Mike Coslo wrote:
Roy Lewallen wrote:
. . .

What will cause it to vary? In any case, just make the capacitance
large enough so the reactance is always small compared to the ground
impedance, then it won't matter.

Well, I could be wrong, but if one side of the capacitor is on the
inside of the hull, and the other side is the sea water, is not the
motion of the ship going to affect that? ships move up and down quite a
bit, and low draft ones can have a *lot* of that hull out of the water,
and then a few seconds later have water coming over the bow.

Well, I was envisioning a plate on some part of the hull which always
had water on the other side. If the hull on the other side of the plate
comes out of the water, you'll of course effectively lose coupling to
the water from that part of the plate. But again, if you make the plate
large enough so that enough of the plate always has water on the other
side of the hull to make a low impedance, the variation won't matter.

Sounds like you might have to make the plate cover a fair portion of the
hull to insure that there's always water on the other side of some of
it. If the entire hull comes out of the water, just remember to say
"mayday" really quick every time the hull hits the water. Other than
that, seems to me you'll probably be too busy to be playing with the
radio anyway.

Roy Lewallen, W7EL