Three-electrode Tube Research Articles

Продажа Ли де Форестом прав на аудион AT&T и ее значение для развития радиотехники

The preparation and holding of the presentation of Lee de Forest’s audion, which contributed to the sale of his patent rights to AT&T, is considered. The role of J. Carty and John S. Stone in the presentation was noted. Harold D. Arnold’s experiments with the audion and Hendrik van der Bijl’s audion theory set the stage for industrial production of vacuum triodes for telephone repeaters. It is shown that the industrial production of a thermionic three-electrode vacuum tube has made it possible to develop innovative commercial telephone repeaters and achieve progress in long-distance telephony.

Electrical Engineering Hall of Fame: Lee de Forest

In 1922, the Institute of Radio Engineers (IRE) selected Lee de Forest as the fifth recipient of its Medal of Honor. He was cited for "his major contributions to the communications arts and sciences, as particularly exemplified by his invention of that outstandingly significant device: the three-electrode vacuum tube, and his work in the fields of radio telephonic transmission and reception". He served a term as president of the IRE in 1930. He also received the Edison Medal of the American Institute of Electrical Engineers (AIEE) in 1946, becoming one of only seven to receive both the Medal of Honor and the Edison Medal prior to 1962. He became known for having a rather flamboyant personality and was a very prolific inventor, receiving more than 300 patents during his career. Like some other pioneers in radio and electronics, he expended considerable time and energy on litigation related to his patents.

E. H. Armstrong — Edison medalist

IF we review the advances in electrical technology in the past 25 years, one development stands out from all others, electronics, and specifically the application of the three-electrode vacuum tube. It is appropriate to recall here that the original electronic tube was the two-electrode tube of Edison, in whose honor the Edison medal was established. Others subsequently applied this “Edison effect” in radio detection and introduced the control electrode, but the action was viewed as that of a trigger, as in the modern thyratron, which is of limited application. The real foundation for the unlimited development which we have witnessed was laid by the Edison Medal recipient, Doctor Edwin Howard Armstrong, in an article published in the Electrical World in December 1914. Here the common engineering tool, the characteristic curve, was employed for the first time to show how the tube amplifies; and the theory was substantiated by oscillograms which Armstrong had taken. The previously mysterious action of the tube as a rectifying detector with a grid capacitor was elucidated in the same way.

A New Electron Tube Having Negative Resistance

The dynatronic and magnedynatronic systems commonly used to obtain a negative resistance by means of triodes or tetrodes are characterized by the fact that the potential of the active electrode (the anode) is not the highest potential in the system; an electrode (the grid or the screen grid) at a higher potential is necessary in order to take off the secondary emission current from the anode in such a way that a falling characteristic is produced in the anode circuit. The present paper deals with a three-electrode tube of such design that the negative resistance is obtained in the circuit of the electrode possessing the highest potential in the system.

Further Extensions of the Theory of Multi-Electrode Vacuum Tube Circuits

The response of circuits containing vacuum tubes with any number of electrodes due to impressed electromotive forces, and under such circumstances that the time of transit of the electrons is negligible, is discussed when arbitrary feedback is present between the circuits connected to the electrodes, each of which may carry conductive current. The use of the theory is illustrated by obtaining first and second order effects in typical three-electrode tube circuits. In a previous paper in the Bell System Technical Journal, October, 1934, the treatment was restricted to three-electrode tube circuits in which it was assumed that the amplification factor of the tube was constant and that no conductive grid current was present. In the present paper these restrictions are removed.

Theory of Multi-Electrode Vacuum Tubes*

Physical principles underlying the characteristics and performance of multi-electrode vacuum tubes are presented in simple form in this paper. Presentation of the subject is based, as far as possible, on the well-known theory of the three-electrode tube. It is shown that the definitions of electrical tube parameters applicable to triodes are, with certain modifications in their interpretation, also applicable to tubes having more than three electrodes.

AN ELECTROMAGNETICALLY CONTROLLED THREE-ELECTRODE VACUUM TUBE

A three-electrode tube in which the electron current is controlled by means of a magnetic field instead of the customary electrostatic field. This is accomplished by means of a special type of ``grid'', the construction of which determines the static characteristic of the tube.

A Direct Measurement of the Intensity Variations of the Helium Lines with Voltage

The intensity variations with voltage of some of the brighter lines of the low voltage helium arc spectrum were determined by means of a recently developed photoelectric spectrophotometer. The radiation was developed in a copper ball, 20 cm in diameter. The equipotential cathode and grid from a commercial three-electrode tube formed the internal structure, the sphere itself being the anode. This arrangment gave an extremely bright spectrum, even at the striking voltage, with a relatively low current density in the space. The results on $5016 (1^{1}S\ensuremath{-}2^{1}P)$ and on $6678 (1^{1}P\ensuremath{-}2^{1}D)$ were generally smooth curves. Lines $4026 (1^{3}P\ensuremath{-}4^{3}D)$, $4471 (1^{3}P\ensuremath{-}3^{3}D)$, and $5876 (1^{3}P\ensuremath{-}2^{3}D)$, show a region of constant intensity with arc voltages from 27 to 35 volts, thereafter increasing smoothly. Line $4713 (1^{3}P\ensuremath{-}3^{3}S)$ shows definite maxima near the critical exciting potentials. The accurate linear relationship between the intensity of the light admitted to the photoelectric cell and the amplified output of the photoelectric cell was established by a separate experiment. For the measurements on the spectrum lines, every intensity measurement was referred to a standard lamp operated at a constant resistance. The absence of oscillations in the arc current was shown by a vacuum tube voltmeter.

Investigation of Resonance Curve with Respect to Variation of Capacity

An investigation of the possibility of using a vibrating variable condenser in a Hartley Oscillatory circuit to modulate the radiofrequency of the circuit, and a study of the effect of u,sing the same type of condenser in a receiving circuit to modulate its radio frequency. Introduction This paper is the result of a piece of work started in September, 1930, by Professor Lyon and the writer at K. S. 'C. The work is still being carried on. In the revised edition of the Radio Manual by Sterling which came out about one year ago this same problem under the heading of Frequency Modlulation is suggested with a method of procedure. Efforts to find out from the author or editor what work has been done on the subject so far have failed. This article did not reach us until this spring when a revised edition of the Manual was received. So this work was completed independent of all others. At the present time the vacuum tube is the only means of modulation and amplification that has proved successful for work in radio telephony. With this in mind, it was decided to investigate the possibilities of a mechanical modulator operating by small variation of capacity in one of two coupled radio circuits. When the three-electrode vacuum tube is used as an amplifier and the plate current is plotted as ordinates against the grid voltage, a characteristic curve is obtained. The usefuj, portion of this curve lies between the points a. and b. Figure 1. The resonance curve obtained by plotting the current against the capacity in an oscillating circuit of very low resistance, bears a certain resemblance to the tube characteristic of Fig. 1. When one-half of this resonance curve is compared with that of the useful portion of the tube curve, it is seen that they are very similar. This suggests the possibility of placing a vibrating condenser in the circuit of an oscillator and obtaining effects of modulation and amplification analogous to those ordinarily obtained with the use of a tube. In other words, the construction of a mechanical modulator and, in some cases, amplifier, to replace the vacuum tube. The object of this work was to determine (1) what effect a vibrating condenser, placed in a receiving circuit coupled with an osThis content downloaded from 157.55.39.163 on Wed, 23 Nov 2016 04:26:51 UTC All use subject to http://about.jstor.org/terms

The Relative Intensities of Mercury Lines under Different Conditions of Excitation

The relative intensities of the lines of the $2s\ensuremath{-}2{p}_{i}$ triplet have been measured by a photographic method with a calibrated tungsten lamp as a standard of comparison. The intensity ratios have been found to vary with conditions of excitation due to the absorption of the 5461 and 4047 lines by atoms in the metastable states $2{p}_{1}$ and $2{p}_{3}$. About three-quarters of the 5461 radiation and about one-third of the 4047 radiation were absorbed in a commercial mercury-filled tube with three electrodes when a high plate current was passed through the tube. A lesser absorption was found when an ordinary arc was used and when small plate currents were passed in the three-electrode tube. A tube specially built to excite mercury by electronic bombardment and provided with means for controlling the mercury pressure gave uniform results under various conditions of mercury pressure and plate current, and the double ratio of 8.5:3.3:1 was found for the intensities divided by the fourth powers of the corresponding frequencies. The ratio of 4078:4047 was found to vary with plate voltage in a manner similar to the variation of efficiency of ionization with electron velocity. It was attributed to the presence of two mechanisms of emission giving widely different intensity ratios, namely, excitation of the neutral atom to a higher energy level, and recombination of the ionized atom. A roughly quantitative survey of the intensities of the excitation and of the recombination spectra indicated that in comparison with atoms excited to a higher level by electronic impact as occurs in the arc, recombined atoms will prefer the singlet to the triplet system, while within each system their order of preference is $P$, $S$, $D$, and $p$, $s$, $d$, respectively. Also, within each state, a level at about the height of the $4S$ level is preferred to the others.

Integraph solutions of electron orbits in the Barbhausen-Kurz effect

Abstract The Continuous Integraph has been used to trace the orbits of an electron oscillating within the filament-plate space of a three-electrode vacuum tube, such oscillations being presumably the origin of the Barkhausen-Kurz Effect. The effects of space-charge, initial velocity of emission, and amplitude of oscillations are considered. The results check and extend those of Kapzov found by other methods.

A Study of the Output Power Obtained from Vacuum Tubes of Different Types

Economical operation of the large number of tubes involved in the Bell System makes necessary the adoption of common supply voltages. This requires that repeater tubes of various types be designed to operate at a fixed plate voltage. For this reason the design of amplifier tubes to give as large a power output as possible at the operating plate voltage is of considerable importance. In the case of three-electrode tubes it is possible from theoretical considerations to compute, approximately, the electrical parameters a tube must have in order to give the maximum output power of a given quality obtainable under fixed operating conditions. The electrical characteristics and output of fundamental, second, and third harmonics of two of the more common telephone repeater tubes are given. It is of considerable interest to determine whether greater power output of comparable quality can be obtained from tubes containing more than one grid. Since no sufficiently exact theoretical analysis of multi-grid tubes is yet available to permit the determination of the parameters of optimum tubes, a comparative experimental investigation of a number of such structures has been undertaken. The electrical characteristics and output of fundamental, second, and third harmonics of several such experimental tubes are given. The power output of multi-grid tubes and of three element tubes is compared. The reasons for the comparatively large power output of certain types of multi-grid tubes are discussed.

Secondary Electron Emission from Molybdenum

The secondary electron emission from a very clean molybdenum plate in a simple three-electrode tube has been studied. The number of primary electrons striking the plate was calculated by means of the positive ion calibration method previously reported. The number of secondary electrons per primary reaches a maximum value of 1.15 at 600 volts and then decreases to 1.00 at 2000 volts. One definite discontinuity in the secondary emission curve occurs at 13.5 volts; the others are very small and are not reproducible. The emission increases about 3 percent within a few minutes after heating if the gas pressure is very low and then remains quite constant for a long period of time. The emission decreases with time when there is more gas present. The secondary emission appears to increase by about 4 percent when the temperature of the target increases from the normal operating temperature to 1600\ifmmode^\circ\else\textdegree\fi{}K.

Piezo-Electric Oscillator Circuits with Four-Electrode Tubes

Two new piezo-oscillator circuits using the screen-grid tube are described. One circuit uses feedback through the crystal, which has two pairs of electrodes with connections to the anode, control grid, and filament of the tube. In the other circuit the two electrodes of the crystal are connected. between the anode and control grid. The new circuits are unusually stable and at low frequencies give greater power output than the three-electrode tube circuits. They are particularly useful at those low frequencies for which flexural vibrations are employed. When oscillating at flexural vibration frequencies crystals show a tendency to creep lengthwise until a position is reached which gives maximum power output. If the crystal is displaced from this position it will return to it again.

The Three-Electrode Vacuum Tube as Applied to the Talking Motion Picture

The Phonograph was invented in 1876 and was a household device by 1888. The Motion Picture was invented in 1889 and became a recognized means of public entertainment by 1895. The one is a record of what we hear and the other a record of what we see.

The Screen-Grid Tube

Radio-frequency amplification by means of the three-electrode tube is usually disappointing. With resistance coupling the feedback through the tube is in such a phase relation to the input voltage as to reduce the amplification below that given by the simple equation for voltage amplification. With impedance coupling the feed-back causes self-oscillations when the circuit conditions are such as might be expected to give large amplification. In the shielded grid tube the feed-back is reduced to a negligible amount and the current through the tube is very nearly independent of the plate voltage over the working range. Under these conditions, the voltage amplification becomes the product of the mutual conductance and the load impedance. High impedance in the plate circuit is obtained by using a sharply tuned parallel circuit. With proper shielding such a circuit may be used without producing self-oscillation. At a frequency of 700,000 cycles per second, amplifications of 80 fold per stage may be obtained.

Some Characteristics and Applications of Four-Electrode Tubes

Four-electrode tubes may be classified by their designs and uses as "screen-grid" tubes, "space-charge-grid" tubes, and "double function" tubes. In the screen-grid tube the inner grid is the control electrode and the outer or screen-grid is kept at a fixed potential. The capacity between plate and control-grid is thereby reduced to an almost negligible value. A second result of the screen-grid is a large increase in amplification factor and plate resistance without reduction of mutual conductance. This permits high amplification in connection with high impedance coupling circuits, without undesired regeneration or oscillation. The screen-grid principle has been applied to transmitting tubes as well as receiving tubes. Characteristics of these tubes are given in detail. In the space-charge-grid tube the outer grid is the control electrode and the inner grid is maintained at a fixed potential. The purpose of the inner grid is to reduce the effect of the space-charge around the filament and thereby reduce the plate resistance of the tube. The space-charge-grid tube performs the same functions as ordinary three-electrode tubes, but in general has higher mutual conductance than a three-electrode tube of similar design. Several double function tubes and circuits are described in which both grids act as control-electrodes or in which one grid acts as control electrode and the other as a combination space-charge-grid and control or output electrode. These circuits are sometimes useful but are subject to certain definite limitations.

Grid Current Modulation

The term grid current modulator is used to describe those vacuum tube circuits in which modulation is initially produced in the grid circuit of a three-electrode vacuum tube due to the non-linear grid current-grid voltage relation. Comparison with a representative plate current modulator using the same tubes and the same plate potential shows that by modulating at maximum efficiency in the grid circuit and using the plate circuit solely for amplification, the maximum power output is increased about eight times, the power efficiency is increased about five times and the ratio of sideband output to signal input is increased approximately three times. Under these conditions more carrier input power is needed for the grid than for the plate modulator. This improved performance has been made possible by a detailed study of the fundamental processes involved and by a design of the tubes and associated equipment, such as transformers and filters, to permit these fundamental processes to operate to their best advantage. Normally modulation is also produced in the plate circuit which is shown to be out of phase with that produced in the grid circuit. By inserting high impedances to the input frequencies in the plate circuit, plate circuit modulation is prevented, and the reduction of grid circuit sideband is likewise avoided. By including in the grid circuit an impedance which is high to the desired sideband frequencies, the maximum grid sideband voltage is obtained. In this way the power and modulating efficiencies of the tube circuit are made maximum. Where modulation occurs only in the plate circuit of a tube, the sideband amplitude is proportional to the product of the amplitudes of the input frequencies when these amplitudes are small. In the present type of grid current modulator the sideband amplitude is proportional to the smaller of the two input amplitudes provided the ratio between these is greater than about 3/2. This feature makes the modulator particularly valuable in communication systems. The article concludes with an application of the fundamental principles involved to an experimental carrier telephone system in which the operating features of tubes, filters, and transformers are discussed.

Ionization and Resonance Potentials in Gallium and Indium

The critical potentials of gallium and indium have been experimentally determined by the method of inelastic impact. A simple three-electrode tube and the Hertz-differential tube as a simple three-electrode tube or as a four-electrode tube were used. Ionization was detected by the modified space charge method, by the Lenard method, and by the change in the gap resistance. The following critical potentials below ionization were observed: in gallium vapor 3.07 v. ($2{p}_{2}\ensuremath{-}2s$), 4.22 v. ($2{p}_{2}\ensuremath{-}3{d}_{2}$), 2.70 v. ($2{p}_{1}\ensuremath{-}2s$), 3.8 v. ($2{p}_{1}\ensuremath{-}3d$); in indium vapor 0.30 v. ($2{p}_{2}\ensuremath{-}2{p}_{1}$), 3.03 v. ($2{p}_{2}\ensuremath{-}2s$), 4.07 v. ($2{p}_{2}\ensuremath{-}3{d}_{2}$), 2.8 v. ($2{p}_{1}\ensuremath{-}2s$). Two ionization potentials were observed: in gallium vapor 5.8 and 13.2 v.; in indium vapor 6.3 and 14.1 v. The ionization potentials are judged to be accurate to 0.5 volts.

A Critical Potential of Methane and Its Absorption in the Ultra-Violet

In a previous paper (1) it was stated that the maximum in the current potential curve found in a three-electrode tube with methane must be due either to a resonance potential of methane or to a large transparency for slow electrons. It was further pointed out that the interpretation of maxima in current-potential curves obtained in four-electrode tubes must also take into account the possibility of abnormal transparency at certain velocities. In the meantime Brode (2) has as a matter of fact found a variable mean free path for electrons in methane using the method of Ramsauer,(3) which presumably accounts for the maximum, since it occurs at about the expected velocity.