Are tee's ok on NEMA 2000 drop cables?

[CarinaPDX]

When one considers the cost of all of the electronics connected to the N2K bus, not to mention the rest of the gear and the boat itself, saving a few dollars here is a bit silly - and you don't save anyway. The Maretron Multiport box is a compact and tidy solution, for about $75 street price, which is equivalent to three tees in a row (about $25 each). I don't see why anyone would choose the tees. Personally I have three Multiport boxes on my network and love how clean a solution they are.

Greg

[serendipitous]

Fair point, Greg. It is much less about the cost (although I have loads of extra tee's --- it seems like every instrument comes with one and somehow I have several extra). It is much more about difficulty of pulling even one N2k cable up to the area above the companionway.

I finally completed the cable run (after cutting the connector off the cable and installing a new one after pulling the cable -- with much blood sweat and swearing) and I have a Multiport ready to go.

Tomorrow I modify the holes to fit the new instrument heads..... I hate cutting on the boat!

Thanks again to everyone who chimed in on this. I searched everywhere first and couldn't find it addressed anywhere. It is nice to know the right answer.

[Paul L]

Is the Maretron Multiport device a passive device? Ie, no internal components, just an interconnect?

[Dsanduril]

Originally Posted by Paul L

Is the Maretron Multiport device a passive device? Ie, no internal components, just an interconnect?

Originally Posted by Davidhoy

I work for Maretron...,

Originally Posted by Davidhoy

No electronics, just a more compact and secure way of connecting multiple devices, instead of stringing together multiple tees. It's electrically the same a 4 regular tees.

[Paul L]

Originally Posted by Dsanduril

Yea, I had seen that. I don't understand how the Multiport that only hardwires the drops together is any better electrically than stringing tees on a single drop.
My understanding is that stringing tees on a single drop violates n2k spec, yet somehow doing essentially the same thing in the Multiport is compliant??

[CarinaPDX]

Originally Posted by Davidhoy

No electronics, just a more compact and secure way of connecting multiple devices, instead of stringing together multiple tees. It's electrically the same a 4 regular tees.

Actually I think you will find that it is the same as stringing three tees together, not four. The Multiport has one male and 4 female connectors; the male and one of the female connectors are for the through bus, and the other three female connectors are for device connection for three devices.

PaulL: Doing things in a less than optimal way does not mean they won't work; it just adds some additional degradation to the signal. Signals can degrade quite a bit before the transceivers can no longer accurately pass the data to the attached devices. Doing things "by the book" minimizes degradation, but degradation is a fact of life. The longer the cabling and the more devices attached the more degradation; for most sailboat systems it isn't close to being a problem. Big powerboat networks with dozens of devices and long cable runs can challenge N2K.

Greg

[s/v Jedi]

Originally Posted by CarinaPDX

When one considers the cost of all of the electronics connected to the N2K bus, not to mention the rest of the gear and the boat itself, saving a few dollars here is a bit silly - and you don't save anyway. The Maretron Multiport box is a compact and tidy solution, for about $75 street price, which is equivalent to three tees in a row (about $25 each). I don't see why anyone would choose the tees. Personally I have three Multiport boxes on my network and love how clean a solution they are.

Greg

Here’s a $36 4-port T: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[CarinaPDX]

Originally Posted by s/v Jedi

Here’s a $36 4-port T: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

So where were you when I was buying my network?

That's a nice multiport tee. And a choice of 4 devices or 2 devices. I have mixed feelings about all plastic: it is great for corrosion resistance but I always worry about plastic threads.

Greg

[Paul L]

Originally Posted by CarinaPDX

.....
PaulL: Doing things in a less than optimal way does not mean they won't work; it just adds some additional degradation to the signal. Signals can degrade quite a bit before the transceivers can no longer accurately pass the data to the attached devices. Doing things "by the book" minimizes degradation, but degradation is a fact of life. The longer the cabling and the more devices attached the more degradation; for most sailboat systems it isn't close to being a problem. Big powerboat networks with dozens of devices and long cable runs can challenge N2K.

Greg

I know many non- compliant n2k setups still run fine. My question is how is the Maretron Multiport spec compliant if it is electrically the same as teeing off of a single drop?

[CarinaPDX]

Originally Posted by Paul L

I know many non- compliant n2k setups still run fine. My question is how is the Maretron Multiport spec compliant if it is electrically the same as teeing off of a single drop?

The Multiport is intended to be located in the (linear) bus, not off of the bus, and is no different than three tees in a row on the bus. Using the Multiport or 3 tees on a drop off of the bus, or creating a tee-shaped bus, is not in the spec. It is likely to run fine as well - just isn't the "right" way to do things.

Greg

[Paul L]

Originally Posted by CarinaPDX

The Multiport is intended to be located in the (linear) bus, not off of the bus, and is no different than three tees in a row on the bus. Using the Multiport or 3 tees on a drop off of the bus, or creating a tee-shaped bus, is not in the spec. It is likely to run fine as well - just isn't the "right" way to do things.

Greg

Greg,
Not according to Maretron diagram, at least the way I read it

[s/v Jedi]

Originally Posted by Paul L

Greg,
Not according to Maretron diagram, at least the way I read it

Paul is correct, but there is a catch: for each of the four drop cables running from the 4-port hub to the connected devices, their maximum length is shortened by the length of the cable that runs from the backbone T to the 4-port hub.

[Paul L]

Originally Posted by s/v Jedi

Paul is correct, but there is a catch: for each of the four drop cables running from the 4-port hub to the connected devices, their maximum length is shortened by the length of the cable that runs from the backbone T to the 4-port hub.

So is this spec compliant or not?

[goboatingnow]

Look folks. the issue with T connections on CAN has to to do with signal timing. Since NMEA 2000 is running at a quarter of the max CAN specified speeds it has quite a broad tolerance of bit timing

A T of a T will have no effect , try it it will work. Most NMEA 2000 CAN solutions are lightly loaded so arbitration issues will be few and far

[goboatingnow]

Originally Posted by Paul L

So is this spec compliant or not?

It’s not compliant per se.