US706737A - Wireless telegraphy. - Google Patents

Description

Patented Aug. 12, I902.

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WITNESSES:

INVEN'TI'OR El J , i l v| UNITED STATES PATENT Prion.

REGINALD A. FESSENDEN, OF ALLEGHENY, PENNSYLVANIA.

WIRELESS TELEG RAPHY.

SPECIFICATION forming part of Letters Patent No. 706,737, dated August 12, 1902. Application filed May 29, 1901. Serial No. 62,301. (No model.)

To aZl whom it may concern: conductor is'so constructed that its capacity Be it known that l, REGINALD A. FESSEN- or self-induction, or both, are large, as com- DEN, a'citizen of the United States, residing pared with the value of the aerial Wire comg at Allegheny, in the county of Allegheny and monly usedin the art and distributed with State of Pennsylvania, have invented or dispractical unifurmityalongthe conductor-from covered certain new and usefullmprovements or near its top to a point an or near the instru in Wireless Telegraphy, of which improvement. By thus increasing the capacity and rnents the following is a specification. self-inductionof either of them the frequency to The invention described herein relates tov of the electric oscillationsin the conductors,

to certain improvements in transmission of on and consequently of the waves generated, ergy by electromagnetic waves, and has for will be sufilciently low to produce utilizable its object the production of more eflicient motion in the instrument. lily low fre sending or generating conductors. quency is meant low relative "to the freo .It is a further object of the invention to quency hitherto used in wireless telegraphy.

provide for the production of mechanical The terms sendiug-conductor and removements by the direct interaction oi curceiving-conductor-as hereinafter employed rents induced in the receiving-conductor by indicate allot the circuits of the sending and electromagnetic waves and constant or varyreceiving stations from top to ground if ye grounded, or, if not grounded, from one en- 2c The nvention is hereinafter more fully detreme end to the other extreme end, includd scribed and claims ing all apparatus in series with the circuits, In the accompanying drawings, forming'a while the term "radiating portion indicates part of this specification, Figure 1 is a diasubstantially all of the sending-conductor r5 grammatic'view illustrating a form of appafrom topor extreme end of same to a point 2'5 ratus for the practice of my invention. F'i at or near-junction with the apparatus for 2 is a similar VIBW illustrating a modification efiecting the oscillatory charging and die at the apparatus at the receiving-station. charging thereof, such as sparking terminals,

Fig. 3 1s a sectional elevation of one form of transformer-coils, armature-windings, 620. 8c conductor. Fig. 4 is a top plan view of the v The self-induction of thesending-conductor same, and Fig. 5 is an elevation of a modifi-i can be regulated by increasing or decreasing cation of the conductor. the turns in the coil 2, formedin thewire con- In the experiments heretofore made in wire necti n g the radiating portion 1 with the genless transmission of energy, as in telegraphy, erator 3. The capacity of the sending-ccn- 85 relatively high frequencies.-e. g., of the or ductor can be regulated in several ways-es, 5 der of two million (2,000,000) periods or more for example, by changing the superficial area per second-have been used. It is impossiof the radiating portion 1-by the employhle to produce or utilize mechanical movement of a medium as described in applicaments directly by the interaction of a contion No. 62,303, filed May 29, 1901, or reduc- 9o stantorindependently-varying magnetic field ing the height of the radiating portion with- 0 and a current-induced by electromagnetic out reducing its superficial area. A 0011- waves of such high periodiclties, for the-readoctor of large capacity may be constructed, son that either the element to be moved (as as shown in Fig. 3, having its radiatingp'orthe diaphragm of a telephone) is incapable tion 1 in the form of a cylindrical cage, con- 5 of such rapid vibrations or the vibrations are sisting of a number of parallel wires 4, se-

too rapid to be utilized. In order to utilize cured at theirends to supporting-rings 5, prodirectly the interaction between currents invided with hubs or central sockets 6 for the dueed by electromagnetic waves and a conreception of supporting-rods 7, formed of stant or independently varying magnetic bamboo or other light non-conducting matezoo field to produce motion in one of. two memrial. For convenience it is preferred to form 1 bars of a receiving instrument, one member the cylindrical cagein sections, which can be thereof consisting ofaconstant or independmechanically and electrically connected by ently-varying magnetic field, the sendingthe supporting-rings, as shown. This wire cage or cylinder can be connected to ground in any suitable manner, as by the wire- 8, in which coils -r turns may be formed to adj list .the self-induction of the sending-conductor. Asshown in Fig. 5, the radiating portion may be formed by'a cylinder 9, having continuous metal walls. By employment of sending-conductors having large capacity distributed with approximate uniformity or regularity over a large portion of its length the height thereof may be' reduced without affecting the efficient travel of the electromagnetic waves radiated therefrom. When low frequency is obtained by increasing the capacity alone, or by increasing both capacity and self-induction, the curve of resonance is broader than is obtained by increasing the self-inductance alone, though in the former cases the amount of energy radiated for a given voltage and length of sending-conductor is more than is obtainable with a short resonance curve; Hence to obtain the best results it is preferred to use the two former ductor and a shorter radiating portion are ob-,

tained, and in addition thereto it is possible 'with frequencies of one hundred thousand (100,000) or less to substitute for the induction-coil,-connected in the manner now in vogue, a source ofalternating voltage as the exciting-generator-as,for example,the exciting-generator may be a dynamo, a trans-- formerconnected to a dynamo,or aninductioncoil producing low-frequency oscillations in a primary circuit, the secondarycireuitforming the source of alternating voltage and having one terminal connected to theradiating portion and the other terminal to the ground. border that a dynamo may be used to produce such a high periodicity which, though low as compared with'periodicities heretofore used in wireless transmission of energy, as in telegraphy, is very high as compared with those generated by dynamos commonly used in electrical engineering, it must possess several distinct characteristics. should generate pure sine-waves, because, as is well known, this is the only.f0rm of curve which gives perfect resonance. With a dynamo giving such a curve forming a part of a suitably-constructed sending-conductor it is possible to wind the dynamo so as to generate, folexample, only a thousand volts on open circuit, and yet by means of resonance efifects to obtain a voltage of a bundred thousand volts on the sending conductor. It is possible to obtain resonance effects by use of a dynamo of low internal resistance, as a portion of a sending-conductor of large capacity or self-induction, or.

First, it

both, having these electrical constants suitably proportioned so that the sending-conductor has a natural period identical with that of the dynamo. This obviously renders the machine much cheaper to build and much easier to manipulate for signaling purposes than a dynamo or dynamo and transformer built to give one hundred thousand volts directly. Second, the armature must be of 10W internal resistance, because it of a high resistance the oscillations will be dampened and high resonance voltages cannot be produced. Third, it must be well ventilated, because during the period of sending a signal the current may ru n u p to hundreds or even thousands of amperes. Fourth, the length of wire in the armature must be as small as possible compared with the length of the sending-conductor, for otherwise the electrical constants of the sending-conductor-i. e., of the circuit from the top of the conductor to the ground including the armaturewill be determined too largely by that part of the circuit between the armature terminals and the amount of radiation from the given voltage on the sending-conductor would be much less than would be the case if the armature had relatively lesser length of wire. i In other words, the self-induction and capacity of the armature must be as small a fraction as possible of the self-induction and capacity of the sending-conductor. When the dynamo is said to be in resonance with the sending-conductor, it is meant that the natural period of the whole conductor, from the top of the conductor to the ground including the armature, is the same as the periodicity of the dynamo. ljifth, it is also essentialthat all iron magneticallyinfiuenced by currents in the conductor should be so proportioned and distributed as not to effect the shape of the curve of voltage or to cause loss of power by hysteresis, as in such case there would be'too much dampening. For

these reasons the dynamo may be constructsine-waves as closely as possible, and tho revolving parts formed of magnetic material of high tensile strengtl1,such as nickel-steel.

A dynamo with the revolving part having a high peripheral speed of one-half mile per minute has given ten thousand periods per second, and with a revolving part formed of nickel-steel a peripheral speed of five miles per minute can be safely maintained, giving thereby'one hundred thousand periods per second.- Such peripheral speed can be obtained by the employment of steam-turbine.

It will be evident to those skilled in'the art that instead of using a dynamo giving a thousand volts a dynamo giving a hundred volts may be used with a transformer stepping up to a thousand volts; but in such case the length of wire in the secondary of the the sending-conductor.

transformer should have the same relation to the length of the whole conductor, including the secondary of the transformer, as stated in reference to a dynamo giving a thousand volts.

The best results are obtained when the frequency of the source of alternating voltage, as a dynamo, is equal or approximately equal to the natural frequency of the radiating system. The adjustment of frequencies can be effected by changing the speed of the dynamo. The reason why the best results are obtained whenthe frequency of the dynamo or its equivalent (as a transformer connected to a dynamo) is equal or approximately equal to that of the natural frequency of' the radiating circuit is that when the frequency of the dynamo is less than this the chief effects are electrostatic and magnetic in their nature and there is practically no electromagnetic radiation. Under these circumstances .signals cannot be transmitted to any great distance, as the electrostaticand magnetic effects fall off as a high power of the distance. As the frequency of the dynamo is increased the edects of electrostatic and magnetic in duction continue to predominate until the frequency of the dynamo approaches that of \Vhen this point is reached, if the radiating portion of the sending-conductor has a length which is a large fraction of the total length of the circuit a large amount of energy can be radiated in the form of electromagnetic waves and signals be transmitted a long distance. The reason why the length of the radiating portion of the sending-conductor should be a large fraction of the total length of the, circuit is that if otherwise the circuit would be a poor radiator. If, for example, the length of the radiating portion of the sending-conductor is five feet and the length of the wire in the armatafe is five miles, the amount of energy radiated would be very small compared to what it would be if the length of wire in the armature were only five hundred feet and the radiating portion of the sending-conductor five feet. A further advantage incident to the employment of low frequencies is the fact that there is, as I have discovered, less absorption of the electromagnetic force as the waves travel along the ground than when the waves have high frequencies.

In the form of apparatus shown in Fig. 1 the generator 3 (in this case a dynamo) has one pole connected to ground and the other pole connected bya wire having an induc tance 2 to the radiating portion 1. The sending-conductor which may have its radiating portion of any suitable form, but preferably that shown in either Figs. 3 and 5, has its capacity or self-induction or both adjusted in the manner described, that the electromag netic Waves radiated will have low frequency. At the receiving-station the receiving-conductor 10is connected to one terminal of a translating device 11, as a telephone, the

opposite terminal thereof being connected to the ground. As the frequencies of the waves formed by a piece of fine wire 12, held in ten- V sion between the poles of a magnet 13. By the interaction between the currents passing along the wire 12 and the magnetic field the wire is caused to vibrate and make and break contact with the microphonic contact point 14, which is so adjusted as to be normally out of contact with the wire 12. A circuit, including a battery 15 and relay 16 or other translating device, is formed in part by the contact 14: and the wire 12, so thatwhenever the secondary circuit is completed by the vibration of the wire the relay will be energized.

If the radiating portion be made, as shown in Fig. 5, with varying superficial dimensions-e. 9., with aswellorenlargement17 the electromagnetic waves generated from its different surfaces will have different periodicities, as the periodicity of electromagnetic waves depends, in part at least, on the capacity of the radiating portion at the sendingstation, a similarly constructed conductor may be used at the receiving-station, or two simple receiving-conductors suitably tuned may be used. V

By the use of a sending-conductor of large capacity and having that capacity uniformly distributed certain specific advantages are obtained which cannot be obtained by any Nhen the capacity other style of conductor. is not distributed with substantial uniformity, it is impossible to obtain a sine form of electromagnetic wave, and this form of Wave gives very much better resultsin that it permits of the voltage being increased by resonance to any extent, depending only on the resistance losses. For example, if the resistance" be lowit is possible with an impressed voltage of, say, five to reach a resonant vol.- tage of two hundred or more with a capacity distributed uniformly-2'. 6., with asine-wave, while if the capacity be distributed, so as to give a parabolic wave with a voltage of five, it is not possible to obtain by resonance a higher voltage than twenty-five, since when the capacity is large the resistance is also low on account of the fact that the currents .with these high frequencies flow over the surface of the sending-conductor it follows that with a sending-conductor of large capacity uniformly distributed it is possible to get a sinewave and a low resistance-2'. e., conditions necessary and favorable for the production of large resonant voltages from small impressed voltages, and hence conditions which permit of sending over longerdistancesthan if the sending-conductor were of tities sufiicient &

The effect of locally increasing the superficial area of the sending-conductor or of locally increasing the capacity by any other suitable means is to produce twoor more sets of waves of. different periodicities, the periodicity of the first being dependent upon the electrical constants of the sending-conductor as a whole and the periodicity of the other depending upon the position and amount of localized increase of capacity in the same way as by attaching a weight or spring to a piano-Wire between its extremities additional vibrations in the wire are created.

lly the term electromagnetic waves as used herein is meant waves of a wave length long in comparison with the wave length of what are commonly called heat-waves or radiant heat. By grounded conductor is meant a conductor grounded either directly or through a capacity, an inductance, or a resistance, so that the current in the conductor flows through the conductor to ground, and vice versa, when electromagnetic waves are generated. The terms tuned and resonant are used herein as one including the other.

This invention involves the discovery of the desirability and practicability of using radiant electromagnetic waves of a frequency lower than has heretofore been recognized as desirable or practicable and in the devising of a considerable number of very meritorious features combined in an apparatus or system whereby the energy of such waves may be successfully radiated in quanfor practical use over long distances. a

In constructing an apparatus that will give practical results with such low-frequency waves novel features have been devised, some of which are of general utility in generating and radiating waves of the higher and more usual frequencies, and these are hereinafter claimed in terms thereof in other than the specific connection for which they are primarily intended.

The amount of radiation possible for a given system is dependent, among other things,

upon the frequency,

and, other things being equal, the amount is less for the lower frequencies. "In order, therefore, to radiate large amounts of energy by low-frequency waves, I take advantage of the rise of voltage due to resonance effects brought about by a properproportioning of inductance and capacity, so that the phases of the impressed electromotive force and the current coincide in time. g

Resonance effects in a vertical conductor which will cover the use.

grounded at one end depend upon the quan tities of the conductor which make it a good oscillator, and this is measured by the amount that the resistance is less than the square root of four times the inductance divided by the capacity-that is, the amount of R is less than i j; but in such a conductor the best conditions of resonant oscillation require that the length of conductor be one-fourth the length of the fundamental wave oscillating therein. It is evident then that if the conductor be a plain wire of ordinary size and the capacity and inductance employed for tuning be small the wave lengtlttherein will be substantially the length in the ether of a wave of the same frequency, which for a frequency of ninety thousand is two miles, and the resistance which acts to cut down oscillation would be that of eight miles of wire for each complete wave or oscillation, so that the tenth wave or oscillation, for example, would have been subject to the resistancelosses of eighty milesofwire. Where,

however, the inductance and capacity are large, the length of the sending-conductor and its subsequent resistance detrimental to oscillation may be greatly decreased, for the frequency of the fundamental wave-that is, the natural period of such a conductorvaries inversely as the square root of the capacity multiplied by the square root of the inductanee-that is, inversely as the quantity or value l dent that instead of increasing L and O in equal proportions to get a large total I\/ 1'] (j necessary for a good oscillator one of these factors may be increased, while the other re- Now since the condition of resonance is that C L W =1 it is evimains constant or is decreased. Large inductance, however,would involve large resistance, which is bad, as shown, while increase of capacity in accordance with my invention is advantageous in many ways, as will be pointed out. -I therefore make the capacity large and the induction correspondingly small, thereby making the quantity M large and correspondingly shortening my sending-conductor and greatly reducing my resistance,

The large capacity I distribute uniformly over substantially all of the radiating portion of the conductor, thereby further reducing instead of increasing the resistance and at the same time providing a large effective radiating-surface. The further reason why the capacity is thus distributed is that with any other arrangement pure sine form of electromagnetic wave, because any local increase of capacity tends to produce two or more sets of waves of different periodicities.

In order that I may radiate large amounts of energy, I make the radiating-conductor over which the capacity is distributed a large fraction of the total length of. the sending-conductor. This points another advantage of relatively and absolutely large capacity and corresponding inductance, for unless I was able to greatly shorten the sending-conductor, as I do by their use, it would be difficult to construct a low-frequency radiating-conductor which would be so large a fraction of the length of the whole sendingconductor.

From the above it will be seen that by my invention the internal current losses due to ohmic resistance are largely decreased by using large total capacity and small inductance for the tuning, thereby shortening the length of sending-conductor necessary for a given frequency or for a given wave length in the ether. The shortening of the sending-conductor also facilitates the use of a radiatingconductor which is a large fraction of the wave length. The distribution of the capacity makes possible a better form of wave, decreases the resistance of that part of the sending-conductor, and further increases the radiating-surface.

lVith this system, whereby large amounts of energy may be radiated at a low frequency, I am able to substitute for the induction-coil and spark-gap now in use a dynamo or similar source of alternating voltage.

If the dynamo be used without the sparkgap, I am able at once to produce a continuous train of radiant waves of substantially uniform strength, as distinguished from the wellknown systems wherein the spark-discharge starts a' train of WftVBSiOf rapidly-diminishing power followed by relatively long intervals of no radiation. Furthermore, Where the spark discharge is used I am able, by reason of the persistent oscillation coupled with the low frequency, to greatly diminish and, indeed, to completely bridge over the intervals of no radiation, for with ten thousand sparks per second exciting a sendingconductor of a periodicity of ninety thousand it is evident that if each spark gives only ten oscillations before being damped sufficiently to stop radiation, every tenth oscillation will coincide with the first oscillation produced by the next succeeding spark. Thus the radiation will be practically continuous, and the total energy of the first oscillation produced by the spark will be divided between only nine electromagnetic waves. Now if the frequency were one million and the sparks ten thousand per second it would be necessary to have an oscillator capable of one hundred useful oscillations of a power sulficient to produce useful radiations in order to maintain practically continuous radiation. Theenergy of a single spark in that case would be divided between one hundred radiant electromagnetic Waves and would be too small for practical use over commercial distances.

From the above it will be seen that by keeping R small and the frequency lowI am able to radiate practically continuous streams of electromagnetic waves of an energysuflicient for practically continuous effects at the re ceiving-station. Even in the case where the sets of oscillations do not quite overlap in time it is evident that the intervals of inactivity are decreased by the increase of the time of a train to ten times what it would be with a frequency of one million. This is a great advantage in cases where the receiver is tuned to the period of the transmitter, for the regularity, continuity, and great energy of the waves improve the resonance in a manner that by use of proper devices at the receiving-station more than compensates for the rather broad curve of resonance involved in any use of large capacity for tuning purposes.

In practice it is found that substantial uniformity of distribution of capacity may be obtained by making the conductor uniform in figure from the\top to a point at or near the bottom, as isindicated in Fig. 3. It has been held by some that the capacity of the upper portion of a vertical conductor of uniform cross-section is much smaller than that of the middle or lower portions by reason of its greater distance from ground; but I have found by actual measurement that this is practically not the case, the upper portions having practically the same capacity as the lower portions. The capacity of a conductor with respect to ground is mainly dependent upon its size and shapeand not upon itsdistance from the ground when the distance between the conductorand ground is not small.

I claim herein as my inventionl. A sending-conductor for electromagnetic waves, having a large capacity distributed with substantial uniformity over its radiating portion, substantially as set forth.

A sendingconductor for electromagnetic Waves, having its capacity so adjusted that the waves radiated therefrom have a low frequency, substantially as set forth.

3. A sending-conductor for electromagnetic waves, having its capacity and inductance so adjusted that the Waves radiated therefrom have a low frequency, substantially as set forth.

4. In a system for transmission of energy by electromagnetic waves, the combination of a source of alternating voltage and a conductor in series therewith forming a sending-conductor said sending-conductor being adapted to radiate electromagnetic waves and having its radiating portion of a length which is a large fraction of the quarter-wave length produced by the alternating source of theradiating portion in the medium surrounding the radiating portion, substantially as set forth.

5. In asystem for transmission of energy by electromagnetic waves, the combination of a source of alternating voltage and a conductor in series therewith forming a sending-conductor said sending-conductor being adapted source of alternating voltage, substantially as set forth.

.. queney,

7. In asystem for the transmission of energy by electromagnetic waves, the combination of an alternating-current dynamo and a conductor in series therewith forming a sendingconductor said sending-conductor being tuned to the dynamo and adapted to radiate elec tromagnetic waves and tuned to the dynamo, substantially as set forth.

8. In asystem for tlictransmission of energy by electromagnetic waves, the combination of a sending-conductor so proportioned as to radiate waves of low frequency and an alternating-current dynamo having its terminals connected respectively to the radiating portion of the sending-conductor and to ground, the dynamo being so adjusted that its periodicity is the same or approximately the same as the natural period of the sendingconductor, substantially as set forth.

9. A sending-conductor for electromagnetic waves, formed by an alternating-current dynamo and a conductor in series therewith, one pole of the dynamo being grounded, the

sending-conductor thus formed being so proportioned as to radiate waves of low frequency, substantially as set forth.

10. A sending-conductor for electromagnetic waves so proportioned as to radiate waves of low frequency in combination with a source of alternating voltage having its terminals connected respectively to the radiating portion of the sending-conductor and to ground, the voltage-generator being so adjusted that its periodicity is the same or approximately the same as the natural period of the system when so connected, substantially as set forth.

11. A sending-conductor for electromagnetic waves, formed by a source for continuously generating alternating voltage and a conductor in series therewith, one pole of the source of alternating voltage being grounded, the sending-conductorthus formed being so proportioned as to radiate waves of low frequeney, substantially as set forth.

12. A system for signaling by electromagnetic waves having in combination a conductor adapted to radiate waves of low freand a receiver dependent for its action upon a constant or independently-varying magnetic field and adapted to respond to frequency and a netic waves having low resistance,

currents produced by said waves, substan- "tially as set forth.

13. A sending-conductor for electromagnetic waves of a length much less than a i quarter of the length of an ether wave, having a frequency equal to the natural period of said sending-conductor, and having a radiating portion which is a large fraction of its total length.

14. A sending-conductor for electromagnetic waves having a natural period of vibration much lower than' the period of an ether-wave four times its length, whereby its radiating portion may be a relatively large fraction of the total length of said sendingconductor. p

15. A sending-conductor for electromagnetic waves tuned to a desired low frequency by large capacity and smallindnctance.

16. A sending-conductor for electromagnetic waves having small inductance and tuned to a desired low frequency by a suitably-proportioned large capacity.

l7. A sending-conductor for electromagsmall selfinduction and great capacity, substantially asand for the purpose set forth.

18. A sending-conductor for electromagnetic Waves having low resistance, small self-- induction and great capacity so correlated as to support persistent oscillation of a frequency much less than that of an ether-wave.

of a length conductor. y

19. A system for transmission of energy by electromagnetic waves in combination with a radiating-conductor and a source of alternating electrical energy or potential, said radiating-conductor and source being coordinated and relatively adjusted to radiate a substantially continuous stream of electrofour times that of said sending- .magnetic waves.

20. A system of transmission of energy byelectromagnetic waves including in combination a radiating-conductor and a source of alternating electrical energy or potential,

said radiating-conductor and source being coordinated and relatively adjusted to generate and radiate a substantiallycontinuous stream of electromagnetic waves.

21. A system for transmission of energy by electromagnetic Waves, including in combination a radiating-conductor and a sourcepf alternating electrical energy or potential, said radiating-conductor and source being coordinated and relatively adjusted to radiate a substantially continuous stream of electromagnetic. waves of substantially uniform strength.

In testimony whereof I have hereuntoset my hand.

' REGINALD A. FESSENDEN; Witnesses: w

W. 13. FEARING, S. U. GRAY.

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