DOI:10.1049/ji-3-2.1947.0002

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The service organization for the maintenance and repair of radio and television receivers has developed with the growth of the industry. The paper opens with a reference to the fundamental concepts of “working life” and service, and after a brief historical review examines the basic responsibility of a service organization and the methods by which this may be fulfilled. Personnel and equipment problems are next considered and analysed, and a typical service department is described. Consideration of the interrelationships between service and design is followed by a discussion of the service aspects of television and export as prominent post-war problems. The paper concludes with some notes on future development.

DOI:10.1049/ji-3-2.1947.0003

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The paper describes an automatic test apparatus designed to check, under mass-production conditions and within broad limits of impedance, the multiple circuit paths found in modern radio equipment. While primarily intended as a check of wiring, the instrument operates by comparing with a standard the circuit impedances from point to point, and supersedes the common ohmmeter by working successively on alternating and direct current to provide a degree of discrimination between the reactive and resistive elements of a complex network. The comparison method used in the design provides the necessary flexibility for adaptation to differing production requirements, and it has been found that the apparatus gives a consistently greater degree of reliability in circuit checking than has been attained by purely manual operation.

DOI:10.1049/ji-3-2.1947.0004

出版商:IEE    

年代:1947

数据来源: IET

摘要:

Electrodeless discharges in high-frequency electromagnetic fields were investigated in conditions where the ratio of linear dimensionlof the discharge space to the electromagnetic wavelength λ in air was 10−3<l/λ<10−1, at frequencies between 106and 108c/s. The power introduced into the discharge space varied from fractions of watts to 100 kW, and the electric field strength was varied between tens and hundreds of volts per cm. There are two different types of discharge: “E-discharges,” in which the elementary conductance currents are continued by dielectric currents, and “H-discharges,” with elementary conductance currents in the form of closed curves.When the ratiol/λ is less than 10−1 then the electrodeless discharges in air at atmospheric pressure may exist at distances of the order of centimetres from the current-carrying electrodes. Further development of the ultra-high-frequency technique leads to constructions of electromagnetic radiators in which the dimensionlis greater than the wavelength λ. With such radiators it is possible to have high concentration of electromagnetic energy at distancesxup tol2/λ which may be some metres or perhaps kilometres from the electromagnetic radiator. When 1 ≫ λ andl2≫xλ it is possible for a natural breakdown to occur in an electromagnetic ray.

DOI:10.1049/ji-3-2.1947.0005

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The instrument is intended for use, in conjunction with an accurate chronometer, in short-period comparisons of the frequencies of high-grade 100-kc/s oscillators. The phases of the two inputs are compared in a discriminator, the output of which controls a trigger circuit. Pulses from the trigger control the starting and stopping of the chronometer, which measures the periods of beats between the signals. Comparisons of frequencies differing by about 1 part in 106can be made to an accuracy of 1 part in 1011over the period of a single beat, i.e. about 10 sec.

DOI:10.1049/ji-3-2.1947.0006

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The paper discusses the design and performance of low-frequency selective amplifiers using negative feedback through a parallel-T bridge network. Two basic forms of the circuit giving symmetrical selectivity are analysed, and a method of varying the selectivity while maintaining the magnitude and frequency of the peak amplification constant is indicated. The paper concludes with a brief discussion of the problems which arise in the design of bridge amplifiers having high selectivity.

DOI:10.1049/ji-3-2.1947.0007

出版商:IEE    

年代:1947

数据来源: IET

摘要:

A description is given of a contact device of the high-pressure small-area type, capable of carrying 75 amp at 20 Mc/s, and 150 amp at power frequencies. Whilst relative movement and rotation is provided between the various parts of the assembly, all contacts are of the high-pressure type, and there are no flexible leads or springs carrying current. Examples of its use are illustrated with special reference to improvements in the design of variometers or coupling coils.

DOI:10.1049/ji-3-2.1947.0008

出版商:IEE    

年代:1947

数据来源: IET

DOI:10.1049/ji-3-2.1947.0009

出版商:IEE    

年代:1947

数据来源: IET

摘要:

A description is given of an experimental investigation of a continuous-wave magnetron oscillator, the magnetic field for which is provided by an electromagnet energized by the anode current of the valve. Oscillations can be readily obtained, and they persist over a wide range of anode voltages. With a two-segment-anode valve oscillations take place at the fundamental frequency of a lecher-wire circuit connected to the valve. With a four-segment-anode valve, oscillations at the fundamental frequency of such a circuit are observed at low anode voltages, but as the voltage is increased oscillations at 3, 5, 7 … times the fundamental frequency appear successively. The range of frequency covered by the experiments was 40–750 Mc/s (λ 7.5 m to 40 cm). During oscillation the anode current assumes the value necessary to provide the optimum magnetic field, and, within limits, the number of turns on the electromagnet and the magnitude of the filament current do not affect the action of the oscillator. The operational stability is good, and the danger from an excessive anode current is largely removed.

DOI:10.1049/ji-3-2.1947.0012

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The paper investigates the values of permittivity and permeability of a mixture consisting of a homogeneous material in which particles are embedded. Formulae are found which are valid at high frequencies, so long as the size of the particle is small compared with the wavelength and the packing is not too great.Special cases treated are iron-dust cores and expanded dielectrics in which the “particles” are air bubbles. For ferromagnetic materials, weak fields only are assumed, so that the results refer to initial permeability.On account of the heterogeneity of the mixture, the permeability may become “lossy” (i.e. μ may be complex). Even when the substances are all non-ferromagnetic, the permeability of the mixture may depart from unity, or be complex.

DOI:10.1049/ji-3-2.1947.0013

出版商:IEE    

年代:1947

数据来源: IET