US1471319A - Radiotelegraph signaling system - Google Patents

Description

www-E d., as, 393% H. PRATT ETl AL RADIO TELEGRAPH SIGNALINQ SYSTEM 5 SheetsSheet 1 Fiied Jan. 3. 1921 /M/iwb EN P WITNESS afa-u'. ATTORNEYS m., le, ma. A LME-sw H.PRATT ET AL RADIO TELEGRAPH SIGNALING 4SYSTEM Filed Jan s. 1921 s sheets-snaai 2 ILHI f-/glllfg/J-lL-U.

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WITNESS ci. 16, i923.

H. PRATT ET M.

RADIO TELEGRAPH SIGNALING SYSTEM Filed aan; '3. 1,921 s sheets-sheet 3 lliL /l Z/ WITNESS l I .INVENTORS H ade Pratt Hrfg @nab BY A Patented st. 16, 1923.

HARADEN PRATT, OF SAN FRANCISCO, HAROLD F. ELLIOTT, OF PALO ALTO, EU- GENE B. MURPHY, OF BURLINGAME, CALIFORNIA, ASSIGNORS TO AUGUSTUS TAY- LOR, OF SAN FRANCISCO, CALIFORNIA.

RADIOTELEGRAPH SIGNALING SYSTEM.

Application led January 3, 1921. Serial No. 434,420. i

T 0 all whom t may concern Be it known that We, I-IARADEN PRATr, HAROLD F. ELLio'rr, and EUGENE B. MUR- PHY, citizens of the United States, residing,

respectively, in the city and county of San Francisco, Palo Alto, Santa Clara County, and Burlingame, San Mateo County, all in the State of California, have invented cer,- tain new and useful Radiotelegi'aph Signaling Systems, -of which the following is a specification.

'Ihe invention relates to a radio telegraph signaling system in which audio frequency Wave trains are radiated from an antenna system to Which an undamped Wave arc generator is connected.

It is desirable for several reasons, under certain conditions, to, produce laudio frequency Wave trains from a continuous undamped Wave transmission system and several methods have been suggested for accomplishing such result. In these methods the continuous Wave has been broken up into time spaced groups at such a frequency that the group frequency is Within the range of audibility. This has been accomplished by interrupting the antenna circuit at an audio frequency rate and-'shunting the arc .with a condenser circuit or an oscillatory circuit, into which the radio frequency current passed during the interval that the antenna circuit was opened, or during the time that its resistance was largely increased. TheseA methods all involve the continuous and normal operation of the arc, and during the intervals ofno radiation the energy of the arc is Wasted in the shunt or oscillatorycircuit.

An object of our invention is to produce modulation of the antenna current at audio frequencies, in an arc radio transmitter.

Another object of Vour invention is to eliminate a certain Waste of energy in performing such modulation for producinga more economically operating system.

The invention possesses other advantageous features, some of which, with the foregoing, vvill be set forth at length in the following description, Where We shall outline in full the method of our invention and several forms of systems 'for putting it into practice, which systems are shown in the drawingsaccompanying and forming part of the present specification.l In said draw-- ings, We have shown several systems for carrying out our invention, but it is to be understood that we do notlimit ourselves to such systems, since the method, as ex ressed in the claims, may be embodied in ot er systems.

Referring to such drawings: Figures 1 to 11- inclusive, are diagrammatic representations of different forms of the system of our invention. In accordance with our invention, We provide for the audio frequency modulation of an arc generated radio frequency current, by extinguishing and reignitingsthe arc flame at an audio frequency rate, by suitable means such as an oscillatory circuit resistance control. By extinguishing and reigniting the arc at audio frequency, groups of undamped Waves are radiated from the antenna, the groups being emitted at audio frequency. During the time that thearc is extinguished, there is very -little energy consumption, so that a gain in eiiiciency of operation is obtained.

We have found that it is a fundamental characteristic of the arc, that is, the Poulsen arc, When used as a converter of energy for producing radio frequency currents, that thearc length must increase When the resistance of the oscillatory circuit is increased, if oscillations are to be maintained. Inorder to maintain a longer arc, it is necessary to supply a higher direct current voltage, and, if this is not-done, the arc is immediately extinguished, due to the action of the transverse magnetic field. The voltage of the-direct current generator being maintained substantially constant, When the resistance of the oscillatory circuit 1s in-4 creased, the arc is instantaneously extinguished.

quickly Withdrawn, the extinguished arc- Will immediately reignite, due to the presllO 9.5 We have further found that if the oscil- I' latory circuit resistance is inserted and then tenna circuit at an audio fre uency rate, with extinction and ignition of tlhe arc flame atI the same rate, producing an antenna current with corresponding amplitude fluctuations, producing thus suitable wave trains. ln accordance with our invention, we increase and decrease the resistance of the antennacircuit at audio frequency, thereby interrupting and reigniting the arc at such 'frequency and produce audio frequency wave groups in the antenna circuit.

ln the drawings we have shown several different circuits embodying the system of our invention. Each circuit includes a Poulsen arc generator, comprising'an arc 2 enclosed in an atmosphere containing hydrogen, and subjected to a strong transverse magnetic field produced by the electromagnets 3, which are energized by direct current from the generator l. One side of the arc is grounded and the other side is connected 'to the antenna 5, through the variable inductance 6. Mea-ns are provided for introducing into and withdrawing from the antenna circuit, at audio frequency, resistance suiiicient to extinguish the arc when introduced into the circuit. In the system shown in Fig. 1,the resista-nce 7 is arranged in the antenna circuit and shunted around the resistance is a low-resistance circuit containing a rotary.I motor driven commutator 8, having alternate insulating segments and commutator segments.. rllhe commutator is engagedby brushes having a suitable width. 'lhe rotatingv commutator periodically shortcircuits the resistance 7, so that the resistance is alternately effectively placed into and removed from the circuit. The commutator is rotated at such speed that the arc is interrupted at audio frequency.

ln the system shown in Fig. 2. the resistance 9 is arranged in the commutator circuit which is arranged in parallel with a portion of the oscillatory circuit inductance 6 which is equivalent to introducing the resistance directlyv in series in the oscillatory circuit.

The system shown in Fig. 3 is similar to -that shown in Fig. 2, with the exception that the commutator-resistanc circuit is coupled to the oscillatory circuit br an air-core transformer 12. lin the system shown in Fig. 4r,

lan iron core transformer 13 is employed in place of the air core transformer.

rlhe system shown in Fig. 5 is similar to that shown in Fig. 2, with the exception that the c'ommutator circuit is connected around a condenser 14, instead of around la, portion of the inductance 6.

'lhe s stems shown in Figs. 6, 7, 8 and 9 are mo iications of the lsystems shown in Figs. 2, 3, t and 5 respectively, in which a rotary spark gap device 15 ,is substituted for f the-commutator 8. When the spark gap electrodes come into alinement, the potential in the circuit causes a spark dischargei thereinviare by closing the circuit through the resistance,

' which has the equivalent eect of inserting ,l the resistance in the oscillatory circuit.

ln Fig. 10, we have shown a system showin the application of this method of signa ing-to coupled circuits. 'lhe arc 2 is contained in a closed circuit containing the ca-y pacity 25 rand the transformer primary 26, which is coupled to the secondary 27 in the antenna circuit. rllhe interrupter 28 is associated With the circuit to which the arc converter is connected in the present instance, the interrupter bein arranged to shunt a resistance 29 in the circuit.

The circuits shown in Figs. d and 8, iny volving the use of the iron core transformer coupling, will only lwork properly when there are few losses in the iron core, which condition-it is often. difficult to realize in practice. 'lhe system shown in Fig. 11 will give satisfactory operation with an iron core transformer having substantial losses. ln this .system the resistance 31Vis permanently connected across the secondary of the iron core transformer 32 and .the interrupter 33 is connected across the resistance, so that it operates to short circuit the resistance.

lt is to be understood that-in the above circuits the rotary commutators and spark gaps are so designed as to cause connections or sparks to be made at any convenient audio frequency rate. The times of contact making or sparking which are determined by the relative widths 'of the metallic and insulated commutator segments, or by the relative widths of the electrodes and spaces on the rotary gap disc, constitute a feature of this invention as best results are obtained when a definite ratio in these times is selected.

llt is to be further understood that the resistances and transformer ratios are so selected in each of the above examples that the equivalent resistances, respectively, of the oscillatory circuits, will be as great or greater than the amount required for complete arc extinguishment. 'lhese quantities may be easilydetermined by calculation, or by trial.

'llhe circuit constants are further so arranged that a low voltage is utilized with the commutator connection so that sparking at the brushes of the latter may be a minimum, and a high voltage with the spark gap so that the discharges across the latter may be uniform and regular.

Signaling may be accomplished in any suitable manner, and in the drawings we have shown one form of signaling circuit which is particularly a plicable to the systemof this invention. @onnected around the arc is a circuit 16 containing a resistance and the normally closed signaling key 22. When the circuit 16 is open, radio frequency current is delivered to the antenna and when the circuit 16 is closed, the resistance 17 short-circuits the arc, thereby extinguishing it entirely. The contacts of the relay key 18 may be placed Within the arc chamber in a position which causes the spark produced by their opening, to reignite the arc flame, which feature has been set forth in application Serial No. 368,193, filed in the Patent Office on March 23, 1920 by Harold F. Elliott and patented September 14, 1920, No. 1,352,883.

We claim:

1. The method of transmitting radio sign als by the aid of an arc converter ,and a transmission circuit in such a Way that audio frequency groups may be sent, which comprises inserting in the circuit and withdrawing from the circuit at an audio frequency rate, an energy consuming device, whereby the arc is extinguished and reignited at this rate. v

2. Thel method of producing in an oscillatory circuit, current groups having an audio group frequency, with an arc suitable for generating sustained alternating cur-v rents, which comprises introducing and-- withdrawing resistance from said circuit at v an audio frequency rate, the value of the resistance being such that when introduced l in the circuit, the are is extinguished.

3. A radio v telegraph signaling system comprising an arc, an oscillatory circuit conl nected to the arc, a resistance of such value that when introduced into the circuit the arc is extinguished, and means for introducing the resistance into the circuit and Withdrawing 'it therefrom at an audio frequency rate.

4. A .radito telegraph signaling system,'

comprising an arc, an oscillatory circuit connected tol the arc, a resistance'of such value that when introduced into the circuit the arc is extinguished and a rotary make and break device adapted to introduceJ the resistance alternately extinguishing and reignitingthe varc at an audio frequency, comprising an ener absorbin device and means for connectin in and, disconnecting said device from t e circ-uit at an audio frequency rate. v

In testimony whereof, We have hereunto set our hands.

HARADEN PRATT. HAROLD r. ELLro'rr. EUGENE B. rnv.

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