This is a distillation of several recent postings and other readily
available information on securing a good RF "ground" for a vertical
antenna on a plastic or wood sailboat. The basis for each method was
either reported model results or a presumed "organizational authority"
on the subject (i.e., ARRL, Icom, and SGC).

No ranking or recommendation was intended.

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, but will work as
near-perfect if at the waterline, and may work if attached to hull even
when submerged four feet (awaiting clarification from Roy, W7EL). In
fresh water or low-conductivity water, a ground plate may not function
acceptably. Sometimes used in combination with #4 below. Recommended
only "as a last resort" by Icom.

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.

3) Radials

Even shortened (loaded) radials elevated over seawater work as
near-perfect based on N6LF's NEC-4 modeling. Objections to radials are
safety (high-voltage insulation notwithstanding), tripping hazard,
undesirable RF coupling, and the necessity of either tuning the
radial(s) or installing multiple 1/4 wavelength wires. Radials will be
useful even over fresh water or when boat is on land. Single radials can
provide significant near-vertical radiation which may be useful, but at
the cost of reduced radiation from the vertical radiator. Considered a
viable alternative by Icom but not recommended by ARRL.

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

One of the traditional approaches to marine SSB installations on plastic
and wood sailboats. The mast and rigging often provide the equivalent of
~200 lineal feet of counterpoise wire above deck with additional metal
structures connected on and below deck. Sometimes used in combination
with a grounding plate. If copper is placed inside hull below waterline,
useful capacitive coupling to the water may occur. Will work over fresh
water and on land. This is the method recommended in the ARRL Antenna
Book, where radials, as the only considered alternative, are discouraged
in their discussion for the reasons stated in #3. This type of
counterpoise is also the approach recommended by both Icom and SGC.

5) OCF dipole w/horizontal component along deck

Not commonly used, but obviates the need for multiple resonant radials.
Analyzed by W4RNL. Usually requires a current choke in the coax from
tuner to rig to reduce undesired RF coupling. Suffers from some of the
same objections listed for radials; will also provide some
near-vertical radiation. Will work over fresh water and on land.



Is that where it stands, folks?

73,

Chuck,
NT3G



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chuck writes:


3) Radials

5) OCF dipole w/horizontal component along deck

Is that where it stands, folks?

Beside the name, is there any difference between an OCF dipole and a
single radial?

73
LA4RT Jon

"Jon Kåre Hellan" wrote:
Beside the name, is there any difference between an OCF dipole and a
single radial?

By definition, a "radial" would be physically orthogonal to the
other element. The elements in an OCF are usually collinear.
--
73, Cecil http://www.qsl.net/w5dxp

Jon Kåre Hellan wrote:
chuck writes:

3) Radials

5) OCF dipole w/horizontal component along deck

Is that where it stands, folks?

Beside the name, is there any difference between an OCF dipole and a
single radial?

73
LA4RT Jon

We don't seem to have widely used, descriptive
names for these configurations. Cecil is correct,
and perhaps the OCF referred to should be called
an OCF "L". The vertical radiator with a single,
elevated, horizontal, resonant "radial" perhaps
should be called an "L" dipole.

On inspection, either antenna, on a boat with a
tuner at the feedpoint, could be mistaken for the
other. You could tell the difference only by
observing how the antenna is operated. If the
antenna is operated only on those frequencies for
which the horizontal element is an odd multiple of
a 1/4 wavelength, we would call the antenna an "L"
dipole (or whatever).

If that same antenna were operated not only on
those frequencies, but on all others (HF spectrum)
as well, we would call it an OCF "L".

But if, on inspection, the antenna has multiple
resonant radials, that would unambiguously
differentiate it from the OCF.

Whenever the two antennas are physically
identical, they will obviously operate identically.

Make sense, Jon? Sorry for the confusion.

73,

Chuck
NT3G



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Cecil is correct,

====================================

He usually is!

"Reg Edwards" wrote:

Cecil is correct,

He usually is!

Especially about California wines, a subject upon which I am a guru. :-)
--
73, Cecil http://www.qsl.net/w5dxp

chuck writes:

Jon KÃ¥re Hellan wrote:
We don't seem to have widely used, descriptive names for these
configurations. Cecil is correct, and perhaps the OCF referred to
should be called an OCF "L". The vertical radiator with a single,
elevated, horizontal, resonant "radial" perhaps should be called an
"L" dipole.

On inspection, either antenna, on a boat with a tuner at the
feedpoint, could be mistaken for the other. You could tell the
difference only by observing how the antenna is operated. If the
antenna is operated only on those frequencies for which the horizontal
element is an odd multiple of a 1/4 wavelength, we would call the
antenna an "L" dipole (or whatever).

If that same antenna were operated not only on those frequencies, but
on all others (HF spectrum) as well, we would call it an OCF "L".

But if, on inspection, the antenna has multiple resonant radials, that
would unambiguously differentiate it from the OCF.

Whenever the two antennas are physically identical, they will
obviously operate identically.

Make sense, Jon? Sorry for the confusion.


Sure. Thanks.

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