Are tee's ok on NEMA 2000 drop cables?

[SoonerSailor]

Originally Posted by PerfectPirate

I was surprised to find that the daisy-chaining capability is not built into the Triton II display heads and that the masthead transducer no longer acts as a backbone terminator, which means that the drop cable running up the mast to the transducer will exceed the NMEA-spec maximum length for a drop cable.

In the case of the B&G wind N2K wind instrument, now without the 120 ohm termination: the cable up the mast is not a drop cable for its full length. From the connection to the backbone, it is N2K for a meter or two to an interface. From there, it is not N2K but instead I'm told it is NMEA0183 format.

[ErnestV]

Originally Posted by OS2Dude

Ahm. If you read the description, it says it connects to the backbone via a 'T'. That makes the box 4 'T's on a 'T'. . .

Nope. This makes the box one device (the box) on a drop line. Seen from the devices connected to the box, the box is a main bus, internally it serializes the messages similar to a 183 multiplexer, plus handles all the electrical requirements.
Even if "it works somehow" I wouldn't do it, it might stop working just when you need your instruments most, at 3-oh-30 in the middle of a storm on a lee shore.

[SoonerSailor]

Originally Posted by ErnestV

Nope. This makes the box one device (the box) on a drop line. Seen from the devices connected to the box, the box is a main bus, internally it serializes the messages similar to a 183 multiplexer, plus handles all the electrical requirements.

Even if "it works somehow" I wouldn't do it, it might stop working just when you need your instruments most, at 3-oh-30 in the middle of a storm on a lee shore.

The Maretron box, as David Hoy of Maretron has said in this thread, has no active or passive electronics in it. It really IS a multi-tee just as is the Ancor multi-T linked earlier is. So there are no “electronics” to fail.

The concern with multiple devices on a drop cable comes from greater voltage drop on the thinner power wires in a typical “drop” cable compared to a typical backbone cable. If this is accounted for (you can use a cable marketed as a backbone cable as a drop cable to take advantage of larger power conductors) there is not a problem with teeing off of a drop cable as long as the longest path to a device on that drop is no more than 20 feet.

The Maretron N2K builder will not flag multiple tees off of a drop as long as lengths and voltages are within allowances. You do have to specify cable types and lengths, and current draws (LEN #) of devices for the software to properly analyze your proposed network.

[ErnestV]

Originally Posted by SoonerSailor

The Maretron box, as David Hoy of Maretron has said in this thread, has no active or passive electronics in it. It really IS a multi-tee just as is the Ancor multi-T linked earlier is. So there are no “electronics” to fail.

Ah, thanks! Something new to learn and absorb every day...

[sailingharry]

I believe that the reason the B&g Triton and similar daisy-chained devices are not compliant (and are called compatible) has nothing to do with operational or network limitations, and is exclusively a design philosophy limitation. I believe the intent of the standard is to allow the removal of any device without compromising the network. As soon as you daisy chain an instrument, removal of that instrument compromises all subsequent devices.


Like many, I used and daisy chained Triton instruments on my last boat and found the installation benefits greatly outweighed the design philosophy.

[Nate24]

Originally Posted by s/v Jedi

I checked that but it only lists devices like displays, gps etc., no cabling items there at all.

Also, I think Maretron’s reputation is good enough to assume they don’t put fraudulent claims in their spec sheets

Cables are not certified by NMEA, they are approved, so you will not find them in the certification list