NMEA feed problem to Lowrance Link-8

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robbyc0

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Hi All - looking for help! Upgraded my Navicom RT550 vhf last night to a Lowrance Link-8 so I can get AIS CPAs etc. The RT550 gets it's GPS feed from my Garmin GPS152

Everything went well but when I plugged the working NMEA plug into the Lowrance it cannot see a GPS feed. Unplugged it and back into the RT550 and the feed is fine, so nothing wrong there. Checked the Lowrance menus and it's set to receive an NMEA0183 feed - it's the only option as there is no NMEA2000 for it to see.

Checked the working on the plug and it's exactly the same - GPS152 feeds to green and yellow leads labelled NMES in +ve and -ve. I even connected the feed from the GPS152 to the new cable that came with the Lowrance just in case Navicom wired their plugs weirdly and still no joy.

This should be the easy bit!

The 152 has options to turn on or off parts of the feed - could this be it?

Called Lowrance and they suggested trying swapping the polarity of the feed - is this likely to work?

Or have I got a nice new duff Link-8?
 
Yes it's fixed at 4800 on the GPS152 and the Lowrance can accept either. There is no option to choose the baud rate for input on the Lowrance - only output
 
OK, I've just looked up the manual and it seems it is fixed at 4.8Kb for the NMEA in (Green & Yellow).

Are you certain about the Garmin connections?
 
Just had a quick look at the GPS152 manual. Blue is the NMEA+ out which should connect to the Link NMEA+ (Yellow). The Garmin NMEA- is the -ve supply (Black) and that should connect to the Green.

If that doesn't work try swapping them as Lowrence suggest. RS422, IIRC, is +/-5V.
 
OK that's interesting as the Garmin connections there at the moment (which work on the RT550) are blue and BROWN. So it looks like the Lowrance wants a ground, not a negative then?
 
robbyc0 said:
OK that's interesting as the Garmin connections there at the moment (which work on the RT550) are blue and BROWN. So it looks like the Lowrance wants a ground, not a negative then?
Click to expand...

The Lowrance would want an NMEA- if it could get it, but Garmin, in my experience, always use the -ve as NMEA- so the Lowrance will have to lump it.

So I reckon Garmin Blue to Lowrence Yellow and Garmin Black to Lowrence Green is your best bet. If that doesn't work swap them over.
 
This is interesting. My Link-8 arrived yesterday and replaced a Navicom RT650. They must be made by the same company (I know navicom and Navico are seperate entities but maybe manufacturing is contracted out), as all the mounts used the same holes, all the cables were a direct swap. I had it up and running in less than 5 mins, using the same NMEA input and output as the Navicom with no settings changes.

For a 5 year old design, it still seems pretty up to date so long as you don't look at the SH6500

p.s. My link-8 is fed by a Garmin Oeregon 600 handheld.
 
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As a long shot, is the GPS152 data output set to Garmin protocol? It's incompatible with standard NMEA data so probably wouldn't work with your RT550 either. :( Works well with OpenCPN though!
 
Well that should have worked for me then! There is no Garmin black other than the power lead. Bloody thing worked just now and I put it all together again and now it's not.
 
Right all - I had yellow to blue and green to brown and I disconnected the green to brown just leaving yellow from Lowrance to GPS152 blue. Suddenly I got an AIS collision warning! Looked at the VHF and it was getting a full gps position with JUST yellow Lowrance to Blue Garmin connected. Great! Then I put it all back together again and screwed on the panel and it stopped working. Not great. Took it apart again and connected the new NMEA Cable from the VHF Yellow to Garmin Blue and nothing. Have given up for the night! Given 2 identical NMEA cables to the VHF did not solve the problem, I am wondering if I have a dodgy wire in the Garmin cable
 
robbyc0 said:
There is no Garmin black other than the power lead.
Click to expand...

That'll be the one. It doesn't seem right but that's the way Garmin do things.

Of course you'll also have to understand how it worked temporarily. How are you connecting the wiring up?
 
What is more bizarre is that I did not disconnect or connect anything else - just wrapped up the bare wires and screwed the panel back on. At the weekend I will go back and strip the wires properly to eliminate all insulating tape glue and solder yellow to blue as I know that's right. Maybe it's just dirty contacts where I have been connecting and disconnecting and the very low voltages don't like it. At least now I know both the Garmin and the Lowrance are doing what they are supposed to - just leaves the bit in between!
 
robbyc0 said:
At least now I know both the Garmin and the Lowrance are doing what they are supposed to - just leaves the bit in between!
Click to expand...

Good luck.

By the way, choc block connectors can be a bit of a liability in the long run. You could crimp ferrules on the wire to make them less prone to corrosion or pulling out, but another type of connector would probably be better. I use ring terminal blocks but quite a few posters are keen on Wago connectors.
 
lpdsn said:
Good luck.

By the way, choc block connectors can be a bit of a liability in the long run. You could crimp ferrules on the wire to make them less prone to corrosion or pulling out, but another type of connector would probably be better. I use ring terminal blocks but quite a few posters are keen on Wago connectors.
Click to expand...

I'll solder them once it's sorted. I still wonder whether it might be a dodgy VHF, maybe the little cable at the back before the connector. Given I have re-wired twice with 2 different cables from Garmin to Lowrance it seems odd if the problem is there. I have emailed the shop - if they exchange the set then I can eliminate that. It's a ball ache though, especially as someone on here has said they swapped a 650 to a Link 8 without altering anything - so mine really should have done the same. It's the same set. I remember the wiring for the 550 was a bit trial and error which is why I ended up with blue and brown.
 
Problem solved! Turns out the Lowrance needed a NMEA -ve and the Navicom did not. So bridged green Lowrance to Earth and it all works. Thanks all for valuable help.
 
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