Garmin 172 GPS to Uniden 625 VHF

[ImgMkr3]

I'm hoping someone would please assist me in getting the wiring color codes straight to hook a Garmin 172 to a Uniden 625. Below is the layout of both wiring harnesses.

VHF

Orange - NMEA 0183 out (-)
YELLOW - NMEA 0183 in (-)
GREEN - NMEA 0183 out (+)
WHITE - NMEA 0813 in (+)

RED - NOT USED

BROWN - EXTERNAL SPEAKER
BLUE - EXTERNAL SPEAKER



GPS

BLUE - NMEA OUT (COM1 TX)
BROWM - NMEA IN (COM1 RX)
WHITE - NMEA IN (COM2 RX)
GREEN - NMEA OUT (COM2 TX)

Please take pitty on a newbie and spell it out so a chimpanze could follow the instructions. Not to say that I'm challenged in these regards, but the wife took away my toolbox and won't let me work on the house anymore.

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Thank You in advance for your time and trouble.

Regards,

ImgMkr3

henry@summersmagic.com

 

[wooslehunter]

It appears that the GPS unit has 2 x NMEA ports. I'd guess you can use either but the manual shows Com2 being used. So:

Connect GPS GREEN - NMEA OUT (COM2 TX) to VHF WHITE - NMEA 0813 in (+)
Connect GPS Ground to VHF YELLOW - NMEA 0183 in (-)

The simplest way to connect the ground line is to simply ignore the GPS end and connect the VHF end to ground locally. This is not a good idea and it's best to run a separate cable together with the signal.

You may have to set up some of the menus on both the GPS & the radio. Standard baud rate for NMEA is 4800. GPS ports often have the have the format set to NMEA as well. Garmin have their own data format and ports are sometimes set to the Garmin format by default.

 

[ImgMkr3]

Thank you for the rapid reply I really appreciate it.

I have to admit I'm lost on what you suggest for the ground though. Both the GPS and the VHF are sharing the same wiring block ground connection so for all intent they can see each other, will that suffice?

Thanks again for helping the challenged!

ImgMkr3

 

[pappaecho]

Just a bit of recent experience.
I connected a Garmin 230/152 to a AIS radar system with Nmea out to AIS radar in, and it worked perfectly
I then connected the same feed to a Cobra DSC radar and it did not work.
I then connected the DSC radio NMea -ve ( eg Ground) and the whole system worked fine.
So connect the out to the in, and make sure that the -ve 12 volt is used as the return or ground

 

[wooslehunter]

The ground really depends on the routing for each. The problem is that NMEA is supposed to be a differential two wire system.

The radio input should be an opto-isolator. This is basically an LED plus a photo-transistor mounted together. When the LED lights up, the transistor conducts. Hence you get isolation. A NMEA transmitter is supposed to feed both lines to the LED. The whole idea is to create isolation and also noise immunity. The noise immunity comes from the fact that both signal lines run together so any noise pickeed up on one will also be picked up on the other and cancel out.

The GPS manufacturers have caused a problem in the system since they often only provide a single data feed and no return. Hence you have to use the earth on the GPS as a return.

That's the techno- bumph.

The best idea is therefore to connect two wires to the GPS: one to earth & one to data. Run both of thse together to the VHF.

If it works, then simply connect the GPA data out to the VHF data in + and connect the VHF data in - to ground. the data return path will go through the ground return of the VHF, to the point at which the earths of the GPS & VHF are connected.

For the sake of one wire though I'd recommend the first solution.

 

[terrymccann]

Hi Guys
Can anyone assist me to link up my Comair AIS -2-NMEA receiver to the Garmin gps 172c ?? I cant change the baud rate to 3800 baud on the garmin unit and wondered if there was a way to do this. i'm cruising in Brazil, where there is a 96% import duty, so I can't buy a decent unit or trade in my ICOM vhf for an AIS vhf radio. Maybe I can do this in Trinidad after hurricane season...which does not help me now.