NAVTEX NX-300 Grounding



I'm installing the NX-300 as a stand alone unit without connection to other nav systems or to a PC.
My concerns arise from the paragraph on page 6-4 of the manual beginning with this sentence: "The signal ground and the frame ground are separated, however the power line is not isolated."...
The negative terminal of my battery is connected to the engine block (and to seawater through the propshaft) then from the block to the negative DC distribution panel.
The boat also has about 50 ft of copper foil running along the fiberglass hull and connected to an external lead keel. There is no SSB currently installed but I may install an SSB in the future and make use of the copper foil as counterpoise.
The NX-300 will be installed within 3 ft of both the DC distribution panel and an exposed portion of the copper foil.
Shall I connect the ground wire from the wing nut on the back of the receiver along with the black wire from the cable assembly to the negative DC distribution panel? Should I connect the bare wire from the cable assembly to the negative DC distribution panel also?
The Power cable (Red+ [Fused] and Black-) should be connected to your power system. The bare shield of the power cable should NOT be connected to anything. It is internally grounded to ground out any EMI. If you were to connect it, it would provide a path of electrical flow and result in grounding loops or power differential issues. The Chassis ground (Flynut/wingnut) at the back of the display should at no time be connected to the same electrical point that your power Negative (Black-) is connected to. The chassis ground should be connected to a dedicated grounding system in which it makes water contact via a suitable hull/grounding plate. It is NOT recommended to attach the chassis ground to anything other than a proper grounding system. If you attach a ground wire from the equipment, to a non-ground, you either just attached an antenna or worse; depending on what you attached the wire to.

Thanks for reply.

Neither the cable assembly nor the red wire is shielded. The cable assembly consists of 6 colored wires (w,b,y,g,r,bk) and 1 twisted strand bare tinned wire of about 28AWG. Both the red and black wires are fused. I'm good with the red and black wire. I'm good doing nothing with the other four colored wires. But what is that bare twisted strand wire for, and what do I do with it?

On the diagram on p. 6-3 the wing nut ground isn't named. Page 6.4 uses the terms signal ground and frame ground. I'm assuming that what you call "chassis ground" is "frame ground" aka the wing nut ground. And that a >1.25 sq mm = about 14AWG wire from the wing nut needs a dedicated ground to seawater.

Right away I can rule out pulling the boat and drilling holes to install a Nx-300 dedicated dynaplate. Of the following choices, which do you think is the best course?

1. Bypass the distribution panel and connect it directly to the engine block.
2. Connect it to the aforementioned copper foil which is connected to the external lead keel.
3. Connect it to the existing dynaplate which is the ground for the 8 shrouds which extend up the mast. The dynaplate is also connected, by order of my insurer, through a keel bolt to the external lead keel.
4. Connect it to a bronze seacock.
5. Punt.

A complicating factor: My next install is an already purchased Fax30... Does that need its own seawater ground also?

Thanks for your assistance!

Regards, Pat
Officially everything needs to have a proper ground. In the real world, most smaller boats tend to leave the fly nut "as is" because they don't have a dedicated grounding system. The "twisted strand bare tinned wire " is the end of the cable shield wire. I recommend you don't connect it to ANYTHING. Furuno has started fusing the black (Neg -) on many of the newer cables, to provide extra protection. Nothing I said prior, changes. The Chassis (frame) ground (flynut) should not go to the same electrical point as the negative powering the unit. As a Furuno rep I have no choice be repeat "officially" you should have a proper dedicated ground for your electronics.
Ok. One last clarification: By "as is", you mean that most smaller boats do not connect the fly-nut/wing-nut ground to anything?