US1773503A - Vacuum-tube circuits and the like and method of controlling the same - Google Patents

Description

Aug. 19, 1930. E. R. STOEKLE 1,773,503

VACUUM TUBE CIRCUITS AND THE LIKE AND METHOD OF CONTROLLING THE SAME Filed Aug. 1925 W. 2 5.2. N 5 w Patented Aug. 19; 1930 UNITE D ,sT TES nnwnv 1a.. sr'oEKLrroF iyrinwnuxnni WISCONSIN i VACUUM-TUBE cmourrsfANn ITHE LIKE AND rrnrnon on CONTROLLING 'rrrnv SAME Application file'd August; 7, 1925 j sri'a1 f1vo} 4s,76a 7 This invention relates to improvements 'in vacuum tube circuits and'the like, and the method of controlling the same, particularly with regard to circuits employed in radio communication. k

In an electrical circuit includingso-called negative resistance, it is-well known that the phase 1 relation between the voltage drop 'across the resistance and the current through lathe resistanceis an important factor in determining whether or not the circuit will generate electrical oscillations. a

The types of negative resistance devices commonly used in'circuits for radio com- ,15 munication usually employ three electrode thermionic vacuum tubes, electric are, or gaseous discharge devices. Since the three electrode vacuum tube is most commonly used insuch circuits, the new methodof oscillation control herein described, will refer particularly to the vacuum tube, although it is equallyapplicable to other types of negative resistance devices. I One object of thisinventifo'n is to provide 2 an improved methodof controlling the tendency of the radio frequency tubes tooscill'ate in so-called radio frequency amplifying-receivers. I f .j 1 Another object is to provide an improved ,130 method of controllingthe oscillation of an electrical circuit including a negative resistance device. 1 I

Another object is to provide an improved method ofcontrolling theoscillation of radio frequencyvacuum tubes whereby the range of oscillation control .is greatly increased as compared to existing methods. l

Another object is to :provide improved means whereby the inductance and the re.-

I sistance in the plate circuit of a vacuum tube may be simultaneously varied for the purpose of controlling electrical oscillationof the circuit. v i f v, T

Another object is to provide animproved method of controlling the transfer of oscillating energy between successive stages of a vacuum tube radio-frequency amplifier. H

Other objects and novel features of this improved method and means for controlling vacuum tube circuits, Will be apparent from Figure 1 shows diagrammatically a radio receiving circuit employing a radio frequency the following specifications and the accom pan ying dra'wingsf; g 1 1 -Embodim ents"of 'the invention are shown in the accompanying drawings in which 2- amplifier tube and a det'ector tube with the new m'ethodof oscillation control.

Figure 2 shows-diagrammatically.a two stageradio frequency amplifier with the new method of oscillation control and a detector. Figure 3 showsa single stage radio frequency amplifier and detector with the new' metho'dof oscillation control applied to the radio frequency -transformer,-' coupling the detector'tothe amplifier;

PATE T o mcrf f Referring to Figure l, the aerial 1 is coupled'to the grid 2 of the first vacuum tube by m'eans'of the primary and secondary coils 3' and4. The" variable 'condenser 5serves to tune thegrid circuit of the first tube. The

plate circuit of 'this'tube includes the inductive primary coil "6, the auxiliary coil 7-, resistance'8 and a fixed condenser 9.

v The secondary 1'0 of'the'above mentioned radio frequency transformer is tuned by 'me'ans ofa vfariable'condenser 11 and isconnectedithrough the grid condenser 12 and grid leak1j8--to-the-grid '14 of the, detector tube. The battery 15 maintains the plates 24 and16 of the amplifier a'nddetector tube V respectively, a-t a positive potential with re-- spect to the filaments 17 ,and.18. Battery 19 suppliesgthrough the resistance 2O a: current for heatingthe filaments. 17 and 18'; Telephone receivers 21 :are connected to the plate circuit vofi the detector tube in 'the usual .ma e i e .op ra bnbfthe circuit shown in Fig;

ure 1, is as follows :Electr,ical oscillations received upontheaejrial are impressed upon the} grid 2- in theus ual manner. jThese osci-llations cause corresponding variations in the electronjflow from the filamentl? to the plate 24;o'f the vacuum tube. These variationsin the platecurrenti pass through coils 6 and 7 and through the condenser 9,-back tothe fil'a-,

merit; portion ofj' 'the oscillating current isuhowever, divertedfrom the coil? via the resistance 8, the amount of such diversion 3 of current being dependent upon the position of the movable contact 22 on the resistance 8. The condenser 9 is of sufficient capacity'to readily allow the passage of high frequency current so that very little of such current will pass through the battery 15. Direct current is supplied from the positive terminal of this battery through the resistancejS, 1n-

ductance 7 and coil 6 to the plate 24 of the vacuum tube. The negative end of battery 15 is connected to the filament circuit inthe usual manner. y p The resistance 8 is preferably non-inductive and may have a value. of. the order of 200,000 ohms although the invention is not limited to this value. It is also preferably-ta pered so that its resistance per unit length decreases as the contact22 moves toward'the point 23. As the contact 22 approaches 23, the portion of the resistance 8' in parallel with the coil 7 is progressively decreased, while the portion of resistance 8 in series with the .battery 15.,is progressively increased. Therefore, the inductive value of coil 7, which is effective in the oscillating plate circuit, is progressively decreased, while the resistance in series with the voltage supply 15 is increasech thus decreasing the direct current voltage applied between the plate 24 andthe filament 1?. 'It-is, therefore, apparent that a movement of the contact 22 towards point23 produces a simultaneous decrease in the inductance effective in the oscillating circuit and in the direct current voltage applied between plate 24 and fila; ment 17. v

If the'vacuum tube generates oscillations at a given frequency with the contact 22 at a position removed from 23, it will be found that as 22 moves toward 23, the generation of oscillation at that frequency will gradually disappear. This disappearance of the gen: erated oscillation is due to two factors. First, a decrease in eifective inductancein the oscillating plate circuit'which changes the phase relation between the current through the vacuum tube and the voltage applied. Second, a decrease in applied voltage so that the so-called capacity feed-back etween the plate 24 andthe grid 2 is decreased. It has been found that this simultaneous variation of the effective inductance in the oscillating circuit and of the direct current voltage impressed upon this circuit produces a very smooth control of the oscillation of the tube over a'wide range of frequencies.

Figure 2 shows the same general principle of oscillation control applied to a radio receiving circuitemploying two stages of tuned radio frequency amplification and adetectorl The radio frequency. amplifying tubes are shown respectively at 25 and 26 and the detector at 27. .The grid circuits of these tubes have inductive secondary coils 28, 2 9 and30,

tuned by means of the variable condensers 31, 32 and 33, respectively.

The antenna coil is shown at 34 and the primary coils 35 and 36 are shown respectively in the plate circuits of the tubes 25 and 26. The filament battery 37 supplies heating current to each of the filaments of the vacuum tubes by means of conductors 38 and 39. The common conductor 40 connects together the plate coils 35 and 36.

The auxiliary coil 41in series with the condenser 42, is connected between the corn- 'mon conductor 40 and the common filament circuit conductor. 38. The battery 43 has its negative terminal connected to the conductor 38,- and its positive terminal connected through the'resistance 44 to the conductor 40. The variable contact 45, bearing on this resistance, is connected through the conductor 46 to the auxiliary coil 41. A somewhat lowervoltage is tapped from the battery 43 by means of the conductor 47, which connects through the telephonereceiversto the plate of the detector tube as shown.

I The operation of the circuit of Figure 2. is exactly similar to that of Figure 1, except that the efiective inductance in the plate circuitsof the two tubes 25 and 26 is simultaneously varied bychanging the location of the contact upon the resistance 44; and at thesame time a corresponding variation of the voltage impressed upon the plates of these tubes iseifected. As the contact 45 is moved towards 40, the part of the resistance 44, electrically in parallel with the coil 41, is

progressively decreased, thereby decreasing the inductance of the coil 41 effective in the plate circuits of both the vacuum tubes 25 and 26. scribed decrease of effective inductance, there isa corresponding increase of the resistance in series with the battery 43, thereby decreasing the'voltage upon the plate circuits of both the tubes 25and 26. v

The principle of varying the inductance effective in the plate circuits and at the same time varying the voltage impressed upon these circuits, is shown applied to one and twotubes in Figure land Figure2, respectively, but may be equally well applied to any desired. number of radio frequency tubes.

Figure 3 shows a radio frequency amplifier tube 48 connected in cascade with adetector 49 The antenna coil 50 is coupled to a grid coil 51 which is tuned by means of a variable condenser- 52. The plate coil of the tube 48 has its windings in two sections 53 and 54. The conductors 55, 56, 57 and 58 connect the plate coil in series with the condenser 59 and across the filament and plate'of the tube 48. The resistance 60 is connected by means of conductor 61 to a point on the plate coil intermediate the sections 53 and 54. The positive terminal of the battery 62 is connected to the resistance 60 by. means of the Coincidently with the above de conductor 63. The negative terminal of this battery is connected to the common filament circuit as shown; The secondary coil 64 is inductively coupled to the composite plate. coil above described and is tuned by means of the variable condenser 65. The contact 67is o movable upon the resistance 60 and is connected to the conductors 56 and 57 by means of a conductor 68. The telephone receiver 66 is connected to the plate of the detector tube 49 and to thebattery 62 in the usual manner.

The operation of the circuit described in Figure 3, differs somewhat fromthe operation of'thosedescribed in Figures 1 and 2, in that the mutualinductance of the plate C011 and grid co l coupling successive vacuum tubes, is varied in addition to a variationof the self-induction ofthe plate coil. It is apparent from Figure 8 that the section 54: of

1 48 is decreased, and at the same timethe muincreased, the tendency for the radio lire-IT the plate coil is shunted by a variable portion of the resistance 60. It is further apparent that as the resistance shunting the section varies, theremainder of the resistance 60,

which isin series with the battery 62,1varies in inverse proportion. Therefore, as theresistance shunting 54 is decreased, the inductance effective in theplate circuit of the tube tual inductance between the plat'e'coil of the tube 48 and the grid coil .64 will also be decreased Coincident with the above described decrease in self and mutual induction, there fwill be a corresponding decrease in the voltage eiiective between the plate and filamentof tube 48. Thisis due to the increase of the part of resistance in series with thebats tery 62. r

It is well known that as the'natural f requency to'which the gridcircuits of a multi stage radio frequency amplifier arejtuned is quency tubes to generate oscillations increases. It is further well known thatas the above mentioned natural frequency decreases,

the transfer of energy between successivestages through their mutual coupling also decreases These factors all tend to facilitate the generation of oscillations in the amplifier circuits.

The method of control disclosed in Figure 3 governsthe generation of oscillations by varying theself-induction in the plate coil of the amplifier tube, themutual inductance of thiscoil with respect to the grid coil of I thenext tube, and the voltage impressed upon the plate of the amplifier. The simultaneous control. of these factors by the circuit arrangeoment shown, provides aconvenient'method vices having similar characteristics, may be employed without departing "from the spirit i a 1 V i a v V: 1. In an electrical circuit, includingan or scope,ofthisiiivention-as set forth in the following claimsr- ,o r

electrical discharge device, a source, of voltage in series with said device, an inductance coil in series with said device, an auxiliary inductance coil also" in series with said device,.aresistance having-a variable portion o in parallel with Fsa'id secondmentioned coil,

the remainder of said resistance being in 1 series with said voltage source, meansfor lvarying the i'portionof said resistance in par.-

allel with said second mentioned coil and the i, so

portion in series with said voltage source,

in [inverse "relation, whereby the inductance of said second C011 effective in said circuit, and the voltage mpressed upon said electrical discharge device may be simultaneously varied.

2. In, an electricalcircuit, includingan electricaldischarge device, a source of voltk age in series with said device an inductance coil in series with-said device, an auxiliary inductance coil also in series with said device, an electrical condenser in parallel with said device and both otsaid coils, a resistance having a variable portion in parallel with said resistance being in series with said voltage source, means for varying the portion .95 said secondmentioned coil, the remainder of of said resistance in parallel with-said second mentioned coil and the portion in series with said voltage source,1in inverse relation, whereby the inductanceof said second coil. effective in said circuit, Iandthe v-oltagefimpressed upon said electrical discharge'device may be simultaneously varied.

3. Anelectrical circuit, including a vacuum tube, an inductance coil'in series with the plate of said tube, a second inductance coil in series with said first mentioned'coil,

an electrical condenser in parallel with said. coils and said tube, a resistance in series Wlth said first mentioned coil and a source of voltage, acommon connection for said first and said second mentioned coils and said resistance, a contact movable upon said resistanoe for connectingthe common'terminal of said second mentioned coil and said condenser to a variable 'portionof said resist ance, whereby the portion of said resistance, in parallelwith' said second mentioned 'coil and the portion in series with said voltage 1 source may be vvaried ininverse relationand a simultaneous ,VallaillOIl of the inductance pressed on'said circuit may be accomplished.

effective in said circuit and the voltage im 4:. An electrical circuit including a three electrode vacuum tube, having a tuned grid circuit, a plate to filament-circuit, including a main coil, an auxiliary coil and a condenser, avresistancehaving oneter'mina-l con- 'nected to the common connection between said coils, and another terminal connected toa source of voltage, a variable contact upon said resistance, said contact being con- I nected to the common terminal of said auxiliary coil and said condenser, whereby a varying'portion of said resistance may be connected in parallelwith said auxiliary coil and an inversely varying portion of said resistance may be connected 1n series with said voltage source, for the purpose of controlling the generation of oscillations by said vacuum tube. V

In testimony that I claim the foregoing I have hereunto set my hand at Milwaukee,

in the county. of Milwaukee and State of 7 Wisconsin.

ERWIN .R. STOEKLE.

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