Is RF Ground the same as bonding system?

[Newtrawlerowner]

I'm installing a Raymarine Evolution ACU-400 auto pilot on my 2003 Mainship 400. The old system had a green bonding wire connected to the metal case of the old auto pilot computer. The new system is suggesting connecting "the RF ground" and I'm thinking the green bonding wire is what they are asking for. Am I correct?
Thanks in advance.

 

[STB]

The vessel's ground in this context is the battery negative. For RF, you want a really good ground as even small amounts of current flow, induced or direct, can be disruptive.

Some devices just use the negative power wire for the RF ground and hope it is good enough. For many purposes, it generally is.

Other devices provide a /dedicated/ RF ground connection with the idea that it will be connected straight back to the battery, avoiding any possible resistance or current flow from parallel wiring or a bunch of devices powering off of it along the way.

In vessels where there are multiple devices that support a dedicated RF ground, the idea is that one really good connection can be made from the battery negative to a dedicate RF ground terminal block. And then all of the dedicated RF ground wires can be run there, preventing a bunch of wires going to the battery, which is both messy -- and can degrade the ground through stacked contact resistance.

So, the best thing to do is to run this all the way back to the battery negative, or a dedicated RF ground bus bar. The second best thing is to run it back to the primary negative bus bar also used for current conductors. The third best thing to do is to connect it to a nearby negative wire and hope it is good enough. (But, you don't really want to do that for a device that is set up for a dedicated RF ground).

See pages 62-64 and page 72 of the manual and the attached diagrams, in particular. Note wire (3):
-- https://www.raymarine.com/view/index-id=7690.html

(I know the picture shows the RF ground on the SeaTalk-NG cable rather than at the back of the ACU, but it is the same idea).

I hope this helps.

 

[Alaskan Sea-Duction]

The vessel's ground in this context is the battery negative. For RF, you want a really good ground as even small amounts of current flow, induced or direct, can be disruptive.

Some devices just use the negative power wire for the RF ground and hope it is good enough. For many purposes, it generally is.

Other devices provide a /dedicated/ RF ground connection with the idea that it will be connected straight back to the battery, avoiding any possible resistance or current flow from parallel wiring or a bunch of devices powering off of it along the way.

In vessels where there are multiple devices that support a dedicated RF ground, the idea is that one really good connection can be made from the battery negative to a dedicate RF ground terminal block. And then all of the dedicated RF ground wires can be run there, preventing a bunch of wires going to the battery, which is both messy -- and can degrade the ground through stacked contact resistance.

So, the best thing to do is to run this all the way back to the battery negative, or a dedicated RF ground bus bar. The second best thing is to run it back to the primary negative bus bar also used for current conductors. The third best thing to do is to connect it to a nearby negative wire and hope it is good enough. (But, you don't really want to do that for a device that is set up for a dedicated RF ground).

See pages 62-64 of the manual and the attached diagram, in particular. Note wire (3):
-- https://www.raymarine.com/view/index-id=7690.html

I hope this helps.

Awesome post!!! Thanks for sharing..

 

[STB]

I guess I should add that I am assuming you don't have an actual earthed, dedicated RF ground. But, just in case you have one, for example as might have been installed for an Marine SSB or Ham radio, you'd want to use that.

You'd know you had one of those if you had grounding plate(s) on the outside of the boat connected to a thick mesh wire to wish the marine SSB or Ham radio is once once was connected.

I probably should have mentioned that, but jumped ahead, because I figured an amateur radio or SSB operator would have seen this type of thing before.

For the radio folks....I don't think Raymarine is using the RF ground as a significant antenna counterpoise, so I think the connection to battery negative is more important than the ocean or other underlying body of water. (But, there are folks that know much more about radio than me).

Sorry!

 

[FF]

RF grounds not only have the large underwater plate they also seldom are hooked up with round wire.

A 3 or 4 inch wide piece of rolled copper from the antenna tuner to the plate was usually more common.