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Radio Engineers, Proceedings of the Institute of

Issue 3 • Date March 1938

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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 February 2, 1938

    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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  • Institute news and radio notes

    Page(s): 247 - 275
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  • Corrections

    Page(s): 276
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  • A New System of Inductive Tuning

    Page(s): 308 - 320
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    A sliding-contact variable inductance is described wherein contact reliability over long life is secured by a unique carriage arrangement and parallel nibs at the point of contact. The coil is rotatable, the high-potential contact being taken off a ring at one end. The contactor and unused end of the coil are at ground potential. The entire variable coil is used and the high-frequency limit is determined by a separate adjustable "end" inductance which improves the performance throughout the high-frequency range. The high-frequency limit of a continuous operating range for a given coil is near the natural frequency of the unused part of the coil when the contact is near the high-potential end of its travel. Wide frequency tuning ratios of the order of six to eight are feasible and all-wave continuous coverage may be effected with two switch positions instead of three as required with variable-condenser tuning. Oscillator circuits are described which yield substantially uniform voltage over a ten-to-one frequency range. This widerange characteristic may be obtained even in the ultra-high-frequency region. Wider ranges necessitate improvement in the tracking of the usual superheterodyne input circuit. A method for producing a fourth tracking crossover when the inductive tuner is designed for superheterodyne circuit tuning is described. View full abstract»

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  • A Theory of Noise for Electron Multipliers

    Page(s): 321 - 332
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    The noise in secondary-emission electron multipliers is considered from a theoretical viewpoint. The noise properties of a stage are correlated with its secondary-emission properties: the mean value m and mean-square deviation δ2of the number of secondaries per primary. If IpA2 and IsAf2 denote the mean-square noise current lying in the frequency band Δf in the primary- and secondary-electron currents, then 1aAf2= m2I, PV2+ 622eI,, Af where Īpis primary direct current. This result is applied to many-stage multipliers. For n similar stages I, f2= M2I2PA2+ f 2[ M( M )/ m( m21)] 2eIpAf where M=mnis the over-all gain of the multiplier. View full abstract»

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  • A New Principle in Directional Antenna Design

    Page(s): 333 - 345
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    It is shown that in certain types of directional antenna arrays the gain can be increased by arranging so that waves going from the array elements in the direction of maximum transmission are not strictly in phase at large distances. Three examples are given, an end-fire array and two antennas designed to radiate, as far as possible, only in a horizontal plane. In the case of the end-fire array it is shown that readjustment of any existing antenna according to the ideas proposed here will increase the gain by about 1.8. The other two examples correspond to the kind of directivity generally desired in a broadcast antenna. One of these consists of short antennas placed in concentric rings. A typical array of this type containing 22 short antennas with the radius of the outer ring equal to 1.39λ has a gain of 2.31 as compared with 1.56 for a vertical half-wave antenna. The other example of a horizontally radiating array consists of a single ring of short antennas. An example of this type is calculated which has a gain of 2.0 with a total of 23 antennas placed in a circle with a radius of 1.43λ. These figures are not given as the best that can be done, but only as examples. View full abstract»

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  • Excess-Energy Electrons and Electron Motion in High-Vacuum Tubes

    Page(s): 346 - 371
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    In the development of magnetron oscillators, one of the principal difficulties has been the overheating of the cathode. The present article discusses an effect which is at least partially responsible for this, and which consists in the gaining of excess energy by some electrons, which then bombard the cathode. The effect is of importance also because of its bearing on transit time, orbit shape, tube noise, shape of cutoff curve, etc. Experimental results indicate that a Maxwellian distribution of velocities is superimposed on the orbital velocities, the energy of the random motion being derived from the orbital motion. This leads to the formation of a new type of virtual cathode about the real cathode. The properties of this type of cathode are discussed. Subjects related only indirectly to cathode overheating, but necessary to its understanding, also are discussed, such as current flow and space-charge phenomena for cases in which electrons execute cyclic orbits. Extensive experimental data are included. View full abstract»

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  • Relations Existing between Voltage Impulses of Exponential Form and the Response of an Oscillating Circuit

    Page(s): 372 - 378
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    The superposition integral is used to express the voltage produced in the inductance of a tuned circuit in response to a voltage impulse of exponential form. The expression is given in terms of the voltage and time constant of the impulse and the frequency and decrement of the oscillating circuit. This method is more direct and more easily manageable than the conventional method which expresses the relations in terms of the current produced in the secondary or oscillating circuit in terms of the voltage applied to this circuit by the primary or exciting source. The conventional equation, Ldi/dt+Ri+q/C=E may be quite troublesome with certain forms of voltage E. Comparisons are made between oscillograms of an experimental circuit and curves calculated from theory. A simple graphical method is given for determining the constants of an exponential impulse from the response curve and known constants of the oscillating circuit. General conclusions are drawn which are of interest relative to radio interference. View full abstract»

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  • Characteristics of the Ionosphere at Washington, D.C., January, 1938

    Page(s): 379 - 382
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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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  • Correspondence

    Page(s): 383 - 384
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  • Book review

    Page(s): 385
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  • Contributors to this issue

    Page(s): 386
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Aims & Scope

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

Full Aims & Scope