Re: New VHF antenna = newly discovered electrical leak!

Sv Garulfo


We have a similar issue with our VHF and haven't so far figured out if due to antenna or cabling. (measure of the impedance between the core and shield of the existing system returns a infinite value)

How easy was it to run the new coax cable? What cable length did you get? Is there a dedicated gulley for that cable? Did you find the old cable was damaged by chafing?

On Garulfo, we know the rigging is connected to the bonding system, which we confirmed when tracking a mass leak last year.

As per your mass leak, carbon dust can be the reason for it.

Thomas & Soraya
Garulfo A54-122
Marquesas, FP

On Wed, 20 Nov 2019 at 03:17, Scott SV Tengah <Scott.nguyen@...> wrote:

I’ve had VHF reception and transmission problems and recently replaced my original VHF antenna with a Shakespeare 5215. The male connector threads fit perfectly where the old antenna sat on the masthead, obviating the need for drilling new holes for a mounting bracket. In addition to replacing the antenna, I replaced the outrageously thin RG-58U original coax to lower loss RG8X. There are even thicker and even lower loss cables out there but the thicker cables have minimum bend radii that I’d violate given the routing through the mast so RG8X was my compromise.


I’m not sure if it was the cable or antenna, but my VHF problems were solved and I can now hear and be heard from a much greater distance than before!


However a new issue came up. Because of the way the male connector threads contact the mast, the coax shield effectively connects the mast/rigging to the VHF head unit and the head unit grounding wire then connects it to the bonding system. With this connection made, the Mass- light lit up, indicating an electrical leak! If I disconnected the grounding wire from the VHF head unit body, the mass- goes away. 


It turns out I had an electrical leak going through my rigging for a while now. The evidence was there - rust spots all over the rigging/liferails and some higher than expected (sacrificial?) corrosion on aluminum parts. Per Olivier, it turns out Amel started connecting the mast/rigging to the bonding system around 2009 for this exact reason - an undetected electrical leak in the rigging with boats that don’t get washed often could lead to electrolytic corrosion. 



I would suggest those of you with pre-2009 Amels test for either negative or positive charge through your rigging. If you have a mass tester light and are pre-2009, it will NOT light up unless you make a connection between your rigging and green/yellow bonding system wires. I would think a simple way to make that connection is a temporary jumper wire between the rigging and say the green/yellow wire at your diesel fill-up.


I isolated the leak to my starboard Lewmar V4 windlass motor. It’s the primary one, so I presume age has resulted in carbon brush dust buildup. I assume cleaning it simply involves taking it apart and blowing/wiping away excess carbon dust? Any tips or warnings before I dig into it?

2007 A54 #69
SV Tengah

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