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Old 17-02-2012, 17:07   #1
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Marine-grade wire for NMEA signals

I'm installing a class B AIS transceiver up at the nav station, and I need to connect it to my chartplotter back at the helm.

I can't find any 8-conductor 20 to 22 gauge marine rated-wire, so what's the best wire to use for this application?

Do I need twisted-pair? Will regular cat-5 cable work? (I know it will work, but will it last?)

I ripped out all the wiring the PO had installed, as he had just used regular clear-jacketed Radio-Shack quality speaker wire to connect the GPS to the autopilot, and it was black with corrosion from one end to the other.
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Old 17-02-2012, 17:15   #2
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Re: Marine-grade wire for NMEA signals

You don't need 8 conductor wire to send NMEA. A two conductor wire will work fine. You also don't really need tinned wire unless perhaps you are in a very corrosive environment, such as outside the boat. It does not need to be twisted either. Cat 5 or cat 6 cable will work but you don't need that many conductors.

If you think the ends might be exposed to moisture then use a heat shrink crimp connector and put Tef-Gel on the connector to displace any water that might cause corrosion.
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Old 17-02-2012, 19:30   #3
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Re: Marine-grade wire for NMEA signals

Here's a link for twisted pair wire. I found it in my searches, haven't used it so can't vouch for it and I'm not affiliated with the vendor. They don't state if it's tinned.

NMEA 0183 BiDirectional Twisted Pair Cable | Blue Heron Marine Electronics
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Old 17-02-2012, 20:10   #4
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Re: Marine-grade wire for NMEA signals

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Originally Posted by David M View Post
It does not need to be twisted either.
However, twisted-pair is not a bad idea at all. I don't always use it, especially for short runs, but for long runs I prefer twisted when I have it available. The twisting reduces the interference coming from other wires in close proximity.
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Old 17-02-2012, 20:51   #5
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Re: Marine-grade wire for NMEA signals

It needs to be shielded twisted pair, with the shield connected to the transmitter (NMEA speaker) side ground --only--.

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Old 17-02-2012, 21:02   #6
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Re: Marine-grade wire for NMEA signals

It does not absolutely need to be twisted. I have untwisted wire running NMEA everywhere in my boat and it actually works. Imagine that! Twisting it reduces the chance of electrical noise caused by inductance from other wires.
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Old 17-02-2012, 21:08   #7
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Re: Marine-grade wire for NMEA signals

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It does not absolutely need to be twisted. I have untwisted wire running NMEA everywhere in my boat and it actually works. Twisting it reduces the chance of electrical noise caused by inductance.
Exactly, inductance from sources like SSB or radar are why it should be twisted pair. In perfect conditions it'll work with cloth hangers as conductors, but it is for tough conditions that these specs are designed. The shielding and twisted pair work together to keep the boat going straight ahead even when radar or SSB or microwave etc. are used.

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Old 18-02-2012, 11:17   #8
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Re: Marine-grade wire for NMEA signals

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Originally Posted by oldjags View Post

I can't find any 8-conductor 20 to 22 gauge marine rated-wire
Marine Shielded Signal Cable Wire 20/8 AWG - 25 ft: 91195025 Genuinedealz
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Old 18-02-2012, 12:45   #9
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Re: Marine-grade wire for NMEA signals

OK, that's the stuff I'm looking for! Thanks.

I know I don't really need 8 conductors to run a NMEA signal, but I figure if I'm going to run a signal cable, I might as well have enough conductors to take care of any future needs, plus some spares just in case.

The AIS unit I'm installing has 1 High speed NMEA In and out, 1 low speed In and out, and 1 NMEA 2000 connection. I don't have anything else that's 2000 - compliant yet. But if my chartplotter goes tits-up, maybe I can use my laptop to control the autopilot from the nav station if necessary if I have enough wires going back and forth.
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Old 18-02-2012, 14:28   #10
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Re: Marine-grade wire for NMEA signals

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Originally Posted by s/v Jedi View Post
Exactly, inductance from sources like SSB or radar are why it should be twisted pair. In perfect conditions it'll work with cloth hangers as conductors, but it is for tough conditions that these specs are designed. The shielding and twisted pair work together to keep the boat going straight ahead even when radar or SSB or microwave etc. are used.

ciao!
Nick.
You said "must". I said not absolutely necessary. "Probably should" is most accurate for twisted wire because twisted wire is not absolutely necessary for it to work, but a good idea none the less.
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Old 18-02-2012, 14:30   #11
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Re: Marine-grade wire for NMEA signals

try direct burial cat 5e. pretty cheap because it isnt labeled marine.
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Old 18-02-2012, 14:33   #12
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Re: Marine-grade wire for NMEA signals

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try direct burial cat 5e. pretty cheap because it isnt labeled marine.
Agree. Ubiquity "ToughCable" is pretty good.

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Old 19-02-2012, 09:55   #13
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Re: Marine-grade wire for NMEA signals

Is the fact that cat5 cable is solid conductor and not stranded not an issue?

And those thin little wires are designed to be terminated with a punch-down tool in a cat5 terminal. How well do they work with crimped or screw terminal connections? Just nicking one of the wires when you try to strip it will eventually cause it to break if there's any vibration or regular movement at the connection.

I just don't know if you can trust solid conductor wires in a boat, even if they are designed for outdoor burial service.
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Old 19-02-2012, 15:43   #14
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Re: Marine-grade wire for NMEA signals

OK, I just installed an Icom Class B tranceiver.

It's a neat unit and has 3 NMEA outputs.

Problem is that it uses a sub-D 15 pin connector and to get all functionality you need all 15 wires. VGA cables use the same connectors but do NOT use all wires, apparently only use 8 or 9.

I did find a sub D 15 pin break out box, but I want to mount it a few feet away from the AIS. The supplied cable, which has microscopic wires (~24AWG) is only 12 to 15 inches long.

So now I have to find a 15 conductor, stranded 15 pin sub D to 15 pin sub D cable.

Hint, NOT Radio Shack!!!!!!!!!!
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Old 19-02-2012, 15:56   #15
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Re: Marine-grade wire for NMEA signals

Quote:
Originally Posted by oldjags View Post
OK, that's the stuff I'm looking for! Thanks.

I know I don't really need 8 conductors to run a NMEA signal, but I figure if I'm going to run a signal cable, I might as well have enough conductors to take care of any future needs, plus some spares just in case.

The AIS unit I'm installing has 1 High speed NMEA In and out, 1 low speed In and out, and 1 NMEA 2000 connection. I don't have anything else that's 2000 - compliant yet. But if my chartplotter goes tits-up, maybe I can use my laptop to control the autopilot from the nav station if necessary if I have enough wires going back and forth.
There is no point and in fact your making things harder for yourself in installing more pairs then needed. 2K uses a fixed connector, so to utilize the spare pair, you have to gunter the cable to access the extra pair. Thats a mess and interferes with the integrity of the cable

Pull a proper NMEA 2K stranded twisted pair/shielded cable. In you want extra pairs pull an additional cable.

dave
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