US1551624A - Circuits for wave transmission - Google Patents

Description

Sept. 1, 1925.

1,551,624 J. c. SCHELLENG V CIRCUITS FOE WAVE TRANSMISSION Filed June so, 1924 lnvemor: John C. fiche/leng,

' vent theproductionof spurious oscillations;

Patented Sept. 1, 1925.

UNITED. TA S 'LSSLtZA; PATENT orrlcs.

JOHN G. soIIEImENe, or Ens'r O A GE, NEW ERsEY, AssIGNoR- T0 WESTERN ELEC- ,rRIc coMrAN INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

' omcuITs EoR WAvE TRANSMISSION.

To all whom it may concern:

Be it known that I, JOHN C. SGHELLENG,

a citizen-,ofthe UnitedStates of America, residing at East Orange, in the county of Essex and State of NewJersey, have ins,

vented certain new and useful Improvementsin Y Circuits for Wave Transmission, of which the following is a 'full, clear, con cise, andexact description.

This invention relates to the production,

modulation and transmission of electrical oscillations, and more particularly to the space current type."

productiono-f oscillations byde'vices of the.

an oscillatorof simple construction conven-.

'iently adjustable to generate oscillations of any one frequency within a given range, and tomaintainthe'power output close to the maximum value at "any one frequency.

Other objects of the inv'ention'are to preto improve the efliciencyTa nd thepower factor of the space currentrfrom the oscilla tor device; to connect" theanode of anoscillatorof the spacecurrent 'type through a stopping condenser to a grounded variometer in an antenna circuit in suchla manner that-the antenna isinsulatedirom the v voltage of the ,space cui'rent. source; and toprovi'de a simple circuit in which the I frequency fisfva-riedby means of one variable element and the" powein adjustment is accomplished by means of another variable element; I j I a, .1

Certain features of the present invention are improvements vupon the methods and apparatus disclosed in British Patent No.

156.159, and a theoretical consideration ofproblems encountered in apparatus of the kind referred to will be understood more clearly'upon reference to this patent. I

' In accordance with the present invention, an oscillator utilizing a space current de vice is arranged for adjustment to produce any desired frequency within" a given range,

and is so constructed that the power-gem erated at any frequency is close to the maximum value. A variometer -for changing the frequency offthe generated oscillations automatically adjusts the couplingcontrolling the production oftheoscillations. By con; necting a variable capacity between" the anode and cathode of the space current device, provision is made ;fior improvi n-g the tenna is insulated from the voltageof the. space current source.

:Other features and objects'of the invenphase relation of the oscillator circuits and e and cathode are both grounded'and the antion will be more clearly understood from the following detaileddescription in connection with the appended drawing. One object of'the invention is to" provide fminal connected to antenna 8. is provided with a stationary portion 9 adjacent to the grounded terminal, and arotary portion 10,

variably coupled to portion 9 and connected in series therewith remote from'the greunded terminal. Inductance winding 11 is inductively coupled to; variometer7, and

is thus variably coupled to movable inductmice '10. minals of winding '11 lead, respectivelyfto cathode 2 and grid 4:, the grid connection including the condenser and grid leak *resistance 12 of well known construction. I

Cathode 2 is connected directly to the grounded terminal of variometer 7, and is thus grounded; 'Anode 3 is directly con- Connections from the two ternected to any desired point 'lll inductance 9by adjustment of the variable connection 13 to adjust the ratio of the step-up auto-transformer formed by the anodecathode conne'ctions to variometer 7 and the antenna-ground connections thereto. Blocking condenser'14 connects anode 3 to -in-' ductance 9 and prevents the application to inductance 9 andto' antenna- 8 of the voltage from spacecurrent source 5."

The capacity between antenna 8 and ground, together with the inductance of variometer 7 and reactance inthe associated circuits, form a tuned circuit Whichis predominant in determining the frequency of oscillations. regeneratively produced by virtue of the coupling between variometer 7 between18 and ground on the other.

' Oscillations transmitted through variometer 7 induce similar oscillations in winding 11, the induced oscilla tions being transmitted to grid 4 in a manner well known in the art. The frequency of the generated oscillations is adjusted to any desired value within a. considerablerange of frequencies by rotation of inductance 10 to vary the inductance of variometer 7 and the tuning of the antenna. It will be noted that'variation of the inductance of variometer '7 varies the coupling betweenv variometer 7 in the anode-cathode circuit: and winding 1-1 in, the grid-cathode circuit. The relation between th position of inductance 10 and the position of inductance. 1-1 is so designed that, when the frequency is changed, the coupling between winding-'11 and variometer 7 is adjusted to a value giving close tomaximum power output from the oscillator and giving suitable stability to the operation of the oscillator.

A. sinall'variable. Capacity 15, connected between anode 3-and cathodeil, that is, between variable contact 13 and the grounded terminal of variometer 7, provides a path having-capacity reactance. in shunt to the lower portion ofinductance 9. This capacity is readjusted after changing the frequency of the oscillations so that a stable adjustment-is obtained at properpower and cliic-iency without theproduction ofspurious oscillations. l hese spurious oscillations are ordinarily of considerably higher frequency than those intended to be generated for transmission to the. antenna. Capacity 1.5, apparently becauseof its low im Jedance to oscillations. of parasiticfrequency and its high impedance to wavesintended to be gen: erated, andipossibly for etlierreasons, pro-- vides an-easy means for suppressing the parasitic oscillations. v

The frequency of the oscillation occurring does not ordinarily differ very much from. one of the two resonant frequencies-otthe coupled circuits formed by antenna 8, coil 16-, and the variometer-T on the one hand, and by capacity 15 and the section of-coilf) Ordinarily the coupling between Hand? is made to be. of such phase as to produce the lower of these two frequencies, which is-somewhat lessithan thatof the antenna circuit alonea Condenser-15, by virtue of itscapacity re actance, may be adjusted-sothat the phase angle of'the load into which the tube .isde-: livering power is substantially Zero-.whileat the same time all the other conditions necessary for-the production of stable oscillations are satisfied bythe circuit. In this way both the power output andefficiency of device 1 are maintainedat-satisfactory val us throughout the entire frequency range.

Inductance 16 is a, loading coil-:i'n the anand winding 11;.

tenna circuit which ordinarily has a fined value, being altered onlywhen a general shift in the frequency range is required or when the antenna is changed.

For the purpose of modulating oscillaions in accordance with telephone signals, telephone. transmitter 17 is coupled by trans former 18 to the input circuit 19 of amplifier 20, ofthewell known space current type, the anode circuit 21 of which is supplied with space current by source 5 through choke coil 6, which functions to maintain a substantially constant current-from source 5. Space current through tube is varied in well known manner in accordance with speech-or sound waves from transmitter 17, and, inasmuch as the space current-through coil- 6 is substantially constant, complemen: tary changes are produced in the space current supplied to device; 1, thus causing modulation-of the. generated oscillations in accordance with the speechor soundwaves acting on transmitter 17, the modulated waves being radiated byantenna 8; High frequency choke coil 22 prevents the transmission of high frequency oscillations from device 1 to device 20- and 6. It will be noted that the modulating.- system described utilizes the: well known principleof the Heising constant current modulating system.

hen telegraplrsignalsare to be transmitted, switch 2v is connected; to. its.- upper position, establishing.connect-ion between battery 24- and buzZer 2-j: Intermittent op eration of telegraph key 26 causes-intermittent transmission to tube 20-ofwaves of the frequency of: buzzer "and producesa correspondingmodulation of. the oscillations generated by device lVhat is claimed is 1. In an oscillator, a space currentdevice having an anode, a cathode' and a control element, an antenna circuit having .an-inductance connectedat one of 'its terminals to ground and to said cathode, a portion of said inductance being variably coupled to another-portion of-the inductance, means for capacitatively coupling said-anode to a 'variable point in saiclcothr portion-of the inductance, an inductance conneetedbet'ween said control element and saidcathode and coupled to said other portionof the in ductance, and a variable capacity connected between said anode and cathode:

2'. In an oscillator, a space-current device having. an anode, acathode anda control element, an antenna circuit having an inductance connected at one of its terminals togroundnand tosaid cathode, a portion of said inductance remote fromthegrounded terminal 1 thereof being variably coupled to a portion ofthe inductance adjacent the grounded terminal, means for oapacitatively coupling said-'anOde-toa variablevpointin the portion .ofsaid inductance adjacent said grounded terminal, an inductance connected between said control element and said cathode and coupled to the portion of said antenna inductance remote from "the grounded terminal, and a variable capacity connected between said anode and cathode.

3. In an oscillator, a space current device having an anode, a cathode and a control element, an antenna circuit having an inductance connected at one of its terminals to ground and to said cathode, a portion of said inductance remote from the grounded terminalthereof being variably coupled to a portion of the inductance adjacent the groundedterminal, means for capacitatively coupling said anode to a variable point in the grounded portion of said inductance, an inductance connected between said control element and said cathode and coupled to the portion of said antenna inductance remote from the grounded terminal, and means connected between one terminal of 7 said antenna inductance and the variable point thereinfo'r reducing the'tendency for the oscillator to generator parasitic oscilla tions and for increasing the power output after change of frequency. or

4. In an oscillator, a space current device having an anode, a cathode and a control element, an antenna circuit having an in ductance connected at one of its terminals to ground and to said cathode, a portion ing said anode to said inductance and for varying the value of the inductance between said anode and cathode, a winding coupled to the movable portion of said antenna inductance, connectionsfrom said winding for impressing oscillations on said control member', and means associated with said osto a portion of theinductance adjacent the grounded terminal, means for capacitatively coupling said anode to a variable point in the grounded portion of said inductance, an inductance connected between said control element and said cathode and coupled to the portion of said antenna inductance remote from the grounded terminal whereby oscillations 1 are generated in accordance with the tuning of said antenna circuit, and means whereby the generated oscillations are modulated in accordance with signal waves;

' "6. In an oscillator, a space current device having an anode, a cathode and a control element, a variometer having one of its terminals connected to an antenna and its other terminal connected to ground and to said cathode, an inductance coupled to the movable portion of said variometer and having connections for impressing oscillations on said control member, means connecting said'anode to a variable point between the terminals ofsaid variometer, and a variable capacity connected between said point and one of the terminals of said variometer.

In witness whereof, I hereunto subscribe my name-this 25th day of 1924; a

JoHN*o.so ELLENG,

June, A. -D.,

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