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Radio Engineers, Proceedings of the Institute of

Issue 2 • Date Feb. 1936

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  • [Front cover]

    Page(s): c1
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  • Institute of Radio Engineers - Forthcoming Meetings

    Page(s): c2
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  • Contents

    Page(s): i
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  • General Information

    Page(s): ii
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  • Institute sections

    Page(s): iii
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  • Geographical Location of Members Elected January 8, 1936

    Page(s): iv
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  • Applications for Membership

    Page(s): v - vi
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  • Officers and Board of Directors

    Page(s): vii
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  • Institute news and radio notes

    Page(s): 139 - 158
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  • Preferred Numbers

    Page(s): 159 - 179
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    The history of preferred numbers in this country is given briefly and the present status of recommendations of the American Standards Association is described. The subject is explained, and advantages to design and manufacture which the system affords are outlined. Tables are given of preferred numbers recommended by the American Standards Association, in both decimal and fractional systems, and rules and suggestions for use of the tables in design work. Some possibilities for immediate use in radio design are suggested. View full abstract»

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  • A New Type of Gas-Filled Amplifier Tube

    Page(s): 180 - 189
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    The Raytheon Laboratories have had under development for several years a gas-or vapor-filled amplifier tube. This paper describes the general features of this type of tube and gives the detailed characteristics of some typical designs. A distinctive feature of these gas-filled tubes is the introduction of an auxiliary grid-form electrode which serves as the anode for an ionizing discharge and at the same time as a cathode for the main electron stream which is controlled in the same manner as in an ordinary high vacuum tube. Due to the close spacing of the main electrodes and the relatively low gas or vapor pressure employed, the main electron stream or plate current can be continuously controlled by the voltage applied to the control grid, increasing as the negative bias on the control grid is decreased and decreasing to cutoff as the grid bias is made more negative. Within the voltage limits of each particular design of tube the presence of gas ions between the main electrodes only serves to neutralize partially the space charge, the general form of the characteristics being the same as for high vacuum tubes. The plate resistance however is characteristically low and the mutual conductance much higher than in high vacuum tubes of comparable size. Because of the low space-charge characteristic it also follows that high values of plate current and mutual conductance may be obtained at relatively low values of plate voltage, although normal characteristics are also obtained with plate voltages of several hundred volts. View full abstract»

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  • Some Engineering and Economic Aspects of Radio Broadcast Coverage

    Page(s): 190 - 206
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    The results of a quantitative study of the major factors affecting radio broadcast coverage are given for a frequency range from 200 to 2000 kilocycles and for transmission conditions covering the range normally experienced in the United States The effects of terrain, frequency, and antenna design in limiting the maximum nighttime service range of broadcast stations are discussed and it is shown that these limits are independent of the station power. The effect of terrain and frequency on the power required to deliver a 0.5-microvolt per meter signal at different distances is then shown in a series of curves, and the effect of atmospheric noise and interference considered. The economic aspects of this coverage are next considered and the power per square mile required is shown and the total costs and costs per square mile are given for the same parameters as before. The economic aspects of the proper balance between transmitter and antenna costs are considered and curves given for the frequency range considered. These studies show that it is economically unsound to attempt to cover large areas from a single station under unfavorable transmission conditions; i.e., high frequencies and high absorption. Also that for limited service areas the use of these high frequencies imposes no material hardships and that the lower frequencies should be reserved for stations of national and regional coverage while the lowest frequencies such as are now in use for broadcasting abroad are primarily suitable only for super-power stations of national coverage. View full abstract»

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  • A New Tube for Use in Superheterodyne Frequency Conversion Systems

    Page(s): 207 - 218
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    The major disadvantage of existing methods of frequency mixing is found in high-frequency operation with comparatively low intermediate frequencies, where serious coupling exists between oscillator and signal circuits in spite of, electrostatic screening. Suppressor modulation of a radio-frequency pentode largely overcomes many of the defects but the oscillator voltage required is large and the low plate resistance limits the gain. For these reasons, a new tube has been developed (designated the 6L7) wherein the above disadvantages are largely overcome. The new tube contains five grids: the first grid is a remote cutoff signal grid, the second and fourth are screens, the third is used as the modulator grid controlled by a separate oscillator tube, and the fifth grid is a suppressor. The ideal characteristics of such a tube are derived. The actual characteristics of the tube developed are shown and a brief discussion of the results obtained is given. A discussion of the flow of electron current to a negative grid due to an unusual transit-time effect at high frequencies is given and it is shown that operation with sufficient grid bias reduces the phenomenon. The characteristics of this tube also make it particularly suitable for use as a radio-frequency amplifier in receivers where the available automatic volume control or detector voltage is low; in this case the automatic volume control voltage is applied to both No. 1 and No. 3 grids. View full abstract»

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  • Design of Audio-Frequency Amplifier Circuits Using Transformers

    Page(s): 219 - 232
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    The computation of performance of a transformer at frequencies near resonance is simplified for the case in which the secondary is loaded with resistance. The information is presented in the form of a family of curves in which the generator and load resistances are the dependent and independent variables. The parameter, or third variable, held constant for a given curve, is the ratio of gain at resonance to the gain at some frequency at which resonance effects do not enter. It is referred to as the "resonance gain" and is expressed in decibels rise at resonance. Here the reference level of zero decibels is taken as either the gain at zero frequency for the equivalent circuit, which acts as a low-pass filter, or at infinite frequency for the case of a high-pass equivalent. Frequency response curves are given to illustrate the use of the design charts and to show the effect of varying the ratio of load to generator resistance, keeping the gain parameter constant. A typical curve showing the effect of the ratio of load-to-generator resistance on the phase angle is also shown. Use of the charts for design purposes is explained and numerical examples given. View full abstract»

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  • An Experimental Study of Parasitic Wire Reflectors on 2.5 Meters

    Page(s): 233 - 254
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    This paper presents the results of an experimental investigation of the energy distribution in a horizontal plane due to the juxtaposition of a vertical antenna and parallel parasitic rod-shaped conductors. The reduction of spurious radiation to a minimum, through a special arrangement of the apparatus, results in symmetry of the polar radiation patterns and makes it possible to appraise accurately the dependency of the forward radiation, directivity, and backward radiation on the dimensions of the reflector system. Typical polar distributions of single, double, trigonal, trapezoidal, plane, and parabolic arrays are shown. The distance between antenna and reflector for optimum forward effect, for plane and other multiple-wire arrays, was found to depend, in general, on the number, length, and spacing of the reflector elements. The parabolic reflector is considered in greater detail and, while most of the results are seen to be in qualitative agreement with experiments reported abroad, it is evident that the aperture of a grid reflector is not always a consistent "figure of merit" of its performance. The results of the parabolic arrays are used, finally, to discuss a theoretical formula derived by Ollendorff. View full abstract»

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  • A Method for Determining the Residual Inductance and Resistance of a Variable Air Condenser at Radio Frequencies

    Page(s): 255 - 274
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    When using a variable air condenser as a reactance standard at radio frequencies it is important to know the variation in effective capacitance and power factor with frequency. The procedure outlined in this paper furnishes a method for the measurement of the residual impedances causing such variations. A qualitative discussion of the sources of both residual inductance and resistance is presented. The residual inductance is largely localized in the leads and stack supports. The residual resistance may be considered as made up of a conductance caused by dielectric loss and a resistance caused by ohmic and eddy-current loss. It is pointed out that all these residual parameters tend to remain constant at a single frequency, irrespective of capacitance setting. The procedure for determination of the residual parameters depends upon the measurement of a fixed condenser by a substitution method, using the variable condenser to be studied as standard. At a single frequency the residual inductance of the standard condenser causes a deviation in effective capacitance from the static value which depends upon the setting. The residual resistance caused by ohmic and eddy-current loss causes a variation in effective conductance which also depends upon the setting. If the capacitance and conductance components of the fixed condenser be measured over different ranges of the scale of the standard condenser there will therefore be an apparent variation in their values. Interpretation of these trends yields the magnitudes of the residuals causing them. View full abstract»

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  • Eddy Currents in Composite Laminations

    Page(s): 275 - 286
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    The familiar theory of eddy current shielding leads to an expression for the impedance of a ferromagnetic core inductance coil in terms of the initial permeability and resistivity of the core material, the core geometry, and the measuring frequency. Measurements on a number of different core materials over a wide frequency range have revealed sizeable deviations from the theory in some cases. The discrepancies are especially marked in some specimens of chromium permalloy, the measured inductance over a certain frequency range being of the order of one tenth that specified by the theory. It appears that discrepancies arise when the laminations are not homogeneous, a condition contrary to an assumption of the simple theory. The inhomogeneity takes the form of a thin surface layer which has a permeability much less than that of the interior. By etching off these surface layers, the initial permeability is increased, and discrepancies between the measured variations of impedance with frequency, and those calculated for a homogeneous sheet are removed almost completely. The theory has been extended to take account of the surface layers, and agrees well with measurements on the original unetched laminations when plausible assumptions are made regarding the properties of the surface layer. View full abstract»

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  • Cathode-Ray Oscillographic Investigations on Atmospherics

    Page(s): 287 - 304
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    An analysis of the true nature of the wave forms of atmospherics, when they show rapid time variations, can easily be obtained by using cathode-ray oscillographs with very high speed recording. The author describes the arrangement that he has used for recording and analyzing atmospherics, with his relay construction of high voltage cathode-ray oscillographs. These instruments were connected through amplifiers to horizontal aerials having different heights above the ground. A passing atmospheric produced voltage changes across a resistor inserted in the antenna system, which, provided that special precautions were taken, gave the dE/dt variations of the field E. By applying an integration procedure to the records, it was possible to obtain the true field curves E(t) of the corresponding atmospherics. These observations were made at field stations located in the vicinity of the Institute of High Tension Research, University of Uppsala, Sweden. The results of observations made between February and August, 1934, are dealt with in this paper. About 7500 atmospherics were recorded, of which 600 were selected as typical, and have been integrated. The total duration times of individual atmospherics that were most frequently observed lay between 100 and 150 microseconds. When periodic or quasi-periodic variations were observed, about sixty per cent of such atmospherics showed a periodicity of between five and ten kilocycles per second. The atmospherics frequently occurred in groups composed of a number of separate and individual field variations. The time duration of about seventy per cent of such groups was within 5 × 10-2seconds. View full abstract»

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  • Optimum Operating Conditions for Class B Radio-Frequency Amplifiers

    Page(s): 305 - 315
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    A theoretical analysis of the efficiency and output of a triode operating as a class B radio-frequency amplifier is made. It is shown that for a given tube, plate voltage, and plate loss there is a definite value of load impedance which will give maximum output. Design formulas are developed for determining this load impedance, the proper grid excitation, and the resultant efficiency and output. View full abstract»

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  • A Network Theorem

    Page(s): 316 - 327
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    It is shown that any relation between any of the commonly used parameters of a linear passive network (of any complexity) with two pairs of terminals is the equivalent of some other equally true relation which, by a simple rule for symbol substitution, may be obtained from, but is not necessarily algebraically contained in, the original expression. This symbol substitution theorem applies not only to transducer parameters but also to those quantities which describe the action of the transducer with load, with one exception. Distinguishing between the theorem and the rule for symbol substitution included in it, the rule may be used arbitrarily in cases where the theorem does not apply. By such a process it is shown that there is a closer relationship between certain structures than has heretofore been known. As an incidental to bringing the so-called general circuit parameters under the theorem, these have been expressed in terms of other parameters in such a way that certain minor theorems roughly analogous to Thevenin's theorem result. View full abstract»

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  • Book reviews

    Page(s): 330
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  • Booklets, catalogs and pamphlets received

    Page(s): 331
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  • Contributors to this issue

    Page(s): 332 - 334
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Aims & Scope

This Periodical ceased production in 1938. The current retitled publication is Proceedings of the IEEE.

Full Aims & Scope