Seatalk re-wire

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Caladh

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I have an ST50 instrument setup with a Type 100 course computer etc. Having just viewed the "rats nest" thread, I will
be looking for 3 core- Seatalk/NMEA type cable but nothing obvious seen when Googling. Others have done this job
so where is a good source of this (non-Raymarine) wire ? I guess I'll need about 10m to do the re-wire.
 
prv said:
JG Tech have it: http://www.jgtech.com/Cable.htm

This is the pukka stuff - red and yellow insulated cores and a bare core for the negative, all tinned. If you want it cheaper, I believe stage microphone cable is a common substitute as it also has three cores.
Click to expand...

Not that it matters but isn't JG Tech's "seatalk cable" 2 cores+shield as opposed to 3 cores? I seem to recall being briefly concerned that they'd sent me the wrong thing when I installed my plotter a few years back. Could be wrong, and in any case it works fine...
 
laika said:
Not that it matters but isn't JG Tech's "seatalk cable" 2 cores+shield as opposed to 3 cores? I seem to recall being briefly concerned that they'd sent me the wrong thing when I installed my plotter a few years back. Could be wrong, and in any case it works fine...
Click to expand...

Well, it's the same as what Raymarine supply. Can't quite remember whether the negative is an uninsulated core or a braided shield - I thought the former but maybe I'm wrong.

Pete
 
prv said:
Well, it's the same as what Raymarine supply. Can't quite remember whether the negative is an uninsulated core or a braided shield - I thought the former but maybe I'm wrong.
Click to expand...

The previously installed (presumably from when the boat was new) seatalk wiring had an uninsulated core. The stuff I got from JG Tech had a braided shield. Of course the standard could have changed at some point: My instruments are ST50s with the round connectors. They changed the connectors with the ST60s, maybe they changed the standard wiring? No idea...
 
laika said:
The previously installed (presumably from when the boat was new) seatalk wiring had an uninsulated core. The stuff I got from JG Tech had a braided shield. Of course the standard could have changed at some point: My instruments are ST50s with the round connectors. They changed the connectors with the ST60s, maybe they changed the standard wiring? No idea...
Click to expand...

I'm pretty sure that Seatalk has always been a third uninsulated core rather than braid, though braid will work. A third core is what I got from JG Tech last year. Are you sure it was Seatalk cable you ordered - if so, possibly they sent you the wrong stuff?

Pete
 
Caladh said:
I guess I need the 4-core. Thanks for the link.
Click to expand...

Well, it'll work if you just ignore one of the cores, but if you're inspired by Nigel's beautiful junction boxes then presumably you'd rather do the job properly, with the proper cable? "Raymarine Seatalk cable loose", on that page.

Pete
 
If there's a bare common return core, it will usually be in contact with a foil shield wrapped round the outside. Don't go for unshielded stuff unless you are sure there is nothing, and never will be anything, to cause electrical interference - actually the echosounder will probably be an interefering busybody as may some LED lights so get the best cable you can afford.
 
Seatalk Cables

I cant' speak for cable used with ST50 models with the round connector but I can positively say that RM used 2 core and shield for all the cables with moulded ST60 crescent shaped connectors supplied for my boat in the period 2000-2010. The shield is not actually woven braid, but as I recall, it was wrapped radially around the red and yellow cores.

The Seatalk signal is 0-12V squarewave so is not particularly prone to interference but the shield has to have the same current capacity as the Red wire as it is the -ve return for the power to instruments, many when they are daisy-chained (up to 13 on a 10m run). A Seatalk power feed is recommended to be fused at 5A.

Using 3 core plus shield the same power capacity considerations apply but I don't believe it provides any better shielding, the down side is you have to manage 4 wires at every termination point and when you connect to cables with a crescent connector you are back to 3 wires and the shield is -ve power. Why mix them?
 

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