New chart plotter - shield wire connection

[Carib]

Help please! My new chart plotter has a shield wire. The old one does not. The manual says:

"The power cable supplied with this product includes a dedicated shield (drain) wire for connection to a vessel's RF ground point. The unit can be grounded by connecting the shield wire to the vessel's ground point. On vessels without an RF ground system the shield wire should be connected directly to the negative battery terminal"

How do I know if I have an RF ground point? Assuming I don't, presumably I still just connect the wire to the battery negative terminal although I'm attaching the power wires to the switch panel? The supplied cable won't reach anywhere near the battery so I'll have to extend the shield wire..

I should have know it wouldn't be a case of just plugging it in.. !

 

[pvb]

Just connect the shield to 12v negative at the end of the power cable.

 

[Carib]

Thanks - I reckon I can manage that..!

 

[Travelling Westerly]

Thanks - I reckon I can manage that..!

Have you got an unused dyna plate? I took my SSB system out and used the earthing plate for all my RF drain points

 

[Spirit (of Glenans)]

Can someone explain what an RF drain point is, where it might be found and what it might look like. I've been on this forum a long time and haven't heard of this before.

 

[Baggywrinkle]

It's all about EMI - Electromagnetic Interference - where electrical equipment emits or is susceptible to interference which may or may not cause issues with other equipment in the vicinity.

In laymans terms, cables can be a main source of transfer for EMI, both as a source and receiver. As a source, the cable can either conduct electrical noise to the equipment it is attached to or act as an antenna radiating noise. As a receiver, the cable can pick up EMI radiated noise from other sources and transfer it to the attached equipment. In both cases it MIGHT degrade the operation of the equipment depending on how well it was designed and how sensitive it is to the interference source in the vicinity.

A shield works to prevent EMI in both scenarios.

If your boat has no SSB .... i.e. doesn't have something like this ...



Then just connect it to the 12v negative as already suggested.

A ground plane may be a plate in the hull or a device like this ... KISS-SSB Marine Radio SSB Ground Plane, Icom M802 and all others. | eBay

 

[Carib]

Thanks both - no SSB installed so I'll just use the negative in the switch panel.

That's interesting, Baggywrinkle. I thought it might be to protect against voltage spikes or similar, clearly nothing to do with that.