U.S. patent number 3,670,247 [Application Number 04/122,367] was granted by the patent office on 1972-06-13 for method and device for radiating megametric radio waves.
Invention is credited to Marie Jeanne Augarde, Henri Gutton, Jean Jacques Hugon, deceased, Emile Hugon, Simone Jeanne Georgette Hugon.
United States Patent |
3,670,247 |
Gutton , et al. |
June 13, 1972 |
METHOD AND DEVICE FOR RADIATING MEGAMETRIC RADIO WAVES
Abstract
1. A process for radiating megametric radio waves which consists
in generating an alternating voltage at extremely low frequency
ranging from 1 cycle to 100 cycles per second, applying said
voltage to two points which are immersed within a conductive liquid
mass close to the free surface thereof and distant from each other
by several kilometers in order to create in said liquid mass
between said points and close to said free surface current streams
parallel to said free surface and capable of generating by
radiation electromagnetic waves propagating far off at said
extremely low frequency, and rendering negligible the perturbations
of said waves under the action of the induction effects produced by
the application of said current to said points.
Inventors: |
Gutton; Henri
(Neuilly-sur-Seine, FR), Hugon, deceased; Jean
Jacques (LATE OF Asnieres, FR), Hugon; Simone Jeanne
Georgette (Asnieres, FR), Augarde; Marie Jeanne
(Saint Barnabe-Marseille, FR), Hugon; Emile
(Casablanca, MA) |
Family
ID: |
8732479 |
Appl.
No.: |
04/122,367 |
Filed: |
May 31, 1961 |
Foreign Application Priority Data
Current U.S.
Class: |
455/40; 343/719;
340/852; 343/709 |
Current CPC
Class: |
H01Q
1/04 (20130101); H04B 13/02 (20130101) |
Current International
Class: |
H04B
13/00 (20060101); H01Q 1/00 (20060101); H01Q
1/04 (20060101); H04B 13/02 (20060101); H04b
013/00 (); H01g 001/34 (); H01g 001/04 () |
Field of
Search: |
;343/709,710,719
;340/4,4.5,4A ;250/3,4,5 ;325/28 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Borchelt; Benjamin A.
Assistant Examiner: Birmiel; H. A.
Claims
What we claimed is:
1. A process for radiating megametric radio waves which consists in
generating an alternating voltage at extremely low frequency
ranging from 1 cycle to 100 cycles per second, applying said
voltage to two points which are immersed within a conductive liquid
mass close to the free surface thereof and distant from each other
by several kilometers in order to create in said liquid mass
between said points and close to said free surface current streams
parallel to said free surface and capable of generating by
radiation electromagnetic waves propagating far off at said
extremely low frequency, and rendering negligible the perturbations
of said waves under the action of the induction effects produced by
the application of said current to said points.
2. A process according to claim 1, wherein the liquid mass is
recovered by at least one liquid substance floating thereon, each
liquid substance having a specific impedance comprised between
those of said liquid mass and of the material filling up the space
above said free surface, the impedance of each liquid substance
increasing according to a reverse relation to the distance of said
liquid substance from said free surface, whereby the radiating
properties of the current streams flowing at said extremely low
frequency through said mass between said points close to said
surface are improved.
3. A device for radiating megametric radio waves comprising, in
combination, a source of alternating voltage at an extremely low
frequency ranging from 1 c/s to 100 c/s, a transformer including a
primary winding connected to said source and a secondary winding,
said source and said transformer being disposed close to a greatly
extended liquid mass, two metal floats at the surface of said mass
spaced from each other by several kilometers, two fully immersed
electrodes of large size respectively supported by said floats, an
insulated cable of relatively small length disposed on the free
surface of said liquid mass and interconnecting the first electrode
which is nearest to the transformer and one end of said secondary
winding, and an insulated cable, having a length equal to several
kilometers, interconnecting the second electrode and the other end
of said secondary winding and immersed within said liquid mass at
such a depth that the induction effects resulting from the flowing
of said current through said immersed cable are negligible in the
superficial portion of said mass existing between said electrodes,
said primary and secondary windings being designed to fully match
the load represented by the impedance across said electrodes and
said source of current, whereby the current streams parallel to the
free surface of said liquid mass which are set up between said
electrodes on said free surface and through said liquid mass give
rise to megametric radio waves generating on the free surface of
said liquid mass a plurality of electric fields slightly inclined
in their propagation direction and the horizontal component of
which vertically propagates inwardly and outwardly of said liquid
mass with a slight attenuation while their vertical component
propagates at great distance over said free surface and over land
with an attenuation varying in terms of distance.
4. A device according to claim 3, wherein each electrode consists
of a metal grid.
5. A device according to claim 3, wherein each electrode consists
of a conducting plate.
6. A device according to claim 3, wherein each electrode consists
of parallel-connected metallic wires.
7. A device according to claim 3, wherein the source of current is
constituted by the mains supply.
8. A device according to claim 7, wherein the mains supply are
chopped to obtain coded language.
9. A device according to claim 3, wherein the source of current is
constituted by an alternator.
10. A device according to claim 9, wherein the alternator has an
exciter winding, and further comprising a tape having a program
recorded thereon, and an electronic pulse-generating device
operated in response to said tape and connected to said exciter
winding for exciting said alternator in long pulses.
11. A device according to claim 3, wherein the source of current is
constituted by a conventional valve oscillator.
12. A device according to claim 11, wherein the valve oscillator is
capable of modulation.
13. A device according to claim 3, wherein the source of
alternating current and the transformer are disposed on land in the
vicinity of a shore bordering the sea which forms the liquid mass,
and wherein the first electrode is immersed at a relatively small
distance from said shore, whereby the radiating device is
stationary.
14. A device according to claim 13, wherein the immersed insulated
cable lies upon the sea-bed.
15. A movable device for radiating megametric radio waves, of the
naval type, comprising in combination, a ship having a metal hull,
a source of alternating current at an extremely low frequency
ranging from 1 c/s to 100 c/s disposed on board, a transformer
disposed on board and including a primary winding connected to said
source and a secondary winding one end of which is connected to
said hull, a metal buoy distant from said ship by several
kilometers, an insulating tow-line interconnecting said ship and
said buoy, a fully immersed electrode of large size supported by
said buoy, and an insulated cable, having a length equal to several
kilometers, interconnecting said electrode and other end of said
secondary winding and immersed at such a depth that the induction
effects resulting from the flowing of said current through said
immersed cable are negligible in the superficial portion of the sea
existing between said ship and said electrode, said primary and
secondary windings being designed to fully match the load
represented by the impedance across, on the one hand, said ship and
said electrode and, on the other hand, said source of current,
whereby the current streams parallel to the surface of the sea
which are set up through the sea between said ship and said
electrode give rise to megametric radio waves generating on the sea
surface a plurality of electric fields slightly inclined in their
propagation direction and the horizontal component of which
vertically propagates inwardly and outwardly of the sea with a
slight attenuation while their vertical component propagates at
great distance over the sea and over land with an attenuation
varying in terms of distance.
16. A device for radiating megametric radio waves comprising, in
combination, a source of alternating current at an extremely low
frequency ranging from 1 c/s to 100 c/s, a transformer including a
primary winding connected to said source and a secondary winding,
said source and said transformer being disposed close to a greatly
extended liquid mass, two fully immersed electrodes of large size
distant from each other by several kilometers, means for supporting
said electrodes in immersed condition, an insulated cable of
relatively small length disposed on the free surface of said liquid
mass and interconnecting the first electrode which is nearest to
the transformer and one end of said secondary winding, and an
insulated cable, having a length equal to several kilometers,
interconnecting the second electrode and the other end of said
secondary winding and immersed within said liquid mass at such a
depth that the induction effects resulting from the flowing of said
current through said immersed cable are negligible in the
superficial portion of said mass existing between said electrodes,
said primary and secondary windings being designed to fully match
the load represented by the impedance across said electrodes and
said source of current; between said electrodes, at least a layer
of a liquid substance which floats on said liquid mass, the
substance constituting each layer having natural permeability and
permittivity characteristics such that their natural impedance is
comprised between those of air and liquid of said liquid mass, the
impedance of each layer increasing according to a reverse relation
to the distance of said layer from the free surface of said liquid
mass, and means for keeping each layer between said electrodes.
17. A device according to claim 16, wherein the substance forming
each layer is an insulating substance.
18. A device according to claim 16, wherein the substance forming
each layer is selected from the group consisting of petroleum and
mineral oil.
19. A device according to claim 16, wherein the means for keeping
each layer between the electrodes comprises a basin having bounding
walls of sufficient height to prevent waves from breaking over them
when storm conditions exist over the liquid mass and two of which
are distant from each other by several kilometers, and wherein each
electrode consists of two parallel elementary electrodes of equal
size which are electrically connected at their top, said electrodes
straddling the two walls of said basin distant from each other by
several kilometers, which two walls act as a means for supporting
said electrodes.
20. A submerged antenna usable for emission and reception of
megametric radio waves comprising, in combination, two metal floats
disposed on a greatly extended liquid mass and distant from each
other by several kilometers, two fully immersed electrodes of large
size respectively supported by said floats, a first insulated cable
of relatively small length disposed on the free surface of said
liquid mass and connected to the first electrode, and a second
insulated cable, having a length equal to several kilometers,
immersed within said liquid mass and connected to the second
electrode, said cables being connected, in the case of emission, to
a device for generating high power electrical energy at an
extremely low frequency ranging from 1 c/s to 100 c/s disposed in
the vicinity of the first electrode and, in the case of reception,
to a receiver close to said first electrode and matching with the
antenna, the depth at which said second insulated cable is
immersed, being such that the induction effects resulting from the
flowing of a current at extremely low frequency through said second
cable are negligible in the superficial portion of said mass
existing between said electrodes.
Description
The present invention relates to a method and a device the purpose
of which is to radiate radio waves in the megametric frequency and
which are particularly directed towards long-distance overland and
deep-sea telecommunications.
It is well known that radio waves of comparatively low frequency
comprised, say, between 10 kilocycles and 100 kilocycles per second
will enable considerable transmission ranges to be achieved
overland or underwater. Antennae used to radiate the fields
required to obtain such waves are disposed above ground and
customarily comprise a vertical element the height of which may
often attain 250 meters and an antenna spreader of considerable
area the purpose of which is to produce a capacitance effect with
the ground in order to increase antenna efficiency.
On the other hand, when it is desired to use such waves to
communicate with a submerged receiver unit, depth limitations soon
arise by reason of the fact that sea-water considerably attenuates
such waves. Thus, for a frequency of 100 kilocycles per second, the
attenuation is 11 decibels per meter of water depth, while for a
frequency of 10 kilocycles the attenuation is still 3.5 decibels
per meter of depth.
In order therefore to achieve communication with receivers
submerged at great depth or located at great distance from the
transmitting station, it becomes necessary to use very low
frequencies, included, for example, between 1 cycle and 100 cycles.
For waves of this frequency, the attenuation sustained in sea-water
is 0.35 decibel per meter at a frequency of 100 cycles and only
0.035 decibel per meter at a frequency of 1 cycle per second. The
difficulty consequently resides in building an antenna capable of
radiating electromagnetic energy on such low frequencies. As an
example, and by way of comparison, an antenna which for a frequency
of 10 kilocycles has a vertical arm 250 meters high and a wire
spreader stretching over 25 acres would require for operation at a
frequency of 100 cycles per second a height of 25,000 meters and a
wire spreader stretching over 2,500 acres. These figures are enough
to show that it would be virtually impossible to build such an
antenna.
With a view to permitting telecommunication with radio receivers
submerged at great depth or located at a great distance from the
transmitting station above ground, or else situated at very great
altitude above the earth, the present invention has for its main
object a method for radiating megametric radio waves, which
consists in producing alternating currents at ultra-low frequency
included between 1 cycle and 100 cycles per second, and causing the
horizontal flow, in sea-water and as close as possible to the
surface of the water and over distances of several kilometres, of
said alternating currents, in order to obtain, by radiation of the
ultra-low-frequency radio energy supplied by said currents,
megametric Zenneck waves having an electrical field vector slightly
inclined in the direction of propagation, the vertical and
horizontal components of said vector respectively enabling receiver
stations which are located at great overland distances and
submerged at great depth to be reached.
It is a further object of the invention to provide a submerged
antenna whereby the aforementioned method may be put into practice,
characterized by the fact that it comprises two metal floats
distant from each other by several kilometers and supporting
fully-immersed electrodes of large size, one of which is connected
by an insulated surface cable to the secondary winding of a
transformer the primary winding of which is connected to a source
of current generating in said secondary winding a difference in
potential across said electrodes which alternates therebetween at
the extremely low frequency to be used, ranging from 1 c/s to 100
c/s, the secondary winding of said transformer being connected to
the other electrode through the medium of an insulated cable
immersed at great depth or lying on the sea-bed, the said primary
and secondary windings being designed to fully match the load
represented by the impedance across said electrodes and said source
of current.
The electrodes preferably consist of metal grids, conducting plates
or wires connected in parallel. The source of current may
conveniently be a mains supply, or be an alternator or a
conventional valve-type oscillator. In cases where a mains supply
is used, the latter may be chopped in order to obtain coded
language. The valve oscillator may be susceptible of modulation or
not.
The description which follows, with reference to the accompanying
drawings given by way of example only and not in any limiting
sense, will give a clear understanding of how the invention may be
performed and will bring out further particularities thereof.
In the drawings,
FIG. 1 is an explanatory diagram showing how the Zenneck waves are
propagated above ground and under the sea.
FIG. 2 is a schematic illustration of a first embodiment of a
submerged megametric-wave antenna according to the invention
equipped with electrodes consisting of metal grids.
FIG. 3 is an explanatory diagram showing how the use of the
submerged antenna according to the invention leads to the
generation and propagation of Zenneck waves.
FIG. 4 is a schematic illustration of a second embodiment of a
submerged megametric-wave antenna according to the invention.
FIG. 5 is a schematic illustration of a third embodiment of a
submerged megametric-wave antenna according to the invention.
FIG. 6 is a schematic illustration of the manner of propagation of
Zenneck megametric waves up to an immersed receiver unit.
FIG. 7 is a schematic illustration of a method of exciting a
submerged megametric-wave antenna according to the invention by
means of an alternator.
FIGS. 8 and 9 schematically illustrate two other embodiments of the
electrodes equipping the antenna according to the invention and
respectively consisting of conducting plates in FIG. 8 and of
parallel-connected metallic wires in FIG. 9.
FIG. 10 is a schematic illustration of a method of exciting a
submerged megametric-wave antenna according to the invention by a
mains supply which is chopped to obtain a coded language.
FIG. 11 is a schematic illustration of a method of exciting a
submerged megametric-wave antenna according to the invention by a
conventional valve oscillator.
FIG. 12 is a schematic illustration of a method of exciting a
submerged megametric-wave antenna according to the invention by a
valve oscillator associated to a modulator.
Low frequency electromagnetic waves cannot be propagated over large
distances above ground unless the "electrical field" vector of the
waves is vertical. In fact however, and as shown in FIG. 1, the
electrical field vector E of such low frequency waves is always
slightly inclined towards the direction F of propagation above the
surface of the earth. This vector may be resolved into a horizontal
component Ex and a vertical component Ez. The type of wave which
generates this electrical field E is known as a Zenneck wave. The
vertical component Ez of this electrical field E, travels great
distances in the direction F above ground and becomes attenuated as
the distance increases; this component enables reception stations
located very far from the transmitting station to be reached. The
horizontal component Ex of this electrical field E will travel
perpendicularly to the surface of the earth in the direction f and,
if the wave be travelling over the sea, attain with sufficient
amplitude and relatively low attenuation a receiver set submerged
at great depth. In FIG. 1 these attenuations are represented, for
depths of z.sub.1, z.sub.2 and z.sub.3, by the vectors E.sub.1 x,
E.sub.2 x and E.sub.3 x.
FIGS. 2 to 5 show various possible embodiments of submerged
antennae which enable an ultra-low-frequency radiation of radio
energy generating such Zenneck waves but which retain a size
compatible with practical possibilities.
Referring now to FIG. 2, positioned on the surface of the sea are
two floats 1, 2 distant by L kilometers from each other and
respectively supporting fully immersed large-size electrodes
consisting, say, of grids 3 and 4. There is established, across
said grids 3 and 4 and alternatingly therebetween at an extremely
low frequency ranging for example from 1 c/s to 100 c/s, a
difference in potential obtained by means of a transformer 5
disposed in the proximity of the sea and the primary and secondary
windings 6 and 7 of which are designed to fully match the load
represented by the impedance existing across said grids 3, 4 and
the source of alternating current at said extremely low frequency.
Said source of current may consist of a mains supply which may be
chopped by a chopper 30 (FIG. 10) to provide coded language, or
alternatively of an alternator (when the utilization frequency is
different from the mains supply frequency) or of a conventional
valve oscillator 31 (FIG. 11) which may be modulated or not by
means of a modulator 32 (FIG. 12).
Under the effect of the electromotive force developed in the
secondary winding 7, an alternating current said extremely low
frequency is established in the sea across the grids 3 and 4 in the
form of streams parallel to the surface, such as i1, i2, i3. These
current streams are channelled by insulated cables 9, 10, of which
one, the cable 9 connected to the grid 3 which is nearest to the
transformer 5, runs above the surface of the sea and has a
relatively small length, while the other, the cable 10 connected to
the grid 4, runs along the sea-bed and has a length of several
kilometers. Under such conditions the current streams i become
comparable to the streams of current circulating in an antenna and
generate at said extremely low frequency electromagnetic waves
propagating far off. If the perturbation of said waves under the
induction of the current flowing through surface cable 9 is
negligible, for rendering negligible that of said wave under the
action of the current flowing through immersed cable 10, it is most
important that said cable 10 should run along the sea-bed at as
great a distance P as possible from the surface current streams. In
fact, the direction of the current flowing through cable 10 being
opposite to that of the streams i referred to, the opposing effect
generated by said current is markedly attenuated owing to the
losses due to the conductivity of the sea-water for the fields
which are propagated across the water depth P. Therefore the energy
radiation produced by said current streams i will not be attenuated
by the oppositely directed radiation produced by the immersed cable
10. In practice, this depth P will be of the order of some tens of
meters.
Since the length of the current streams i (a few kilometers) is
always very small in comparison with the wavelength used (several
megameters), the radiation resistance of such an antenna is low yet
nevertheless sufficient to give rise to considerable radiated power
in response to currents of high intensity, and, when the antenna is
made to operate with long pulses, this radiated power may
substantially exceed the emitted powers which are customarily
radiated by radio-telegraphy stations, for frequencies comprised
between 10 and 30 kc/s, and which are limited by the corona effect
or by insulation faults.
FIG. 3 shows how, whereas the current streams are horizontal, a
vertical electrical field may be formed with this type of antenna.
The streams i parallel to the surface of the sea set up an
electrical field E parallel thereto and parallel to a magnetic
field H which is perpendicular to the plane of the figure and
likewise parallel to the water surface. The lines of force l1, l2,
l3, of the electrical field E curve across the two ends of the
antenna since, due to the fact that the wavelength is much greater
than the length of the antenna, the lines of force of said
electrical field E form into semi-circles above the current
streams, as is well known to radio engineers. Thus the line of
force l1 produces two electrical fields E'.sub.1 and E".sub.1, the
line of force l2 two fields E'.sub.2, E".sub.2, the line of force
l3 two fields E'.sub.3, E".sub.3, and so on. The fields E' and E",
which are opposite to each other, travel only outwardly from the
antenna, along F' and F" respectively, and do not interfere with
each other any more than do the magnetic fields H' and H".
As stated precedingly, the electrical fields E'.sub.1, E".sub.2,
E'.sub.3 and E".sub.1, E".sub.2, E".sub.3 have horizontal
components capable of travelling through the sea and vertical
components which travel along the surface of the sea and of the
ground. These components thus allow receiver sets submerged at
great depth beneath the sea or located at great distances on land
to be reached. The semi-circular lines of force of the electrical
field E, located above the current streams, ensure propagation of
the electrical fields E.sub.1, E.sub.2 and E.sub.3 in the
atmosphere, thereby permitting extra-terrestrial communication with
space vehicles.
The radiation capacity of this type of antenna can be improved by
reducing the difference between the characteristic impedance
Z.sub.o = .sqroot..mu..sub.o /.SIGMA..sub.0
of free space and the characteristic impedance
Z.sub.1 = .sqroot..mu..sub.1 /.SIGMA..sub.1
of sea-water, where .mu..sub.o and .mu..sub.1 are the
permeabilities of air and sea-water respectively and .SIGMA..sub.o
and .SIGMA..sub.1 their respective permittivities or specific
inductive capacities. Thus, should there be disposed above the sea
a medium of permeability .mu..sub.2 and permittivity .SIGMA..sub.2,
in sufficient thickness and in such a way that the characteristic
impedance
Z.sub.2 =.sqroot..mu..sub.2 1.SIGMA..sub.2
of this second medium should be comprised between the
characteristic impedance Z.sub.o of free space and the
characteristic impedance Z.sub.1 of sea-water, then efficiency will
be improved to an extent which be all the greater as the medium of
characteristic impedance Z.sub.2 is thicker. Similarly, if there be
added above said medium of characteristic impedance Z.sub.2 a
further medium of permeability .mu..sub.3 and permittivity
.SIGMA..sub.3 having a characteristic impedance
Z.sub.3 = .sqroot..mu..sub.3 /.SIGMA..sub.3
included between that Z.sub.o of air and that Z.sub.2 of the first
medium, then the efficiency of such an antenna will be further
improved to a marked extent.
FIG. 4 shows a possible embodiment of a submerged antenna of this
type. This particular antenna model features a vast basin bounded
by walls 11 and 12 of sufficient height to prevent waves from
breaking over them onto the antenna even when heavy seas are
running. The grids 3a and 4a which serve as electrodes are placed
along the length of two opposite walls 11 and 12 and are prolonged
by equal-sized grids 3b and 4b arranged outside the basin bounded
by those walls. By reason of the shorter path to be followed,
current streams such as i1, i2, i3 occur mainly between said walls
11 and 12 rather than outside them. The transformer 5 feeds said
grids 3a and 4a through the medium of the insulated cables 9a and
10a.
The supply cable 10a is carefully disposed along the bottom of the
basin, whereby its natural radiation is caused to be attenuated by
the depth P of sea-water to be crossed. This type of antenna
operates in two media. The first medium 13, consisting of
sea-water, is at the bottom, whilst the second medium 14, the
constants .mu..sub.2 and .SIGMA..sub.2 of which are such that its
characteristic impedance
Z.sub.2 = .sqroot..mu..sub.2 /.SIGMA..sub.2
is included between those Z.sub.o and Z.sub.1 of air and sea-water,
is above it. The second medium 14 may consist, for example, of
petroleum or mineral oil, or any other chemical product which will
not react in contact with sea-water and the characteristic
impedance of which is included between that of air, namely 377
ohms, and that of sea-water, which is very low. The characteristic
impedance of a mineral oil could be 263 ohms, for example.
In the embodiment of a submerged antenna shown in FIG. 5, this
antenna, which is of the mobile type, takes the form of a metal
ship 15 carrying the transmission equipment 8, 5 and towing a metal
buoy 2a through the medium of an insulating tow-line 16. To this
buoy is fixed a grid 4c which acts as the second antenna electrode,
the first being the metal hull of the ship 15. The transformer 5 is
bonded to the ship at 17 and connected to said grid 4c via the
insulated cable 10b. Said cable 10b is lone enough to ensure that
its average depth below the surface of the water is great.
Horizontal current streams such as il, i2, i3 are set up between
the hull of ship 15 and the grid 4c as soon as a voltage is
established across the terminals of the primary winding of
transformer 5.
FIG. 6 shows how a signal from the transmitter is received by a
receiver 18 located on the sea-bed and equipped with an appropriate
receiving antenna 19. The horizontal component Ex of the electrical
field E and the magnetic field H perpendicular thereto, both of
which are parallel to the water surface, are propagated towards the
bottom of the sea and reach the antenna 19 of receiver 18 after a
degree of attenuation resulting from passage through a depth of
water P. Concurrently, the vertical component Ez of the electrical
field E is propagated through the air in the direction of arrow
F.
FIG. 7 shows an embodiment of the transmitting device according to
the invention operating in conjunction with an alternator and
disposed on the shore. An alternator 20 connected to the primary
winding 6 of the transformer 5 is driven by a motor 21 powered off
a three-phase main supply 22. The said alternator is excited in
long pulses through the medium of its exciter winding 23 connected
to a pulse-generating electronic device 24 of any type whatsoever.
In the particular embodiment illustrated in FIG. 7, this pulse
generator 24 is operated in response to a tape 25 bearing a program
recorded thereon in accordance with any principles well-known per
se.
It is manifest that many modifications suggested by technology or
practical considerations may be made to the embodiments described
hereinbefore. By way of example, instead of consisting of grids,
the electrodes could be constituted by parallel-connected
conducting plates 28, 29 (FIG. 8) or wires 28, 29 (FIG. 9).
Similarly, and in accordance with the well-known principles of
reciprocity, the antenna described as a radiation emitter may
likewise be used as a receiver. When such is the case, matching
between the antenna and the receiver proper is achieved by known
means such as a booster transformer.
* * * * *