cable is also a ground which may or may not be the one you want.
As Roger L said, gota read the instructions.
Also, most people wouldn't pay for a VHF radio with an integrated GPS since they'd probably want a different feature set than the integrated GPS would offer—since most integrated GPS units would not be chartplotters.
A better DSC radio will have both NMEA in and NMEA out connections, a lower quality one will only have the NMEA in connection. The NMEA in connection is for the GPS to provide Lat/Lon position information to the VHF, which is then transmitted if you use the DSC functions of the VHF. The NMEA out connection allows the radio to plot the position of boats contacting you via DSC on your chartplotter. Not all chartplotters support DSC position input information, but most newer ones do.
How you connect these will depend on what GPS unit you have.
On a Garmin, you have to connect the VHF radio's NMEA In - cable to the Garmin's 12 VDC ground, since the Garmin uses the 12 VDC ground as their NMEA signal ground. You would connect the Garmin's NMEA Out + wire to the VHF Radio's NMEA in +.
If your radio is capable of doing NMEA out, and your chartplotter supports DSC position input, then you'd have to connect the VHF radio's NMEA Out - cable to the Garmin's 12 VDC ground, and connect Garmin's NMEA In + wire to the VHF Radio's NMEA Out +.
A better DSC radio will have both NMEA in and NMEA out connections, a lower quality one will only have the NMEA in connection. The NMEA in connection is for the GPS to provide Lat/Lon position information to the VHF, which is then transmitted if you use the DSC functions of the VHF. The NMEA out connection allows the radio to plot the position of boats contacting you via DSC on your chartplotter. Not all chartplotters support DSC position input information, but most newer ones do.
How you connect these will depend on what GPS unit you have.
On a Garmin, you have to connect the VHF radio's NMEA In - cable to the Garmin's 12 VDC ground, since the Garmin uses the 12 VDC ground as their NMEA signal ground. You would connect the Garmin's NMEA Out + wire to the VHF Radio's NMEA in +.
If your radio is capable of doing NMEA out, and your chartplotter supports DSC position input, then you'd have to connect the VHF radio's NMEA Out - cable to the Garmin's 12 VDC ground, and connect Garmin's NMEA In + wire to the VHF Radio's NMEA Out +.
Great minds think alike
Could be...
I had this idea just this week: http://forums.catalina.sailboatowners.com/showthread.php?p=671305#post671305
You don't need a full featured GPS, just a "locator" and if it made it easier to hook up without wires, it'd be worth paying for it INSIDE the VHF. Think of it as a backup GPS for position only.
Not funny!How do you connect the GPS to the VHF for the DSC to show current position? Why don't they just build the GPS right into the radio?
Could be...I had this idea just this week: http://forums.catalina.sailboatowners.com/showthread.php?p=671305#post671305
You don't need a full featured GPS, just a "locator" and if it made it easier to hook up without wires, it'd be worth paying for it INSIDE the VHF. Think of it as a backup GPS for position only.
Thanks, dawg
BUT, I think what the basic idea was to do it without a chartplotter, which most folks already have whether it be a handheld like our Garmin GPSMap 76 Cx or a fancier chartplotter. That was the point of NOT buying yet another chartplotter. And I don't want a chartplotter down below where my base VHF resides. And my handheld GPS is upstairs. My base VHF is downstairs and I can'ty wire 'em together without buying another $300 GPS. That's nuts.
It'd be great to just get a basic radio that has a GPS chip in it without a chartplotter to avoid having to wire a GPS to a VHF. Like the handheld Standard mentioned above.
If built in (not handheld) VHFs are less than $100, then paying $100 with one to be able to use DSC with a built in GPS would make marketing sense.
BUT, I think what the basic idea was to do it without a chartplotter, which most folks already have whether it be a handheld like our Garmin GPSMap 76 Cx or a fancier chartplotter. That was the point of NOT buying yet another chartplotter. And I don't want a chartplotter down below where my base VHF resides. And my handheld GPS is upstairs. My base VHF is downstairs and I can'ty wire 'em together without buying another $300 GPS. That's nuts.
It'd be great to just get a basic radio that has a GPS chip in it without a chartplotter to avoid having to wire a GPS to a VHF. Like the handheld Standard mentioned above.
If built in (not handheld) VHFs are less than $100, then paying $100 with one to be able to use DSC with a built in GPS would make marketing sense.
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