VHF GPS DSC Success

[rpwillia]

I posted this when I was trying to get it to work on the 310 forum, but I finally got it all working. :dance::dance::dance: First let me thank the tech support at Standard Horizon (Devin Massens) who after a couple of emails and phone calls helped me figure out the problem. I now have my Garmin GPSMap 176 and my Humminbird 785C2 sending GPS data to my Standard Horizon VHF radio. I am still not sure if my Raymarine S1 Autopilot sees the GPS, but I think it does (need some more boat time to test).

First off none of these guys have very good documentation, and when it was not working there was no indication why. I believe the end result was that when I added the extra ground connection on the signal connector out of the radio direct to the ships ground panel it all started working. This was one of several things Devin and I talked about (did I have a good ground).

In the end it was very simple to do and once it worked it was very obvious. I added a picture of the VHF front panel although it is a pretty crappy picture, but I think you get the picture. As noted in the picture, if you do not have GPS data the areas on the left of the display are dashes where the time and latitude and longitude data should be. It was all pretty frustrating up to that point as I could see the NMEA sentences with a meter from the Garmin and Humminbird outputs, but the radio was acting like nothing was there.

This enables the DSC feature in the radio with the red panic button so if I ever need help it sends a digital DSC message to the Coast Guard with my coordinates as well as my MMSID. Hope this helps. Ray

 

[LooseDiamond]

Thanks. I need to set up mine also, just procrastinating. Not sure how to do this with my handheld GPS, in terms of plugging in, where to put wires, etc. Thought of a connection under the cockpit seat that I could bring out and plug in while under way. Any suggestions? Garmin GPS 76C and ICOM M302...

 

[Witzend]

So Ray, basically it came down to connecting a separate ground for the NEMA connection of the VHF. The normal power ground did not supply the proper communication ground.

 

[rpwillia]

Ground

So Ray, basically it came down to connecting a separate ground for the NEMA connection of the VHF. The normal power ground did not supply the proper communication ground.

Correct. Not sure why as the ground should be the ground, but adding the extra one below helped. I wonder if there was some sort of impedance or noise the wire was picking up.

For "Loose Diamond" If you have the round 4 connector on your Garmin you are probably already using the red and black power connectors. All you will need to do is connect the brown wire (GPS out or +) to the GPS in connector on your ICOM (you will need to check your manual on that). With Garmin you also need to make sure it is putting out NMEA 0183 at 4800 baud - you can find that in your menu. Garmin has their own proprietary format that they default to (at least on my unit).

 

[sailingdog]

Actually, it is a fairly well known issue with the Garmin brand of GPS units that they use the 12 VDC ground as the signal ground for their NMEA 0183 connections. Another issue is that Garmin's have a default setting of their own proprietary protocol for the serial ports, and for other equipment to work with them, the ports have to be changed to the NMEA 0183 protocol, instead of the default Garmin proprietary protocol, and set for 4800 baud, 8 bits, No parity, and 1 Stop bit.

BTW, you really shouldn't have two NMEA talkers (the two GPS units) sending to a single listener (the radio). The NMEA specifications don't allow this, and there is a possibility that the two talkers would hash each others information, since there is no flow control under the NMEA 0183 protocol AFAICT.

What would make more sense is to have only one of them talking to the VHF and the two GPS connections on a single-pole double-throw switch. This would allow you to choose which GPS is talking to the VHF. The VHF, if it is a better one, should have an NMEA 0183 output to the Hummingbird, to show the DSC call position information on it. I don't believe the Garmin 176 will show DSC position info on it.

If you have further questions, please ask.

I posted this when I was trying to get it to work on the 310 forum, but I finally got it all working. :dance::dance::dance: First let me thank the tech support at Standard Horizon (Devin Massens) who after a couple of emails and phone calls helped me figure out the problem. I now have my Garmin GPSMap 176 and my Humminbird 785C2 sending GPS data to my Standard Horizon VHF radio. I am still not sure if my Raymarine S1 Autopilot sees the GPS, but I think it does (need some more boat time to test).

First off none of these guys have very good documentation, and when it was not working there was no indication why. I believe the end result was that when I added the extra ground connection on the signal connector out of the radio direct to the ships ground panel it all started working. This was one of several things Devin and I talked about (did I have a good ground).

In the end it was very simple to do and once it worked it was very obvious. I added a picture of the VHF front panel although it is a pretty crappy picture, but I think you get the picture. As noted in the picture, if you do not have GPS data the areas on the left of the display are dashes where the time and latitude and longitude data should be. It was all pretty frustrating up to that point as I could see the NMEA sentences with a meter from the Garmin and Humminbird outputs, but the radio was acting like nothing was there.

This enables the DSC feature in the radio with the red panic button so if I ever need help it sends a digital DSC message to the Coast Guard with my coordinates as well as my MMSID. Hope this helps. Ray

 

[sailingdog]

This is relatively easy to do, once you understand the peculiarities of the Garmin setup.

Connect the Icom's NMEA 0183 IN+ to the Garmin's NMEA 0183 OUT+ wire and then connect the Icom's NMEA 0183 IN- wire to the Garmin's 12 VDC ground wire.

If the VHF has DSC position NMEA 0183 output, you could connect it to the NMEA 0183 input on the GPS, but the Garmin 76C doesn't support DSC position information—so there's no need to do so.

As pointed out, you really have to make sure the serial port on the Garmin is set for NMEA 0183 protocol, instead of the default Garmin proprietary protocol, and set for 4800 baud, 8 bits, No parity, and 1 Stop bit.

Thanks. I need to set up mine also, just procrastinating. Not sure how to do this with my handheld GPS, in terms of plugging in, where to put wires, etc. Thought of a connection under the cockpit seat that I could bring out and plug in while under way. Any suggestions? Garmin GPS 76C and ICOM M302...

 

[LooseDiamond]

Thanks y'all...

 

[Scott B]

Is the NMEA 0183 a wire with specific connectors or a standard of comunnication between components. Do I need a special wire or ? I have an Icom VHF and Raymarine instruments. The Icom has a single NMEA 0183 IN.

 

[Ken Palmer]

And why did you have two GPS receivers connected at the same time?

 

[sailingdog]

No, the NMEA wiring isn't special in any way. It is just a serial signal—either RS-232 or Rs-422. YOu can have a single GPS feed up to four listener devices without much issue—so you can have your Icom VHF and the Raymarine instruments (if you have an NMEA 0183-to-SeaTalk bridge) listening to the one GPS unit.

Is the NMEA 0183 a wire with specific connectors or a standard of comunnication between components. Do I need a special wire or ? I have an Icom VHF and Raymarine instruments. The Icom has a single NMEA 0183 IN.

 

[rpwillia]

... BTW, you really shouldn't have two NMEA talkers (the two GPS units) sending to a single listener (the radio). The NMEA specifications don't allow this, and there is a possibility that the two talkers would hash each others information, since there is no flow control under the NMEA 0183 protocol AFAICT. ...

The Garmin is a backup now that sits stored below in case I need it. I went with the Humminbird as it is color and has 3x the display size so I don't need reading glasses to read the Garmin with it's 2.2" black and white display.