US2014733A - Vacuum tube system - Google Patents

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. VACUUM TUBE SYSTEM Filed July 28, 1932 6 Sheets-Sheet l Mil/i8 SUPP must 1 JLp/us: 2 g INVENTOR CLARENCE w. HANSELL ATTE) NEY Sept. 17; 1935.

C. W. HANSELL VACUUM TUBE SYSTEM Filed July 28, 1932 6 Sheets-Sheet 2 M M M INVENTOR j CLARENCE W. HANSELL ATTORNEY Sept. 17, 1935. c w HANSELL 2,014,733

VACUUM TUBE SYSTEM Filed July 28, 1932 6 Sheets-Sheet 3 540/0 m'wrr 40/0 INVENTQ'R CLARENCE w. HANSELL ATTORNEY P 1935- c. w. HANSELL VACUUM TUBE SYSTEM Filed July 28, 1932 6 SheetsSheet 4 w W W a n N NQQQ w m 3g 1 1 y Y 8w m Y wm w c B. m I? m M i T 1 LT B a i fin m a v Sept. 17, 1935. c w N E 2,014,733

VACUUM TUBE SYSTEM Filed July 28, 1932 e Sheets-Sheet s INVENTOR I CLARENCE w. HANSELL I Kama ATTORNEY Sept. 17, 1935. c w; HANSELL I 2,014,733

' VACUUM TUBE SYSTEM Filed July 28, 1952 6 Shets-Sheet s INVENTOR CLARENCE w HANSELL V ATTORNEY Patented se t. 11, 1935 Clarence w. nnneeu. Port Jefferson, N. a, assigner to Radio Corporation of America. a corporation of Delaware Application July :8, 1932, Serial No. mass This invention relates improved'vacuum 7. tube circuits such as oscillators, push-pulli'ampliflers, frequency multipliers, frequency modulators and the like, wherein the vacuum tube 5 filaments or cathodes are heated by alternating current and the other electrodes are Supplied with power from rectifiers or other sources oi. impure direct current containing. alternating components of potential and current.

1 It is an object of this invention to provide a simple and inexpensive system toreduce the undesired noise'or ,hum :eifects caused by the use of alternating current power supply for the vacuum tubes by preventing the addition'of our- 15 rentnoisearisinginvarioustubesandpartially or totally balancing out such addition of current noise.

In the past, it hasbeen customary to app y direct current to the vacuum tube filaments or 20 cathodes when such tubes are required for use in high-grade telephone transmitters and further more, to provide a high degree of smoothing out of potential variations in the supply for the other electrodes. The equipment required to do this 25 is very intricate, unreliable' and expensive.

- In the past much. has been accomplished in reducing the eifects of alternating currents on the filaments of vacuum tubes by means of careful tube design. l'here' are also available for low power equipment, vacuum tubes with'indirect cathode heaters forwhich alternating current may be used.

' There are not, however, available tubes for use in high power transmitters wherein'it is pos- 35 sible to use alternating current and still obtain a high quality or output for radio telephone transmitters which have been designed along conventional lines.

With my invention it possible to use existing types of tubes employing alternating current for heating the filaments without exceeding the allowable limits of tube noise required to obtain a high quality of radio telephone output.

based is the general circuit arrangement of the vacuum tube filament heating transformers in such a manner that when alternating currents of different phases are applied to diiferent vac- 50 uumtubesinthe samesystem, the diflerencein time orphaseofthenoisearising inthevarious tubes will prevent their addition and, instead, willacttocancelouttheundesired noiseorhum A further understanding of my invention will The principle upon which my invention is be accomplished by referring to thefollowing drawingsin which, Fig. 1 is a conventional diagram of a pushpull radio frequency amplifier wherein both tubes receive filament power from the same sin- 5 gle phase power source:

Fig.2 is a diagram of a radio frequency pushpull amplifier, in which the filament of each vacuum tube is heated by a separate power sup- P y, each being diiferent in phase:

Fig. 3 is a diagram ofv an amplitude modulated stage of a radio telephone transmitter when in thefilaments of the radio frequency amplifier tubes are supplied with alternating current from two diiferent phases of a three-phase power source, and the three modulator tubes are also supplied from diil'erentphases;

Fig. 4 is a diagram'of aradio' frequency ampliher with a two-phase power supply originating from a three-phase source by using T-connected 29 transformers; 1

Fig. 5 is a diagram of a radio amplifier and/or frequency multiplier systems with the filament of each successivestage,supplied with a current from a 'diflerent phase;

Fig. 6 is a diagram ofxanamplifier with-a polyphase power sup ly for. heating the filaments of the vacuum tubeswith currents from different phases, and, in addition, the alternating come from diiferent phases;

Fig. fl is a curve indicating very approximately the wave form of the noise or ripple procurrent supply of the grid bias rectifiers also duced in each tubefof the amplifier circuit" shownin Fig.1;

Fig. 8 is a" curve indicating the wave form and relative amplitude ci the noise or ripple produced in the 'output. circuit of Fig. 1, which is due to the addition ofthe effects in the two tubes; e r

Fig. 9 is a cm've'indicating the wave form and relative amplitude of the noise or ripple produced in the output 0! one tube shown in Fig.2; w p v Fig. 10 is acurve indicating the wave form and 4 relative amplitude of the noise. or ripple produced in the other tube shown in Fig. 2;

Fig. 11 is a curve indicating the wave form and relative amplitude of the noise or ripple producedin the combined output of both tubes shown in eitherFig. 2 or-Fig. 3 when the twofilament powersources have a degree phase relation;

Fig. 12 is a curve indicating the wave form and relative amplitude of the noise or'ripple 5 an oscillator circuit,

produced in the circuit which is shown in Fig. 2 or Fig. 3 when the filaments connect to two phases of a three-phase power source instead of to a two-phase source;

Figs. 13, i4 and 15 are curves indicating the wave form and relative amplitude of the noise or ripple produced in each of the three modulator tubes shown in Fig. 3; and

Fig. 16 is a curve indicating the wave form and relative amplitude of the noise or ripple produced in the combined output of the three modulator tubes connected as shown in Fig. 3.

' In Fig. 1 I have shown the conventional and almost universal method used of applying alternating heating current to vacuum tubes in a push-pull radio frequency amplifier. It is to be noted that here both tubes receive filament power from the same single phase power source. With such a system each tube is subjected to changes in impedance as the instantaneous heating current varies. Several of the causes of this impedance change are,

First, since the. electron emission current drawn from the filament varies approximately in proportion to the 1.7 power or the square of the potential gradient at the filament it follows that an increase in potential at one end of the filament, and a decrease of equal value at the other, will not balance out their efiects upon the average current. Due to the approximate square law characteristic of electron fiow, the current leaving the negative end of the filament will increase much more than the fiow at the positive end of the filament decreases. The result is a distorted wave of fluctuation in anode current and effective anode impedance at a rate corresponding to twice the frequency of the heating current. The wave form of the noise or ripple produced in each tube is approximately like that shown in Fig. '7.

Second, the filament heating current fiow sets up a magnetic field around the filament and this field deflects theelectrons flowing to the anode. The electron defiectionsalso vary the anode current and tube impedance approximately as shown by. the curve in Fig. "I.

In addition, the temperature of. the filament tends to follow the variations of the alternating cur-rent though this effect is usually small in commercial tubes.

Therefore, when both filaments are supplied from the same phase, as shown in Fig. 1, the

undesired noise and modulations in the two tubes are additive in the amplifier output circuit. They produce undesired phase and amplitude modulation noise in the output of the amplifier as well as distortion of any useful modulation which may be present. If the tubes were part of would be produced. The noise wave form and strength corresponds to the addition of two separate curves such as Fig. '7, and results in a curve as indicated by Fig. 8.

According to my invention, if the power sup.

ply to the filaments are separated, as shown in Fig. 2, and current supplied to one filament from a source differing in phase from the source used for the other tube, then the noise and distortion due to the filament currrents in the two frequency modulation It will ,be noted that this resultant in the output circuit has only about 20 per cent the amplitude of that obtained when the filament currents to the tubes have the same phase. (Fig. 8). If the power supply is assumed to be 60 cycles, the chief component of hum from each tube is cycles. This 120 cycle component is almost completely balanced out when the two-phase power supply is used. I have noted that the effect upon the various hum frequencies is as follows:

60 cycles-Not present originally 120 Do -Balanced out Do Combine 90 degrees out of phase 240 Do Still adding 300 Do Combine 90 degrees out of phase 360 Do Balanced out 420 Do Combine 90 d'egrees'out of phase 480 Do Still adding 540 Do Combine 90 degrees out of phase 600 Do Balanced out In cases where two phase (90 degree) power supply is not available, it is still possible to obtain considerable improvement by connecting each of the two push-pull tubes of Fig. 2 to difi'erent phases of a three phase supply. In this case the unbalanced hum is roughly as shown in Fig. 12. In this case the remaining value of peak hum is reduced to only about 42% of that obtained when the filaments are lighted from the same phase.

In Fig. 3 there is shown an amplitude modulated stage in a transmitter to which my invention has been applied. In this figure the filaments of the two radio frequency amplifier tubes are supplied from two diiferent phases of a three phase source. There are also shown three modulator tubes, each supplied with filament current from a difirent phase of the power source. Of course, three groups of tubes could be used. The balancing of hum in the modulator alone is illustrated in Fig. 16. It will be noted that the bill-- ancing in the modulator reduces its hum to about 7% of that which it would have had if all tubes had been supplied from the same phase.

In Fig. 4 there is shown the Scot or T connected transformers which one may use to supply two tubes of a push pull amplifier with two phase power from a three phase source. Obviously, I may also use T connected transformers to convert two phase power to three phase, where this is required, or I may use other transformer arrangements for control of phase.

In addition to balancing the effects of filament hum, I mayalso apply the same principles to reducing the eifect of rectifier ripples in vacuum tube equipment such as shown in Fig. 6 wherein a radio telephone transmitter employs two single phase full wave grid bias supply rectifiers, operated from power sources .of different phase, one of these being in the exciter or drive unit and the other in the power amplifier. Originally such transmitters had both bias rectifiers supplied from the same phase of the power supply so that their effects were additive in the outputs of the transmitters. It will be noted that the use of polyphase power for filament heating or rectifier supply introduces a need for more than one regulating device, such as rheostats, in most cases. I may avoid extra complications in operation by placing these devices or rheostats all on one handle or control element so that all are adjusted simultaneously.

Although I have shown and illustrated the application of polyphase filament heating power to several circuits such as modulators and push-pull radio frequency amplifiers, it should be undermeters, etc;

stood that I have used these only for illustrations. 1 can apply the same principle in paralleled tubes, in all other circuits or systems-such as oscillators, balanced modulators, amplitude modulators, phase modulators, frequency modulators, also all other kinds of vacuum and gaseous tube amplifiers or relays including screen grid tubes, pentodes, frequency multipliers, detectors, Vacuum tube volt- Likewise, I may apply my balancing scheme to rectifiers of all kinds so that when their effects are combined in the circuits which they supply, they will not add but will tend to oppose. Also, I have found that, in many cases, by suitable choice or rectifier for said grids, separate transformer means forsupplying said filaments with alternating currents from a polyphase power supply source, and a phase arrangement of said polyphase power supply source for both transformer means and said bias rectifier whereby undesired hum is balanced out of said output circuit.

2. A push-pull amplifier system having an input circuit and an output circuit, said system comprising a plurality of electron discharge de'-' vices each having a grid, a platevand a filament,

;a plurality of bias rectifier: for the grids of said electron discharge devices, separate transformer means for supplying said filaments and said bias rectifiers with alternating current from a polyphase power supply source and a phase arrangement of said polyphase power supply '5 source for both transformer means and said bias rectifier, wherebyundesired'hum is balancedout 1 01' said output circuit.

' 3. A push-pull amplifier system having an input circuit andan output circuit, said system com- 10 prising a plurality of electron discharge devices. eachhaving a plate, a-grid and a filament, a'bias rectifier for said grids, separate transformer means for supplying said filaments with alternating currents from a polyphase power supp y 15 source, a separate regulating resistance for each of said transformers, and a phase arrangement of said polyphase power supply source for both transformer means and said bias rectifier whereby undesired hum is balanced out of said output circuit.

4. A push-pull amplifier system having an input circuit and an output circuit, said system comprising a plurality of electron discharge devices each having a plate, a grid'and a filament, a bias rectifier for said grids, separate transformer means for supplying said filaments with altemating currents froma polyphase power supply source, a separate regulating resistance for each of said transformers and a common control means to adjust each of said regulating resistances simultaneousiy, and a phase arrangement of said.

polyphase power supply source for both trans-- jformer means and said bias rectifier whereby undesired hum is balanced out of said output circuit.

CLARENCE W. '35

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