US1347328A - Radiosignaling system - Google Patents

Description

A. N. GOLDSMITH. RADIOSIGNALING SYSTEM. APPLlcmou mw mm2. 19u.

QM; bornes ALFRED N. GOLDSMITH, 0F YORK, N. Y., ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION 0F 'NEW YORK.

RADIOSIGNALIN'G SYSTEM.

Application led March 29. 1917. Serial No.

To all whom it may concern:

Be it known that I ALFRED N. GoLDsMrrH,

a citizen of the United. States, residin at New York, in the county of New York, tate of New York, have invented certain new and useful Improvements in Radiosignaling Systems, of which the following is a specification. A

My present invention relates to the production of radio frequency continuous electrical oscillations for use in a. signaling system, and to ymeans for controlling theamplitilde of such oscillations in accordancewith the variations fin the amplitude ofia signaling current such, Afor examplepas a current produced by sound waves.

It has been found that an velectron discharge device `of the type known as pliotron consisting of a filamentaryelectron emitting cathode, an anode and a discharge controlling grid inclosed 4in an envelop evacuated to such a degree .that ythe device is operatively independent of positive gas ionization at voltages above tlus ionization voltage characteristic of whatever `residual gas remains Vwithin the envelop, may be utilized to advantage for the reduction of radio fre uency continuous oscillations. Devices of t is type have been described by D1'. Irving Langmuir in a paper published in the Prooeed'n s `of the Institute of Rad-o Engineers of eptember 1915. In order to utilize such oscillations for radio signaling and particularly for radio telephony, it is necessary to modulate or vary the amplitude of the oscillations supplied to the radiating s stem in accordance with variations in the signaling current. A pliotron ma also be used to advantage as an amplifier o variable currents since by reason of its property of being operable at high voltages the energy output which maw he obtained from a single device is much greater than that obtainable from previously known electron discharge devices in which gas ionization takes place and affects the operation even at low voltages. One of the objects of my invention is to provide an improved system in which pliotrons are used for supplying modulated radio frequency currents to a radiating system.

A further object of my invention is to provide a circuit arrangement in which a Single source of energy may be utilized for Specification of Letters Patent.

Patented July 20, 1920.

supplyingv the operating current or potential for a lurality of pliotrons which are used for di erent purposes.

carrying my invention into effect I utilize an electron discharge device, which is preferably a pliotron, for producing radio frequency oscillations, I impress an oscillating potential obtained from this oscillator upon the secondary o f a transformer which is connected to the grid circuits of a lurality of pliotrons connected in para lel in order to produce an amplified radio frequency current which will supply the desired amount of energy for the operation of the radiating system. The radio frequency potential which is supplied to the grid circuits of the amplifiers is modulated by means of another pliotron whose plate circuit includes the transformer secondary. The resistance of the modulating pliotron is varied by varying the potential of its grid in accordance with variations in the signaling current. As the resistance of the modulating pliotron is varied a variable amount of current is caused to flow therethrough from the transformer secondarv and the potential across the secondary is varied accordingly. As a result the current output of the ampli- Hers will vary in accordance with the variations in the signaling current. In order that a single source of current may be utilized for heating a number of filaments of the different pliotrons I arrange the system in such a way that one terminal of each such lament is at earth potential. This arrangement also enables me to utilize a single source of energy for supplying the operating current for the oscillators and for the power am liliers.

he novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof will best be understood by reference to the following description taken in connection with the accompanying drawing in which I have indicated diagranimatically one way in which my invention may be carried into effect.

The pliotron 1 comprising the usual filamentary cathode 2. anode 3 and grid 4 inclosed in an evacuated envelop is employed turns which may siderable amount radio frequency oscillations, and l term this the master oscillator. 'l`lie anode and grid of the master oscillatorI are connected to'a circuit which comprises an inductance 5 and a variable condenser (i by means ol which the circuitl isA tuned to the frequency of the oscillations which are to he produced. Energy for the operation ofthe lmaster oscillator is supplied to the plate circuit by thedlrect cufrren't gem erator 7 which is connected to the cathode :ind'ariode','r the cathodeA being grounded atS. `)ondfrnserltl'prevents the direct current component of the plate current from flowing through inductance. An indncta'nce 1t) 1n series with the generator ianda condenser- 11 in parallel therewith serve to smooth out any irregularities in the current suppl-y and a choke coil 12 which 1 term a radio frequency chokel coil prevents the radio freuexicyy component of the plate current from owing through the generator 7. .It has been Vcustomary heretoore to" regard any large inductance as achoke coil for radio frequency currents. 'All inducta'nces howe'rcr have distributed capacity f between the be44 considered as a condenser in 'parallel with the'4 inductance. This capacity will serve to by-pass a con of radio frequency energy for producing unless' the capacityris such that the` natural period of the coilv resulting from its 1ni radio frequency the battery 14, a radio capacity is Y approximately ductance and which is to equal to that of the frequency he choked out. If the coil is so designed, it will act as a high impedance to the desired currents and by the term radio frequency choke coil I mean a coil which is designed ito offer a high impedance of this sort to the radio frequency currents which will tend to flow in the circuit in which it is employed.

'l'he cathode 2 of the -master oscillator is connected to a point 13 in the inductance 5 which point maybe varied as desired in order to obtain'the most efficient operation of the system. It will usually be found desirable to apply to tential with respect to the filament in order to adjust the normal current through the pliiotron to a point on its operating chal;- aeteristic which will be most favorable for its operation. This potential, which will usually be negative, may be obtained from frequency choke coil 15 being included in the circuitto. prevent radio frequency currents from flowing through the battery 14. The condenser 16 will prevent the short-eircuiting of battery 14 through inductance 5. rEhe direct current generator 17 with an induetance 18 in series therewith furnishes current for heating the cathode ofthe master oscillator and also lier the cathodes of thecther pliotrons as indicated. lV'hile the circuit which l have the grid a definite podesmihed above For producing oscillations is the one which l prefer other circuit arrangements may be used without departing from the scope of my invention.`

The indnctance 5 forms theI primary of a rad-io freqaiency transformer, one end of the secondary 19 of which is connected to the cathodes of a series of amplifying pliotrons 20, 2l, 22, which are all connected in multiple. Wliule l. have indicated only three pliotrons thus connected, as many may he used in this way as desired or as may be ynecessary to secure the desired output in the radiating system.V A suitably selected point 23 in the secondary 19' is connected to the grids of the amplifiers through a con'- dcuser 24 and a resistance 25. llhe grids of' these ampliliers are maintained ata definite potential with respect to the cathodes by means Aof the battery 14, a radio frequency choke coil 26 in series therewith pre venting radio frequency currents from flowing through the battery and the condenser lpreventi'ng the Short circuitingof the battery through secondary 19 of theitransformer. Without the resistance 25 thereis a tendency for the amplifiers to oscil'late at an audio frequency or tooseillate at radio frequency because of the internal capacity coupling of the pliatrons between the electrodes. rl`he resistance 25, however, effectively prevents the setting up of theseundesirable oscillations.

The `generator T furnishes Vcurrent for the operation of the plate circuits of the amplifiers and the anodes of the amplifiers in the present case are connected through a condenser 2 and a variable contact 28 to in dnetance 29 which is included in circuit with the antenna 30. By connecting the plate circuit of the amplifiers to the antenna in this way a definite best impedance may be secured as a load on the amplifiers. It has been found that the amplifiers operate most eliiciently when the impedance of the load circuit has a particular value, this value de pending u on the characteristics of the amplifiers. ince the antenna system as a Whole may not. have the desired impedance l include in the load circuit only enough of the antenna impedance to give the desired value. It will of course be lapparent that the output of the amplifiers may be supplied to other load circuits than an antenna if desired.

The output of the amplifiers is a function of the voltage impressed upon their grids from the transformer secondary 19, this voltage being due to the alternating current o f radio4 frequency produced in inductance 5. If the transformer secondary 19 be shunted by a variable resistance the voltage across it will vary as a Jfunction of the value of the resistance. For a very high resistance the voltage will be practically the same as for ail open circuit and the output of the amplifier will be a maximum. l* or a short circuit the input voltage'and high frequency output of 'the amplifier will both be zero. For intermediate values'of resistance the amplifieroutput will depend uponthe particular value of the resistance.

In the present case I einplo a pliotron 31, as `a'} variable resistance s unt to the transformer secondary 19, the resistance of the pliotron `between cathode and anode being la function of its gridvoltage` When this voltage is highly negative with respect to thecathode the resistance is very high` as the grid'volta e is made less negative or evendpositiveA t e resistancebecomes correspon ing smaller. AA definite operating potential maybe supplied tothe grid of pliotron 31V by means of the connection 32 to 'batteryl through the radio frequency choke co1l'33. This pliotron I term the infodulator' `Whilefthe pliotron is the preferred form of modulator, other forms of L, controllable l,elements may be adapted for lthe dsiredvpurpose.

i' 'In the system illustrated Ethe potential of the ,modulator grid is varied 7in accordance wfitlrvariation's in a telephone'current produced byn'vthe.telep'honetransmitter 34 which is included in a local circuit v'with lbattery 35 and the `primarily 36 ofan audio frequency transformer. he telephone current thus produced 4is amplified by impressing the potential of the transformer `secondary 37 upon the ii-id of a pliotron amplifier 38. Current for the operation of this am lifier is derived from the battery 14 throng the connection 39'.` rThe plate circuit of amplifier 38 in-A ciu-des the primary 40 of a transformer the secondary 41 of which is in circuit with the `grid of modulator 31. The grid of ampliier 38 is given a definite operating potential by means of the battery 42. By this arrangement 'the potential of the grid of modulator 31 is made to vary in accordance with variations in the telephone current. The resistance ofthe modulator and hence the radio frequency potential applied tothe grids of the amplifiers and the outputof the amplifor y the modulator fiers are, as a result, all variedlin accordance with thevariations,in the telephone current. hadio frequency choke ooit-13 prevents the alternating component .of the amplifier current from flowing through generator 7.

It Will be noted that the modulator is connected across all of transformer secondary 19` while only a portion of secondary 19 is connected in the grid circuits of the amplifiers. This arrangement may be reversed if desired or both connections may be made to the same point in secondary 19. The object et varying the points of connection is to secure the most eiiicient operating voltages late circuit and the amplifier gridA circuits. It will usually he found desirable to connect the circuits in the manner indicated, as by this connection the modulator plate circuit will operate at u higher voltage than that applied to the amplifier grids and this condition will be most suitable for efficient operation. i

While I have described a system for producing radio frequency currents which are modulated in accordance with variations in a locally produced telephone current, my invention is by no means limited in its usefulness to this particular purpose. It will be apparent that the telephone current employed may equally well be one whiclris derived from a long distance line throll'gh' one or more line amplifiers such as 38. It will also be apparent that the system may be utilized for radio telegraphy by varying the modulator grid potential in accordance with variations ina .telegraphc current` l. have also described the electron discharge devices used as pliotrons since by reason of the ability of such devicesl to operate at high voltages, their use is preferable whenever it is desired to control more than a few watts of electrical energy. It will be apparent, however, that in so far as the principle of operation is concerned other devices in which gas ionization or conduction plays a part in the operation may be equivalents of liotrons.

llihat Iclaim as new and desireto secure by Letters Patent of the United States is:

V1. The combination in a radio signaling system of a pliotron oscillator having a resonant circuit associated with its anodeand grid and so arranged that radio frequency oscillations will be produced in an inductance included in said resonant circuit, a seccnd inductance coupled to the first mentioned inductance and connected to the grid circuits of a pluralit 1 of' pliotron amplifiers connected in parallel, a pliotron modulator having its cathode and anode connected to said second inductance, means for producing a current by sound Waves, a pliotron amplilier for amplifying the current thus produced and for varying the grid potential of said pliotron modulator in accordance with variations in the amplified current, a com-l mon direct current source of potential for supplying energy to the plate circuits of' said pliotron oscillator and said first mentioned amplifiers, a common direct current 'source of potential for fixing the normal potential of the grids of said oscillator, first mentioned' amplifiers and modulator, and supplying current to the plate circuit of the second mentioned amplifier, radio frequency choke coils for reventing radio frequency currents from owing through said direct current sources and a direct connection between the plate circuits of the amplifiers and a radiating antenna, said connection being variable in order to adjust the impedance in the load circuit of the, amplifiers to a. collie suitable for the most efficient operar. tion of the system.

2. The combination in a. radio sigmilinrg,1 system of n plioltlron. oscillator having o (munt circuit usslwiuted with its inode :rnd grid and so arranged that radin frequency oscillations will be reduced u i en mdiur tance included in sai resonnnt circuito sccond inductance coupled to the ,first uientioned inductenoe and connected to the. Jrid circuits of n plurality of liotron, om) 1` ers connected in parallel, a p intron mo ulator having its. cathode end anode. cciilnotedto said second inductencemeans for vordying the grid potentiel-einem nlietroirino ulator in accordance .with variations 1n e current produced, by sound waives, e common d1 rect current sourceoif potentiel for supplying energy to the plete circuits of Seid pho,- tron oscillator and said amplifiers, o common direct current source of .potentiel for fixing the normal potentiel of the grids oft said osoillutor,l amplifiers and modulator! radio frequency choke coils fory preventing radio frequency currents. from -owing through said diirect current sources onda, direct connection between the plete circuits of the amplifiers and a radiating antenna, said connection being variable in order to adjust the impedance in the load circuit of the am. ilers to a value suitaihle for the most eicient operation of the s stern. Y

3` The combination in a radio, signaling system of means ier producinA radio frequency oscillations and supplying them to an nduetance in the grid circuits of a C{nlnrnlity of pliotron amplifiers connecte in parallel, a. pliiotron modulator having its cathode and anode COnncted to said inductrunce, means for varying the grid otentiol of seid modulator in accordance willi variations in a signaling current, a. common direct current source of potential for fixing the normal potential of the grids of seid nmulifiers und modulator, radio frequency Ih Ye coils for preventing radio frequency currents from flowing through saiddirect current source, and a direct connection between the plate circuits oi the amplifiers dnd a radiating antenne., seid connection being variable in order to adiustthe impedance in the lood circuit of the amplifiers to n value suitable for the most eiicient operation of the s stem.

l. he combination in a radio signalling system of n pliotron oscillator having a resonant circuit associated therewith 'and so arranged that radio frequency ,oscillations will be produced in an inductaince ,included in said resonant circuit o second inductence coupled to the first mentioned ind'uctence and connected inthe gridcircults of a luralt of pliotron amplifiers connecte in para lel, a pliotron modulator hav-ing its cathode and anode connected to Said Second iuductonce, means for applying to the eethode and :inode of Suid modulator it difieront voltuge than that applied 4to the grid circuits of the amplifiers, end Ineens for varying the grid potentiel o'snid modulator in accordance with variations in n signaling current.

5. The combination in n radio signaling system of o pliotron oscillator having e resi onent circuit associated therewith and so wronged. that Indio frequency oscillations. will be produced in an inductence included in said resoimnt circuit, :i second inductnnce coupled to the first mentioned induct'anoe :ind connected in the grid circuits of a plu,- rolity of pliotron amplifiers 4connected in parallel, :i pliotron mO-(luhttor l'lwlg its cathode and anode connected to Vseid Second inductaincc, ineens for varying the grid potentiol of said modulating pl'otron in acordance with variations in o signal, 0'- cur rent an earth connection to thecnt "Iddon oi' said oscillator, ompliliersand modulator-fond n common direct. current source. of .potentiel for supplying energy to the plete circuits of said oscillator und said empliier.

6. The combination in nfredio signaling system of plotron oscillator herring :t resonant circuit associated therewith `end so, arranged that radio 4frequency oscillations will be produced in en inductance incliided in said resonant circuit, e second inductence coupled to the first mentioned inductaqnce and connected in the grid circuits of a lu rnlity of pliotron amplifiers connect in perellel, a. pliotron, modulator having its cathode and anode connectedv to Sndseconrl inductunce, means for varying the grid potcntial of said modulntor, in accordance with variations in s signaling current, an earth connection tothe cathodes of seid oscillator, amplifiers and modulator, e common direct current source of potentiel for supplying energy to the plate circuits of seidv oscillator und said amplilier, and e common direct current source of potential Jfor fixing the normal potential of the grids of said oscillator, am pliers and modulator.

7: The combination in n radio signaling system of n pliotron oscillator having e reS.- orient circuit associated therewith and so arranged that radio frequency oscillations will he produced 1n an lnductnnce included in e said resonant circuit,` a second inductance coupled to the iirst mentioned inductonce andconnected in the grid circuits of a, plurnlt of pliotron amplifiers connected in por lel, a. pli'otron modulator having its cathode and anode connected to said second inductance, means for varyin the grid potential of seid modulating p otron in accordance with variations in a signalin current, an earth connection to the catho es of said oscillator, amplifiers and modulator, a

common direct current source of potential -for supplying energy to the plate circuits of said oscillator and said amplifier, a common direct current source of potential for fixing the normal potential of the grids of said oscillator, amplifiers and modulators, and radio frequency choke coils for preventing radio frequency currents from fiowing through said direct current sources.

8. The combination in a radio signaling system of means for producing radio frequency oscillations and supplying them to an inductance in the grid circuits of a plurality of pliotron amplifiers connected in parallel, a pliotron modulator having its cathode and anode connected to said indnc tance, means for varying the grid potential of said modulator in accordance with variations in a signaling current, a common direct current source of potential for fixing the normal potential of the grids of said amplifiers and modulator and radio frequency choke coils for preventing radio frequency currents from flowing through said direct current source.

9. The combination in a radio signaling system of means for producing radio frequency oscillations and supplying them to an inductance in thegrid circuits of a plurality of pliotron amplifiers connected in parallel, a pliotron modulator having its cathode and anode connected to said inductance, means for varying the grid potential of said modulator in accordance With Variations in a signaling current and a common direct current source of potential for fixing the normal potential of the grids of said amplifiers and modulator.

10. The combination in a radio si maling system of means for producing ra io frequency oscillations and supplying them to an indnctance in the grid circuits o l' a plurality of pliotron amplifiers connected in parallel, a pliotron modulator having its cathode and anode connected to said inductance`r means 'for varying thc grid potential of said modulator in accordance with variations in a signaling current, an earth connection to the cathodes of said amplifiers and modulator and a common direct current source of current for supplyingr heating current to the cathodes of said amplifiers and modulator.

11. The combination in a radio signaling system of means for producing radio frequency oscillations and supplying them to an indnrtanre in the grid circuits of a plurality of pliotron amplifiers connected in parallel, a variable resistance device connected to said inductance, means for varying the resistance of said device in accordance with variations in a signaling current and means for applying to said variable resistance device a different voltage than that applied to the grid circuits of. the amplifier.

12. The combination in a radio signaling system of an antenna and a plurality of pliotron amplifiers arranged to supply modulated radio frequency currents to said antenna, the plate circuits of said amplifiers being connected to said antenna by direct connections, and said connections being variable in order to adjust the impedance in the load circuit of the amplifiers to a value snitable for the most efficient operation of the supply system.

In Witness whereof, I have hereunto set my hand this 27th day of March, 1917.

ALFRED N. GOLDSMITH.

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