Info

Resultant values of up for two triodes in parallel. a variable-w tube may materially decrease the cross talk, as it is called, in radio receivers. This cross talk is a modulation of a selected carrier wave by a modulated carrier wave having a different frequency. Since the variable-w feature is usually Grid Voltage eg in Volts Fiq. 89. Voltage ratio of a triode having cylindrical electrodes and a separately heated cathode. Variable grid mesh. Grid Voltage eg in Volts Fiq. 89. Voltage...

Conditions For Maximum Power

In studying the conditions for the development of maximum power in the plate circuit of an amplifier, several cases arise according to the initial conditions stated for the problem. 125. Maximum Power Output When Tube and Eg Are Given. If the conditions are that the impressed alternating grid voltage A Eg is given and fixed, and it is desired to find Rb to be used with a given tube so that maximum power is developed in Rb, then, as shown in Chap. VIII, the condition is The value of the maximum...

Special Tubes

Distortion in an amplifier due to non-linearity of the characteristic curve was discussed in Chap. XII. Consider specifically the particular kinds of distortion and interference which can exist in a radio-frequency amplifier. Assuming that the plate circuits of the radio-frequency amplifier are tuned, only those frequencies produced by distortion which are in the neighborhood of the resonance frequency pass through the amplifier. One common form of interference in a...

HwLn w

The energy of an escaped electron is not lost but merely transformed in part into potential energy. The work w is ordinarily expressed in terms of a potential such that times the electronic charge e is-equal to the work w, or e w (in absolute units) If is in volts and e in absolute electrostatic units, The equivalent voltage is often called the electron affinity and is different for different substances. The quantity is of the greatest importance because it indicates the comparative difficulty...

Threeelectrode Tube Or Triode

Previous to the year 1907, practically the only use to which the two-electrode tube was put was the rectification of alternating currents, either for power purposes or as a Fleming valve detector in the reception of radio messages. These applications will be described in later chapters. Lee de Forest1 in 1907 made a most important and valuable improvement in the vacuum tube, which very much expanded its field of usefulness. His invention consisted in the addition of a third electrode adapted to...

Theory Of Superimposed Currents

Most problems in electrical engineering are concerned either with direct currents only, or with alternating currents only. In some special problems, those concerned with a microphone in the telephone art, for example, currents flow which are composed of an alternating current superimposed upon a direct current. In problems of this type, the theory and calculation of the circuits may be more involved than in the simpler cases. The elements of the theory of superimposed currents are added here...

Regeneration For Large Amplitudes

Part I is limited in its application to problems in which the electrical variations are very small. This limitation was imposed because the triode, which forms a part of the circuit, has a curved characteristic, and its internal resistance rp and voltage ratio uv vary over the characteristic curve. If only sufficiently small variations are considered, a very fair approximation to a true solution is obtained if these tube parameters are considered constant. With this limitation, the e-p-c....

Rbj

Linear, 586 Detection coefficient, of diode, 489 measurement of, 503 of triode, 518 Detection for large amplitudes, 565-587 grid-circuit detection, 573, 581 plate-circuit detection, 565, 581 transrectification, 565, 567 Detection for small amplitudes, 480-534 measurement of, 503 of modulated signal, 490 of two modulated signals, 495 of unmodulated signal, 481 Detection for small amplitudes, by triode, 512-534 grid-circuit detection, 512, 515, 518, 520, 532 measurement of, 527, 531 of modulated...

Introduction

The expression vacuum tube signifies a variety of devices all of which have in common a closed envelope or bulb made usually of glass or quartz, into which are sealed one or more electrodes and from which the air has been mostly exhausted or replaced by some other gas at reduced pressure. These tubes are capable of passing electric currents between their electrodes and, because of the passage of the electric currents, various effects are obtained which make...

Vacuum Tube

-40 -20 0 20 40 60 80 100 120 Potential of Second Grid in Volts, egg -40 -20 0 20 40 60 80 100 120 Potential of Second Grid in Volts, egg Fig. 321. Curves of kTT vs. e for a tetrode. French Bi'gril tube. Fig. 322. Curves of vs. e 2 for a tetrode. French Bigril tube. Fig. 322. Curves of vs. e 2 for a tetrode. French Bigril tube. similar to that used in developing the e-p-c. and e-g-c. theorems for a triode and will not be given in detail for a tetrode. The final expressions for the...

Dynamic Measurement Of Triode Coefficients

Attention has been called to the importance of the triode coefficients in expressing the performance of the triode, and in the development of its theory. The determination of the coefficients is usually made by direct methods known as dynamic methods. These methods make use of networks in one branch of which is a telephone receiver or its equivalent. An alternating potential, usually of a frequency of 1,000 cycles per second, is impressed across two points of the network, and the constants of...

Vor

Is a fairly satisfactory factor of merit of the detector provided Z i can be so chosen as to make useful a large fraction of the fictitious voltage A2E i , If, however, the oscillatory circuit is to be designed after a choice of the detector is made, the criterion is to obtain the largest A2E i AE0 2 possible. This is attained when the factor is as large as possible, which is true when kL0o h is small compared with tjq. As the values of tj0 and L0m depend so much upon factors of design which...

Er

About one hundred times that of tungsten. It is to be noted that the upper group of observations for oxide-coated emitters is for filamentary cathodes, while the lower group is for separately heated cathodes. The latter group would be expected to show a lower efficiency than the former group. 62. Cooling of Ends of Filament. In an actual tube the whole of the filament is not at the same temperature, owing to the conduction of heat away from the filament by the end connections and supporting...

Nomenclature And Letter Symbols

Before developing further the theory of vacuum tubes, a suitable system of notations or letter symbols must be adopted in order to denote easily the many different quantities involved. Although several schemes of notation have been suggested, no one system as yet has come into general use. A satisfactory system of symbols is urgently needed because of the exceptionally large number of different components and aspects of the same quantity necessary to be distinguished in this field. For example,...

Q

AEg pip AEo, and Ci should be at least as large as Cpg and preferably larger. In the scheme shown in Fig. 247c, the effects of Ri and Ri, the resistances of and L-2, have been neglected. In calculating by Eq. 520 the fraction of the input voltage which acts upon the grid, the resistances Rj and R2 must be considered. For Fig. 247c AE - 3 C fi gt -aEo 521 If in Eq. 521 , Ljoj 0, then AEg gt so that for some frequencies AEg may be much greater than AE0. It is of considerable practical importance...

R

Thermionic Voltmeter

And the deflections of the instrument can be considered to be due to the change of fv. The resistance fv for the quiescent point becomes rp when an a-c. voltage is impressed on the grid. The treatment of such bridge systems may follow the usual method, the plate-load resistance being fi 2 J B fi 3 Rg -f - fi l fi 3 Rg RB R sRgjRi RB Rl R2 - Rb - RG R2 -RG Rs -Rs where RB and Rg are the resistances of the battery and galvanometer. The fraction of the change in plate current, due to an impressed...

Theory Of Two Magnetically Coupled Circuits Without Regeneration

Derivation of the Currents in Coupled Circuits. Let the two circuits have the constants shown in Fig. 196. The impressed electromotive force Ea has a frequency M 'he equations describing the con- Fig. 196. Magnetically-coupled circuits. Fig. 196. Magnetically-coupled circuits. 1 The theory in this chapter was published by the author in greater detail in Proc. I.R.E., 12, 299 1924 . REGENERATION IN COUPLED CIRCUITS WITH SIGNALS 345 and Z2 j Liaj0 - jX2 C2u0 Solving these equations, the...

Regeneration In Coupled Circuits With Small

XIII it was shown that in effect a regenerative tube reduces the resistance of a single circuit with which it is associated. Frequently, in practice, a regenerative tube is associated with one of two coupled circuits. The purpose of the present chapter is to extend the treatment of regeneration to two magnetically coupled circuits and to show that in this case also regeneration, in effect, reduces the resistance of the circuit with which it is directly associated. The analysis includes...

Regeneration In Coupled Circuits With Small Signals

Theory of Two Magnetically Coupled Circuits without 140. Derivation of the Currents in Coupled Circuits. . 344 141. Conditions for and Value of Maximum Secondary Current. . . . 346 142. Conditions for and Value of Max. Max. Secondary Current . . . 347 143. Study of the Space Model for Secondary Current 348 144. Sections through the Space Model for Secondary Current 355 145. Conditions for and Value of Maximum Secondary Voltage. . . . 359 146. Locus of Max. Max. Secondary Voltage 360 147....

W rCia V CM

The effect of Ci upon the effective radio-frequency voltage on the detector will be considered, but Eq. 606 shows that from the point of view of the low-frequency operation, if the term containing Ci is appreciable compared to unity, the ratio given by Eq. 606 varies with frequency and frequency distortion is present. This indicates that Ci should be small. The circuit containing Zi is resonant to cat when CiZ Li. This condition gives the greatest frequency distortion for values of wi near the...