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You mentioned correctly grounding the device several times in your webinar. For a fibreglass sailing yacht, would it be preferable to ground the unit to the DC -ve which is connected to the engine block or the copper SSB ground plates on the outside of the hull?
Hi @Neziak
We would recommend it is grounded to a ground plate on the outside of the hull.
Sometimes this will be shared and a common ground for other electrical equipment.
Thank You
Hi Sam. We don’t involve ourselves in marine work but have several decades of experience in land mobile, cellular, public safety and government communications. So please pardon my really dumb questions []:
I’m guessing you mean “bond” to the ground plate on the outside of the hull rather than “ground” to it. If I’m right, does it make a difference if the watercraft is to be operated in salt or fresh water?
Would you not expect that circuit/path to involve a common, low impedance ground to which all electronics and the vessel’s engine would be bonded? If not, do you have any concerns vis-a-vis differences in potential (actually, everything from low-V/f hum to EMP) between the Peplink device and other components?
Just curious … like I said, we’re really dumb about maritime applications.
Hi Rick
The grounds of the AC, DC, and RF systems on a boat are all “bonded” together. Their common ground is tied to the hull, or to a metal bar attached to the underside of the hull, which makes an electrical connection to the seawater. It’s still referred to ground even though it is going into the sea rather than the ground. This is just a carry over from the term on land based electrical aplications.
Salt water conducts electricity much better than fresh water so the grounding is going to be better in salt water than fresh water.
OK. Entirely logical. TU @Sam_Norris! Is a metal plate/bar always present on the underside of the hull? And, does the surface area vary depending on whether salt or fresh water ops are intended, I wonder?
The ground plates on my boat at the moment are exclusively for the SSB radio. Nothing else is connected to it.
Other devices have their casings connected to DC -ve which through the -ve bus bar is connected to the engine block leading to a prop shaft in the water.
Does this change your thinking about which we should connect the ground to?
Hi @Rick-DC
All vessels will have some metal exposed at some point. All these metal items should be bonded together so they are on the same potential voltage (0V). These will also be bonded to zinc anodes (sacrificial anodes) which need to be replaced regularly.
These anodes show before and after. This type is generally installed inside heat exchangers on engines.
This image shows anodes on the external part of the hull. Each one of these are mounted on bolts which should be bonded together.
The surface are should be calculated for worst case scenario e.g. fresh water operations but in fresh water you will have less corrosion issues so the anodes are not required as much.
Hi @Neziak
SSB radios should be grounded according to manufactures instructions. Icon have a pretty comprehensive article about this which pretty much mentions grounding to as many possible metal objects below the water line as posable. On a sailing yacht, a lead keel would be sufficient. This lead keel and other metal objects should already be bonded together to allow the anodes to work. http://www.icomcanada.com/techbulletin/tb1/antena_grounding.pdf
Thanks for the Icom document. This is very educational. Icom make the distinction between and RF ground and a D.C. ground. They indicate that it is good practise that they should be independent. This is how our boat is set up. An RF ground for the SSB to a Copper plate on the side of the hull and a D.C. ground through the -ve to the engine block.
Should the Peplink casing (ground screw) be bonded to the RF ground by copper foil or to the D.C. ground (or DC -ve in our case) by normal round wire to the engine block?
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