VHF DSC Connection to GPS

[Phil Layer]

I am trying to wire my GPS to my VHF DSC capable radio. The diagrams suggest the NMEA In on the radio is connected to the NMEA out on the GPS. Then, the NMEA Out on the radio is connected to the NMEA in on the GPS.

The VHF actually has two sets of NMEA connectors. One set says NMEA In (+) and NMEA Out (+) while the second set says NMEA In (-) and NMEA Out (-).

I've tried both sets to the GPS but the radio says the GPS is not connected when I run the self test feature.

I found a discussion board on Google in which a fella says to connect the NMEA In (+) to the GPS NMEA Out and connect the NMEA out (-) to the GPS Ground Wire.

Could that be correct?

Yes, I am an idiot but I swear, I won't ask any more dumb questions if someone can answer this one.

[tracker]

I think your negitive wires all go together. And as you said the others go the way you said. I must say though the specs on all these radios and plotters is vague.

[KeyWest]

If you can give me the brand/model of the GPS and the radio I can get the exact wiring diagram you need. But in general:

To send your position TO the radio FROM the GPS:

NEMA OUT (+) on the GPS connects to the radio NEMA IN (+)
NEMA Out (-) on the GPS goes to ground
NEMA IN (-) on the Radio goes to ground

A lot of equipment assumes (-) is ground so you don't have to ground it. But, in your case, since it is showing a (-), ground it.

To send information from your radio back to the GPS:

NEMA Out(+) from the radio to NEMA IN (+) on the GPS
Same thing about the (-) wires - ground em.

Many GPS's require you to turn on the NEMA signal out. So, if I have the model I can look up the manual online and tell you which page and what the setting needs to be.

Hope that helps.

[Phil Layer]

Keywest,

The GPS is a Garmin GPS V and the radio is a Uniden UM525.

I figured out how to turn the NMEA mode on the GPS.

I'll try the (-)'s to the ground and report back.

Thanks for the help!

[Phil Layer]

Well, that settles it. Keywest is my new best friend.

Grounding the two wires from the radio labeled NMEA In (-) and NMEA Out (-) did the trick.

As Tracker mentioned, the diagram did not show this.

Thanks much! I owe you one.

[Moldy45]

Dean is the man no doubt, I have that same radio and a garmin 178c. Dean made me hook those little wires up right!.
The instructions didnt do didly for me or should i say lack of instructions

[PaulS]

My GPS Garmin 188C only has 2 input/outputs for NMEA. Do you know if I can connect multiple devices to a single NMEA out? I have a TR1, VHF, and FlowScan that all want info from the GPS. I'm hoping I can just use my first NMEA in/out for the TR1 autopilot and then use the second NMEA out to feed both the VHF and the FlowScan. The VHF will also feed the second NMEA input on my GPS but the FlowScan doesn't have an output so there's no conflict there.

GPS NMEA IN 1 - TR1
GPS NMEA OUT 1 - TR1
GPS NMEA IN 2 - VHF
GPS NMEA OUT 2 - VHF + FlowScan

From what I've read on the NMEA protocol it's a simple send with no handshaking so I would think that you can just splice the output wires to multiple devices and they'll never know the difference. One you spice it too many times you'll start running into resistance issues but how about just 2 or 3?

-Paul

[tracker]

I think you are right and can hook it up just the way you have stated. I believe that is very simalar to mine.

[KeyWest]

Yep, not a problem. Specs are that up to three listeners per NEMA line are possible. But I've done up to 4. So, if your GPS is talking (output), you can connect up to 3 listening devices (inputs) per line.