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.

Will

I don't think Icom would jack you around about this, do you really?
Marine radios are a large part of their business and they do know their
business. Uhmmm...this isn't one of those ionosphere posts is it?

Butch




Will wrote:
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.

Will

In article ,
Butch Magee wrote:

I don't think Icom would jack you around about this, do you really?
Marine radios are a large part of their business and they do know their
business. Uhmmm...this isn't one of those ionosphere posts is it?

Butch




Will wrote:
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.

Will

No, Not an Ionsphere Post, just a guy who has no clue about the
technology that he wants to use, and he is asking questions, trying
to learn. From the replys he has received so far, he is finding out
that 99% of the hams, don't have a clue about MF/HF Marine Radio
Antenna systems Design, either. I suggest that he head on over to
rec.boat.electronics, and ask Larry, Gary S., Old Chief Lynn, or one
of the other Old Salts, that have been doing these installations for
decades, and have the experience in the technology being asked about.
Most hams think that MF/HF Marine Radio Antenna Systems design should
follow the same rules that Land Startions use. Well that isn't the case,
and usually ends up is a "**** Poor", marginal system that only talks
"when the Band is open", and "when the Band is open" even a wet noodle
will radiate enough to communicate.

Me

Will wrote:
"Does sea water make a good enough ground without radials?"

It`s the best you can get in a boat at sea, The point is to get a good
connection to the sea. You don`t need radials for that. That`s why a
thin copper plate is recommended. Copper is durable and poisonous to sea
organisns which may foul the surfaces of other materials.

Skin effect applies. Bolting to a spot inside a metal hull means the RF
must travel from the bolt location inside the hull (it can`t penetrate
the hull) to an edge where it reaches from the inside surface to the
outside surface and thence to the waterline.

DC resistsance of a conductor is resistivity x length divided by
crossection. AC resistance is more but proportioned to the DC
resistance. A large crossection or area produces a low resistance.
That`s why the plate is better for contacting the water than a wire.
Its also why the seawater has a low resistance despite a higher
resistivity than copper. The huge crossection of seawater has very low
resistance in most cases and its reactance is low too. Low resistance
and low reactance make a good path for RF.

Best regards, Richard Harrison, KB5WZI

A 6" square plate makes an adequate ground when immersed in salt sea
water. That is unless the transmitter power exceeds 10 kW.

http://www.photolib.noaa.gov/nurp/nur09010.htm

This photo is of the barge over the Tektite II habitat; Summer 1970.
I operated W2YRQ from inside the habitat with a Hy Gain 14 AVQ attached to
this steel barge.
We also dropped some heavy cable in the water with the conductors unwound.
Worked great.
73
H.
NQ5H

PS
Reg is usually right.


"Reg Edwards" wrote in message
...
A 6" square plate makes an adequate ground when immersed in salt sea
water. That is unless the transmitter power exceeds 10 kW.

Reg Edwards wrote:
A 6" square plate makes an adequate ground when immersed in salt sea
water. That is unless the transmitter power exceeds 10 kW.

I wonder.... It has been awhile since I checked, but does AES or HRO
still sell those 8 ft "water rods" ? ?.....George

On Tue, 23 May 2006 23:44:50 +1000, Will
wrote:
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?

Hi Will,

Below is better than above, to say the least. How much below is
immaterial.

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

Skip the pursuit of the Holy Grail in radials, this may lead you to
start carrying buckets of dirt which screws up buoyancy.

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

Probably more surface area.

All ideas and comments appreciated.

How good (or poor) sea water is for matching and loss, is seeing the
glass 3/4's empty. How good sea water is for propagation is seeing
the pitcher nearby and filling your glass several times.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Tue, 23 May 2006 23:44:50 +1000, Will
wrote:
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?

Hi Will,

Below is better than above, to say the least. How much below is
immaterial.

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

Skip the pursuit of the Holy Grail in radials, this may lead you to
start carrying buckets of dirt which screws up buoyancy.

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

Probably more surface area.

All ideas and comments appreciated.

How good (or poor) sea water is for matching and loss, is seeing the
glass 3/4's empty. How good sea water is for propagation is seeing
the pitcher nearby and filling your glass several times.

73's
Richard Clark, KB7QHC

A few additional questions along these lines for the group (with some
paraphrasing):

1. What is the skin depth in salt water at 14 MHz? How would this affect
a ground plate at four feet below the surface?

2. What would the ohmic losses be over a one square foot by 33 foot path
through salt water?

3. How well would the ground plate work on fresh water bodies, such as
much of the Chesapeake, the Great Lakes, and various rivers and
tributaries often used by cruisers? How would it compare with radials
over fresh water?

4. Can anyone cite a published and reproducible study in which the RF
losses through salt water were measured and compared with losses through
one or more copper wire "radials" on or below deck of a typical cruising
vessel? Or is there a published theoretical analysis of this comparison?
Looking for more than the casual, anecdotal stuff.

5. Will a four foot length of wire dropped into sal****er provide a
"good" RF "ground" and on what is the answer based?

I need enlightenment!

Thanks, and 73,

Chuck
NT3G

chuck wrote:

A few additional questions along these lines for the group (with some
paraphrasing):

1. What is the skin depth in salt water at 14 MHz?

About 2.4 inches.

How would this affect
a ground plate at four feet below the surface?

A ground plate at that depth would be invisible to RF. It might as well
not be there. This is, of course, assuming it actually has 4 feet of
water above it and not a boat's hull and air.

2. What would the ohmic losses be over a one square foot by 33 foot path
through salt water?

Let's see, salt water conductivity is about 5 S/m, which is 1.524 S/ft.
So the *DC* resistance of that piece of sea water would be 1.524 * 33 /
(1 * 1) ~ 50 ohms. But the RF resistivity would be much greater because
only the outer few inches would carry any current.

3. How well would the ground plate work on fresh water bodies, such as
much of the Chesapeake, the Great Lakes, and various rivers and
tributaries often used by cruisers? How would it compare with radials
over fresh water?

Fresh water is quite a different story. The skin depth in *pure* fresh
water at 14 MHz is 156 feet. But "fresh water" is far from pure.
Unfortunately I don't have any ready data on "typical" "fresh water". So
the skin depth is somewhere between 2.4 inches and 156 feet. Not much
help. If the water is pretty pure, radials near the surface would be an
improvement over a ground plate.

4. Can anyone cite a published and reproducible study in which the RF
losses through salt water were measured and compared with losses through
one or more copper wire "radials" on or below deck of a typical cruising
vessel? Or is there a published theoretical analysis of this comparison?
Looking for more than the casual, anecdotal stuff.

No. An NEC-4 model shows a one-foot wire to provide a nearly perfect
ground in salt water. But that falls far short of your requirement.

5. Will a four foot length of wire dropped into sal****er provide a
"good" RF "ground" and on what is the answer based?

Yes, but one foot does just as well -- any current on the wire will drop
to essentially zero within the first foot, so the remainder might as
well not be there. This is from an NEC-4 model.

I need enlightenment!

So do we all.

Roy Lewallen, W7EL