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Old 31-07-2018, 09:35   #1
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Cutting / splicing a Simnet Ethernet cable

Has anyone had luck cutting and then splicing a sim net Ethernet cable?

Ld
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Old 31-07-2018, 10:07   #2
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Re: Cutting / splicing a Simnet Ethernet cable

I don't recall anything special about it. It's just a 5 wire cable. What's the issue?
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Old 31-07-2018, 10:56   #3
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Re: Cutting / splicing a Simnet Ethernet cable

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Originally Posted by lamadriver View Post
Has anyone had luck cutting and then splicing a sim net Ethernet cable?

Ld
No idea about simnet, but cat 5 ethernet for computers can't be spliced. Something to do with the twisted pair etc. If you really have to do it buy a coupler, but its still not recommended (for computer networks).
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Old 31-07-2018, 11:56   #4
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Re: Cutting / splicing a Simnet Ethernet cable

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Originally Posted by Macblaze View Post
No idea about simnet, but cat 5 ethernet for computers can't be spliced. Something to do with the twisted pair etc. If you really have to do it buy a coupler, but its still not recommended (for computer networks).
I wouldn't say "It can't be spliced".. However, by splicing it you run the risk of introducing cross-talk in the pairs (which is what the twist removes). If you splice it carefully and only untwist a couple of inches of the wires, then you won't have any problems.

Pretty sure Simnet is exactly the same. Splice it carefully without removing a bunch of the twists.
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Old 31-07-2018, 12:16   #5
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Re: Cutting / splicing a Simnet Ethernet cable

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Originally Posted by travellerw View Post
I wouldn't say "It can't be spliced".. However, by splicing it you run the risk of introducing cross-talk in the pairs (which is what the twist removes). If you splice it carefully and only untwist a couple of inches of the wires, then you won't have any problems.

Pretty sure Simnet is exactly the same. Splice it carefully without removing a bunch of the twists.
"...can't be spliced by me" :-)
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Old 01-08-2018, 22:09   #6
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Re: Cutting / splicing a Simnet Ethernet cable

If you are really worried just put an rj45 connector on each end with a coupler

Or splice with those 3m gel filed connectors that yiu sweeze on the side. Not sure what called. For Telecom
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Old 01-08-2018, 23:42   #7
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Re: Cutting / splicing a Simnet Ethernet cable

Are we talking about SimNet or about Ethernet? They are not the same. But either way, they can be spliced and/or connectorized in the field.

SimNet is just Simrad's version of NMEA 2000, which is a 250kbit/s serial signalling system based on CAN. The cable carries power (up to 5A per spec) on one pair (usually larger) and differential signalling on a second pair (usually smaller). The cable is shielded, making for a 5th "connection."

The NMEA 2000 specification allows for either standard connectors or terminal strips for connecting the cables:

Quote:
Two methods are provided for connecting to the network backbone cable: barrier strips or a standard cable and connector. These connections are used for connecting segments of backbone cable together, for connecting terminations at the two ends of the cable, for connecting the network power source, and for connecting nodes.

Barrier strips are only recommended when the connections are made in a protected location, or when they are installed in a weatherproof enclosure, thus meeting the requirements for Resistance to Environmental Conditions for exposed equipment in IEC 60945. Barrier strips positions must be either numbered or color-coded in accordance with the definitions in the standard.
Click image for larger version

Name:	<a title=NMEA 2000 Terminal.PNG Views: 80 Size: 87.7 KB ID: 174748" style="margin: 2px" />

Depending on your environment you may or may not introduce noise by breaking the shielding at a terminal strip. This can be alleviated/reduced by installing the strip in a metal box (aluminum?) and electrically connecting that box to the shield terminal.

Since all of that works within the standard splicing the same cable is just not that far away. Best practice would be to maintain the shield. There are products made to do this, or you can get a piece of tinned copper braid (if you have a piece of larger coax cable you can just grab a little braid from that), slide it over the cable before splicing, then spread it over the splice area and connect to the shield on both sides.

OTOH hand, if you are talking about Ethernet at either 10Mbits/s or 100Mbits/s (don't know of any marine systems using Gig yet, but wouldn't be surprised) then you are probably better off connectorizing rather than splicing. Properly installed connectors minimize untwisting and result in less cross talk introduction than having to untwist 4-5 twists on each side in order to get a splice in place.
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Old 01-08-2018, 23:57   #8
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Re: Cutting / splicing a Simnet Ethernet cable

Simnet has been dropped now, but yes since it's just a basic 5 wire canbus connection it can be spliced. The problem is the tiny wires make it difficult. You can use a block connector but they are bulky and ugly.
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