When I first started sailing I never thought about what kind of information you needed to navigate a vessel. My eyes, ears and senses seemed like enough to take a boat out to sail. Now being a boat owner and having been through some fun and interesting scenarios and then imagining other future scenarios has caused me to rethink what would be useful to help me navigate around the world. I really have no idea what would be needed but I can imagine different places and the different ways of navigating that I’ll probably need. Having depth is handy but wouldn’t being able to get a three-dimensional image of the bottom to know you’re in a good anchorage be nice? Maybe trying to get into an obscure lagoon that requires some interesting ways of avoiding reef obstacles. Perhaps just being able to see on a radar obstructions ahead that I can’t see due to fog or adverse weather would be nice. Having the ability to hail a vessel that might be on a collision course with me would be nice. Embracing technology is great but then what happens when one or many of your instruments fail?
I really don’t like to think about being without depth, GPS or a compass to help me and all of the other instruments stay on course and protected from running aground. I do know that if I can get them all speaking the same language I will have a pretty awesome navigation system. When I bought Satori she came with an old Magellan GPS Chartplotter that was also able to take the instrument data and display it on the multifunctional display. When I turned it on, not only was it not able to connect to the GPS but it also had no preloaded map cards so I removed it. Satori did have a VHF radio, depth, water temperature, wind speed and direction and a compass that spoke the Seatalk language and those were displayed on the face of the companionway for viewing in the cockpit. There was also a speed over water sensor but it wasn’t functional. I brought an iPad, iPhone, a bluetooth GPS and installed a new VHF radio that had an AIS receiver but I discovered that the AIS receiver needed a GPS connected through a NMEA 0183 network from another device that could deliver the coordinates to display AIS targets. After two weeks of navigating with an iPad, I realized that it’s a great way to navigate along with the cockpit displays and something called an ‘auto helm’ in the navigation area of the cabin. I could anchor and monitor my depth and also track my position and set an anchor alarm to make sure I didn’t drag anchor. When the GPS disconnected from the iPad I would switch to my iPhone and use iNavX with the built-in GPS and also as a backup to monitoring my position. I knew that using a smartphone and tablet was not a good way to be precise but it actually did a great job even if it wasn’t completely dependable. It worked well using Garmin’s BlueChart mobile iPad app as it used vector graphics instead of raster, which is much easier to view and also the chart icons of buoys and any other useful navigation points displayed the information about each point (icon) such as if a buoy had a light and what the flashing interval and color was. Also having depth and mooring buoys on the chart was very helpful. The only time I wished I had more was when I was motoring at six knots in the fog or at night. It was then that I decided why radar would be useful. Since most of my winter has been working on plumbing and the temperatures have been pretty cold I have held off from getting my navigation setup, until now.
One thing that finally took after many months of learning about it is how all of the instruments interface. I already have a Seatalk network for wind speed, wind direction, heading (compass), depth, water temperature and speed over water. I also have a nice radio that can identify AIS targets and allow me to hail another AIS target vessel by simply pushing the ‘call’ button on the VHF radio. What I really wanted was the ability to be seen by another vessel. I knew radars can trigger a ‘radar beacon’ whereas my radar becomes a transponder for any other radar. With the combination of Racon and AIS I would show up to most vessels and then the other pleasure-craft I could use my own radar to discover and avoid. Since my old multifunctional display was tossed, I spent part of the winter researching the best way to get all of my navigational equipment talking to each other. How can I still use my iPad and the Garmin Bluechart mobile app but also be able to see radar and AIS targets? Bring on the Vesper Marine AIS transponder and GPS with wifi. By sending all of the other Seatalk and NMEA 0183 data to it, the transponder can act as a gateway to any NMEA 0183 or NMEA 2000 wired network and any app that uses wifi to collect NMEA data. Add a multiplexer to take all data from all sources and pipe them into one output, to the transponder which can then send the data further to NMEA 2000 and wifi.
I chose the new Garmin 820 as my multifunctional display, and later if I want I can add the best sonar technology available for consumers and then also connect an HD radar to it. The display also has a wifi networking ability that can speak to it’s own Bluechart apps. Not only can I use iNavX but also the Garmin BlueChart apps and both receive all of the data from all other devices. It’s a great solution and has a nice upgrade path for future-proofing the setup. Since I have this all figured out I thought it would be handy to explain how it all hooks up.
NMEA 0183 basics, talking and listening
The most important part of understanding how NMEA 0183 works is simply by the talk/listen protocol. Simply put, if I’m a NMEA 0183 compatible device then I can listen and possibly use another compatible device that is NMEA 0183 compatible. Hopefully that device will have what the other device needs. Here is where the problem lies: If one of my devices needs data from more than one other device then I have a communication bottleneck. Since a single device can only listen to one other device then I need a way to collect that data. This is the job for a multiplexer. The multiplexer can listen to up to four devices, collect the data into one data stream and then talk to up to six other devices (two outputs, three devices each). The one I installed can also take Seatalk so the multiplexer’s job really is to translate all “conversations” into two languages: NMEA 0183 and NMEA 2000. Send that data back to a wifi transmitter and you can connect any smartphone, tablet or computer to it and any app that communicates with NMEA 0183 data can display it for navigation. It’s really not too complicated once you understand the protocol (can listen to only one, can talk to up to three). Then the only other thing to understand is the need to connect a shield from the output of any NMEA 0183 along with the negative and positive leads. When connecting to an input the shield will not have a place to connect so it can be omitted.
Powering the multiplexer with Seatalk
I am powering the multiplexer using a cable that is “daisy-chained” from another Seatalk device. In this case I use the red Seatalk wire as the positive NMEA input in input number 4a under “NMEA In” and the Seatalk yellow wire as the input number 4b. I also need to add the red wire to the 12v input and then the shield wire in the ground input. This will both power the multiplexer but also allow for it to collect data and transmit it to it’s outputs. My problem lies with when I want to simply run the VHF yet have it still be able to list AIS targets without using the multiplexer, which happens to depend on the seatalk network, which turns on the sounder, speed/water temperature sensor, wind sensor and compass instruments. So to eliminate the dependency I will build a bypass that can accept the AIS transponder data and can also be powered by the radio circuit. A switch will solve this issue. It’s not imperative right now but will certainly have some benefit while counting amps.
Gathering other NMEA 0183 Talker Data
I’m only connecting two devices aside from the Seatalk that I will want to use as part of the network. First is the VHF radio and I will only want the DSC data since the AIS transponder will also have data from other AIS transmitters (targets). For the AIS transponder I want to collect both GPS and AIS transmission data. So the combination of Seatalk, transponder and VHF I have the following data: depth, water temperature, wind speed, wind direction, heading, speed over water, DSC, AIS and GPS. To output the talking portion of the multiplexer I simply use a 4-row dual-jumper terminal block to distribute each output to up to three other units. If you’re going to do this install, I suggest that you find bulk NMEA 0183 cable that has an exposed shield cable as this does not exist with NMEA 2000 or Seatalk 1,2 & NG. It may be difficult to find and I don’t know a source. I just repurposed the long Vesper Marine cable that came with the transponder and shortened it and then connected it to a terminal block and then connected the cable to the VHF radio to extend the NMEA 0183 length to reach the multiplexer. Do not make the mistake of getting a serial bus multiplexer. Either get a USB, wifi or bluetooth version to simplify configuring the device. I did make the mistake and sat there with the opened package wondering how I was going to take three bare cable plugs and get the unit to talk with my computer via USB. Why didn’t I just buy a USB version?
NMEA 0183 vs NMEA 2000
The biggest issue with NMEA 0183 isn’t just the ‘talk up to three times but only listen once’ scenario but also the wiring scheme. NMEA 0183 usually takes only two wires to send and another two to receive per unit. There is also a need for shielding the listening circuit without needing to shield the talking cables. Usually you can bypass this when the unit is sending both talking and listening cables to a multiplexer and distribution block, or when only two units are interacting but either may not be the case. I have a tiller pilot that serves no purpose except for listening in on the talking circuit but I need to shield the cable I send to the pilot. Try searching for 22 gauge marine shielded wire. Most likely you’ll end up buying 4, 6 or even 8 conductor cable and lobbing off all but two or four conductors at the end and pay more than $1 per foot. You may even go with unshielded cable, two strands of red/black but this could have issues.
NMEA 2000 plays much better. There are universal plugs that work on every device similar to USB which powers the unit and exchanges data for every attached unit. They call it a ‘backbone’ which is a multi talk/multi listener network that takes care of both shielding, communication and power. If you have three units you simply need to ‘T’ off for one of the units similar to the way plumbing works. You can buy cables in just about any length in increments of six feet and it really is plug and play technology. The way I am able to get NMEA 2000 is through the Standard Horizon transponder and the only unit so far that needs it is a chartplotter. I am not certain yet but I believe I can also send waypoints all the way from the chartplotter to the tiller pilot, which is on NMEA 0183 or Seatalk if I choose to power the pilot on the same circuit as the rest of the Seatalk components.
MMSI, Ship Station License and Call Sign
I suppose I could post about this elsewhere but I figure this is as good of a place as any. If you’re new to the whole AIS/DSC technology and are ready to take the plunge, DO NOT get your MMSI number from BoatUS unless you’re NOT planning on using a call sign for ship-to-ship hailing. I made the mistake of getting my MMSI when I bought my VHF radio but didn’t realize that the unit needed GPS to view AIS targets. Later when I bought the AIS transponder and then decided to get a dedicated call sign or better put, a ship station license from the FCC, I had already locked the MMSI numbers into the radios so I had to send both units back for reprogramming. The ship station license was about $160 and lasts for 10 years before needing to renew. It’s also transferrable to another person in case you ever sell your vessel and you can add your EPRB number so the FCC has your communication ID’s tied together.
What’s Next? Black Box – Crowdsourced
One of the issues I have with the NMEA data networks is the lack of simple low energy black boxes. How hard is it really to program a unit to save the NMEA data to a solid state disk like an SD card? If I had a way to upload the data to my computer I could track all of my routes, watch the weather/wind trends much closer, follow my course and even log the AIS targets. Some of the information could be handy to publicize my routes but data like DSC positioning could be crowd sourced for tracking all AIS broadcasting targets throughout the world. Currently the only way to track a vessel is with radio towers on shore but being able to send your own course and other AIS targets that you receive could prove useful for getting a better history of where all broadcasting vessels were located at any given point when another vessel is within the receiving range. With Paxor technology you could also send a limited set of your NMEA data to shore via SSB radio so the shore network can track your position and vessel condition at all times. It’s possible but just not quite there yet and whoever develops the infastructure will do us all a great service. For now I will see if a Raspberry Pie computer can keep a log of a subset of NMEA data that my NMEA components produce so I can later mess around with building visualization tools from the data. Something most salty dogs could care less about but modern pups can enjoy.
Anyways, I spilled my thoughts so others can hopefully learn about this process. I hope is was useful for newbies like me. Next is getting radar installed, solar keeping my batteries charged and SSB radio for long distance communication.