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Proceedings of the IRE

Issue 5 • Date May 1939

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Displaying Results 1 - 17 of 17
  • [Front cover]

    Page(s): c1
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  • National Convention

    Page(s): c2
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  • Table of contents

    Page(s): nil1
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  • Information about the Society

    Page(s): nil2
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  • Precipitation-Static Interference on Aircraft and at Ground Stations

    Page(s): 301 - 316
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    The effect of precipitation static on aircraft reception is described and a history of previous work on the subject given. The results of an expedition assembled by the United Air Lines for a study of the subject are described under a series of chapter headings. The meteorological conditions producing the static areas were explored by flights through them and the theory of their formation is discussed. Flight tests of all known types of antistatic antennas were made in bad-weather areas and their effectiveness compared. A theory that the interference results from corona produced on the plane structure was developed and tested by mounting the plane on insulators and charging it to 100,000 volts with all radio equipment and personnel on board. A method for reducing the corona was developed as a result and proved by flight tests. A study of the electromagnetic radiation from corona discharges was made with a synthetic static generator and the operation of the metallically shielded antistatic loop antennas explained and its limitations established. A commercial form of plane discharge system was developed and its advantages and limitations are described. The application of the aircraft results to ground radio reception is discussed. View full abstract»

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  • The Application of Negative Feedback to Frequency-Modulation Systems

    Page(s): 317 - 331
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    Negative feedback can be applied to a frequency-modulation receiver of superheterodyne type by causing a portion of the output voltage to frequency-modulate the local oscillator in such phase as to reduce the output signal. As a consequence of this arrangement the effective frequency modulation of the intermediate wave is diminished by the feedback factor. This reduction is accompanied by a decrease in noise and distortion. Restoration of the original signal level by increasing the degree of modulation at the transmitter brings about a corresponding increase in signal-to-noise ratio provided the disturbance is not too great, while distortion ratios are improved to about the same extent. These effects are treated analytically for the case where the disturbance level is sufficiently low to permit simplifying assumptions to be made. The results are in general agreement with observations made on an experimental laboratory system. Comparing the feedback system with a frequency-modulation system using amplitude limitation, the ratio of signal level to noise level in the absence of modulation is identical in two systems. During modulation the noise level increases in the feedback system by an amount depending upon the ratio of the effective frequency shift of the intermediate-frequency wave to the signal band width. By keeping this ratio small, the increase in noise during modulation can be made relatively unimportant. In cases where the disturbance level is high, phenomena have been observed which are very similar to those encountered when amplitude limitation is used. View full abstract»

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  • The Relation of Radio Sky-Wave Transmission to Ionosphere Measurements

    Page(s): 332 - 347
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    A simple, rapid, graphical method is given for obtaining maximum usable frequencies and effective reflection heights of radio waves, from vertical-incidence measurements of the critical frequencies and virtual heights of the various layers in the ionosphere. The method consists of the use of "transmission curves," which are superimposed on the curve of frequency against virtual height, observed at vertical incidence. The intersection of the curves gives the level of reflection in the ionosphere. The factors considered in deriving the transmission curves are variation of virtual height with frequency, effect of the curvature of the ionosphere and earth, influence of the earth's magnetic field, and absorption by or reflection from lower layers in the ionosphere. A chart is included for rapid calculation of the factor sec ϕ0, used in plotting the transmission curves. View full abstract»

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  • Characteristics of the Ionosphere at Washington, D.C., March, 1939

    Page(s): 348 - 349
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    Data on the ordinary-wave critical frequencies and virtual heights of the ionospheric layers are presented for the period indicated in the title. The monthly average values of the maximum usable frequencies for undisturbed days, for radio transmission by way of the regular layers is also provided. View full abstract»

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  • Institute news and radio notes

    Page(s): 350 - 357
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  • Books

    Page(s): 357
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  • Correspondence

    Page(s): 357 - 358
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  • Contributors

    Page(s): 358
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  • Commercial Engineering Developments

    Page(s): ii - vi
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    First Page of the Article
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  • Current Literature

    Page(s): vi
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  • Engineering directory [advertisement]

    Page(s): x
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  • Index [to advertisers]

    Page(s): x
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  • Positions open

    Page(s): x
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Aims & Scope

This Periodical ceased production in 1962. The current retitled publication is Proceedings of the IEEE.

Full Aims & Scope