Reg, G4FGQ wrote:
"Anything you toss into the sea water makes a good ground."

Certainly correct if "anything" is a low-impedance RF path.

If "skin effect" prevents penetration to a copper plate on the hull,
fine. RF has then made the transfer to the sea at a shallow depth.
That`s the goal.

Best regards, Richard Harrison, KB5WZI

In article ,
(Richard Harrison) wrote:

If "skin effect" prevents penetration to a copper plate on the hull,
fine. RF has then made the transfer to the sea at a shallow depth.
That`s the goal.

Bull****, where do you guys come up with this stuff....Skin Effect is a
a Boundry Thing, and the hull of the vessel is the "Boundry of the Sea
Water" even if it is 10 feet below the sea surface.

You wrote:
In article ,
(Richard Harrison) wrote:

If "skin effect" prevents penetration to a copper plate on the hull,
fine. RF has then made the transfer to the sea at a shallow depth.
That`s the goal.

Bull****, where do you guys come up with this stuff....Skin Effect is a
a Boundry Thing, and the hull of the vessel is the "Boundry of the Sea
Water" even if it is 10 feet below the sea surface.

Finally someone gets it! This is what Roy said way back in his first
report of his modeling, that the ground plate if fastened to the hull
will be on the surface of the water even if it happens to be several
feet below. The other side of the ground plate is air. In other words
the hull is displacing the water. Unless of course the boat has sunk.

For the guys that are referencing the N6?? Article about very short
elevated radials over sea water; please note that he is saying those
short elevated radials are tuned with loading coils.
Elevated radials will not work unless they are 1/4 wave resonant or
tuned with a loading coil.

73
Gary K4FMX

wrote:
You wrote:
In article ,
(Richard Harrison) wrote:

If "skin effect" prevents penetration to a copper plate on the hull,
fine. RF has then made the transfer to the sea at a shallow depth.
That`s the goal.
Bull****, where do you guys come up with this stuff....Skin Effect is a
a Boundry Thing, and the hull of the vessel is the "Boundry of the Sea
Water" even if it is 10 feet below the sea surface.

Finally someone gets it! This is what Roy said way back in his first
report of his modeling, that the ground plate if fastened to the hull
will be on the surface of the water even if it happens to be several
feet below. The other side of the ground plate is air. In other words
the hull is displacing the water. Unless of course the boat has sunk.

It is interesting to speculate about the
proportion of displacement currents passing
through the air to the inside of the hull and then
through the hull to the grounding plate, vs. the
proportion passing from the surface along the
water-hull interface to the Dynaplate.

As Roy pointed out, one reason seawater "works"
despite its low conductivity relative to copper is
that a high percentage of the "ground" return
current is concentrated very close to the antenna
where path conductance is high. If the water path
from the surface to the Dynaplate is vertical
(four feet) does that mean return currents must
pass through four additional feet of seawater and
thus will encounter greater losses than if the
Dynaplate were at the surface?

Or will the vertical water path "collect" the same
or even greater return currents than a horizontal
water path? I've heard of radials sloping up and
away from the antenna at 45 degrees, but 90
degrees? (Assumes tuner ground terminal directly
adjacent to Dynaplate on other side of hull) Ought
to be easy to model.

Interesting, no?


For the guys that are referencing the N6?? Article about very short
elevated radials over sea water; please note that he is saying those
short elevated radials are tuned with loading coils.


Yes. That is what he reported on his modeling.

Elevated radials will not work unless they are 1/4
wave resonant or
tuned with a loading coil.

This is not at all obvious to me except at a
semantic level. And lest anyone misunderstand,
Gary is not suggesting that N6LF made that statement.

Is an automobile body (on land) conceptually
analogous to non-resonant, elevated radials? Does
it work? Would it work less well over seawater
(let it levitate or make very quick QSOs)?

Would a random length whip on HF work with a tuner
and a single, non-resonant wire about 25 feet
long, in lieu of the auto body? Would it work less
well over seawater?

If you're with me this far, the next question is
"how much better or worse?". And then on to the
other tradeoffs: radiation patterns, safety,
simplicity, RF coupling, etc.

Alternatively, we can explore why it won't work.


73
Gary K4FMX


73,
Chuck
NT3G

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chuck wrote:


As Roy pointed out, one reason seawater "works" despite its low
conductivity relative to copper is that a high percentage of the
"ground" return current is concentrated very close to the antenna where
path conductance is high. If the water path from the surface to the
Dynaplate is vertical (four feet) does that mean return currents must
travel along four additional feet of seawater (at the hull-water interface)
and thus will encounter greater losses than if
the Dynaplate were at the surface?

OOPS!

"pass through" should be changed to "travel along"
and the parenthetical expression (at the
hull-water interface) should be added for
clarification. Text above has been so edited.

Sorry about that.

Chuck

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Chuck wrote:
"If the water path from the surface of the Dynaplate is vertical (four
feet) does that mean return currents must travel along four additional
feet of seawater (at the hull-water interface)---?

Maybe, but there is a lot of area in that path. The hull-water interface
includes the entire submerged surface of the hull. It has been assumed
in this thread that the sail-boat hull is fiberglass, an insulator. The
impedance of fiberglass is vastly different from that of seawater.

The great mismatch between fiberglass and seawater means a radio wave
traveling along one of the surfaces won`t be readily absorbed into the
other.

Dynaplate is a name given copperfoil on a roll. Dynaplate is also a name
given a copper plate which has been etched to increase surface area
thereby increasing its contact area with water.

The surface of seawater contacting a boat hull is continuous with the
horizontal surface of the sea.

Vertical polarization is effective over seawater. Horizontal
polarization is ineffective. The sea short-circuits the voltage wave.

A horizontal wire can produce vertically polarized radiation. The
Beverage antenna works over poor soil. On page 720 of Kraus` 3rd
edition of "Antennas" is the "Flush Disc" antenna which produces
vertically polarized radiation over a highly conductive surface. It`s a
radiator in a pit and should be useful in a vessel.

Best regards, Richard Harrison, KB5WZI

Chuck wrote:
"If thee water parh from the surface to the Dynaplate is vertical (four
feet) does that mean return currents must pass through four additional
feet of seawater and thus encounter greater losses than if the Dynaplate
were at the surface?"

Well, the Dynaplate is at the surface of the water in contact with the
hull. That surface makes a turn to the horizontal at the sea surface.

The Dynaplate could also be connected by copper strap(s) on the
extertior of the insulated hull so as to contact the sea at a shallower
depth depending on the list (tilt) and trim of the boat. Capacitive
coupling through an insulated hull is usually comparatively easy at RF.

Best regards, Richard Harrison, KB5WZI