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Radio Engineers, Proceedings of the Institute of

Issue 8 • Date Aug. 1937

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Displaying Results 1 - 19 of 19
  • [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 July 7, 1937

    Page(s): iv - v
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  • Applications for Membership

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

    Page(s): viii
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  • William H. Doherty, Recipient, Morris Liebmann Memorial Prize, 1937

    Page(s): 922
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  • Institute news and radio notes

    Page(s): 923 - 936
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  • Development of the Projection Kinescope

    Page(s): 937 - 953
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    This paper discusses the general requirements and design of Kinescope tubes for projecting television images. A picture 18×24 inches in size having a brightness in the high lights of 0.9 candle per square foot appears to be an acceptable minimum for home television reception. Several years of developmental work were required before the problems of designing a suitable projection system were clarified. This clarification led to a developmental Kinescope which closely approaches the minimum brightness requirements. The possibilities of further improvements in electron guns, fluorescent screen materials, and optical systems are discussed. View full abstract»

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  • High Current Electron Gun for Projection Kinescopes

    Page(s): 954 - 976
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    One of the problems in the art of reproducing a scene by television is to obtain an image of adequate size. Because of this there has been considerable interest in projection systems where a small, high intensity image reproduced on the face of a projection Kinescope is thrown onto a viewing screen of the desired size by a suitable optical system. The light output and the definition of these systems has been limited by the inability of the electron gun to provide a sufficiently large beam current in a small spot. This paper describes an electron gun giving large beam current in a small spot. The design of this electron gun is based on the results of the present investigation which shows that the ratio of the current in the first crossover inside the radius r to the total space current is I/Is=1-ε-ar2E where E is the voltage applied to the first crossover forming system and a is a constant for any given cathode temperature, potential distribution, and geometry. Inasmuch as the total space current varies approximately as E3/2, the concentration of current in the first crossover increases very rapidly with voltage. A description is given of an electron gun based on this theory. All available voltage is used to form a small intense first crossover whose edges are sharply defined by a first crossover defining aperture. A magnetic final focusing lens reimages this first crossover on the fluorescent screen. This electron gun gives beam currents of 1. View full abstract»

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  • Theoretical Limitations of Cathode-Ray Tubes

    Page(s): 977 - 991
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    The current density in a focused beam of cathode rays is shown to have an upper limit defined by I = I0(Ee/kT+1) sin2φ, where I is the maximum current density obtainable in the focused spot, I0is the current density at the cathode, E is the voltage at the focus relative to the cathode, T is the absolute temperature of the cathode, e is the electronic charge, k is Boltzmann's constant, and φ is the half angle subtended by the cone of electrons which converge on the focused spot. The cases in which the focused spot is an image of the cathode, and in which it is a pupil, or "crossover", are considered separately, and the above formula is shown to apply to both. The necessary initial assumptions are (1) that electrons leave the cathode with a Maxwellian distribution of velocities, and (2) that the focusing system is free from aberrations and obeys the law of sines. Aberrations may reduce the current density, but nothing can raise it above the value defined. In the Appendix the focusing properties of a uniform accelerating field are calculated. The virtual image of a plane cathode formed by such a field suffers from spherical aberration. The diameter of the circle of least confusion formed by electrons from a single point is approximately equal to the distance the electrons can travel against the field by virtue of their initial velocities. View full abstract»

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  • A Circuit for Studying Kinescope Resolution

    Page(s): 992 - 1011
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    Several of the characteristics of a cathode-ray tube which determine its usefulness as a Kinescope for television reception are outlined. Various means for studying these characteristics are discussed. A system is outlined for studying Kinescope resolution by breaking the picture into alternate black-and-white picture elements arranged in checkerboard fashion. A practical application of this system is described for a television system using a picture frame of approximately 340 lines repeated thirty times per second. The deflection and grid-signal frequencies that are involved are discussed. The problem of synchronizing these frequencies is covered and the circuits developed for this purpose are described. Some of the results obtained with these circuits are shown. View full abstract»

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  • An Oscillograph for Television Development

    Page(s): 1012 - 1033
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    First Page of the Article
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  • The Brightness of Outdoor Scenes and Its Relation to Television Transmission

    Page(s): 1034 - 1047
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    The average brightness of typical outdoor scenes has been determined by computation and by measurement. The average brightness of some scenes was found to be over 1000 candles per square foot, and of other scenes nearly zero. In many cases the average brightness lay between twenty and 200 candles per square foot. The sensitivity of a present-day television system using the Iconoscope has been found to be sufficient to permit the transmission of pictures with good quality when the average brightness of an average scene was greater than about fifteen candles per square foot. This sensitivity is sufficient for the transmission of parades, races, baseball games, and many other outdoor events. Football games, which last until near sunset, cannot always be satisfactory reproduced. Some of the Iconoscopes used in these tests are of added sensitivity, which has been achieved by means of a silver evaporation process, as well as by careful control of the purity of the materials. View full abstract»

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  • Television Pickup Tubes with Cathode-Ray Beam Scanning

    Page(s): 1048 - 1070
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    Television pickup tubes which use cathode-ray beam scanning, although only one class of television pickup devices, may be made in a variety of ways, a number of which are described in this paper. In these tubes, the function of the electron beam is to release secondary electrons from the target, the number escaping being modulated by electrostatic fields, magnetic fields, orientation of electrodes or changes in the secondary emission ratio of the target. The Iconoscope is a well-known example of modulation by electrostatic fields produced by photoemission from the target. A conducting photocathode when used as a target, however, acted as if its secondary emission ratio were decreased by light. A copper plate oxidized and treated with caesium transmitted a picture with some time lag. Photoconductive materials exposed to light and scanned by an electron beam were made to develop potential variations over their surface and thereby transmit a television picture. Aluminum oxide and zirconium oxide, treated with caesium, were used in this manner. Selenium, used as a photoconductive material, also transmitted a picture. Germanium used as a target sensitive to heat radiation was able to transmit a picture, probably as a result of some thermoelectric effect. The most sensitive tubes tested were those in which an electron picture was focused upon a scanned, secondary electron emissive target. The scanning and picture projection operations may be separated by using a two-sided target. Coupling between the two sides was obtained by conducting plugs through the target. View full abstract»

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  • Theory and Performance of the Iconoscope

    Page(s): 1071 - 1092
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    Field tests have shown the present standard Iconoscope to be a very satisfactory television pickup device. However, from a theoretical point of view the efficiency of the Iconoscope as a storage system is rather low. The principal factors responsible for the low efficiency are lack of collecting field for photoelectrons, and losses caused by the redistribution of secondary electrons produced by the beam. Limits to the sensitivity of the standard Iconoscope are set by the ratio of picture signal to amplifier and coupling resistor noise. Experimental and theoretical determinations indicate that an excellent picture can be transmitted with from two and one-half to six millilumens per square centimeter on the mosaic. Two methods are considered by which the sensitivity may be increased. The first is by the use of secondary emission signal multipliers and a low capacitance mosaic, while the second makes use of secondary emission image intensification. The sensitivity limits for the two cases are calculated. View full abstract»

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  • Contributors to this issue

    Page(s): 1093 - 1094
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Aims & Scope

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

Full Aims & Scope