On Tue, 30 May 2006 09:21:56 -0400, chuck wrote:

If anyone spots any errors of fact or significant omissions, I'd welcome
appropriate "recalibration". Thanks in advance.

1) Grounding plates

Will not work if submerged as much as four feet

Hi Chuck,

Don't know how you got this miss-impression.

2) Wire in water

A one-foot length of wire immersed near water surface is sufficient for
near-perfect results based on W7EL's NEC-4 model results. Assumed
performance is similar to grounding plate.

This conclusion is conflict with the first, making it a mystery how
you came to either in summary. The focus on "water surface" is as
though you are trying to force it work like a pool of mercury. Water
is NOT a ground plane in the sense of conductivity. Water is a
terrible conductor. It is only its huge mismatch with air that gives
it such superb propagation, not match, characteristics. Distinguish
between the two.

3) Radials

Even shortened (loaded) radials elevated over seawater work as
near-perfect based on N6LF's NEC-4 modeling. Objections to radials are

The objections are they are wholly unnecessary when ground is so
easily achieved by conventional means. You would need 120 radials to
shield against the loss you perceive, and that loss doesn't matter
when you stand to gain so much in propagation. You couldn't even
field a tenth of these radials. At HF, and maintaining their tune
and symmetry, you would be lucky to fit in 2. At that stage of the
game, there is absolutely no match advantage over conventional
techniques aboard a small craft (and at HF you don't qualify for any
thing other).

4) Counterpoise (i.e., mast, forestay, shrouds, lifelines, engine, metal
tanks, 100 square feet of copper, keel, rudder, etc. bonded together)

This type of
counterpoise is also the approach recommended by both Icom and SGC.

Only because it is already available and doesn't ask you to go any
further for no obvious advantage.

5) OCF dipole w/horizontal component along deck

Not commonly used,

Who would choose a complicated design over so many simple ones?

Is that where it stands, folks?

If you want a dipole, make a VERTICAL dipole, even a lousy one.

Finally, and to repeat, learn the distinction between matching and
propagation. Your focus on matching issues is like seeing your glass
3/4ths empty. Looking at the propagation advantages in comparison is
like seeing a pitcher of water nearby that will fill that glass a
dozen times.

73's
Richard Clark, KB7QHC

Richard, there you go again, overcomplicating quite simple matters
with your Shakespearian, Queen Elizabeth the 1st English.

Anything you toss into sea water makes a good ground.

You can consider the connecting lead to be a part of the ground sytem
or a part of the antenna. Take your pick. You will get precisely the
same answers, on analysis, whatever you do.
==========================================

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 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

Richard Clark wrote:
On Tue, 30 May 2006 09:21:56 -0400, chuck wrote:

If anyone spots any errors of fact or significant omissions, I'd welcome
appropriate "recalibration". Thanks in advance.

1) Grounding plates

Will not work if submerged as much as four feet

Hi Chuck,



Hello Richard,

Perhaps the context for the summary was unclear.
My objective was simply to identify several
existing recommendations for obtaining RF grounds
on plastic and wood vessels over sal****er.
Regrettably, I lack knowledge of any published
theoretical or empirical comparison of these
proposals that provides an objective, quantifiable
measure of performance.

Don't know how you got this miss-impression.


That it will not work if submerged as much as four
feet? From Roy's report on his NEC-4 modeling. It
is presumably based on the known skin depth of RF
at 14 MHz.

2) Wire in water

A one-foot length of wire immersed near water surface is sufficient for
near-perfect results based on W7EL's NEC-4 model results. Assumed
performance is similar to grounding plate.

This conclusion is conflict with the first, making it a mystery how
you came to either in summary. The focus on "water surface" is as
though you are trying to force it work like a pool of mercury. Water
is NOT a ground plane in the sense of conductivity. Water is a
terrible conductor. It is only its huge mismatch with air that gives
it such superb propagation, not match, characteristics. Distinguish
between the two.


Well, some of what you are saying is pretty much
what I had thought. If you read my posts on the
other thread, you'll see where I was heading.

We agree that seawater's conductivity is lower
than copper's but greater than earth's. We agree
that a single ground rod driven into the earth
will perform poorly as the only return path for a
vertical antenna over land, but at least in some
cases will perform better than if it were not
there. Will a wire dipped into the sea perform
better than the ground rod driven into the earth?
I doubt there is much disagreement on that, even
though water might be characterized in relative
terms as a "terrible conductor". The only relevant
question, then, is "how much better?" and so far,
the only numerical answer that I am aware of has
come from NEC modeling.

The characterization I reported of a wire dipped
into the sea is based on Roy's modeling, assuming
I have not misunderstood of course. Others have
made the same point, but now we have model results
to support it.

BTW, I have just discovered a response from Roy to
one of my posts on the other thread that is
available on Google, but has never shown up on
either of the two newsgroup subscriptions I have.
Roy addressed some of my concerns in that post so
if you have not seen it you might do a search for
it on Google.


3) Radials

Even shortened (loaded) radials elevated over seawater work as
near-perfect based on N6LF's NEC-4 modeling. Objections to radials are

The objections are they are wholly unnecessary when ground is so
easily achieved by conventional means. You would need 120 radials to
shield against the loss you perceive, and that loss doesn't matter

What loss is it that I perceive? N6LF's results
show near lossless results with only four
shortened radials over seawater.

when you stand to gain so much in propagation. You couldn't even
field a tenth of these radials. At HF, and maintaining their tune
and symmetry, you would be lucky to fit in 2.

Other studies have shown a single elevated radial
over land to lose less than one dB over a perfect
ground plane.

At that stage of the
game, there is absolutely no match advantage over conventional
techniques aboard a small craft (and at HF you don't qualify for any
thing other).

4) Counterpoise (i.e., mast, forestay, shrouds, lifelines, engine, metal
tanks, 100 square feet of copper, keel, rudder, etc. bonded together)

This type of
counterpoise is also the approach recommended by both Icom and SGC.

Only because it is already available and doesn't ask you to go any
further for no obvious advantage.


Well, what makes life interesting is that to
advocates of the other approaches, there are
obvious advantages.

5) OCF dipole w/horizontal component along deck

Not commonly used,

Who would choose a complicated design over so many simple ones?


Multiple resonant radials that cover the popular
marine and ham bands on a small boat are not seen
by all as simple. One might ask the same question
of those who advocate the counterpoise approach,
since the wire in the water is simpler. I think
choosing the best system (broadly defined to also
consider operation over fresh water and
near-vertical radiation when important) will be
easy if we can only get some objective,
reproducible data and/or analysis.


Is that where it stands, folks?

If you want a dipole, make a VERTICAL dipole, even a lousy one.


Certainly worthy of consideration. Many backstay
antennas are probably operated as half-wave
vertical dipoles (end-fed, of course) above 10 MHz
or so.

Finally, and to repeat, learn the distinction between matching and
propagation. Your focus on matching issues is like seeing your glass
3/4ths empty. Looking at the propagation advantages in comparison is
like seeing a pitcher of water nearby that will fill that glass a
dozen times.

I didn't address any matching issues at all that I
can see, Richard. Sorry if I misled you.

All of the alternatives utilize the same seawater
for propagation and the same vertical radiator.
They differ in whether there is any high-angle
radiation from a horizontal radiator, and possibly
in the magnitude of their "ground return losses."


Appreciate your comments.

73,

Chuck


73's
Richard Clark, KB7QHC

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On Wed, 31 May 2006 16:44:40 -0400, chuck wrote:

That it will not work if submerged as much as four
feet? From Roy's report on his NEC-4 modeling. It
is presumably based on the known skin depth of RF
at 14 MHz.

Hi Chuck,

You are drawing conclusions from different facts. These plates are
successfully put to this very purpose every day. There is no model
that says that a dynaplate submerged 4 feet "will not work." The
object lesson is that it will merely be a tie point to the length of
wire that is working every inch to it, and that the current in the
last inch will, in all likelihood, not see any benefit of that plate,
IF AND ONLY IF that wire travels through the water, or in very close
proximity to the water. The plate is not ineffective, it is merely
redundant.

If the wire travels through the interior of the boat, where most
transmitters reside, that dynaplate will conduct just as well, and at
as high a current as is necessary for a modestly efficient connection.
This is, after all, the whole point of installing these plates.

Other's have commented you can as easily wire to the engine (if you
have one) to create one great big gobstopper of a capacitor to the
water. Capacitors work quite effectively too, they are called
counterpoises. No engine? The same surface area in metal will
substitute. Too much surface area to equal effectively? Move the
capacitor plate closer to the hull, and reduce the area by proportion.
Does it matter your hull is fiberglass? None whatever.

What loss is it that I perceive? N6LF's results
show near lossless results with only four
shortened radials over seawater.

You still don't know how much loss there is through conventional
means, then, do you? "Near" lossless is not quantitative data.

Other studies have shown a single elevated radial
over land to lose less than one dB over a perfect
ground plane.

You have terrible sources for "other studies," then. That elevated
radial must be up a wavelength. How does this relate to "RF grounding
methods for sailboats?"

Well, what makes life interesting is that to
advocates of the other approaches, there are
obvious advantages.

You still don't have anything that amounts to more than testimonials.

Multiple resonant radials that cover the popular
marine and ham bands on a small boat are not seen
by all as simple.

Exactly. Why would you want to do it?

If you want a dipole, make a VERTICAL dipole, even a lousy one.
Certainly worthy of consideration. Many backstay
antennas are probably operated as half-wave
vertical dipoles (end-fed, of course)

Then it ceases to be a dipole.

I didn't address any matching issues at all that I
can see, Richard. Sorry if I misled you.

Every comment of yours that contains counterpoise, radial, loss, skin
depth, length of wire, or connection is a matching issue.

All of the alternatives utilize the same seawater
for propagation and the same vertical radiator.
They differ in whether there is any high-angle
radiation from a horizontal radiator, and possibly
in the magnitude of their "ground return losses."

If they all utilize the same seawater for propagation and the same
vertical radiator, they all suffer equally - it stands to reason there
is no difference given all the "sameness." It also stands to reason
by your assertion that they differ, that they do not all use the same
seawater or vertical.... Which is it? Let's skip that and cut to the
heart of the matter. How MUCH different?

Start with a conventional untuned vertical using a dynaplate and tell
me, in dB, how much better any other scheme is. Let's confine this to
a practical situation where the rig is under cover and inside the boat
and that you need two leads, one from the tuner antenna connection,
and another from the tuner ground connection.

73's
Richard Clark, KB7QHC