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+--- Thread: Wiring the shield? (/thread-1702.html)
- fish2live - March 20, 2012
I've been doing a rewire of my electronics and there is a detail I don't fully understand. Some of the wires are shielded. Some of the shielded wires have also been cut. I'm trying to learn some rule about when or how to connect the shield to something else.
On some things, like my Shipmodul multiplexer, there are a/b connectors plus a shield connector. I read somewhere that the shield only gets connected at one end of the wire. Which end, and how do I know that?
My current understanding (that is, a guess) is this: the shield captures stray RF signals that might induce electrical noise and routes them to ground. Since "ground" means several things on a boat, in this example I am referring to grounding in its strictest sense; providing an entirely separate alternate path to source, which here is the negative terminal of the battery.
Now, if the shield is connected to a ground in the device, and that device has a ground terminal on the back of the case, it seems that connecting a wire shield at both ends must allow current to flow continuously along essentially the same path, rather than a separate alternate path back to the negative terminal. I suspect that I'm missing an important detail here. Would the shield become a more powerful antenna (thus making electrical noise worse) if it is connected at both ends?
To confuse matters, it appears from the schematic in my radar that the shield up to the array is connected at both ends.
Surely there is some good information somewhere to understand this, but so far I have not located it. Can anyone else explain this problem? Surely we've all faced the issue before, and no doubt many incorrect solutions have been created.
- GPSNavX - March 20, 2012
You might get a wider response posting on more general purpose forums like ..
http://www.cruisersforum.com/forums/
http://www.thehulltruth.com/marine-electronics-forum-19/
- iaanhayden - April 22, 2013
The shield should be attached to ground (chassis) as close to the cabinet entrance issue as likely. The shield is attached utilizing a clamp or an ENC-safe twisted cord gland (PG-gland) or other procedure that can ensure an efficient high frequency attachment.