Roy Lewallen wrote:
Michael Coslo wrote:


Back around the beginning of this thread a thought occurred to me,
and I'm surprised that no one else mentioned it.

Unless we are planning on putting out ship on the great Salt lake,
of one of the few other salt water inland lakes or seas, we're going
to be putting the thing in the ocean.

Immediately, one sees that if a ground is at the surface of the
water, at many points it will be 4 or more feet under the water. Dem
boats rock! There are moments that it will be quite a distance under
water, depending on the sea state.


Use a bare wire, and the top few inches will do the job regardless of
how much additional wire goes below the water. As I've said before,
there's no harm in having additional wire below the water; it simply
doesn't do anything useful.

The problem is that as the boat rocks, the length of the wire to the
ocean surface will vary in length, which will change the antenna's
impedance. So a plate just inside or outside the bottom of the hull (or
someplace that's always below the water line) would seem to me a better
idea from a practical standpoint. Surely some boater who understood
basic electromagnetics has thought about this and devised a method
that's both practical and effective.

Depending on the load, the water line is going to be different,
and will be changing constantly as fuel and food is used.

Certainly any capacitive coupling through the hull makes for a
variable capacitor? Does this have an effect?


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.

Will we eventually come to the conclusion that we can't put radios on
ships?? ;^)


It wouldn't surprise me if some folks reach that conclusion. Millions
firmly believe much more ridiculous things.

Hehe, I've seen that actually happen....


- 73 de Mike KB3EIA -