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19-09-2021, 15:33
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#1
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Registered User
Join Date: Feb 2009
Posts: 80
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Are tee's ok on NEMA 2000 drop cables?
Hello all,
I am replacing the display heads over our companionway and will have several N2k displays within inches of each other. Is it ok to tee them off a common drop cable? The geography makes it unwieldy to run multiple drop cables (very narrow channel to run cable) and I prefer not to dead-end the backbone there.
I know that this is the purpose of the Maretron Multiport but it seems overkill (and $$$) for my needs.
Thanks in advance for your help,
Peter
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19-09-2021, 20:12
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#2
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Registered User
Join Date: Jan 2020
Location: Hilton Head, SC, USA
Boat: DeFever Raised Pilot House 49
Posts: 237
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Re: Are tee's ok on NEMA 2000 drop cables?
No but just as easy to extend the backbone to the location you want. Add multiple T’s to the backbone extension there and put the terminator back on the end of the last T.
__________________
Jeremy
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19-09-2021, 22:10
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#3
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always in motion is the future

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 20,121
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Re: Are tee's ok on NEMA 2000 drop cables?
Quote:
Originally Posted by serendipitous
Hello all,
I am replacing the display heads over our companionway and will have several N2k displays within inches of each other. Is it ok to tee them off a common drop cable? The geography makes it unwieldy to run multiple drop cables (very narrow channel to run cable) and I prefer not to dead-end the backbone there.
I know that this is the purpose of the Maretron Multiport but it seems overkill (and $$$) for my needs.
Thanks in advance for your help,
Peter
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You can’t do that. If there’s room for two cables, loop the backbone through that area and back, with 2-port or 4-port T-connectors. If there’s only room for one cable, use the Maretron 4-port multidrop.
__________________
“It’s a trap!” - Admiral Ackbar.
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19-09-2021, 22:26
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#4
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Registered User
Join Date: Jul 2005
Location: Bellingham
Boat: Outbound 44
Posts: 9,319
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Re: Are tee's ok on NEMA 2000 drop cables?
Deleted
__________________
Paul
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20-09-2021, 03:13
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#5
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Nearly an old salt
Join Date: Jun 2009
Location: Lefkas Marina ,Greece
Boat: Bavaria 36
Posts: 22,801
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Re: Are tee's ok on NEMA 2000 drop cables?
Actually in practice CAN bus at 250 kB/s is very tolerant of “ unusual “ bus wiring
So it will work
__________________
Interested in smart boat technology, networking and all things tech
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20-09-2021, 07:51
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#6
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Registered User
Join Date: Sep 2016
Location: Lake Erie, PA
Boat: Jeanneau Tonic 23
Posts: 555
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Re: Are tee's ok on NEMA 2000 drop cables?
Goboatingnow is correct that it will "probably" work, especially since most boat networks are not at the extreme limits of NMEA 2000 capabilities and your instruments are close together. To be officially correct, you need to have multiple drops or get a multi drop box such as the maretron multiport box.
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20-09-2021, 10:34
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#7
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Registered User
Join Date: Nov 2014
Location: Atlanta, GA
Boat: Catalina 30
Posts: 711
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Re: Are tee's ok on NEMA 2000 drop cables?
Officially everything I've read says NO but that is in effect what the Marlon box seems to be doing, and it is theoretically NMEA approved.
Are you planning to attach the displays directly to the 'T's?
As mentioned previously, a loop of backbone cable would eliminate any potential issue of using 'T's on drop cables and not require a terminator. If you don't have the space for a loop, ANCOR has 90 degree connectors. Two of these would turn you around in a tighter space. Or you may be able to just run the backbone all the way across.
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20-09-2021, 10:36
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#8
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Marine Service Provider
Join Date: Feb 2012
Location: Vienna, Austria
Boat: Vagabond 47
Posts: 939
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Re: Are tee's ok on NEMA 2000 drop cables?
Ähm. Why do you think they sell it?
As long as you stay on one backbone it is no problem but do not use a T on another T-line
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20-09-2021, 10:44
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#9
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Registered User
Join Date: Sep 2016
Location: Lake Erie, PA
Boat: Jeanneau Tonic 23
Posts: 555
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Re: Are tee's ok on NEMA 2000 drop cables?
Quote:
Originally Posted by OS2Dude
but that is in effect what the Marlon box seems to be doing, and it is theoretically NMEA approved.
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I would think that the maretron multiport box had electronics inside to avoid the power loss and reflection problems that would otherwise occur.
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20-09-2021, 10:48
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#10
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Registered User
Join Date: Dec 2009
Location: Cruising, now in USVIs
Boat: Taswell 43
Posts: 1,055
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Re: Are tee's ok on NEMA 2000 drop cables?
Following. Our 0183 network is dated and showing signs of needed upgrade.
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20-09-2021, 11:00
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#11
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Registered User
Join Date: Nov 2014
Location: Atlanta, GA
Boat: Catalina 30
Posts: 711
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Re: Are tee's ok on NEMA 2000 drop cables?
Quote:
Originally Posted by moseriw
Ähm. Why do you think they sell it?
As long as you stay on one backbone it is no problem but do not use a T on another T-line
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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'. . .
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20-09-2021, 11:06
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#12
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Registered User
Join Date: Nov 2014
Location: Atlanta, GA
Boat: Catalina 30
Posts: 711
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Re: Are tee's ok on NEMA 2000 drop cables?
Quote:
Originally Posted by JBP
I would think that the maretron multiport box had electronics inside to avoid the power loss and reflection problems that would otherwise occur.
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Possibly, but when I looked at the specifications page and wiring diagram on their website, I did not see any mention of such additional wiring. The diagram just shows all the lines connected directly to the drop cable. They could have omitted these details for 'proprietary' reasons. . .
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20-09-2021, 12:35
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#13
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Registered User
Join Date: Jul 2016
Location: West Palm Beach, FL
Boat: Catalina 470
Posts: 1,131
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Re: Are tee's ok on NEMA 2000 drop cables?
Quote:
Originally Posted by serendipitous
Hello all,
I am replacing the display heads over our companionway and will have several N2k displays within inches of each other. Is it ok to tee them off a common drop cable? The geography makes it unwieldy to run multiple drop cables (very narrow channel to run cable) and I prefer not to dead-end the backbone there.
I know that this is the purpose of the Maretron Multiport but it seems overkill (and $$$) for my needs.
Thanks in advance for your help,
Peter
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I work for Maretron, and you can do what you're suggesting, though it is not the ideal/best way of doing things. Just do NOT add another terminator on the end of that multi-tee drop cable. There should only be two terminators, one on each end of the main backbone.
Maretron has a free tool called N2KBuilder. It allows you to graphically lay out your network, and it will warn you of any potential issues. It's not only for Maretron devices, it supports any NMEA 2000 device as long as you can provide information such as the device instance and LEN (load equivalence number). You can download it from Maretron's website at https://www.maretron.com/products/N2KBuilder.php
Regards,
David
__________________
“Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.” – Mark Twain
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20-09-2021, 12:39
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#14
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Registered User
Join Date: Jul 2016
Location: West Palm Beach, FL
Boat: Catalina 470
Posts: 1,131
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Re: Are tee's ok on NEMA 2000 drop cables?
Quote:
Originally Posted by JBP
I would think that the maretron multiport box had electronics inside to avoid the power loss and reflection problems that would otherwise occur.
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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.
__________________
“Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.” – Mark Twain
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20-09-2021, 13:14
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#15
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Registered User
Join Date: Feb 2009
Posts: 80
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Re: Are tee's ok on NEMA 2000 drop cables?
Thanks for the info all.
It sounds like the most correct way is to route the backbone to above the companion way. Unfortunately in my case, the existing channel through the cabin side is bare thick enough for the two SeaTalk1 cables that go there now and simply wont accommodate two legs of a backbone.
I will either use the Maretron Multiport or dead-end (and terminate) the backbone there. Unfort7nately this means a lengthy loop of backbone to serve the instruments at the pedestal and stern and back again amidships to the companionway…
Oh well… if boats were easy everyone would be doing it… [emoji3]
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