US2461306A - Oscillator-amplifier radio circuits - Google Patents

Description

Feb. s, 1949. J J. ANTALEK 2,461,306

OSCILLATOR-AMPLIFIER RADIO CIRCUITS Filed May 31, 1943 5 Sheets-Sheet 1 OUTPUT AF OUTPUT INVENTOR.

fa/up .IAnZaZek ATTORNEY Feb. 8, 1949. J. J. ANTALEK 2,461,306

OSCILLATOR-AMPLIFIER RADIO CIRCUITS Filed May 31', 1945 4 5 Sheets-Sheet 2 IN V EN TOR. JZFMLJAZZ Z'aZeir Feb. 8, 1949. J. J. ANTALEK 2,451,306

OSCILLATOR-AMPLIFIER RADIO CIRCUITS Filed May 31, 1943 5 Shets-Sheet s IN VEN TOR. Jofimf Feb. 8, 1949. J. J. ANTALEK OSCILLATOR-AMPLIFIER RADIO CIRCUITS 5 Sheets-Sheet 4 Filed May 31, 1943 INVENTOR. JomJ'AnZ'aZek BY fl 44M 0L Feb. 8, 1949. J. J. ANTALEK 2,461,306

OSCILLATOR-AMPLIFIER RADIO CIRCUITS 7 Filed May 31, 1943 5 Sheets-Sheet 5 Patented Feb. 8, 1949 QSCILLATOR-AMPLIFIER RADIO CIRCUITS John J. Antalek, Chicago, 111., assignor to The ticn of'Illinois Rauland Corporation, Chicago, 111., a corpora- Application May 31, 1943, Serial No. 489,235-

7 Claims.

This invention relates to electronic tubes and the. circuits connected thereto, especially relating to. devicesemployed. in. connection with radio reception. and. transmission.

One purpose ofthis inventionis to provide circuits utilizing. a single. electronic tube, in which circuits such tube will perform a plurality of functions, such as the functions which hitherto harerequired the .use of more than one electronic tube;

Another purpose of this invention-is to provide aI-radio telegraph or, telephone receiver in which the total number of electronic tubes required is reduced below that. hitherto found. necessary, more: particularly in. connection with radio receivers of the. superheterodyne type.

Still another purpose of this invention. is to providea radio receiver in. which an. electronic tube normally functioning to cooperate with the remainder of the receiver for the purposes of signalreception, willlikewise. function as a source of electrical oscillations of predetermined frequency; which oscillations may be utilized to calibrate the receiver as a whole.

A still. further. purpose of this. invention is to provide. a circuit in which a single electronic tube functions simultaneously as an audio frequency amplifier and as a radio frequency oscillator.

Yet another purpose of this invention is to provide a. radio receiving circuit in which an electronic tube-functioning as an audio frequency amplifier, obtains its grid bias voltage by simultaneously functioning. as anos-cillator at a superaudible frequency, the superaudible oscillations giving rise to thebias required by the tube as an audio frequency amplifier.

Another purpose of this. invention is to. provide a radio receiving device inwhich av single electronic. tube performs thesimultaneous functionsof auoscillator producing a beat note with an incoming signal, of: a. diode type, detector of such. signal, and of anaudio amplifier of the signal, after detection.

A; still' further object. of this invention is to provide, in a superheterodyne radio receiver, a circuit in. which a single electronic tube functions simultaneously as anv amplifier of intermediate requencies and of audio frequencies, thereby allowing the eliminationof at least one electronic tube hitherto employed to fulfill only one of these functions.

' A yet further object of this inventionis tov provide aradio transmittingcircuit inwhich. a single electronic: tubefunction-s. both as. an oscillator,

' 2 with or Without crystal'control, and as a speech amplifying tube.

Still further objects and. advantages of this invention will be apparent to those skilled in the art, among which advantages are those of economy of material, space and weight, in radio telegraph or telephone transmitters and receivers. Such advantages are. of particular importance in connection with portable radio transmitting and receiving equipment,

Reference is now made to the accompanying drawings, where Fig. 1 is a schematic diagram showing a portion of a complete circuit, according to this invention, wherein a single electronic tube of the multi-element type, performs the function of a detector, an audio frequency amplifier and a crystal controlled oscillator.

Fig. 2A is a. schematic representation of a portion of a circuit wherein a single triode is used simultaneously as a high frequency oscillator and as an audio-frequency amplifier.

Fig. 2B is a schematic drawing of a portion. of a circuit, utilizing a single tetrode to accomplish the same results given by the triode of Fig. 2A.

Fig. 3A is a schematic representation of a portion of the circuit of a radio receiver of the superheterodyne type, illustrating the use, according to this invention, of a single electronic tube of the multi-element type as an amplifier of received signals at an intermediate frequency, as a detector of suchamplified signals, and likewise, as an amplifier at audio frequency ofthe thus detected signals.

Fig. 3B is a schematic showing of amodified form of the circuit of Fig. 3A.

Fig. 4A isaschematic showing. of aportion. of a circuit wherein a single tetrode is simultaneously used, according to this invention, as anaudio frequency amplifier and. as a. crystal controlled oscillator.

Fig. 4B is a schematic showing of a modification of the circuit, of Fig. 4A, in which a variable frequency oscillator circuit is substituted for the crystal controlled oscillator circuit of Fig. 4A.

Fig. 5 is a schematic showing of a radio telephone transmitter embodying certain principles of this invention, including a crystal controlled oscillator circuit.

Fig. 6 shows schematically a modified form of a portion of the circuit of Fig. 5, employing an oscillator circuit wherein. the frequency is determined by the electrical constants. of a coil and a condenser. in lieu of. the crystalcontrol shown in.v Fig. 5.

Fig. 7 shows a circuit using a single tube as a beat frequency oscillator, a detector and an audio amplifier.

Referring now to Fig. 1, there is here shown the portion of a superheterodyne receiver immediately following the portion thereof where amplification has been accomplished at an intermediate frequency. The input transformer shown at I may conveniently have its primary I0! tuned by condenser I02 to the intermediate frequency employed by the receiver, while the secondary I03 is similarly tuned by condenser I04, to the same frequency The intermediate frequency is applied through lead I05 to the diode plates I05, I06 of electronic tube I07. The intermediate frequency return to ground is made through by-pass condenser I08, and cathode I09 of tube I0! is likewise grounded. Resistor H0 acts as a filter resistor for the intermediate frequency, in connection with by-pass condenser II'I, connected to the ground at one side. Resistor H2 is likewise shunted to ground across condenser III and constitutes a potentiometer type volume control by virtue of the variable connection point I I3 through which the rectified and filtered audio frequencies are taken off, via audio grid coupling condenser Iii, and applied through radio frequency filter resistor H5 to control grid IIG of tube I01. The potential of grid II6 is maintained via grid leak resistor I I1, connected from the lower end of resistor H5 to the ground.

The amplified audio frequency output of tube IE1 is taken off from the anode H8 thereof and supplied to the audio frequency output terminals H9, H9, via audio frequency coupling condenser I and from ground connection I2I. The D. C. operating energy for anode H0 may be derived from any suitable source such as that indicated at I22, via anode load resistor I23, the anode like wise being connected to ground through radio frequency by-pass condenser I23.

The screen grid I24 of tube I01, is kept at a suitable D, C. potential by connection to the source indicated at I22, via voltage dropping resistor 525, beingeffectively maintained at ground potential, with respect to A. C., by means of audio frequency by-pass condenser I26. Likewise interposed between by-pass condenser I26 and screen grid $124, is inductance I 27, of which a portion may be shunted out by means of switch I28. Shunt connection I29 also is extended from screen grid I24, via output coupling condenser 30. This shunt output connection serves as a means whereby the oscillatory energy developed, as hereinafter explained, by tube I0'Lmay be applied to another desired purpose, for example to the input of a radio frequency tube located at a prior point of the receiving circuitl The operation of tube I01 as an oscillator, is brought about as a connection of a piezo-electric crystal ISI between control grid I56 and ground point I32. Inductance, I21 should be so designed that its resonant frequency, when connected as shown, will match that as shown of piezo-electrio crystal I3I, or some harmonic thereof. The closure of switch I28 will destroy such resonant relationship, and thereby will cause tube I01 to cease functioning as an oscillator, if so desired.

The output of tube I07 functioning as an oscillator may be used for several purposes. If connected as above-described, to an earlier portion of the receiver, or as indicated by dotted line I40, to the primary of the last intermediate frequency tube of the receiver, it may be employed as a dii producer of the beat frequency used in the intermediate frequency amplifier stages of the receiver. Alternatively, the various harmonics of crystal I3I may be fed back into the receiver and employed as calibration frequencies therefor.

Still another mode of employment of the circuit of Fig. l, contemplates that the crystal oscillator controlled section of tube ill? shall be arranged to deliver an oscillatory output at a frequency approximating that employed in the intermediate stages of the receiver, so that an audio frequency beat note may be produced by suitable combination of these two frequencies, thus enabling audio frequency reception of unmodulated continuous wave signals. For this last mentioned application, it may be found expeditious to substitute for the crystal control of frequency, an oscillatory circuit employing actual physical inductance and capacity, as will be understood by those skilled in the art.

Making reference now to Fig. 2A, the electronic tube 200 has its control grid 20I connected via radio frequency choke coil 202, to the secondary winding 203 of audio frequency input transformer 204, primary winding 205, of this transformer, being supplied with the audio frequency input signals. Audio frequency by-pass condenser 206 is connected to the ground and constitutes a portion of the return path for the audio frequency signals to the cathode 201 of tube 200. The static potential of control grid 20I is maintained by grid leak resistor 208, also connected to the ground.

The audiofrequency output of tube 200 is conveyed from the anode 209 thereof, to primary winding 2 I0 of output transformer 2 I I, the audio frequency output of the entire amplifier being drawn from secondary winding 2I2 of transformer 2. Radio frequency by-pass condenser H3 is connected directly from anode 209 to the ground and functions to prevent the development of unwanted radio frequency across winding 2I0, the origin of such pot n-tials being hereinafter explained.

The cathode 20'! oftube 200 is connected to an intermediate point of inductance 2M, this inductance functioning to determine production of oscillations by tube 200. The lower end of inductance 2I4 is grounded, and the upper end thereof is connected to control grid 201 via oscillator grid condenser 2I5. It will be apparent to those skilled in the art that this mode of connecting the grid, anode and cathode, respectively, of tube 200, to inductance 2 I4, constitutes a wellknown type of oscillatory circuit employed in connection with electronic tubes.

When tube 200 is set into oscillation by reason of the oscillatory circuit connection just described, there will be developed across resistor 208, a D. C. potential which will serve to maintain control grid 20I at a suitable D. C. potential, for the proper functioning of tube 200 as an audio frequency amplifier. The reason for the presence of radio frequency by-pass condenser 2I3 will now fully be apparent.

In Fig. 2B the audio frequency input through grid coupling condenser 250 to control grid 25I of tetrode 252, via radio frequency filter resistor 253. Control grid 25I is likewise connected to ground via grid leak resistor 254. Anode 255 of tube 252 is likewise grounded with respect to radio frequency, by means of by-pass condenser 256 and derives its operating energy from any suitable source, such as that indicated at 3+, via primary winding 257 of audio frewith the anode circuit Of tube 3i quency output transformer 258, from "the secondary -winding2'59 of which is "delivered suc'h audio frequency output. A voltagedroppingresistor "266 is connected rbetween the source of energy just described and the *screen ;grid 261 of tube 252, this screen grid being by-matssed to ground by condenser 262. r

The oscillatory function of tube "252 is- 'brought about by'the'connectio-n of the cathode 263thereof to -an intermediate point on inductance 264, this inductance being grounded at its "lower 'end and connected at its upper end via oscillator grid condenser '265 to control 'grid 251 of the tube. Since the-dual='functioning of tetro'de 252 and the maintenance of control grid 25lat the proper operative "D. C. potential by means of resistor 25s, are brought about inthesame-Tashion-as alreadydescribed'in connection with Fig. 2A,a detailed recitation thereof is thought unnecessary.

Referring now to Fig. 8A, th, signal-bearing currents received at'antenna 353i) and ground'ttl pass through the primarywinding 3832 of the-antenna coupling transformer t3, the secondary winding 304 of which transformer is suitably tuned by variable condenser '395. One end of secondary 335 is connected 'to control grid 386 of mixer or converter tube 387, while-the other endof secondary 3M-is grounded via by nass condenser'SBB. Resistor Still alior'ds a bias ior'grid *lations. "The output of mixertubeBllI is taken from the anode 3W "thereoigand transformer 3 l 8 has the primary windings l t connected in series This 'primary winding is tuned'to a 'suitabl'eintermediate frequency equivalent to the' beat frequency produced by tube 3%! and its associated circuits/by -means-o'f condenser "320. The anode supply circuit extends from the lower portion of trans- 'former Sta to thepointin'dicated by 13+, indicating any suitable source-ofD. Cfhigh-potential. 'The'remaininggrids fiM and 322 of tube 301 may conveniently obtaiirth'eir voltage supplyfrom the same source which ieeds the anodeofthe tube, via a voltage dropping resistor e23, being suitably by-passed tmground :via condenser 32%.

'The intermediate frequency'signal bearing energy derived from tube 38'! and the associated circuits just described, will then :appear insesondary :winding 325 of l-Ftransfo-rmer M8, this last winding :being rlilrewise-tuned by condenser J3Zfift0 a'frequency; corresponding toithat to which the primary windingoftransformert8 is tuned. Secoridarywvinding 325 is. connected at one end to control gridi-32l of amulti-element tube 132%, 'and isrconnectedrat theother end'to'gmund via "IF by epass condenser-1:32 9. Tube vr323 'hasathe cath- =ode silflsgroundediand thcscreen gridcfifil thereoi-niay receive its energy from' 'theicommonzsupcply indicated at 3+, through :a suitable voltage :dropping resistor Q32 andri-s by-passed {to ground shy-[condenser i'EtheiIFsignals fed-tozgridruzl will be amplified "by tube 328 and the amplified signals appearingon the-anode 33:3 of this tube are fed into primary winding 335 of a second intermediate frequency transformer 3.5-3.6, this primary being tuned by condenser 33? to the frequency of such :Il'? signals and being Icy-passed to ground via condenser 33?. Secondary Winding 3380i transformertsii islikewisetuned by con-- denser-339 andfeedseleinent 1M3 oi tubetfis, this tube-element functioning to afford diode detector action. The low frequency signals resulting from suchidetecting action app-ear acrossload resistor 13%, the usual smoothing or intermediate frequeue-y by pass condenser 6&2 and IF filter resisttor 3 3i being connected from the lower end of winding 338 M the ground, the path for resistort li being vie/load resistor 3%.

The audio frequency signals which have resulted from the IF amplification and detection 'just described will then feed back via conductor 3 32 to the lower end of secondary Winding 325 of transformer Due to the relatively low impedance presented byt-his winding" to audio frequency currents, such signals appear, practically 'unreduoed in intensity, upon control grid '32? of tube 323. In .tl'iismanner, the amplifier section of tube 328 :willperformthe additional function or" amplifyingthe audio frequency currents fed :into grid 1321, While at the same time it is ampli- :iying the'IF currents, as previously described;

The amplifiedv audio-output of tube appears w-across the anode load resistor it-3. it will be :noted that the lay-passing action or condenser 33'! allows the intermediate frequency signals fed to primary winding 335 of transformer 33%, to

pass directly to ground without being weakened by :passage through the resistor just described. From the junction point between the upper end-ofresistor 343, which resistor likewise servesrto'supply anode potential to tube 328, and the lower end of primarywinding-335, is taken-a ead 3 3d, through which the ultimate amplified audio-frequency outputbi tube passes, via audio frequency coupling condenser "3 5 and is fed to volume control i345, :oi the potentiometer type, ultimately reaching ground through conductor. 341.

'Atit irt, is shown an output or 'power amplifier tube whichperforms only the single iunction'of 'handlingthe audio frequency signals fed to the 'gri'dfd thereof-from Volume control'fi lb. Tube :tfiilzhas the grid bias suitably determined by cathode resistoriii'il, by pass condenser 355 connectediin shunt therewith Screen grid liil and anode 353 of tube :3- l 8,-may conveniently receivetheir potential from a common source indirouted at 13+. The audio frequencyoutput of tube :tdil'is fed to the primarywinding 35 of output transiornrerisdt, from, the secondary winding 3156 113i which such audio frequency-output maybe atalren.

Inzthe recei-ver just describedthe plural functioning oirtube allows the eliminaticn ofthe intermediate frequencyainplifier tube which has 'ihithertobeen found necessary, thus allowing the receiver to "be-built with greater economy of ma- :teriaLspac-eandweight.

Referring now to Fig.3B, the antenna circuit 'andtheunixer tube circuits, including the input circuit to tube "328, are shown respectively as identical with the like portions of Fig. 3A and :bear identical reference numerals. The diode element ten :of tube 328 likewise is fed from an intermediate frequency transformer see, having aytuned secondary -:circuit x338, .339, in :the same fashion as indicated in Fig. 3A. This secondary circuit is by-passed for intermediate frequency to ground by condenser 342, and an intermediate frequency filter resistor 341 is placed in series with the diode load resistor 390, the audio frequency output appearing across resistor 380 The tuned primary circuit 335, 33?, of this transformer is placed in series with the circuit of screen grid 331 of the tube, instead of being placed in series with the anode 335 thereof. Voltage dropping resistor 332 is connected between the lower end of this tuned primary circuit and the source of high voltage which feeds the anode circuit of tube 328. but by-pass resistor 333, connected directly between the lower end of the tuned primary circuit and the ground, serves to prevent loss of intermediate frequency energy in resistor The audio frequency output from the anode circuit of tube 328 appears across plate load resistor 343, which, in this case, is directly coupled at its upper end to anode 334 and Icy-passed with respect to intermediate frequencies, directly to ground by condenser 33?. The lower end of resistor 353 is connected directly to the source of anode potential by means of conductor 34 3'. The amplifier audio frequency output of tube 328 is delivered through stopping condenser 345 and may be withdrawn between the open side of this condenser and the ground as indicated in Fig. 318 by the legend "AF output. In Fig. 3B the final output tube corresponding to tube 058 of Fig. 3A, is omitted, since its function is identical with that indicated in Fig. 3A.

The placing of transformer 350, feeding intermediate frequency energy to the diode portion of tube 320, causes this tube to function as a triode amplifier of intermediate frequency energy, while the fact that the audio frequency output is drawn from anode 334, causes the tube to function as a tetrode, with respect to the audio frequency amplification. This mode of connection results in less gain at the intermediate frequency. However, the oscillation of the anode load circuit from the intermediate frequenc circuits connected to this tube, allows the use of a larger size anode load resistor as element 343, thus rendering possible a greater audio frequency amplification, without causing any reduction of the intermediate frequency gain. In practice it has been found that the overall gain of the circuit indicated in BB is somewhat less than that of the circuit indicated in BA, but the isolation of the audio frequency output has been found desirable in certain applications.

Referring now to Fig. 4A, tube 400 has connected between control grid 401 and anode 492, a crystal 503, which causes the tube to function according to the type of the so-called Pierce oscillator. At the same time the tube receives an audio frequency input from terminals 404, through coupling condenser 405 and resistor 406, the grid 451 being maintained at a suitable potential by means of a grid leak 40?. The anode 402 is isolated by radio frequency choke coil 008, but the audio frequency output passes through this choke coil and appears across the primary 409 of output transformer 519, available across the secondary winding 411 of this transformer. A suitable source of anode energy is indicated at 13+ and this same source may conveniently be fed through voltage dropping resistor 412, to screen grid 413 of the tube, a suitable by-pass condenser 414 being provided.

In Fig. 4B is shown tube 400 with a similar audio frequency feed circuit, as indicated by like reference numerals. In this case, the radio frequency oscillation of the tube is brought about by connecting the cathode 450 to a suitable intermediate point 451 of inductance 452, the upper side of this'inductance being coupled by oscillation condenser 453 to grid 401, while the lower end of the inductance is grounded at 454.

A variable condenser 455 is shunted across coil 452 and serves to determine the frequency of oscillation of the circuit. In this case, there is indicated a resistance coupled output circuit from anode 402 of the tube, including by-pass condenser 450, load resistor 45?, and coupling condenser 458, the audio frequency output being available between the free side of condenser .558 and the ground, as indicated on the drawing.

The combination audio frequency amplifier and radio frequency oscillators, as shown in Figs. iA or 43 may have their radio frequency output utilized for any convenient purpose, such as to feed a mixer tube, as a beat frequency oscillator, and so forth, as previously mentioned in connection with the circuit of Fig. 1.

In Fig. 5 is indicated a radio telephone transmitter, where microphone 5130 serves to modulate energy received from battery 501 and is coupled via input transformer 502 and radio frequency choke coil 503, to the grid 504 of tube 505. A crystal 506 is connected between grid 504 and the ground while the return D. C. path of the grid is completed through biasing resistor 50'', shunted by by-pass condenser 508. The operation of this biasing resistor, when tube 505 is in oscillation at a frequency determined by crystal 506, is similar to that already described in connection with Fig. 2A, the higher frequency oscillations thus creating a suitable D. C. bias for tube 505.

The screen grid 50?: of the tube is employed as an anode, and variable capacity 5m, shunted across inductance 5i 1, constitutes the oscillatory tank circuit, tuned to the frequency of crystal 505. This constitutes a tuned grid-tuned plate oscillator, the output of which is coupled via grid coupling condenser 512, to power amplifier tube 513, the grid 514 of this tube being maintained at a suitable potential by grid leak resistor 515. Tube 513 is anode modulated by the audio frequency output derived from the anode 516 I of tube 505, this anode being suitably by-passed with respect to radio frequency by means of condenser 517, while the audio frequency output thereof is impressed via modulation transformer 518, and the anode tank coil 519, connected to the anode 525 of the power amplifier tube 513, this anode tank coil being tuned by variable condenser 521 to the frequency of crystal 505. A suitable radio frequency by-pass condenser 522 shunts the'the secondary winding of transformer 518.

The voltage dropping resistors, by-pass condensers and high voltage connections of the screen grids of tubes 505 and 513 are indicated in conventional fashion, and a detailed description thereof is thought to be unnecessary. A complete radio telephone transmitter is thus obtained, with the employment of only two electronic tubes.

Referring now to Fig. 6, there is here indicated an alternative arrangement of tube 505, in which a self-excited oscillator circuit takes the place of the crystal 506 cf Fig. 5. The input transformer 502, is connected to control grid 504 via the lower portion of a split inductance 600, indicated by the dotted lines in Fig. 6. The upper '9 portion of inductance-800 is introduced in series with the circuit connected to the screen grid'56-9 of tube50'5, and is tuned by condenser fifll, thus constituting the tuned tank circuit'determining the radio frequency period ofthe circuit. A suitable radio frequency by pa'ss condenser 602 is connected from the upper end of the-secondary of transformer -592 to the ground, thus affording a-direct path for the radio frequency currents circulating through the lower portion of split inductance 600.

The radio frequency grid coupling condenser 5 l-2,-by-pass condenser 5l1 and modulation trans former 518 are connected in the same fashion as shown in Fig. 5 and it is thought unnecessary again to indicate the radio frequency power amplifier tube and antenna'connections, since these 5 may be made idential with those shown inFi xd Making reference now to Fig. 7,'=there ish'ere shown a portion of'a superheterodyn'e type'radio receiver, including the last'stage of intermediate frequency amplification, together with the input and output coupling devices therefor. Likewise there is shown in this figure a multi-element-lectronic tube connected both to the input and the output of this final stage of intermediate frequency amplification. This last-mentioned tube functions simultaneously as an oscillator, pro- 'ducing current of a frequency which'will beat with the intermediate frequency, as a diode typedetector and as a high gain'audio frequency amplifier.

Tube 190 is shownas of the tetrode'type;butit is understood that this tube may be-of-any 'other type suitable for intermediate frequency ampli fication, for example a pentode, and-changes in the circuit here shown, in order to adapt it for the use of such other type tube, will be apparent to those skilled in the art. Cathode m of tube 100 is kept at a suitable operating potential by means of bias resistor 102, by-passed by condenser !03. Heater lil imay be fed with energy from any. suitable source (not shown). The control grid 105 is kept at a potentialdependentupon the potential of conductor H15, as feed through filter resistors 70"! and 108. The use of such variable potential in orderto secure automatic volume control is well known in the artand a detailed description thereof isltherefor'e thought to be unnecessary. Input transformer 1'08 =is shown with a primary winding 109, suitably tuned by a capacity I i ll, while secondary winding ll is likewise tuned by capacity H2. The output of transformer 103 .is .fed between control grid T05 and the ground, the latter connection being made via intermediate frequency by-pass condenser H3. Screen grid H4 is fed from a suitable high potential source indicated at H5 by the legend B+, through voltage dropping resistor H6 and is by-passed to ground by condenser H1.

The amplified output of tube is taken from the anode 1 l 8 thereof and fed to primary winding H9, suitably tuned by condenser 120, of intermediate frequency output transformer 'l2l. Secondary winding I22, of transformer 12l, also suitably tuned by capacity 123, is connected between the detector element 124 of multi-elcment tube 125, and the ground, the latter connection being made via intermediate frequency by-pass condenser I26. The rectified output of the detector portion of tube 125 passes through diode filter resistor '121,by-passed to ground by another intermediate frequency condenser I28, and to resistor 129. This last resistor 129 is connected at its lower extremity to the ground and may resist 1 0 c'onvenicntl y be provided with a movable contact 130, functioning as a volume control, "and feeding audio frequency energy through boupling con denser 13 lfto the audio frequency amplifier section input-of tube T25.

Tube F2 5 has the cathode 32 thereof grounded vand cathodelheater 133 may be-fedi'from imys'uitable sourceof'e'n'ergy (not shown). The audio 7 frequency input for tub'e' Tl 2 5, obtained via *aud-i'o fr'equency couplingcondenser 73 i is fed throu h radio frequency isolating resistor 134, tocontrol grid 135, the potential Of this control grid bihgmaintained at a suitable value via grid leak resistor 133i, -'cqnr-icc'ted from the lower end of resi's tor 133' to the ground.

The amplified audi'o frequency output of tube 3 2% is taken from the anode 13! thereof, a-hd appears across output terminals 13 3, as iridihated by the-legend appended thereto. Anode 131 is fed from-'any suitable source of energy, as indicated at 'l iiii' by th'e' legend l3+, through-plate load resistor 1 4i]. Any radio frequency components of the current taken fromanodel-tl are *by passed to ground by asuitable condenser-Hi.

The oscillation generating action of tube is brought about bet-ween control grid and screen grid "142. Apreferably variable inductance i 33, tune'd'bya shunt-capacity T44 to the intermediate frequency, or to some subharlnonic thereof, is connected --directly to'ascreen grid 1 E2 and -via coupling condenser 14?: to control =grid we. "The supply-cf energy for screen grid 1 22 may -'conveniently be obtained from the same source as "thesuppl'y for the anode thereof, as indicated at 146, via voltage dropping resistor WM, 'by passed to ground with respect both to radio and audio frequencies by condenser 158-. The direct current voltage applied Via resistor '"F fl is--connected to an intermediate point 1-43 upon inductance W3. A switch fill, grounded at "one side; serves optionally to connect sc'reen; grid 1 42 to ground; via-a relatively high capacity condenser 15L Whenswitch fill is closed, the connectionofxscreen grid 152% groundserves'eifec- 'tively zto short-circuit a portion of i n'ductance "T43, in as far as intermediate frequency oscillations-are concerned. Therefore, the M this switch serves to "prevent the pr od'u sucho'scillations b'y tub'e' 12%, while 'at the ame time allowing the l other functions of this tube to continue uninterruptedly. I

The intermediate fre'quen'cy' Y energy appearing atthe upper end of' inductance we is transmitted 'viaconductor voltage 'coupling condenser 753, to the upper end of secondary wind ing H! of transformer I08, as shown by the connection at point "154. The intermediate frequency, the period of which is determined by the constants of inductance M3 and capacity 14,

is suitably adjusted, as by the variation of'the value of inductance 143, so as to be sufficiently different from that of the intermediate frequency due to an incoming signal and appearing at winding H i, so that a beat note, usually of an audio repeat in detail such other functions performed by tube 125.

What is claimed is:

1. In a combination amplifier and oscillator, an electronic tube having cathode, control grid and anode, circuit means oscillating at a frequency range outside the audio frequency range, said circuit means comprising an inductance connected at the ends thereof between control grid and anode, and connected at an intermediate point to the cathode, means for feeding audio frequency energy to said control grid, means for withdrawing audio frequency energy from the anode, grid biasing means comprising a resistor connected between said grid and ground, and a capacity bypassing said resistor for said audio frequency energy, and establishing across said resistor a bias potential.

2. In combination, a tetrode having a cathode, control grid, screen grid and anode, an inductance connected at the ends thereof between control grid and anode and tapped at an intermediate point to the cathode, a coupling condenser and filter resistor in series with said control grid, means for feeding audio frequency energy to the free end of said coupling condenser, means for withdrawing audio frequency energy from said anode and a grid biasing resistor connected between the common point of said coupling condenser and said filter resistor and ground, to produce oscillations outside of the audio frequency range and establishing a potential across said grid biasing resistor, oscillations being filtered out by said filter resistor from the audio frequency energy feeding means. 7

3. A device according to claim 1, in whichthe audio energy feeding means comprise a first transformer and the audio energy withdrawing means comprises a second transformer and also including a condenser effectively in shunt with the primary of said second transformer, so as to bypass said primary as to oscillatory energy.

4. In a combined oscillator and amplifier, a multi-element electronic tube having cathode, control grid and anode, means for feeding audio frequency energy to said control grid, means for withdrawing amplified audio frequency ener y fromsaid anode, circuit means oscillating at a frequency range outside the audio frequency range and connected to said control grid and said anode to bias said grid, and filter means connected respectively to said control grid and said anode, whereby oscillatory energy is substantially prevented from reaching said audio fre- 12 quency feeding and withdrawing means, and means for energizing said tube.

5. A device according to claim 4 in which said circuit means comprise a tuned tank circuitconnected at the end thereof effectively between said control grid and said anode and connected at an intermediate point to said cathode.

6. In combination, an electronic tube including input and output electrodes, circuit means for feeding audio frequency energy to an input electrode, circuit means for withdrawing amplified audio frequency energy from an output electrode, means for biasing said input electrode, said biasing means including circuit means connected thereto and oscillating at a super-audible frequency, and a biasing resistor also connected thereto, and filter means interposed between input electrode and audio frequency feeding circuit means and between output electrode and audio frequency withdrawing circuit means, respectively, said filter means passing said audio frequency, whereby said tube functions simultaneously as an oscillator and as an audio frequency amplifier.

7. In combination, an electronic tube having cathode, control grid and anode, and means for energizing said tube, oscillating circuit means comprising an inductance connected from control grid to anode and tapped to the cathode, audio frequency feeding means connected to said control grid, audio frequency output means connected to said anode, a grid bias resistor connected between said control grid and ground, and means substantially isolating said resistor from the oscillating currents, whereby the action of said oscillating circuit means upon said control grid establishes a direct current potential drop across said grid bias resistor and thereby biases said tube as an audio frequency amplifier.

JOHN J. ANTALEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,896,268 Willoughby Feb. '7, 1933 2,023,780 Cottet Dec. 10, 1935 2,059,587 Klotz et a1 Nov. 3, 1936 2,066,333 C-aruthers Jan. 5, 1937 2,165,764 Pitsch July 11, 1939 2,285,372 Strutt et al. June 2, 1942 2,293,151 Linder Aug. 18, 1942

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