Originally Posted by donradcliffe
I insulated the vhf mount, but a temporary fix would be to disconnect the antenna from the back of the radio
when you are not using it.
Yes, its possible that this could be the cause of your zinc's frying, especially if you have grounded the mast to your keel
Yes, I've started disconnecting my radio, but I'd like to get to a more permanent solution that avoids me forgetting to do this, or forgetting to reconnect before the radio is used.
To an earlier comment, lights and instruments aren't an issue because their fixtures are plastic or otherwise not connecting ground to the mast.
Why do we have this problem? The mast is grounded to our iron keel, the antenna mount and base are not insulated from the mast. This results in our keel being electrically connected to the boat's ground, including our prop. Our keel is not fully encapsulated, though we try. This all creates a battery
that results in about 300 mV. I measured this between the coax connectors when I had them apart.
I could also disconnect the bonding wire between the mast and keel, though I'm pretty sure that would go against ABYC standards.
As far as building my own DC block with a capacitor, I have thought about that too but in the interest of time, I'd just as soon buy one. I have seen several offered but not with the PL-259/SL-239 connectors that I could easily install.