Sea Talk NG cable - anything special?

[Cantata]

Having recently bought an autopilot kit, I'm thinking about locating the components around the boat. The Raymarine kit comes with a set of wiring for Sea Talk NG. Extra extension cables are bloomin pricey.
Old Sea Talk cables were nothing special and could be happily extended by patching in regular wiring. Anyone know what's inside Sea Talk NG cables? Bit drastic to cut one to find out...!

 

[Ric]

Well I have cut and spliced two spur cables today as it was not possible to pass the end-connectors through the various tubes and gaps. They are definitely well constructed and a lot of effort seems to have gone into making them robust and resistant to EM interference.

The first spur cable I cut open had four wires - red/black for power and white/blue for data, plus a shield filament cable. The construction was like an ethernet cable - red and black twisted together with their own foil shield, and the white/blue twisted with their own foil shield. Intertwined with all of this was a fabric reinforcement.

Surprisingly, the second cable, which was a bit longer but otherwise identical to the first externally (white/black), had a fifth wire (yellow). I presume this is to guarantee data integrity over a longer overall length.

I very carefully soldered the joins and rebuilt the twists, foil shields and reconnected the filament shield and the performance seems ok. However, given the effort which Raymarine have put into these cables (compared to Seatalk1) my guess is that the performance would be very poor if you just bodged a length of 4/5 filament flex between two end plugs.

 

[prv]

Surprisingly, the second cable, which was a bit longer but otherwise identical to the first externally (white/black), had a fifth wire (yellow). I presume this is to guarantee data integrity over a longer overall length.

Actually I think there are some flavours which include an original ST1 core for backwards compatibility. Yellow would make sense for that.

Pete

 

[Cantata]

Thanks Ric, very timely and useful response! I think I may end up buying some extra cables...

 

[Hoolie]

NMEA2000 connectors are 5-way including sheild. Seatalkng is a 6-way connector that adds a seatalk1 connection. Raymarine do an NG to 1 connecting cable.

 

[lpdsn]

I've a damaged spur cable I picked up in a boat yard

Basically it is four wires in two pairs. The power and signal pairs are separately shielded then the whole lot is shielded too. I haven't taken it apart enough to see if the pairs are twisted.

I've also seen photos on the web that show a bit of variation, so maybe Raymarine aren't that fussy themselves.

The backbone cable is higher rated than the spur cable.

NMEA2000 is not exactly a state of the art bus. Bog-standard (I don't know the actual reference of that standard off the top of my head) Ethernet cable is designed for 100Mb.

If I were doing it again, I'd make as much of the bus as possible standard DeviceNet. Not cheap either, but there are various options and it will save a bit over Seatalk ng.

There's also an Actisense box that allows you to wire in two backbones and four spurs. Also allows you to power the two backbones from separate circuits if you want to be that fancy. You could make your own shielded junction box if you really wanted to.