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NMEA networking between chartplotter and radio
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jkidd



Joined: 23 Oct 2006
Posts: 1609
City/Region: Northern, Utah
State or Province: UT
C-Dory Year: 2007
C-Dory Model: 22 Cruiser
Vessel Name: Voyager
Photos: Voyager (JK)
PostPosted: Fri Aug 05, 2022 11:42 pm    Post subject: Reply with quote

ssobol wrote:
I use the 4-port blocks. The power lead goes into one end and the other end is terminated giving you the full port availability (and only requires one terminator). If you expand you can get another 4 port block and a drop cable to connect the blocks. The terminator on the first block gets replaced with the drop cable and then the terminator is moved to the end of the second block. If you have all your NMEA 2K stuff near each other, the 4-port blocks take up less space and have fewer failure points.


I have to disagree with leaving one of the terminators off. The terminators measure 120 ohms and they are in parallel in the circuit. So when both terminators are in the circuit you will measure 60 ohms. Your network should measure 60 ohms when resistance tested. 120 ohms means there is only 1 terminator, and 40 or less means there are too many. Not having the right resistance could leave having intermittent problems crop up in the future. The Nmea 2000 spec calls for both terminators to be in place.

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Jody Kidd
KE7WNG
Northern, Utah

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zuunami



Joined: 10 Aug 2021
Posts: 223
City/Region: Fort Bragg
State or Province: CA
C-Dory Year: 2006
C-Dory Model: 16 Cruiser
Vessel Name: Oh Buoy!
Photos: zuunami
PostPosted: Sat Aug 06, 2022 12:39 am    Post subject: Reply with quote

Everything I've read or seen says that both terminators are needed.

On another note, I knew when I started this research that the Garmin chartplotter and SH VHS with ais could be directly wired together. I thought that a backbone would be great to start with to then attach other sensors/devices along the way. I'm discovering that the Mercury motor unit is $600 (if our 2006 40 hp is even capable), and must be programmed by a dealer (3 hours away through the mountains). Well, how about a battery sensor to easily check the charge, not finding anything. An additional monitor just for the AIS receive would be nice, but we only have so much room on the helm dash. A wind sensor, no, it's windy here usually.

So, while it's been fun and informative, and I'm sorry but very grateful for everyone's time, now I'm not sure it's even practical for us! lol

Karen

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Karen W. and Robert R.- Fort Bragg, CA - Oh Buoy!
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zuunami



Joined: 10 Aug 2021
Posts: 223
City/Region: Fort Bragg
State or Province: CA
C-Dory Year: 2006
C-Dory Model: 16 Cruiser
Vessel Name: Oh Buoy!
Photos: zuunami
PostPosted: Sat Aug 13, 2022 9:45 pm    Post subject: Reply with quote

Well, hooray, I finally found a couple of reasons to do a nmea 2000 backbone, (and I just wanted to anyway but couldn't find a reason to justify it:)

1. The wiring that would connect the garmin chartplotter to the SH GX2400 radio (to access the radio's AIS receive) are really too short to reach each other and would need splicing.

2. The SH radio uses a cable to transfer firmware and software updates (unlike the garmin chartplotter that uses a micro sd card). Since I'm the only person in the world that doesn't have a laptop, that means I need to transfer the data from my PC to the radio through a cable, requiring that I set up the radio next to my computer with a battery. Hmm, not sure what SH is thinking Smile With nmea 2000, I can at least easily disconnect the radio and bring it inside to do any updates. Maybe I'm missing something with the SH, but tech support said the radio needs to be connected to power to do the updates, so I'm not aware of any other choices. Tech support has gotten back to me in 24 hours with two emails I sent, so I have to give them major kudos for that.

3. If we want to bring the units inside for the winter, we easily can.
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zuunami



Joined: 10 Aug 2021
Posts: 223
City/Region: Fort Bragg
State or Province: CA
C-Dory Year: 2006
C-Dory Model: 16 Cruiser
Vessel Name: Oh Buoy!
Photos: zuunami
PostPosted: Tue Aug 23, 2022 8:32 pm    Post subject: Reply with quote

Well, contrary to the advice of Steve-in-SEA who started this post, I decided to go with Ancor instead of Garmin nmea 2000 components because the Ancor cables were the length I needed to make a less messy wiring conglomeration in our small 16. So far, no luck, so I have to go back and check all my connections. I have a 4port block backbone, with Ancor's T power connector that goes on the end, then terminators on each end. Then drop cables to the chartplotter and to the VHF. For future expansion, we would add cabling to the other side of the power T.

One of the things I noticed in looking again at jkidd's diagram earlier in this post, and elsewhere, is that it doesn't show any separate power connection for the chartplotter or the VHF? Maybe that's my problem, I have them both going to power...

I'll recheck all my connections, maybe it'll magically work when I turn everything on again tomorrow. Or, there's always nmea 183 Smile
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zuunami



Joined: 10 Aug 2021
Posts: 223
City/Region: Fort Bragg
State or Province: CA
C-Dory Year: 2006
C-Dory Model: 16 Cruiser
Vessel Name: Oh Buoy!
Photos: zuunami
PostPosted: Wed Aug 24, 2022 8:44 pm    Post subject: Reply with quote

It all works perfectly now that I found my stupid mistake, which is too embarrassing to share. Ok, I will - I was so intent on cleaning up the wiring and making it all neat and tidy that I missed connecting the Garmin drop cable to the backbone Smile

I apologize for the post Sad

I have to say that I love the Garmin, it's so easy to use, and a 9" screen is so worth it.
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Marco Flamingo



Joined: 09 Jul 2015
Posts: 1154
City/Region: Seattle
State or Province: WA
C-Dory Year: 2004
C-Dory Model: 16 Cruiser
Vessel Name: Limpet
Photos: Limpet
PostPosted: Thu Aug 25, 2022 11:30 am    Post subject: Reply with quote

Having re-read the thread, I see that I was contemplating getting an AIS transponder (for the Chiton not the Limpet. That's been done.
Part of the reason was that I could get my radio (GX2400) to show AIS targets on the Garmin MFD using NMEA 0183, but not when I changed to my new NMEA 2000 backbone. It didn't really matter because my new transponder gave me AIS targets on the Garmin.

But it raises two questions (projects). Can NMEA 0183 and 2000 be used at the same time? I could simply reconnect the VHF via 0183 and, should the AIS transponder go down, I'd still have another source for AIS (receive only) via the VHF 0183.

Second, I thought that I had read somewhere that it was possible with a VHF/MFD connection to see an AIS vessel on the touch screen, touch it to get vessel info and MMSI (which I can do), but also have an option to call the vessel using the touch screen to hail the vessel via the VHF. Does this sound like something my system could do? Maybe it was just in a dream. It would save having to read the MMSI off the screen and enter it into the VHF, or get the vessel name from the screen and then find it in the list of AIS targets on the radio, both of which could be clunky and time consuming. Getting an instant vessel name and quick radio contact would be great just via the Garmin screen.
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