US1691338A - Aerial system - Google Patents

Description

F. CONRA D AERIAL SYSTRH Filed Oct. s, 192::

T I 14\ 315 g 6 16 wnuassss; mvzugc n d gran/v 0/7/0 ATTORNEY Patented Nov. 13, 1928.

UNITED STATES; PATENT OFFICE;

FRANK CONRAD, OF .P-ITTSBURGH, EENNSYLVANIA, ASSIGNOR TQ: WESIINGI- IOU SE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA;

AnJaI L sys'rnm.

Application filed 0otober5, 1923. Serial nofeceyoa.

. My invention relates to, aerial systemsifor the radiation othiglrtrequency energy.

Broadly speaking, my invention has for one of its objects the construction of an aerial system which shall have a maximum ll.Cl1lJ.-' tion resistance and which shall operate at the is to provide a radiating system consisting ofan aerial and counterpoise connected by a minimum length, of conductor, in order that the inductance in the radiating circuit may be as small as possible "for a given height and that the ratio between the radiation resistance and the total resistance of the system may be as large as possible. y i I It is an object, also, to provide an aerial and counterpoise rad iatingfsystem of such dimensions as to radiate at some chosen wave len rt-h which system shall also be of such construction as to permitof the aerial and coun terpoise together servlng as the elevated capacity element of a secondgradiating system whose other capacity element is the ground.

It is further an object of my invention toso construct and energize an aerial and counterpoise system that it is possible tose'nd two signalson two different wave lengths simultaneously. I v 7 It is a still further object. of my invention 7 to so connect the aerial and counter oise s sand counterpoisesystem changing the freteintoan oscillation generator as to minimize the effect of changing constants of the aerial quencies of radiated signals.

,In practising my invention, I provide an aerial. elevated above the ground, 'a counterpoise placed between, the aerial and the ground, and aconnecting wire, between aerialand counterpoise, which is of minimum lengthand which may even be a straight conductor. I also provide a source of high-frequcncy energy which may be a triode, oscillator, an are or other suitable generator. I connect the source of highdrequency energy to thefaerial circuit at a point other than the electrical midpoint, as will later he explained. I may also connect a conductor between the electrical midpoint and the ground, which conductor may contain an inductance, coupled to a second source of'highi-requency energy.

Otherobjects and structural details; ofmy invention willbe apparent from thefollowing description and claims, when read in connec tion with the accompanyingdrawing,wherein Figure l is a diagrammatic view of circuits and apparatusembodying my invention.

Fig. a similar view of amoditication. Fig. 8 is a similar view ofa secondmodification adapted for the radiation of-two treoi i .s.

In the system of Fig. 1, I provide an elevated capacity oraerial l and a counterpoise 2 that are connected;togetherby a conductor The constants of the aerial andcounterpoise may preferably be chosen of such. value i that the electricalvmidpoint of the system,

when in oscillation, will lie upon the conductor 8 at point a. A ground wire 5 may be connected to point 4t and to ground G, it desired, or may be omitted, Without hindrance tothe oscillationof the system. composed of aerial l, counterpoiseQ and conductor-8f A source ofhigh-trequency energy 7 may be of any suitable type, such as a thermionic triode generator, an are, a sparln or other source. The oscillation generator 7' is con- 'nected to the aerial radiation system composed of aerial 1, counterpoise 2 and'lead wire 3 by a conductor 8 and condenser 9. Connection is made to'apoint 11 onk-ond-uctor 3, this pointbeing so chosen that it is'not the electrical midpoint of the oscillating system. i d 3 Fig. 2 shows my inventionwith aminor modification. It may be'desiredflto transmit alternatively at more than one wave length from an aerial and oountei'poise system. This can be done'by constructing aerial and counterpoise with such constants that one of the desired jtre'q uencies willbe obtained by the use of a straight lead wire between aerial ,n by I similar reference numerals.

and counterpoise. The other frequency may then be obtained by introducing. into the lead wire either additional inductance or additional series capacity according as the other frequency desired is lower or higher than the first chosen frequency.

This construction is shown in Fig; 2 in which structures corresponding to those of Fig. 1v are indicated by similar reference characters. In addition, an inductance 12 and a short-circuiting switch 13 are shown. I

Fig. 3 shows diagrammatically the structure of my invention required for transmitting two signals at dii'ierent wave lengths simultaneously. in Fig. 3, structures identiportion of the totalhigh-frequency resistance of the aerial system. It isalso well known that a maximum radiation resistance in any antenna system is favored by a minimum inductance in the radiating circuit for a given frequency; that is, an aerial system will radiate best when it has no inductance coil in the lead connecting aerial and coun'terpoiseand when the inductance of the connecting lead itself is a minimum. 1 Under these conditions,

the aerial, when energized, is said to oscillate at its fundamental frequency. Conversely, the maximum radiation resistance is obtained in a given aerial when itoscillates at its fundamental frequency.

It is well known in the art that, in, an

antenna system consisting of an aerial and counterpoise, it 1s possible to find a point in the circuit which remains at zero potential qwith respect to the ground even though the antenna system be energized into oscillation. This point is a potent al node with respect to ground and likewise a current loop, the current node and potential loop occurring at the afree ends of the oscillating system. This point of constant potential or potential node may be called the electrical midpoint of the oscillating system. .One ofits characteristics is that it may be connected to ground by a conductor without current traversing the rounding conductor.

It 1s further possible to connect a second source of hi h-frequency energy to the elec- 'trical midpoint of such an oscillating and cause electricaloscillations to take place system between the antenna system as a whole and the ground without interfering with the oscillations of the antenna and counterpoise themselves, thereby obtaining duplex operation- In operation, the radiating system composed of aerial 1, counterpoise 2 and lead 3 will have a definite natural period of oscillation. The oscillation generator 7, which is a source of high-frequency energy, is adjusted to the same frequencyasthe normal period of the radiation circuit by means which are well known to those skilled in the art. The condenser 9 is then adjusted to such value as to give adequate transfer of energy from generator to radiator without obtaining coupling so close as to produce undesirable reaction between generator and radiator circuits. Under these conditions, high-frequency current oscillations will build up in the radiation system to a valuedetermined oscillation of the system. The presence of lead 5, however, drains off any atmospheric or other undesired energy. I

When it is desired to transmit at a different frequency, the change in. constants of the radiating system may be produced by the introduction of additional impedance, which may be an inductance 12, shown in Fig. 2, or may be a condenser. The additional impedance represented by inductance coil 12 maybe brought into and out of the circuit by means of a short-circuiting switch as shown.

Aerial 1 and counterpoise 2 may be considered together as an ordinary elevated capacity and connected to a ground at their electrical midpoint,'un'der which condition they will function together as an antenna. Since a ground connection may be made through the electrical midpoint of the antenna and counter-poise system without'efl'ecting its oscillation as'a whole, it is obvious that it is possible to connect it with the ground by means of connection 5, and an additional inductance coil let, which will then serve as a means for the transfer of energy from another high frequency generator. Under these con ditions, the aerial andcounterpoiso structure is made to serve together as one capacity element of the oscillator system of which the other capacity element is the ground. The generator? than transmits signaling energy to "the aerial and counterpoise at one frequency,and generator v16 transmits energy through inductance coil 14 to the samesystem and causes it to oscillate at the same time at a different frequency forthe transmission of a different signal. n

The use ofthe oscillation driver 7 loosely coupled to the radiation circuit'composed of the aerial 1, counterpoise 2 and lead 3'allows the radio-frequency generator 7 to oscillate at a frequency, which, while adjusted to the same value as'that of the radiating circuit, is set by its own constants independently of the constants of the radiating circuit. This means that energy is supplied for radiation at a constant frequency which is not affected by minor changes in the constants of the radiating circuit of the kind produced by swaying of the antenna or the conductor leading thereto in the wind or by movement of objects below or between aerial and counterpoise which changes the effective capacity between them.

This construction is of particular advantage in signaling with short-wave undamped signals. These signals are received by methods which require heterodyning by a local oscillator circuit at the receiving station to produce a beat note, which is received by the operators ears, its frequency and pitch depending upon the relationship between the incoming and the local frequencies. change in the radiating frequency at short waves is sufficient to transfer the beat note out of the range of audibility, resulting in the loss of signals when even a minor change of constants of the radiating circuits takes place. My system, by virtue of the loose-coupled connection between radiator and generator, keeps a fixed frequency and thereby avoids this difliculty. 1

Furthermore, the fact thatrthe oscillation generator is loosely coupled to the radiating circuit permits of the transfer of energy only at the frequency to which both circuitsare tuned, thereby largely avoiding the radiation of harmonics.

Also, the fact that it is possible to connect the aerial, counterpoise, and lead systems to ground at an electrical midpoint, without influencing the oscillation of the system, enables the system, as a whole, to be used as an aerial which, in turn, permits the radiation of the second set of signals supplied from another energy source.

While I have shown only three embodiments of my invention in the accompanying drawing, it is capable of other changes and modifications without departing from the spirit thereof, and I desire, therefore, that A minor 7 ductive influence, and a single-conductor link circuit therebetween.

3. An antenna system comprising anaerial, a counterpoise, a conductor therebetween of minimum length, an oscillation generator at a distance greater than its sphere of inductive influence, and single-conductor link circuit therebetween having impedance means therein.

4:. A radiation system for high-frequency energy comprising an aerial, a counterpoiseand a linear conductor therebetween, an oscillation generator at a distance greater than its sphere of inductive influence therefrom, a single-conductor link circuit therebetween, a ground connection to a voltage-node point on said linear conductor, and a radio-frequency supply associated therewith.

5. A system for the radiation of high free quency energy at a chosen frequency comprising an aerial, a counterpoise, and a conductor therebetween of minimum length, the areas and separation of said aerial and counterpoise being such that the desired resonant frequency is obtained with said conductor therebetween of minimum length, an oscillation generator, and a link circuit therebetween having a capacitance between sections thereof. p In testimony whereof, I hereunto subscribe my name this 2nd day of October, 1923.

FRANK CONRAD;

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