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

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

In article ,
Richard Clark wrote:

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

This is exactly right. If they all use the same water for RF Ground,
and vertical, for the antenna, then the only difference is, "How much
coupling from the ground stud on the antenna tuner does each system give
to the water?" And that is the Thousdan Dollar question. DynaPlate,
Bonded RF Ground System, wires, radials, whatever, all, just make up one
side of the capacitor, with the water as the otherside and the distance
between is the dielectric. More effective coupling equals lower
impedance RF Ground. All this talk of Modelling is just so much FuFurrR,
for anyone who has installed MF/HF Marine Antenna Systems on these type,
wood or plastic vessels. Anyone with much experience in the field will
tell you, simply, get as much surface area as possible, bonded with
low impedance connections, (Copper Strap) and get it as close to the
water as possible. The Physics of building a bigger capacitor is:
Have as much surface area as possible, with the least space between the
plates. This isn't Rocket Science, it is just basic physics, and all the
crap about tuned counterpoises, and copper screens in the overhead, and
the like is just that...... crap...woun't work, never has, and never
will.
It doesn't take a NEC Modelling Software Package to figure this out, it
just takes some common sense and a bit of OJT Experience....

Bruce in alaska
--
add a 2 before @

chuck wrote:
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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I would also add that sea waters conductivity is not a consistent as
some seem to think. The salinity of salt water varies with temperature.
NASA has surveyed most of the world oceans using microwave radar and
salinity if far from consistent. This fact combined with tidal flows,
man made pollution from storm water drains and other factors makes
"connecting" to sea water seem dubious.

If we assume you can connect to sea water, do you want to place most of
your current in such a small area? I doubt someone could keep this
connection clean enough in seawater to be efficient. This fact combined
with electrolysis will lay waste to any connection very quickly. Maybe a
gold plated conductor might be able to survive in a salt water environment.

The way most people install radials in yacht would make them elevated,
rather than buried below skin depth. N6LF has indicated in his modeling
that short radials as long as .1 wavelength work just as effectively as
0.5 wavelength radials over sea water. Since you not trying to combat
ground loss whats the point of trying to build a radial field when 2 or
4 .1 wavelength radials will do the job? Besides building a elevated
radial system will have some capacitance to ground. A single radial
should over sea water capture most of not all of the antenna return
currents

Besides from all the posts i have read burying something like a
Dynaplate below skin depths is akin to burying your rf current below a
copper plate. I also believe there is a rule of thumb that 5 skins
depths is the maximum return on investment in using the available
conductive depth of any material. Its probably that its only ever the
piece of wire to the dynaplate thats working as a short radial. I dont
see how anyone can say a dynaplate could ever work when below skin depth?

One thing i am curious about is that if you suspend a radiator or
conductor well below skin depth in air whats the radiation efficiency
like of that conductor? To me on a yacht it looks like a conductor
suspended in a U channel suspended in air with the top open and
exposed. Maybe it will operate like a waveguide with some cut off
frequency, this is a wild guess.Maybe someone who can model conductors
below ground can model this. Most yachts have at least 3ft of freeboard
above water to play with.

But who knows there seems to conflicting advice on several points.
Maybe Roy can clarify all these issues with his models.

Bob

bob wrote:
. . .
One thing i am curious about is that if you suspend a radiator or
conductor well below skin depth in air whats the radiation efficiency
like of that conductor? To me on a yacht it looks like a conductor
suspended in a U channel suspended in air with the top open and
exposed. Maybe it will operate like a waveguide with some cut off
frequency, this is a wild guess.Maybe someone who can model conductors
below ground can model this. Most yachts have at least 3ft of freeboard
above water to play with.

But who knows there seems to conflicting advice on several points.
Maybe Roy can clarify all these issues with his models.

There's no good way to model this situation with the tools I have.
Conceptually, though, you can get a fair idea by imagining the sea to be
made of metal. The boat makes a depression in the surface, and you can
connect to the metal at the bottom of the depression just as you can
anywhere else on its surface.

Imagine that the depression is perfectly round and symmetrical, with a
grounded vertical extending up from its center. The current flowing into
the "ground" connection at the bottom of the depression will flow along
the conductor's surface, up the sides of the "dish" to the flat water
surface. The total current flowing from the center of the dish upward to
the flat surface will equal the current flowing up the vertical wire
near its base. The fields from the two will nearly cancel, so there'll
be little radiation from the vertical in the region below the flat
surface of the water. The vertical above that point should radiate
normally. This simplification will of course be modified by the reality
of a non-symmetrical hull, but it helps in getting a general idea of
what will happen.

Another way to look at the situation is to view the depression as the
outer conductor of a shorted coaxial cable, with the "ground wire"
extending down to its center as its center conductor, and the shorted
end the bottom of the depression. This shows you'd get some inductive
reactance in your connection to the surface of the water. A rough
calculation would probably get you in the ballpark of the actual value.
This doesn't represent loss, however.

The main thing, though, is that connection to the water requires a
conductor either in contact with or capacitively coupled to the water's
surface or only a very short distance below it (assuming salt water),
whether the surface is below the boat's hull in a depression or on the
flat surface of the ocean.

Roy Lewallen, W7EL

Roy Lewallen wrote:
bob wrote:
. . .
One thing i am curious about is that if you suspend a radiator or
conductor well below skin depth in air whats the radiation efficiency
like of that conductor? To me on a yacht it looks like a conductor
suspended in a U channel suspended in air with the top open and
exposed. Maybe it will operate like a waveguide with some cut off
frequency, this is a wild guess.Maybe someone who can model conductors
below ground can model this. Most yachts have at least 3ft of
freeboard above water to play with.

But who knows there seems to conflicting advice on several points.
Maybe Roy can clarify all these issues with his models.

There's no good way to model this situation with the tools I have.
Conceptually, though, you can get a fair idea by imagining the sea to be
made of metal. The boat makes a depression in the surface, and you can
connect to the metal at the bottom of the depression just as you can
anywhere else on its surface.

Imagine that the depression is perfectly round and symmetrical, with a
grounded vertical extending up from its center. The current flowing into
the "ground" connection at the bottom of the depression will flow along
the conductor's surface, up the sides of the "dish" to the flat water
surface. The total current flowing from the center of the dish upward to
the flat surface will equal the current flowing up the vertical wire
near its base. The fields from the two will nearly cancel, so there'll
be little radiation from the vertical in the region below the flat
surface of the water. The vertical above that point should radiate
normally. This simplification will of course be modified by the reality
of a non-symmetrical hull, but it helps in getting a general idea of
what will happen.

Another way to look at the situation is to view the depression as the
outer conductor of a shorted coaxial cable, with the "ground wire"
extending down to its center as its center conductor, and the shorted
end the bottom of the depression. This shows you'd get some inductive
reactance in your connection to the surface of the water. A rough
calculation would probably get you in the ballpark of the actual value.
This doesn't represent loss, however.

The main thing, though, is that connection to the water requires a
conductor either in contact with or capacitively coupled to the water's
surface or only a very short distance below it (assuming salt water),
whether the surface is below the boat's hull in a depression or on the
flat surface of the ocean.


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.

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?

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


- 73 de Mike KB3EIA -