Garmin GPS #128 to ICOM #421 VHF

ERICH

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Can the Forum help ?
I am trying to connect the GPS to the VHF but cannot work out how to do it ( tried looking in the manuals ?)
Has anyone successfully managed to do this connection and exactly how ?

thanks

ERICH
 

gandy

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I connected a Garmin GPS 120 to Icom 421 last year, no problems.

Check the interface is set to NMEA/NMEA, not Garmin's proprietory protocol which is the default on both of mine. Set baud rate to 4800, which I think is the default, but make sure.

Garmin don't have separate NMEA negative leads. The Icom 421 expects a separate NMEA+ and NMEA- from the GPS. The actual connections from Garmin 120 were..

Garmin NMEA Out (Blue) to Icom NMEA In+
Garmin Ground (Black) to Icom NMEA In-

Tony S
 

duncan

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As Tony say's it's the blue and black. The 421 uses a wired 3.5mm plug to NMEA in - centre to the Blue garmin wire and screen (outer) to the Garmins black (earth) connection then plug into the unit.

Configuring the Garmin unit's Com port to NMEA out is one common issue - connecting the earth direct to the NMEA -ve the other.

421 will accept most formats of the NMEA sentence - certainly 1.5 and 2.0 so leave that at default, as baud rate, to start with.

finally do not forget that you will not see your positon displayed on a 421 unless you have entered your MMSI number.
 

Birdseye

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would be interested in hearing if you succeed. I have been trying to do the same with a Garmin 76 - both Garmin and Icom blame each other because it doesnt work.
 

qetoo

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I have a Garmin 128 and have successfully connected it to my laptop computer and autopilot. The Garmin 128 has a NMEA output on pin 3. That means it is a NMEA "talker" on pin-3. As I understand it, you can have up to three "listeners" connected to one "talker". [You cannot connect two "talkers" together.] While I am not connected to a VHF, I would expect you would connect pin 3 on the Garmin 128 to the NMEA Input pin on the VHF. I show my wiring diagram at:
http://carlten.tripod.com/Navigation/navigation.html
 

Martinet

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I'm also getting crazy trying to connect a Garmin 76 with my ICOM 421. I know I have the wiring correct, the GPS works fine but de ICOM does not display anything. Also tried with a Garmin 12XL and got nothing. Would you please explain a bit more what Garmin or ICOM said about it?.

Thanks
 

gandy

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Have you checked that the Garmin (s) are sending out normal NMEA data? Most Garmins default to a proprietary protocol. On my Garmin 12 (not XL) you need to go to the Setup Menu, then Interface, and change the first item to NMEA/NMEA.

If you can connect the Garmin to a PC, using Hyperteminal you should see the NMEA data being spewed out.
 

Martinet

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Yes. I'm going to try with the hyperterminal now but I had used it before with a Route 66 driving software in my computer and it worked fine.
Yes, I had configured the output to NEMEA and have even tried all the combinations of parameters of the NEMEA settings in the GPS. I've checked also the GPS with a tester and when you set it to no output it gives a continuous -5.0V. When set to NEMEA it cicles.
I would say it is not a hardware problem but a logical/software one. There is nothing that can be set in the ICOM, at least that I know of.
thanks.
 

gandy

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I don't know Route 66 software, but the PC application I used (Memory Map) needed the Garmin set to Garmin's protocol not to NMEA.

I think its worth checking with Hyperterminal just to make sure its sending the correct stuff.

With several people having similar issues, I wonder if there's some common factor with the battery powered Garmins. The Garmins use DC ground as one side of the NMEA signal instead of a designated NMEA negative. Maybe that should be connected to the boat's DC negative.

I think I'll try my Garmin 12 on the Icom next weekend. See what happens.
 

Martinet

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I just connected the GPS 76 to the hyperterminal and the readings are fine.
I wonder if someone who has succesfully connected his Garmin to an ICOM 421 could send us the log of the
hyperterminal. I think that I could get some ideas from comparing the outputs I get from mine and some succesfull outputs.

Thanks. Jaume.
 
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