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Radio Engineers, Proceedings of the Institute of

Issue 5 • Date May 1928

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Displaying Results 1 - 21 of 21
  • [Front cover]

    Page(s): c1 - c2
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  • Contents

    Page(s): 539
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  • General Information

    Page(s): 539
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  • Officers and Board of Direction, 1928

    Page(s): 540 - 541
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  • Institute sections

    Page(s): 542
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  • Greenleaf Whittier Pickard - Second President of the Institute, 1913

    Page(s): 544 - 545
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  • Contributors to this issue

    Page(s): 546 - 547
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  • Institute activities

    Page(s): 548 - 559
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  • Obituary [Thomas R. Bristol]

    Page(s): 560
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  • Studies of High-Frequency Radio Wave Propagation

    Page(s): 561 - 578
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    Studies of multiple signals of high frequency have been made upon a quantitative basis with reference not only to the round-the-world signals (sometimes called echo signals) but to nearby echoes which have a very much shorter time of arrival. A method of predicting in advance the the likelihood of round-the-world echoes occurring between any two different stations has been worked out. Further studies of nearby echoes show a remarkable retardation on very high-frequency signals coming from the Rocky Point stations to Washington, these signals traveling an actual distance varying from 2900 kms. to over 10,000 kms., although the great circle distance is only 420 kms. The apparent violation of the skip distance law by these stations as observed in Washington has been explained. The nearby echo signals have been tentatively assumed to be due either to reflections from a heavily ionized region in the neighborhood of the magnetic poles or more likely to be due to scattered reflections thrown backwards from the first and second zones of reception, which follow the skip distance region. This throwing back of the signal thus permits under certain conditions the reception of the signal on very high frequency within what is really the skipped zone, the signal having entered this zone by a very indirect route and with a considerable time retardation as compared with the direct route. Influence of both nearby and round-the-world echo signals upon various types of radio communication have been briefly discussed. View full abstract»

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  • The Status of Frequency Standardization

    Page(s): 579 - 590
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    The measurement of frequency, hitherto of laboratory interest only, has become of first-rank importance in reducing radio interference. This has come about through the increasing use of all available radio channels particularly at broadcasting and higher frequencies. While an accuracy of one half per cent was satisfactory five years ago, accuracies a thousand times as good are now sought. The piezo oscillator is meeting the needs of this situation in large part. Much effort is being devoted to making the piezo oscillator as constant as possible. Commercially available piezo oscillators, without temperature control, are generally reliable to about 0.03 per cent, just barely enough to meet the Federal Radio Commission's requirement of one-half kilocycle. In order to reach greater accuracy, considerable work is being done on the primary standards of frequency, to insure the highest constancy and accuracy. The Bureau of Standards and other organizations are engaged on a cooperative program to attain an accuracy of 0.001 per cent. Comparisons with other nations show that the national laboratories of the larger countries are already in agreement to about 0.003 per cent. Temperature controlled piezo oscillators will probably allow the holding of station frequencies so close that several stations can broadcast on the same frequency without heterodyne interference. Use of these or equivalent devices is vital to the maximum utilization of the very high frequencies; the separation of 0. View full abstract»

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  • Discussions

    Page(s): 590 - 592
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  • Detection by Grid Rectifiction with the High-Vacuum Triode

    Page(s): 593 - 613
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    The theory of detection of small signals by grid rectification with the high-vacuum triode of the 201A type is briefly discussed by means of the mathematical method of Carson. Special attention is given to the grid-leak, grid-condenser arrangement. The relation between the non-linear distortion and the degree of modulation and between the frequency distortion and the grid impedances is discussed. A convenient method is described for experimentally ascertaining the frequency distortion in detection and illustrated by means of the results in a typical case; this distortion is compared with that due to resonance in the r.f. amplifier circuits. A method of securing efficient grid-rectification in the super-heterodyne system is described. The detection coefficients for the 200A alkali-vapor tube are given in an appendix. View full abstract»

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  • Recent Developments in Low Power and Broadcasting Transmitters

    Page(s): 614 - 651
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    Various types of radio transmitting equipments are described, ranging in output from 200 to 2000 watts. The application of master-oscillator power-amplifier circuits for low-and medium-frequency transmitters is explained, and the uses of quartz crystal control for high-frequency and broadcast transmitters are described. A brief explanation is also given of the equi-signal system of radio beacon transmission, which promises to become an important aid in the navigation of aircraft. View full abstract»

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  • Apparent Night Variations with Crossed-Coil Radio Beacons

    Page(s): 652 - 657
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    The combined effects of apparent wave direction shifts and fading, of signals from a crossed coil type of radio beacon as received on airplanes in flight at night, are described. A brief explanation of the operation of such a beacon is given. The results of observations of similar signals at night received on an automobile, together with some general conclusions, are mentioned. View full abstract»

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  • Oscillographic Observations on the Direction of Propagation and Fading of Short Waves

    Page(s): 658 - 665
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    The short-wave transmission path is generally but not always located in the vertical plane through the transmission and receiving points. Direction finding depends upon determining the direction of the wave at the receiving point; it does not give accurate results when the twilight zone is in the way of the wave path. The angle between the earth and the direction of short-wave propagation varies continuously and the changes in this angle are much larger than the changes in angle of propagation in the horizontal plane. The observations are consistent with the view that the fading is mainly caused by wave interference. View full abstract»

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  • An Automatic Recorder for Measuring the Strength of Radio Signals and Atmospheric Disturbances

    Page(s): 666 - 670
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    A description is given of apparatus for automatically recording the field strength of low-frequency stations and atmospheric disturbances. The receiver, amplifiers, rectifier, and recorder are switched on by relays controlled by a clock and arranged so that for different 5-minute periods during the hour the strength of several stations may be recorded. The sensitivity of the system remains constant over long periods, provided the filament and plate currents do not change. Calibration can be made at any time from either a radio-frequency or audio-frequency source. Typical curves of the variations in signals and atmospheric disturbances are shown. View full abstract»

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  • Use of an Oscillograph for Recording Vacuum-Tube Characteristics

    Page(s): 674 - 680
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    This paper describes the method involved and results obtained in using an oscillograph for plotting photographically vacuum-tube characteristics. The main requirement is an alternating voltage of fairly pure wave-form with as few harmonics as possible. The "dynatron" action of vacuum tubes is shown very clearly when large alternating e.m.f.'s are applied to the grid. Static and dynamic characteristics can also be quite easily recorded. View full abstract»

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  • Book reviews

    Page(s): 681 - 692
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  • Geographical Location of Members Elected April 4, 1928

    Page(s): 693 - 694
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Aims & Scope

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

Full Aims & Scope