Insulation diameter vs Impedance OR how to get 20dBi out of ashort Dipole
 

Yuri Blanarovich wrote:

OK, here is the one for the experienced and theoriticians:

How about antenna made of wires, submerged just below the surface of water,
partially salinated (brakish) or sea water. Would it couple to this huge
"water antenna" (variations of insulated vs. bare elements) or connect/tap
to it?

I don't understand. You're asking about the coupling between a submerged
antenna made of wires and a "water antenna"? What's a "water antenna"?
How close together are the two antennas?

Any submerged antenna would have to be very shallow if it's to receive
signals from above the water -- the attenuation of fields traveling
through salt water is very high (~16 dB/foot at 1.8 MHz). If it's very
deep, it might as well not be there at all.

Roy Lewallen, W7EL

Insulation diameter vs Impedance OR how to get 20dBi out of a short Dipole
 

On Mon, 1 May 2006 17:24:48 -0400, "Yuri Blanarovich"
wrote:

How about antenna made of wires, submerged just below the surface of water,
partially salinated (brakish) or sea water. Would it couple to this huge
"water antenna" (variations of insulated vs. bare elements) or connect/tap
to it?

Hi Yuri,

Sure.

73's
Richard Clark, KB7QHC

"Ocean as antenna"
 

Let me change the subject, in order not to interfere with original thread.

OK, let me try to elaborate based on what I know and have observed.

We know about the effect of distilled water on submerged radiator, it
shrinks the dimensions due to dielectric constant. I am not going to distill
the Barnegat Bay.

We know that salt water or brackish water have high conductivity and act to
radio waves as reflector and we can take the advantage of this property by
using suitable antenna over or next to it.

There is low penetration of such water surface by radio waves, but there
should be some RF currents induced close to the surface of said water, (da
poor conductor).

The question:
is there concentration of induced RF currents near the surface, and if so,
can we tap them by furnishing proper antenna - transducer?
It may be that the whole sandwich of water is just shunted to ground, or is
there enough resistance between the ground and surface to allow enough of
workable current/signal to collect.
The idea is to "gamma match" the giant "water antenna" which is the water
surface, in similar fashion as it is done say with aircraft body surface and
a slot (antenna).

I do not remember this mentioned in the books I have and I wonder if it is
possible to harness the ocean as an antenna. Jus' wanted to make sure we do
not overlook potential "antenna" at our feet.

73 Yuri, K3BU




"Roy Lewallen" wrote in message
...
Yuri Blanarovich wrote:

OK, here is the one for the experienced and theoriticians:

How about antenna made of wires, submerged just below the surface of
water, partially salinated (brakish) or sea water. Would it couple to
this huge "water antenna" (variations of insulated vs. bare elements) or
connect/tap to it?

I don't understand. You're asking about the coupling between a submerged
antenna made of wires and a "water antenna"? What's a "water antenna"? How
close together are the two antennas?

Any submerged antenna would have to be very shallow if it's to receive
signals from above the water -- the attenuation of fields traveling
through salt water is very high (~16 dB/foot at 1.8 MHz). If it's very
deep, it might as well not be there at all.

Roy Lewallen, W7EL

"Ocean as antenna"
 

On Mon, 1 May 2006 19:32:20 -0400, "Yuri Blanarovich"
wrote:

The question:
is there concentration of induced RF currents near the surface,

Hi Yuri,

Certainly. More so above the surface than below. It stands to reason
as that was the best way for it to get beneath the surface by coming
in from above. Now, if you are searching for another trapped layer
for RF, you have to allow that seawater is pitifully lossy even if it
does present a huge shiny interface. Anything "trapped" in it is
consumed by it in very few feet.

An RF wave has to overcome a huge mismatch to get any power into the
sea. Over the entire HF band that SWR is a minimum 19:1. In the 160M
band the SWR is 75:1.

73's
Richard Clark, KB7QHC

"Ocean as antenna"
 

Sorry for the top post.

can the premise be restated as follows:

"Could an insulated wire in a lossy conductive medium [AKA ocean water]
near the surface be modeled as a slot antenna in a lossy plane?"

+ + +

Yuri Blanarovich wrote:

Let me change the subject, in order not to interfere with original thread.

OK, let me try to elaborate based on what I know and have observed.

We know about the effect of distilled water on submerged radiator, it
shrinks the dimensions due to dielectric constant. I am not going to distill
the Barnegat Bay.

We know that salt water or brackish water have high conductivity and act to
radio waves as reflector and we can take the advantage of this property by
using suitable antenna over or next to it.

There is low penetration of such water surface by radio waves, but there
should be some RF currents induced close to the surface of said water, (da
poor conductor).

The question:
is there concentration of induced RF currents near the surface, and if so,
can we tap them by furnishing proper antenna - transducer?
It may be that the whole sandwich of water is just shunted to ground, or is
there enough resistance between the ground and surface to allow enough of
workable current/signal to collect.
The idea is to "gamma match" the giant "water antenna" which is the water
surface, in similar fashion as it is done say with aircraft body surface and
a slot (antenna).

I do not remember this mentioned in the books I have and I wonder if it is
possible to harness the ocean as an antenna. Jus' wanted to make sure we do
not overlook potential "antenna" at our feet.

73 Yuri, K3BU




"Roy Lewallen" wrote in message
...

Yuri Blanarovich wrote:

OK, here is the one for the experienced and theoriticians:

How about antenna made of wires, submerged just below the surface of
water, partially salinated (brakish) or sea water. Would it couple to
this huge "water antenna" (variations of insulated vs. bare elements) or
connect/tap to it?

I don't understand. You're asking about the coupling between a submerged
antenna made of wires and a "water antenna"? What's a "water antenna"? How
close together are the two antennas?

Any submerged antenna would have to be very shallow if it's to receive
signals from above the water -- the attenuation of fields traveling
through salt water is very high (~16 dB/foot at 1.8 MHz). If it's very
deep, it might as well not be there at all.

Roy Lewallen, W7EL

"Ocean as antenna"
 

"Dave" wrote Sorry for the top post.

can the premise be restated as follows:

"Could an insulated wire in a lossy conductive medium [AKA ocean water]
near the surface be modeled as a slot antenna in a lossy plane?"

+ + +

and...
if there is such an effect what is the best way to "catch the RF waves"
grazing the shining ocean surface. More like - can it work besides just
being modeled?

I have been using "dog loop" antenna, originally RF dog fence around 3/4
acre lot, which is basically wire loop burried about 1 inch below the
surface. It has about 600 ohms and works like a goofy Beverage, low noise
pickup and still delivering reasonable signal on 80/160. That's why this
bugs me, like using floating antenna?

Just wondering if there is any potential in this or if anything was written
up in the antenna books pro or con.

Yuri, K3BU/mm


Yuri Blanarovich wrote:

Let me change the subject, in order not to interfere with original
thread.

OK, let me try to elaborate based on what I know and have observed.

We know about the effect of distilled water on submerged radiator, it
shrinks the dimensions due to dielectric constant. I am not going to
distill the Barnegat Bay.

We know that salt water or brackish water have high conductivity and act
to radio waves as reflector and we can take the advantage of this
property by using suitable antenna over or next to it.

There is low penetration of such water surface by radio waves, but there
should be some RF currents induced close to the surface of said water,
(da poor conductor).

The question:
is there concentration of induced RF currents near the surface, and if
so, can we tap them by furnishing proper antenna - transducer?
It may be that the whole sandwich of water is just shunted to ground, or
is there enough resistance between the ground and surface to allow enough
of workable current/signal to collect.
The idea is to "gamma match" the giant "water antenna" which is the water
surface, in similar fashion as it is done say with aircraft body surface
and a slot (antenna).

I do not remember this mentioned in the books I have and I wonder if it
is possible to harness the ocean as an antenna. Jus' wanted to make sure
we do not overlook potential "antenna" at our feet.

73 Yuri, K3BU




"Roy Lewallen" wrote in message
...

Yuri Blanarovich wrote:

OK, here is the one for the experienced and theoriticians:

How about antenna made of wires, submerged just below the surface of
water, partially salinated (brakish) or sea water. Would it couple to
this huge "water antenna" (variations of insulated vs. bare elements) or
connect/tap to it?

I don't understand. You're asking about the coupling between a submerged
antenna made of wires and a "water antenna"? What's a "water antenna"?
How close together are the two antennas?

Any submerged antenna would have to be very shallow if it's to receive
signals from above the water -- the attenuation of fields traveling
through salt water is very high (~16 dB/foot at 1.8 MHz). If it's very
deep, it might as well not be there at all.

Roy Lewallen, W7EL

"Ocean as antenna"
 

Yuri Blanarovich wrote:
"Dave" wrote Sorry for the top post.
can the premise be restated as follows:

"Could an insulated wire in a lossy conductive medium [AKA ocean water]
near the surface be modeled as a slot antenna in a lossy plane?"

No. To my knowledge, a slot antenna requires a thin plane, which an
ocean doesn't resemble. I imagine you could make one in a solid like a
chunk of metal, but believe that the hole depth would have to be a
substantial fraction of a wavelength.


+ + +

and...
if there is such an effect what is the best way to "catch the RF waves"
grazing the shining ocean surface. More like - can it work besides just
being modeled?

Not sure what effect you mean. But NEC-4 models interactions at, above,
and below a medium like water with reasonable accuracy.

I have been using "dog loop" antenna, originally RF dog fence around 3/4
acre lot, which is basically wire loop burried about 1 inch below the
surface. It has about 600 ohms and works like a goofy Beverage, low noise
pickup and still delivering reasonable signal on 80/160. That's why this
bugs me, like using floating antenna?

I think you'll find that a buried antenna will work more and more poorly
as the ground conductivity gets better and better. As an extreme, how
well do you think it would work if buried in an Earth-sized chunk of metal?

Just wondering if there is any potential in this or if anything was written
up in the antenna books pro or con.

I think you're on your own. The path is clear for you to be the first to
make great discoveries! Just be sure to take a little time off along the
way to do make those coil measurements.

Roy Lewallen, W7EL

"Ocean as antenna"
 

Yuri Blanarovich wrote:
....
and...
if there is such an effect what is the best way to "catch the RF waves"
grazing the shining ocean surface. More like - can it work besides just
being modeled?

From
http://www.mso.anu.edu.au/cas/presents/don.html

I quote
"Joe Pawsey took me up to Dover Heights that first day to the cliff-top
interferometer. It was a very cunning device. As the sun rose above the
ocean there was a reflected ray off the ocean, received by the antenna,
and then the direct ray; this formed an interferometer - like a Lloyds
mirror type thing - this was the array that found that the Crab Nebula
was a radio source, and also did much of the early work on Cygnus"

"Ocean as antenna"
 

"Roy Lewallen" wrote
K3BU:
Just wondering if there is any potential in this or if anything was
written up in the antenna books pro or con.

I think you're on your own. The path is clear for you to be the first to
make great discoveries! Just be sure to take a little time off along the
way to do make those coil measurements.

Roy Lewallen, W7EL

Just stumbled on this item, indicating that youze guyz might be defficient
in more areas and I should revise my treatment of some of your previous
answers.

from Johnson - Jasik, Antenna Engineering Handbook, 2nd Ed., p. 5-21:

"The brevity of this review requires omission of many interesting topics
concerning loop antennas. In recent years, there has been considerable study
of loop antennas in close proximity to or embedded in material media such as
the ocean, the earth, or a plasma. The electrical characteristics of loops
in these instances can be quite different from those of loops in unbounded
free space, as described in this review. The major applications of this work
are in the areas of subsurface communication and detection (geophysical
prospecting).
The loop antenna near a planar interface separating two semi-infinite
material regions, such as the air and the earth, has been investigated
extensively. When the loop is electrically small, it can be approximated by
an elementary magnetic dipole, and the electromagnetic field away from the
loop can be determined from the classical analysis of Sommerfeld. If the
field near the electrically small loop is required, the approximation by a
magnetic dipole may no longer be adequate, and a loop with a finite radius
and a uniform current must be considered. For the electrically large loop
near a planar interface, an analysis that allows a nonuniform current in the
loop, such as the Fourier-series analysis for the circular loop, must be
used."

So this idea goes into "to do" pile to be researched or explored.


73 Yuri, K3BU

"Ocean as antenna"
 

On Tue, 16 May 2006 18:48:27 -0400, "Yuri Blanarovich"
wrote:

Just stumbled on this item, indicating that youze guyz might be defficient
in more areas and I should revise my treatment of some of your previous
answers.

from Johnson - Jasik, Antenna Engineering Handbook, 2nd Ed., p. 5-21:

The product of Xerox....

So this idea goes into "to do" pile to be researched or explored.

Hi Yuri,

Just so you get to that first instead of 'splainin' it.

You might visit the library for a copy of R.W.P. King's "Antennas in
Matter," of which I have a copy. You've gotten the short answer from
us, the long answer doesn't change the outcome.

73's
Richard Clark, KB7QHC