US1806813A - Electron tube energizing method and apparatus - Google Patents

Description

y 5, I 5. F. MIESSNER 1,806,813

ELECTRON TUBE ENERGIZING METHOD AND APPARATUS Filed 65. 4, 192a 2 Sheqts-Sheet 1 y 6,1931. B. F; MIESSNER 1,806,813-

ELEQTRON TUBE ENERGIzIriG METHOD AND APPARATUS Filed Feb. 4, 1928 2 Sheets-Sheet 2 ism ,L

Patented May 26, 1931 UNITED STATESYQPATENT OFFICE BENJAMIN F. MIESSNER, OF SHORT HILLS, NEW JERSEY, ASSTGNOB, BY MESNE AS- SIGNMENTS, T RADIO CORPORATION TION OI DELAWARE OF AMERICA, 01 NEW YORK, N. Y. A CORPORA- ELECTRON TUBE ENERGIZ ING' METHOD AND APPARATUS Application filed February 4, 1928. Serial No. 251,807.

The present invention relates generally to methods and apparatus for energizing elec-' tron tubes for operation, and particularly the energizing of three electrode vacuum tubes 5 for amplification and detection from unsteady sources of potential including commercially available alternating current sources.

An object of the invention is to so use and 1 control the fluctuating components of the energizing currents that the hum effects at the output end of an amplifying system so energized are substantially eliminated or are made sufli'ciently small to satisfy practical requirements.

A particular object of theinvention is the provision of methods and means for energizing single or multiple stage vacuum tube'systems, such as radio receivers, in a way to cffect a substantial reduction in theexpensive and bulky materials heretofore used'in the filter portions'of such systems without sacrificing hum reduction efliciency.

Other objects and benefits will be obvious.

to those skilled in the'art from the following description with its reference to the figures of the accompanying drawings, like reference characters representing like parts so far as possible in'the several figures.

Fig. l-diagrammatically illustrates the invention in the. simple form of an energized single stage of audio frequency amplifica-v tion, and is particularly suitable for an explanation of the fundamental features involved. 1

. Fig. 2 illustrates the invention in like manner to Fig. 1 with the exception that it provides for radio frequency amplification.-

Fig. 3 shows the invention extended to multiple stage amplification.

' Fig. 4 shows the invention applied to a complete radio receiving system includin radio frequency amplification, detection-an audio frequency-amplification, and includes additional novel features;

In Fig. 1 there is shown a three electrode vacuum-tube amplifier VT including grid, filament and plate electrodes, 9, f andp respectively, the filament being shown as'heated by current from a battery through a var tion of the able resistance in a conventional way, itbeing understood'that any of the. well-known methods of heating'are applicable. The input circuit is shown to have an input through a transformer T for alternating currents to be amplified, and the output circuit is shown to have an output for the amplified currents through transformer T The transformer T and T are conventionally indicated as low or audio frequency transformers, though electrolytic rectifiers and the like. The source may have associated with it filtering or energy storing devices in kind. and manners well known, including choke coils or resistances in detail.

Practically all' manners of operation of three electrode vacuum tubes require a so-' called negative grid bias to' brin the point of operation of the device-at a J esired porwhen the ate electrode ispositively energized sufficiently strong to permit of response throughout a desired extent of the. characteristic curve,' and some of the more or less recent power amplifying tubes Because the tubes are usual y employed as amplifiers, and in man instances are followed by one or more ad itional stages of'amplifica'tion, the procedure of deriving the grid iasing potential from an unsteady source has common to radio receiver practice require rather high grid bias potentials, such as am ative 45 volts.

and condensers, though itis a particular purpose of the invention. to reduce the extent of use of such filtering .and energy storing devices to an extent heretofore not deemed prac-v ticable in practice, as will be later pointed out late current characteristic curve been viewed with considerable apprehension in systems where hum elimination, when energizing from such a source as commercial alternating current is deemed essential, as

in the case of commercially competitive broadcast recelvers. For this reason COIlSlderable effort has been made to free the energy used for grid biasing from fluctuations or ripples before application to the grids.

Since the degree of grid bias is a more or less fixed requirement for proper functioning of a tube for a desired purpose the bias cannot well be tampered with even if doing so would aid in arriving at other desirable results. It is a feature of the present invention that any desired degree of grid bias for amplifying, detection or other purposes of tubes can be met when accompanied by a high order of fluctuating or rippling energy from an imperfectly filtered source, and hum production desirably controlled without any detrimental sacrifice in the desired function of the tube. In fact, in lieu of striving to avoid fluctuating energy at the grid .the invention deliberately contemplates a substantial amount of it, but under such control that it is effectively used for hum elimination.

Continuing with Fig. 1 it is seen that the fluctuating current energy from source B passes from negative terminal B through resistance R in the grid circuit to filament 7, then to plate p .by reasonof the positive potential thereon from source B, and back to positive terminal 13+ by way of the primary of output transformers T Obviously this fluctuating current energy passing through rimary of T results in passing hum energy orward-with the desired signal energy unless something is done to prevent the result. The usual practice is to minimize the hum effect by smoothing out the current from source B as-much as practicable by the use of an elaborateamount of expensive filtering materials, such as choke coils and condensers.

The fluctuating current passing through R in the rid circuit derives for the grid a negative uctuating difference of potential the average value of which should, through choice of value of R for value of current, be the negative grid bias that the particular tube requires for the particular function contemplated, as for example maintaining the average value of plate current at the middle of the plate current characteristic curve for amplified repeating. With the connections shown the rippling component of the id bias will, including the amplifying ability of the tube, tend to neutralize tendency of the plate current to fluctuate by reason of the energizing current; that is, a ripple in the bias more negative than the average value of the produced negative bias will tend to reduce the plate current at the same moment that a simultaneous ripple in the positive oppositely acting it would be most fortunate 1 in normal arrangements for operating the 7 tube they were equal, as hum production would be automatically completely neutralized. In all the usual functions of tubes so far as practice has appreciated them the two effects are not equal, and therefore there is considerable residual fluctuating current passing through primary of transformer T to transfer its hum effect forward to the ultimate output along with the desired signal. For example, in thecase of amplified repeating if the resistance R were so chosen that the rippling component of the grid bias were large enough to neutralize the rippling component of the plate potential then the average value of the grid bias would be large enough to stop flow of plate current or, as it is termed, block the tube instead of permitting operation at the midd e of the plate current characteristic curve, recognized as most desirable for amplified repeating. These considerations bring out the fallacy of a common practice in the art of shunting a bias developing resistance R with acondenser to lessen the rippling component of the developed biasing potential when the plate electrode is energized from the same source. In general an increase in the rippling component of the grid bias is needed under such circumstances.

The present invention increases the rip pling component of the biasing potential while maintaining the average value just right for the particular tube and its purpose of use, and at the same time decreases the rippling component of the plate current without interferring with the desired average value of the plate current, and all in such a way that with the aid of the amplifying abilitfy of the tube any desired degree and phase 0 hum neutralization can be secured. It is a feature of some of the desirable modifications of the invention, particularly in multiple stage amplification operation, that hum currents of one or another phase be left in one stage for use in neutralizing hum currents in anot pling energy phase and e leave hum currents of opposite phase.

Again referring to Fig. 1, it is seen that I include a resistance R which may be variable for varied results, and a condenser C in series therewith in a connection between filament 7 and the negative side of the output element T in the plate circuit. The condenser C prevents the direct current component of the energy from source B from taking this path, and thus still confines it to the path by way of filament 7'. plate '0 and primary of will leave hum currents of one ficient grid rippling energy will llll er stage. Obviously excess grid riptransformer T but does permit the path to pass energy of the rippling component, thereby diverting some of the energy of the rippling component from primary of T and at the same time decreasing the impedance to rippling current energy of the circuit as a whole connected to source B, but in such a way that substantially all the energy passes through bias developing resistance R thereby increasing the rippling component of the bias for use against the decreased rippling component through primary of T- The effectiveness of the arrangement of Fig. 1 on hum elimination in practice is striking. For example, I have found when using as a source B current from an ordinary GO cycle commercial alternating current house supply system rectified by a vacuum tube I can, by choosing proper values of resistances R and condenser C, eliminate all of the choke coils of a well designed filter and reduce the capacity of the filter condensers to less than one-half value and yet produce'a hum elimi-v nation superior to that had with the full equipped filter, and this while maintaining R just right for best grid bias of the tube for amplified repeating.

In general I have found for good hum elimination a ratio of R to Ri of the order of the amplification of the tube being used where the system is operating as an amplifying repeater, and a capacity of condenser C such that its reactance to the rippling component of the energizing energy is substantially less in ohms than'the resistance of R in ohms.

In general I find it desirable to employ -resistance R for fixing the magnitude of the rippling current, and to make the capacity of 0 large in order to introduce as small a phasing effect as may be practically desirable. Excellent results may be had with a capacity of C much less than the capacities of the condensers employed in well designed filter systems. For example, I have eliminated along with all filters choke coils 10 microfarads out .of 18 microfarads of a commercial filter when commutated direct current it may be desirable to use some condenser capacity across the rectifier as an energy storage element.

The operation may be viewed as a matter of ratio of average value of potental to potential of fluctuating component. In the or dinary system the energizing potentials of-- grid and plate are derived from the same fluctuating current passing through resist-- ances for each electrode, so that the ratio of average value to fluctuating value of derived grid potential is equal to the ratio of averagevalue to fluctuating value of derived plate po tential. Since the correct operation of the stantially alike in characteristics. a signal input through transformer T the tube so to speak, it is obvious that with this equality of ratios the fluctuating grid potential cannot fully neutralize the fluctuating potential. I overcome the. difficulty by'so distributing the energizing fluctuating current with respect to grid and plate circuits that this equality of-ratios no longer exists with respect to the potentials 011 the electrodes per se, and so choose a ratio on the plate side greater than the ratio on the grid side, or-a proportionately lesserripple on the plate than on the grid.

Fig. 2 Shows one way of applying the invention to a stage of radio frequency amplification, and differs from Fig. 1 in that T and T are radio frequency transformers asv sociated with radio frequency tunable cir- 85 cuits 1 and 2 respectively. Condensers C C and C are the usual radio frequency bypass condensers to confine radio frequency currentsto the radio'frequency portion of the system, radio frequency choke coil CH being also effective in this connection. These by-pass condensers are of too small capacity to have any noticeable effects on the functioning of the energizing system, usually of the cycle order. In this figure, though it may apply to any system, the filament of tube VT-is shown heated by alternating current from a source S through a transformer T usually of the step-down type. In order to lessen humdisturbances arising from ener- 10o gizing the filament with raw alternating current the grid and plate circuits are shown connected to the filament system atan approximate point of neutral potential through a potentiometer P. It is of course under- 105 stood that the filament may be of the low voltage-low temperature type to further avoid hum difliculties if it is to be energized by'raw alternating current; The provisions for energizing the grid and plate electrodes 110 from a fluctuating source of potential and for neutralizing humare shownas in Fig. 1 and do not require a repetition of explanation since the amplification of radio frequency currents does not alter the modeof 115 operation.

Fig. 3 illustrates one manner of employing the invention with a lurality of amplifiers of the same kind whic provides'for using a' single grid bias resistance and hum neutral- .120

izing connection for all of the stages. The amplifying tubes VT VTg and VT aresub- There is The tubes are connected in cascades through transformers T and T and have a final output through transformer T The tubes are shown energized through two input terminals 'I and I whichmay be for example a commercial direct current supply'system 13o having an undesirable commutating ripple. The filaments of the tubes are connected in parallel across the line, the potential for the filaments being reduced to a suitable degree by means of a resistance R. The plate circuits of the tubes are connected in parallel across the line through a common lead L connected to the positive side of the line. The grid circuits are connected to the negative side of the line through a common lead L The resistance R develops a negative grid bias for all of the tubes while the resistance R and condenser C, connected across the common plate circuit lead L and the common filament system, provides a hum neutralizing connection effective for all of the tubes. As in the case of Fig. 1, the resistance H can be chosen of proper value to give the correct grid biasing potential for operating all of the tubes as amplifying repeaters, and the values of resistance R and condenser C are so chosen as-to permit sufficient rippling current to pass through resistance Il to produce a rippling potential on the grids of the several tubes to neutralize the rippling components in the plate circuits of the several tubes. If the commutation at the source is very poor a condenser K, indicated in broken lines, may be employed in shunt to the input terminals as shown.

Fig. 4 shows the invention applied to a popular type of radio broadcast receiver having two stages of radio frequency amplification including vacuum tubes VT and VT a stage of detection including vacuum tube VT and two stages of audio frequency amplification including vacuum tubes VT,

and VT The radiofrequency stages and detector stage are coupled through radio frequency transformers T T and T by way of tunable circuits 1, 2 and 3 respectively. The detector stage and audio frequency stages are interlinked through audio frequency transformers T and T The output is shown to include a loud speaker, or other suitable translating device LS, which is connected to the output of' tube VT through choke CH and condenser G a common mode of association of the translating device with the output end of such a system. An antenna A, or other suitable form of radio collector, is coupled to the input end of the system. Resistances R, and R in the grid connections of tubes VT and VT indicate one conventional method of stabilizing these tubes against oscillation. The combined resistance and condenser arrangement GL in the grid lead of detector tube VT; indicates the usual grid leak-stopping condenser arrangement used in connection with detector tubes. Condensers C C C C and C are the usual radio frequency by-pass condensers to confine radio frequency action to desired portions of the system.

Vacuum tubes VT and VT the radio frequency amplifying tubes, and vacuum tube VT the first audio frequency amplifying tube, are usually of the same characteristics and energized with grid and plate potentials to the same degree, and are so arranged in Fig. 4. Detecting tube VT is usually energized in the matter of plate and grid potentials differently from -the other tubes of the system, and in recent commercial practice it is common to employ as adetecting tube a so-called indirectly heated cathode type, and I have shown this type having an indirectly heated cathode f in conjunction with a heater element 7. It is also usual to employ as the final or output tube one of higher power than the other tubes, requiring considerably higher grid and plate energip ing potentials, and I have included this feature in the system of Fig. 4. The complete system therefore provides for handling tubes of three different types.

I provide for energizing all of the tubes in all respects from a source of alternating current S, such as the ordinary commercial 60 cycle lighting system, through a transformer system having a primary P and a series of secondaries S S S3, S1; and S I rectify the alternating current of secondary S by means of rectifying tube VT as a source of energy for the plate and grid circuits of all of the tubes, the secondary S providing for heating the filalnent'of the rectifying tube VT The filaments of the two radio frequency tubes VT and VT and the first audio frequency tube VT. are heated with raw alternating current from secondary winding S Recent practice provides for the filaments of these tubes being of the low voltage-low temperature type, as an expedient towards reducing hum effects resulting from voltage and temperature effects by reason of the use of raw alternating currents, and therefore usually require a transformer secondary adapted for low voltage and high current, and different from secondary windings adapted for the detector tube and the power output tube. The heater element of the detector tube VT 3 is shown energized by raw alternating current from secondary winding S The filament of the power output tube VT is shown energized by raw alternating current from secondary winding S A storage condenser K is connected across the output terminals of the rectifier system, the positive terminal B+ of which is connected to the plate electrode of power tube VT to give the maximum developed energizing potential to the plate of this tube. The negative terminal B- of the rectifier system is connected to the grid electrode of tube V'lr" The resistance R develops the necessary gridbias, usually high, for tube VT;,.

amplifying tubes VT VT and VT, do not require the same high energizing potential as the plate of tube VT the over-all potential of the filter system is reduced for the plates of these tubes by a resistance R to arrive at a second potential connection B+ to which the plate electrodes of'the three tubes are connected. Since any hum roducing disturbances in tube VT are subject to amplification in tube VT it may be found in fpractice that the smoothing out of'the rectied current by condenser K is not sufficient for this first audio frequency tube VT so that an additional condenser K ma be added at the point of taking off the plate potential for this tube.

A resistance R common to the grid circuits of these three like amplifying tubes provides for creating the desired grid biasing potential for all of them, while the resistance R and condenser C provide for the hum neutralizing connection 'for'all of these tubes, this bein in accordance with the arrangement of ig. 3' for handling a plurality of like tubes. A potentiometer P is connected across the filament supply circuit common to these three tubes, and the grid bias resistance and hum elimination connection are connected to this potentiometer just as in the case of tube VT,,. The connection Y provides for the usual practice of grounding the negative or B- sidefof the system.

Since detector tube VTg usually requires a still smaller plate energizing otential, provision is made, for further re ucing the potential available across terminals B+ and B- by a suitable resistance R to arrive at anew terminal connection B" to which the plate electrode of the detector tube is connected. Since any hum disturbances in .the

detector tube are subject to double amplification in tubes VT and .VT it may be desirable to add for the benefit of the detector tube another condenser K It, provides for securing the desired grid bias forv the detector tube, if such be' used,

I and a resistance R and condenser C" provide for the hum neutralizin connection for use in the nfanner describe in connection with Fig. 1. Since this detector tube is shown to include an indirectly heated cathode f" electrically independent of the raw alternating current heating supply, the grid biasing resistance and hum neutralizing connec A resistance tion are shown connected to this cathode in being followed by steps of amplification,

I have found that this is a refinement that may be eliminated in practice without introducing any detrimental degree of-hum production, and particularly if other procedure .for eliminating residual hum efl'ects is resorted to. For example, I find that if the arrangement does not completelyneutralize all hum producing conditions n the circuits of tube VT a little residual hum in the circuits of tube VT may be utilized to advantage for neutralizing the residual hum in the circuits of tube VT by introducing this residual hum from tube VT, in the grid circuit of tube VT in such phase that the two effects neutralize. The production of the hum effects in tube VT of the correct phase and degree can be controlled by proper adjustment of resistance R, and neutralizing circuit elements R and C, as previously explained in connection with Fig. 1. Also slight adjustments of the contacts on potentiometers P and P provide for producing residual hum effects for neutralizing purposes from one stage to the other. This process of neutralizing from stage to stage may be extended to include these eflects asbetween detector tube VT and the succeeding audio frequency tubes, and may be even further extended to include effects as between the detector and audio fr uency portion of the system and the radio equency portion of the system. While the radio frequency 1 transformers of the radio frequency portion of the system do not permit oftransferring directly from stage to stage the low frecarried throughthe radio frequency portion.

of the system to the detectorwhere, by detection, they are sifted out as low frequency effects, and can be passed forward with amplification. It is therefore very desirable ina combination system of many tubes asillustrated in Fig. 4 to utilize the possiblhty of what. might beterm'ed a clean-up of residual hum by means of this stage-to-stage bucking, or neutralizing effect. To this end, it may be undesirable to eliminate completely al l of the hum in output tube VT and circults, but' rather to create therein some hum effects of proper-degree and phase to neutralize those that may come forward from tube VT .The effectiveness of this stage-to-stage l30 buckin is made most apparent by a simple test. or example, I have adjusted a systemsubstantially in all respects like that of Fig. 4 so that no hum could be heard in the loud speaker, and then short circuited the primary winding of transformer T to eliminate transfer of all low frequency currents from tube VT. with the result that a most substantial hum was created in the loud speaker. This is a clear indication that the final adjustment provided for an overadjusting in tube VT and circuits to neutralize the hum effects coming forward from tube VT and its circuits, and which efiects may include those originating even in advance of tube VT I have even removed the neutralizing con nections R' and C for the amplifying tubes and R and C" for the detector tube, resulting in passing considerable hum energy forward through transformer T and neutralized this large amount of hum energy by adjusting the neutralizing connection of tube VT, to give a substantial fluctuating current of correct phase to oppose this incoming hum current. In fact, I have found the procedure so effective as to be entirely satisfactory and well within the standards of commercial requirements for alternating current operated broadcast receivers.

While I have illustrated and described my invention in specfic ways, I-have done so merely forthe purpose of explanation. Its application in many ways other than those illustrated and described will be immediately obvious to those skilled in the art and no limitations are intended by reason of the applications chosen merely for explanatory purposes.

Having fully described my invention, I claim: 4

1. In a system including a three electrode vacuum tube having-grid, filament and plate electrodes, the combination of a source of current having a fluctuatin means for energizing the gri electrode of said tube for operation including an energy consuming element through which said current is passed to derive a potential for said electrode, connections for passing said current through said tube by way of said filament and plate electrodes, and reactive-resistive means for diverting a desired portion of the fluctuating component only of said current from the path through said tube.

2. In a system including a three electrode vacuum tube having grid, filament and plate electrodes, the, combination of a source of current having a fluctuating component for energizing foroperation the grid and plate electrodes of said tube, means for energizing said electrodes oppositely in polarity by the current energy of said source, and reactiveresistive means for diverting from said plate component,

electrode a desired portion of the fluctuating energy component only of said current.

3. In a system including a three electrode vacuum tube having grid, filament and plate electrodes, a source of current having a fluctuating component for energizing said grid and plate electrodes for operation, and reactive-resistive means for diverting a desired portion of the fluctuating component only of the ener of said source from said plate electrode w ereby the fluctuating energy components on said electrodes are more completely neutralized in their effects on the operation of said tube. 4

4. In a system including a three electrode vacuum tube having grid, filament and plate electrodes, a source of current having a fluctuating component'for energizing said grid and plate electrodes negatively and positively respectively for operation, means for divid; ing the average value of the potential of said source into two average values of potential required by said electrodes for the operation of said tube in a predetermined manner, and

means for dividing difierentl-y the values of the fluctuating com onent of the potential of said source applicc to the respective said electrodes.

5. In a system including a three electrode vacuum tube having id, filament and plate electrodes, a source 0 current havin a fluctuating component connected negatively to said grid electrode and positively to said plate electrode, a resistance connected between the negative terminal of said source and said filament whereby current flowing through said tube from filament to plate electrodes passes through said resistance to create a negative fluctuating potential on said grid, and a reactive'resistive connection for diverting from said filament-to-plate path a portion of the fluctuating component only of the current energy flowing through said resistance. 1 v

6. In a system including a three electrode vacuum tube amplifier having 'rid, filament and plate electrodes, in ut and output circuits, the combination 0 'a source of current having a fluctuating component for energizing said grid and plate electrodes negatively and positively respectively for operation, and connected thereto by way of sald input and output circuits, a resistance connected between a point in said input circuit and said filament of such value that the fluctuating output circuit including in series a condenser and a resistance having a value of the order of the value of said resistance between input circuit and filament multi lied by the amplification factor of said tu 7. In a system including a three electrode vacuum tube having input and output electrodes and circuits and a filament, a source of current having a fluctuating component for energizing said input and output electrodes negatively and positively respectively connectcd thereto through said circuits, a resist ance connected between said input circuit and filament, and a connection between said filamentand said output circuit including a resistance and a condenser in series, the reactan-ceof said condenser in ohms to the fluctuating component of said current being less than the resistance in ohms of said series resistance.

8, In a system including a three electrode vacuum tubeamplifier having input and output electrodes and a filament, high frequency input and output circuits connected to said electrodes, a source of low frequency fluctuating current for energizing said input and output electrodes negatively and positively respectively through said circuits whereby said tube acts as an amplifier of high frequency currents, a resistance connected between a point in said input circuit and said filament, a resistance and condenser in a series connection between said filament and apoint in said output circuit, and low capacity high frequency by-pass condensers in shunt tosaid res] stances. I

9. In a system including a plurality of three electrode vacuum tubes of like characteristics having grid, filament and plate electrodes, and connected in cascade for am plified repeating, a single source of current having a fluctuating component for energizing the grid and plate electrodes of said for connecting all of said plate electrodes in parallel to the positive terminal of said source, a connection common to the filaments of all of said tubes, a resistance connected between said common filament connection, and the negative terminal of; said source,.

and a resistance and condenser connected in series between said common filament connection and the positive terminal of said source. 10. In a system including a plurality of three electrode vacuum tubes of like characteristics having grid, filament and plate electrodes, and connected in cascade for amplified repeating, a single source of current having a fluctuating component for energizing the grid and plate electrodes of all of said tubes negatively and positively respectively for operation as amplifiers, means common to all' of said-,tubes for deriving fromsaid source a negative potential for all of said grid electrodes, and means including a reactive-resistive element forpassing fluctuating current components only common to all of said tubes controlling the neutralizing of the fluctuating energy component of said source as between said grid and plate electrodes in each of said tubes.

11. In a system including a plurality of three electrode vacuum tubes for performing different functions or the same functions in different degrees, and having grid, filament and plate electrodes, a single source of current having a fluctuating component for energizing the grid and plate electrodes of said tubes negatively and positively respectively for operation in their respective functions, a plurality of means for deriving from said source a plurality of negative potentials for the grid electrodes of said tubes, and a plurality of means including reactive-resistive elements for the passage of fluctuating current component-s only associated with several of said tubes for controlling the neutralizing of the fluctuating energy components of said source as between the grid and plate electrodes of said plurality of tubes. 12'. In a system including a plurality of three electrode vacuum tubes having grid, filament and plate electrodes, saidgrid and plate electrodes requiring diiferent degrees of energizing potential in different tubes for operating the systemas a whole in a desired manner, a single source of current having a fluctuating component for energizing the grid and plate electrodes of all of said tubes, means for dividing the potential of said source as many times as there are tubes to be differently energized, a plurality of means for deriving from said source different negative' potentials for said grid electrodes, a plurality of connections for applying the positive divided potentials'of said source to different ones of said plate electrodes, and a plurality of means for controlling the neutralizing of the fluctuating energy componcnts of said source as between the grid and plate electrodes of the several differently energized tube-s. I

13. In a system including a plurality of three electrode vacuuin tubes having grid, filament and plate electrodes, said tubes being connected in cascade, the combination of a single source of current having a fluctuating component-for energizing the grid and plate electrodes of all of said tubes, means for deriving from said-source negative potentials for said grid electrodes, 'means for deriving from said source positive potentials for said plate electrodes, and means asmciated with one of said tubes and its circuits for neutralizing the fluctuating components of said energizing source together with the fluctuating components introduced into said tube and circuits from other tubes and circuits of said cascade arrangement.

14. In a system including a plurality of three-electrode vacuum tubes, having grid filament and plate electrodes, said tubes being connected in cascade for 'stage-to-stage operatlon, a single source ofcurrent having a fluctuating component for energizing the grid and plate electrodes of all of said tubes, means associated with the last tube and circuits of the series for controllably producing hum currents therein, and connections between said last tube and the preceding tubes for transferring from the preceding tubes hum currents to the last tube, whereby the combined residual hum in the last tube of the system is controllably neutralized.

15. In a system including a pluralityiof three electrode vacuum tubes, having grid, filament and plate electrodes, said tubes being connected in cascade with circuits to successively amplify high frequency modulated currents, detect the modulations in said current, and amplify the resulting low frequency currents, a single source of current having a fluctuating component for energizing the grid and .plate electrodes of all of said tubes, a plurality of means for deriving from said source diiferent negative potentials-for the grid electrodes of said tubes so functioning that different potentials are required, and means associated with the last tube of the series for controlling the hum currents arising therein from said energizing source and transferred thereto from preceding tubes energized from the same source.

16. The method of energizing the grid and plates electrodes of a three electrode vacuum tube for operation from a source of current having a fluctuating component which consists of so distributing the'energizing current that the ratio of the-average value to the fluctuating component of the derived grid potential is different from the ratio of the average value to the fluctuating component of the derived plate potential.

17. The method of energizing the grid and plate electrodes of a three electrode vacuum tube for o eration from a source of current having a uctuating component which consists of so" distributing the energizing current that the ratio of the average value .to the fluctuating component of the derived grid potential is less than the ratio of the average value to the fluctuating component of the derived plate potential. V

18. In a system includirig a three electrode vacuum tube, the method of energizing the grid and the plate electrodes thereof for operation from a source of current having a fluctuating component and neutralizing fluctuating effects which includes developing the required grid potential from said source, dividing said current into a plurality of parts With the fluctuating components thereof in aiding phase and one of them flowing through said tube, and opposing the fluctuating component of said part flowing through said tube by the action of the fluctuating component of said grid potential through the amplifying action of said tube.

19. In an amplifier system, the combination of a thermionic tube having a grid, filament and plate, a source of unidirectional current of fluctuatin voltage, the high potential terminal of said source being connected to said plate, a resistance connected between the low potential terminal of said source and said filament, the grid-filament circuit of said tube including a portion of said resistance .Whereby a biasing potential of a value dependent upon the space current of said tube is impressed upon said grid, and means for impressing through a resistively influenced reactance a desired fluctuating voltage from said source across said resistance while maintaining the current flow through said resistance substantially equal to the space current of said tube.

20. In an amplifier system, the combination of a thermionic tube having a grid, filament and plate, a source of unidirectional current of fluctuating voltage, the high potential terminal of said source being connected to said plate, a. resistance connected between the low potential terminal of said source and said filament, the grid-filament circuit of said tube including a portion of said resistance whereby a biasing potential of a value dependent upon the space current of said tube is impressed upon said grid, and means for impressing a desired amount of fluctuating voltage from said source across said resistance while maintaining the current flow through said resistance substantially equal to the space current of said tube, said means consisting of a condenser and a second resistance series related and connected between the high potential terminal of said source and the filament of said tube.

21. In an amplifier system, the combination of a thermionic tube having a grid, filament and plate, asource of undirectional' current of fluctuating voltage,the high potential terminal of said source being connected to said plate, a resistance connected between the low potential terminal of said source and said filament, the grid-filament circuit of said tube including a portion of said resistance whereby a biasing potential of a value dependent upon the space current of said tube is impressed upon said grid, and means for impressing a desired amount of fluctuating voltage-from said source across said resistance while maintaining the current flow through said resistance substantially equal to the space current of said tube, said means consisting of'a condenser and a second resistance series related and connected between the high potential terminal of said source and the filament of said tube, thereactance of said condenser to the current flowing therethrough being substantially less than the ohmic re sistance of said second resistance.

. 22. In an amplifier system, the combination of a thermionic tube having a grid, filament and plate, a source of unidirectional current of fluctuating voltage, the high posistance series related and connected between the high potential terminal of said source and the filament of said tube and condensers shunting said first named resistance and said series related condenser and second resistance.

In testimony whereof I hereunto aflix'm'y signature.

' BENJAMIN F. MIESSNER.

consisting of a condenser and a second resistance series related and connected between the high potential terminal of said source and the filament of said tube, said second resistance having a value of substantially the amconnected to said plate; a resistance connected,

plification constant of said tube times the first mentioned resistance.

23. In an amplifier system, the combina-v tion of a thermionic tube having a grid, filament and plate, a source of fluctuating voltage, the high potential terminal of said source being connected to said plate, a resistance connected between the low potential terminal of said source and said filament, input and output devices for radio frequency signal current, the grid-filament circuit of said tube including said input device and a portion of said resistance whereby a biasing potential of a value dependent upon the space current of said tube is impressed upon said grid, means for impressing through a resistlvcly influenced reactance a desired fluctuating voltage from said source across said resistance while maintaining the current flow through said resistance substantially equal to the space current of said tube, and means for by-passing radio-frequency currents around said resistance and said last mentioned means without effecting the value of the fluctuating current flowing therein.

24. In anamplifier system, the combination of a thermionic tube having a grid, filament and plate, a source of fluctuating voltage, the.

highpotential terminal of said source being between the low potential terminal of said source and said filament, input and output devices for radio frequency signal current, the grid-filament circuit of said tube including said input device and a portion of said resistance whereby'a biasing potential of a value dependent upon the space current of said tube is impressed upon said grid, means for impressing a desired amount of fluctuating voltage from said source across said resistance while maintaining the current flow through said resistance substantiall equal to the space current of said tube, sai -means consisting of a condenser and a second re-

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