US727330A - Signaling by electromagnetic waves. - Google Patents

Description

No. 727,330. PATENTED MAY 5, 1903. R. A. FESSENDEN.

SIGNALING BY ELECTROMAGNETIC WAVES.

APPLICATION FILED IAB. 21, 1903.

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No. 727,330- PATENTED MAY 5, 1903..

R. A. FESSENDEN. SIGNALING BY ELECTROMAGNETIC WAVES.

APPLIOATIOI FILED [AB- 21, 1903.

I0 IODEL. 2 SHEETS-SHEET 2 NM wi w UNITED STATES Patented ma 5, 1903.

PATENT OFFICE.

SIGNALING BY ELECTROMAGNETIC WAVES.

SPECIFICATION forming part of Letters Patent N 0. 727,330, dated May 5, 1903.

Application filed March 21, 1903. Serial No. 148,858- No model-l To all whom it may concern:

Be it known that I, REGINALD A. FESSEN- DEN, a citizen of the United States, residing at Fort Monroe, in the county of Elizabeth City and Stateof Virginia, have invented or discovered certain new and useful Improvements in Signaling by Electromagnetic Waves, of which improvements the following is a specification.

The invention described herein relates to certain improvements in methods of signaling by electromagnetic waves described in Letters Patent No. 706,742,'granted to me August 12, 1902, and has for its object a selective method of signaling which consists in varying the character of the radiationsfrom the sendingestatiou at a rate independent of the natural periodicities ofthe system.

The invention is hereinafter more fully described and claimed.

' .In the accompanying drawings, forming a partof this specification, Figure 1 is a diagrammatic view illustrating the apparatus employed at the sending-station. Fig. 2 illustrates a modification of the sending apparatus. Fig. 3 is a diagrammatic viewillustrating a form of receiving apparatus. Fig. 4. illustrates a form of receiver. Fig. 5 illustrates'a second form of the receiver. Fig. 6 illustrates a modification of the receiver shown in Fig. 5, and Fig. 7 is an end view of the receiver shown in Figs. 5 and 6.

In thepractice of myinvention the primary 2 of a transformer is arranged in series with the vertical conductor 1, which is grounded, as shown. The secondary 3 of the transformer is included in aoircuit consisting of the condensers 4 and 5 and a gap 6, which is normally non-eonducting-as, for example, an air-gap, a WVenhelt interrupter, or similar device. The local circuit, including the secondary of the transformer, the condensers, and the non-conducting gap, is preferably tuned to the periodicity of the sending-conductor l. continuous-current kind and preferably a storage battery, is arranged in series with the I condenser and secondary of the transformer,

and means, such as resistances 7 and 8, are included in the circuit of the generator, preferably, but not necessarily, in opposite legs of the circuit. The generator'maybe ar- A generator 9, preferably of the ture of the gap. Very high voltages may be suitably obtained, if desired, b using a continuous-current generator with revolvingfield and making the sections of the winding of the armature primaries of transformers whose secondaries are connected to a commutator and commutated by revolving brushes. In this way any desired amount of insulation can be obtained, and there is no need for heavy insulation on thegenerator itself, but merely on the transformers and the commutator where there is no-diificulty in using it. The means 7 and 8 govern the rate at which the condensers Land fir'are charged, this function being described in United States Patent No. 706,742,. above referred to.

A motor 10, carrying its armature-shaft a commutator and regttlated as to speed by the tuning-fork 13 in; thef circuit' of the battery 12, as describedjin United States Patent No. 715,203, grantedvDecember 2, 1902, is employed for short-circuiting the retarding means or resistanc'efi,thereby varying the n umber of disohargespei' second at every revolution of' the a'rmatureof the motor. A second tuning-fork l3 and local battery 12* may be employed for regulating the motor, though the same local battery may be used for both forks. When using'the'second tuning-fork and battery, they are adapted to be connected to the motor by means of a switch 14. These tuning-forks have difierent rates of vibration, and hence when one or the other is connected to the motor the latter will rotate at different rates per second, causing a corresponding change in the number of times per secondthat the discharge frequency is changed. As, for example, the circuits may be so arranged that the local circuit, including the secondary of the transformer, the condensers, and gap,

has a natural period of two million per second, and the retarding means, as 7 and 8, may be so arranged that there will be two thousand discharges per second'whenthe resistance 8 is in circuit and ten thousand discharges per second whenit is short-circuited. Then the commutator .11, governed by the tuning- fork 13 or 13, may be so arranged as to effect a change in the rate of discharge (and hence a change in the amount of energy radiated) five hundred times per second. It will thus be seen that we have three different frequencies -first, the electricahwave frequency,

ferred to tune the receiving-station electrically to the wave frequency and to tune the receiver-mechanical] y or electrically, or both, to the independent frequency. In the case illustrated the receivingcircuit would be tuned electrically to'the wave frequency of two million and the receiver tuned mechanically or electrically, or both, to a frequency of five hundred.

The distinct feature of this method is that there is not only electrical tuning, to the Wave frequency, but also tuning either mechanic- ,ally or electrically, or both, to another frequency which is independent of the discharge or group frequency.

It is'notessential that the resistance 8 be employed, as it may be omitted, in which case the commutator 1'1 entirely interrupts the discharges the required number of times per second instead of varying the rate of discharge. ln sending messagesa key is used, which on being depressed short-circuits the retarding means or resistance 8 (or, if this is omitted, closes the discharge-circuit) during the time the signal is being sent. The key 15 may also be arranged to operate in this re verse way-i. e., to interrupt the discharges on being depressed.

The method described herein has the advantage over that described in Letters Patent No. 706,742 in that instead of employing a continuous-current generator an alternatingcurrent generator having a frequency of from ten thousand to one hundred thousand per second, as described in Letters Patent No. 706,737, granted to the August 12, 1902, may be used, inwhich case the energy radiated may be practically constant. Int-he method described in Letters Patent N 0. 706,742 a continuous voltage is used, or, if an alternating generator of the usual frequency is employed,

the lower tuning is made to the frequency of thealternatinggenerator; but when an independent frequency, as" described herein, is used in connection with an alternating-current generator the radiation occurs at fixed intervals of time, though the amount of energy radiated during each commutation may be and with usual frequencies will be unequal, and hence sharp mechanical tuning canbe had.

A particular advantage in the method described herein lies in thefact that a slight variation in the voltage or speed of the generator does not affect the low-frequency tuning or tunin g to the lower frequency, whichin this case is the independent frequency.

As shown in Fig. 1, a rotating commutator 1'1, with a sending-key, may be employed to shunt any desired amount of the resistance. When it is desired to send two or more messages simultaneously, the amount of resistance 7 and of other resistances in the charging-circuit may be varied in substantiallythe same mannenas shown in Fig. 10 of Patent No. 706,742, above referred to. To thisend a suitable shunting device, as'the rotating commutator 11, with a sending-key, is so arranged as to be capable of shunting any desired amount of resistance 7 or other resistances if more than two messages are to be sent, and so impose an arbitrary frequency dilferent from that imposed by commutator 11 and resistance 8 or other commutators and resistances when two or more messages are to be sent sim ultaneously to two or more stations tuned to different independent frequencies;

At the receiving-station the receiver proper, which may be of the constantly-receptive or automatically self-restoring wave-responsive type, may be arranged in series with the receiving-conductor; but itis preferred to arrange such receiver in the circuit of the secondary of a transformer having its primary arranged in series with the vertical. In the circuit of the secondary 21 of the transformer are included capacities 23 and 24, preferably unequal, so as to permit sharp tuning. The circuit consisting of the'secondary of the transformer and the capacities is preferably tuned electrically to the wave frequency of the sending end, and the receiver 25- is preferably tuned mechanically or electrically, or both, to the independent frequency. A suitable form of receiver is shown in Fig. 4 and consists of a thin silver ring pivotally mounted on two silver knife- edges 27 and 28 and resting on a knife-edge of carbon 29 and included with a coil 30, which is in series with the vertical conductor. One of the silver knife-edges, as 27, a portion of the ring, and the'carbon knife-edge 29 are included in a local circuit having a battery and an indicating mechanism, as a'telephone. This construction of receiver is fully shown and described in Letters Patent No.'706,736, granted to me August 12, 1902. Such a ring constructed of No. 40 silver wire has anatural elastic period of vibratiou of about fifteen per second.

A second form of receiver isshown in Fig. 5 and consists of a small tuning-fork 31, made of thin phosphor-bronze about fifteen onethousandths of an inch thickand l1aving,ar-

matures 32 secured to its extremities, preferably formed of layers of No. 40 soft-iron wire. Between the ends ofthe tuning-fork an electromagnet is arranged consisting of pieces of thin sheet-iron wound with a coil of wire whose terminals may be connected in series with the vertical or in series with the secondary of the transformer having its pm- .4 will depend upon the periodicity of the alterquite.

mary connected to the vertical. It is found in practice that it is sometimes beneficial when this form of receiver is used that it should be very nearly tuned electrically to the wave frequency of the sendingstation, but not On waves being received at the sending-station the electromagnet 33 is energized and attracts the prongs of thetuning-fork without change of direction so long as the radiation is being sent. When the motor 10 alters in the manner described the amount of energy sent out, either by changing the number of sparks per second or by entirely interrupting the discharges, the prongs resume their original position. Every time the independent frequency of the sending-station is made equal to the natural period of the tunin g-fork 31 there will be constantly-increasing amplitude of vibration. To produce an indication, one of the prongs may be directly fastened to a telephone-diaphragm 34, as shown in Fig. 5, or a microphonic contact 35, a local battery 36, and an indicating mechanism 37, as a telephone, may be used, as shown in Fig. 6. The circuit including the microphonie contact and telephone may also be tuned electrically to the independent frequency, and this maybe done also when there is no mechanical tuning. The method described herein has a numberof advantages over that described in Patent No. 706,737, above referred to.

First, in the operation of the method de scribed in the patent it is evident that the group frequency would depend upon the voltage of the generator if a dynamo were used, for the higher the voltage the greater the number of discharges per second, and that if an alternator is used, since its voltage is constantly varying, the group frequency nator, since the groups available for mechanical tuning would have the same periodicity as the alternator. Consequently sharpness of tuning will depend upon the speed regulation of the generator in all cases where a dynamo is used It is found in practice that mechanical tuning can be carried to an accuracy of at least one part in four hundred, and it has been carried to a much greater extent, though in general such extreme accuracy is not-necessary. On the other hand, it has been found difficult to regulate the speed of a dynamo within one part in twenty or twenty-five. By this is meant not the average speed, but the extreme values of instantaneous speed upon which the tuning depends. In the Inethod'herein described this dilficul'ty is' entirely overcome, and instead of attempting the extremely-difficult problem of regulating a dynamo (giving, for example, several kilowatts output) to a constant speed of one-fourth of one per cent. the dynamo regulation becomes an almost negligible factor, and the only speed which must be regulated is that of a small motor consuming a few watts of energy and capable, therefore, of

being governed accurately by a standard tuning-fork. The method of mechanicaltuning is thus made practical for the use of a generator other than storage batteries, while before it was only with the greatest diificulty that accurate mechanical tuning could be attained.

In the method described in United States Patent No. 706,737 the number of discharges per second-is limited, because the discharge frequency is the frequency to which the mechanical tuning is tuned. Consequently since it is difficult to tune to very high periodicities mechanically a very high number of discharges per second cannot be used. In the method described herein the number of discharges per second may be very high. For instance, if an ordinary air-gap with air or magnetic blast be used we may obtain fifty thousand or more sparks per second. jbince, however, the independent frequency is independent of the discharge frequencies, we can thus combine the great radiating effect of high frequencies and yet obtain accurate me chanical tuning or accurate electrical tuning, or both, to the lower frequency, in this case to the independent frequency. Being thus rendered independent of the frequency of the alternator we can use a wide range of mechanical tuning with an ordinary alternator of commercial frequency. For example, if the periodicity of the alternator be sixty per second we can obtain mechanical tuning and of course electrical tuning over a range of frequency varying from ten per second up to five thousand and higher from the same altern ator without changing its periodicity. It is not essential that the tuning to the independent frequency be mechanical or electrical alone, as both may be combined, though the use of either alone is preferred to the combination of the two, and in many cases electrical tuning to both wave frequency and electrical frequency maybe used.

In the extreme case, where the discharge frequency becomes identical with that of the wave frequency-as, for example, with a high frequency alternating generator, as shown in Fig. 2the independent frequency may be varied in the same way as inthe case described in Fig. 12'. 6., by means of the tuning-fork. It is preferred to have the commutator 11 with a number of segments, so as to change the discharge gradually and preftoo IIO

erably to have the change vary as a sine.

trical circuitsas, for example, in the field of the dynamo of the auxiliary circuit 3 4 5 6 or in the vertical-with good results, but it is preferred to place it in the position shown.

When the commutator is placed in the vertical, it is preferred to use the form of commutator construction described above, in which the alternation is effected gradually and not abruptly, as by an interrupting form of commutator. This is on account of the fact that the voltages used in wireless telegraphy are so high that if the circuit be interrupted suddenly there vwill be difficulty from arcing between the contacts of the interrupter.

It has been proposed to arrange a vibrating interrupter between the spark-gap and the vertical conductor; but such arrangement is inoperative, and its use has not, so far as known, been attempted.

On account of the high potentials necessary for wireless workit would be practically Y impossible to operate such a vibrator so as to obtain a sufiicient length of insulating-gap, especially with a vibrating form of make and break. In addition to the trouble from areing the interruptions will be irregular, as the duration of the time of activityofthe vertical will not depend solely on the period of the interrupter, but on the distance the vibrating contacts happen to be separated and the spark potential at that time. For example, if the induction-coil primary is broken at a time when the contacts are separated,

say, a distance of half an inch the spark will jump and the vertical will be charged.

contacts have approached to within a quarter of an inch, the first change-spark will take place at a later point of time in the period of the vibration. Hence the times between successive charges and discharges will not be constant, and the tuning cannot be accurate- This d'ifiiculty'cannot be overcome by working in an insulating liquid, as, though the insulation is better before contact, an arc will be drawn in retracting, and it will be but a short time'before insulating power of the'liquid is destroyed.

I claim herein as my 'invention 1. In a system of signaling by electromagwhich consists in varying the character of the radiation periodically at a rate independent of'both the wave and discharge frequencies.

3. In a system of signaling by electromagnetic waves, the method herein described which consists in emitting waves of a given periodicity by discharges of a given periodicity and periodically varying the character of the radiation at a periodicity difierent from the natural periodicities of the system.

If however, theprimary is not broken until the 4. In a system of signaling by electromagnetic waves, the method herein described which consists in emitting waves of a given periodicity by discharges of a given periodicity and periodically varying the character of the radiation at aperiodicitydiiferent from both the wave frequency and the discharge frequency.

5. In a system of signaling by electromag'-- emitted energy and of the periodicity of the generator.

8. In asystem of signaling the method herein described, which consists in emitting energy periodically, periodically varying the character of the energy emitted at a periodicity independent of the periodicity of the emitted energy and of the periodicity of the generator, and operating by the energy received at the receiving-station a receiver tuned to the frequency of the emitted radiation and to the independent frequency.

9. In a system of signaling the method herein described, which consists in emitting energy periodically, periodically varying the character of the energy emitted-at a periodicity independent of the periodicity of the emitted energy and of the periodicity of the generator, and operating by the energy received at the receiving-station a receiver tuned electrically to the frequency of the emitted radiation and mechanically to the independent frequency.

10. In a system of signaling the method herein described, which consists in emitting energy periodically, periodically varying the character of the energy emitted at a periodicity independent of the periodicity of the emitted energy and of the periodicity of the generator, and operating by the energy received at the receiving-station a receiver tuned electrically to the' frequency of the emitted energy, and operating an indicating mechanism tuned to the independent frequency.

11. In a system of signaling by electromagnetic waves, the method herein described which consists in generating electrical waves of a high frequency,by means of electrical discharges ofa lower frequency, and periodically changing the character of. the radiation at a rate independent of the wave frequency and the discharge frequency.

IIO

12. In a system of signaling by electromagnetic waves, the method herein described which consists in generating electrical waves of a high frequency by means of electrical discharges, periodically changing the character of the radiation at a rate independent of the wave frequency and the discharge frequency, and operating by the energy so emitted 'a receiver at a receiving-station, tuned both to the Wave frequency and to the independent frequency.

13. In a system of signaling-by electromagnetic waves, the method herein described which consists in generating electrical waves of a high frequency by means of electrical discharges, periodically changing the character of the radiation at a rate independent of the wave frequency and the discharge frequency, and operating by the energy so emitted a receiver, at a receiving-station, tuned electrically to the wave frequency and mechanically to the independent frequency.

14. In a systemof signaling the method herein described, which consists in emitting energy periodically from a sending-station and periodically varying the character of the energy emitted at a periodicity independent of the periodicity of the emitted energy and of the generator, and producing by the energy so emitted indications at a receiving-station by means of a cumulatively-acting receiver.

15. In a system of signaling by electromagnetic waves, the method herein described which consists in generating electrical'waves of a high frequency by means of electrical discharges, periodically changing the character of the radiation at a rate independent icall y varying the character of such radiation at a rate independent of the natural periodicities of the system and operating by the energy received at the receiving-station a receiver of the character substantially as described tuned to the frequency of the emitted radiation and to the independent frequency.

17. In a system of signaling by electromagnetic waves, the method herein described, which consists in the generation of radiation, varying the character of the radiation periodically at a rate independent of both wave and discharge frequencies and operating at the receiving-station a receiver of the character described tuned to the frequency of the emitted radiation and to the independent frequency.

18. In a system of signaling by electromagnetic waves the method herein described, which consists in emitting waves of a given periodicity by discharges of the given periodicity, periodically varying the character of the radiation at a periodicity different from the natural periodicities of the system and operating by the energy received at the receiving-station a receiver of the character described tuned to the frequency of the emitted radiation and to the independent frequency.

19. In a system of signaling by electromagnetic waves, the method herein described, which consists in emitting waves of a given periodicity by discharges of a given periodicity, periodically varying the character of the radiation at a periodicity different from both the wave frequency and the discharge frequency and operating a receiver of the character described tuned to the frequency of the emitted radiation and to the independent frequency.

In testimony whereof I'have hereunto set my hand.

REGINALD A. FESSENDEN.

Witnesses:

T. L. SCLATER, O. S. MARIE.

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