Will writes:

I want to set up a hf antenna for my sailboat.

I have read various guides from Icom etc.

They suggest running copper foil to a Dynaplate and use sea water as
the ground. How can this work when the Dynaplate is below sea water?

Is sea water equal to copper wire radials as a RF ground system?

Does sea water make a good enough ground without radials?

How can a piece of copper metal about 1 ft square equal several
radials laying on the boats deck?

Why do i have to use copper foil when most other people suggest using
ordinary copper wire?

Over seawater what would be the best number of radials to use
considering that maximum length i can run is 40 ft. I am planning to
use a backstay antenna with a SGC 230 Tuner.

All ideas and comments appreciated.

Well, I don't have personal experience with this. There is a chapter
in the ARRL antenna book, and it basically agrees with ICOM. As to
radials - two comments. First - how do you make sure that they don't
get in the way. And that RF currents won't be a hazard to
people. Second - there are plenty of wires on a yacht. How do the
wires know whether or not they are supposed to act as radials?

*If* there is a better alternative to the traditional backstay using
seawater as ground, it might be the vertical dipole. Feeding would be
tricky, but for single band operation, you could probably feed it
like a J-Pole. I don't see how to make a multiband variant. And you
get the high voltage points close to the deck, which doesn't sound
like a good idea in a damp and salty environment.

There are also people who hoist a horizontal dipole when needed. OK
for recreational radio, not if you need to be able to communicate in
rough weather.

Of course, square riggers are beautiful, and you could use the
yard-arms as a stacked yagi.

73
LA4RT Jon