Can We Talk ?

Love to, does your system know the correct language.

By Bill Ando

Integration of the on-board electronic equipment isn’t something to be taken for granted.  There are two distinct languages in use and they can tongue-tie your system if you’re not careful.
Just because you have a certain manufacturer’s system gracing the bridge aboard your yacht does not mean that a new unit from the same manufacturer will work.  If you purchase a new piece of electronic equipment that is to the National Marine Electronics Association (NMEA) 2000 spec, hoping to integrate it with older equipment, stop, not so fast. Without the intervention of what amounts to a translator these pieces probably can’t talk to each other. In fact, hooking up new equipment without the proper hardware could confuse the entire system.
Let’s say you like your existing system and you just want to change out the GPS. To introduce an NMEA 2000 certified unit into an NMEA0183 system takes a bit of hardware magic.
One such magic act is Simrad’s AT10, which according to its installation instructions “converts data on NMEA0183 format to SimNet/ NMEA2000 format and vice versa.” The instructions include the caveat that there are some sentences (data streams) that it doesn’t read in either direction. It also doesn’t deal with NMEA 2000 sourced AIS information.

The AT10 can be used on other systems, such as Maretron and Furuno says David Gratton, president of Martek of Palm Beach, an integrated electronics expert who helps owners plan and install bridge configurations on new builds or refit bridges aboard their current boats.
Even if you decide to upgrade your system to  NMEA2000 you can install a single manufacturer’s components, or mix in other manufacturers as long as the equipment is all certified NMEA 2000. “However,” David says, “you can’t certify the installation.”  That means that it doesn’t come in a box—the success of the installation depends on the skill of the installer.
David says that the trunk or main power cable of an integrated bridge system—referred to as the backbone—is critical. The backbone can be a maximum of 328 feet if using a mini cable or 656 feet if using a micro/mid cable.
“Drops,” which is techie code for the connecting wire that runs from the backbone to a unit, are limited to 19.6 feet in length. Technically you are allowed 50 drops, but the spec limits the total length of drops to 256 feet. So you’ll want to keep close track of the length of each drop.  Exceeding the spec can result in data timing collisions. “The way that manifests itself is in data loss, data dropping in and out, or in extreme cases, a complete system crash,” says David. He adds, “NMEA 2000 is a far more advanced data system [than NMEA0183], it’s just that it isn’t as plug and play as people think it is.”
Maretron, a manufacturer of marine instrumentation, makes its USB100 that bridges computers to an NMEA network. This allows you to use PC-based vessel monitoring and control software. The gateway provides one simple connection between the network and the PC.
For older PC-based navigation software that requires receiving data in NMEA 0183 format, the USB100 automatically converts information from the NMEA 2000 network to NMEA 0183 sentences. You can continue benefiting from navigational and charting software that you already own while enjoying the many benefits of networked NMEA 2000 instruments.
David says that approximately 50 percent of his work is correcting installations that suffer from faulty engineering. “When you run backbone you need to know the segment length. That is critical,” he says. He adds that dual backbones are gaining in popularity. Not just to overcome the 50-drop limitations of the system, but also to provide redundancy. The one thing to remember if you try this yourself is to assume nothing; don’t hesitate to call a wizard. martekpb.com, maretron.com, simrad-yachting.com