摘要:

Instruments for counting local lightning flashes are reviewed and reasons are given for selecting one particular design for extensive tests. The importance of the aerial configuration is stressed. A 7 m vertical aerial has been adopted as a standard, and the instruments have normally been adjusted to trigger on a 3-volt signal from a built-in calibrator, corresponding to a field change of about 3 volts/m.With this arrangement, on a day on which thunder is heard, there is usually a maximum hourly count exceeding 30 and a total daily count exceeding 100.The effective range of a counter is defined in statistical terms and techniques for its measurement are discussed. Preliminary estimates of the effective range are derived from observations on a few local storms in England; with the standard instrument it is about 30km. More observations are required to confirm the results, particularly in countries with frequent thunderstorms. Equipment should be standardized so far as possible.

DOI:10.1049/pi-b-2.1960.0123

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The use of metres, kilogrammes, amperes, etc., instead of centimetres, grammes, deca-amperes (the C.G.S. unit of current), etc. need not change the method of teaching electricity and magnetism, for it does not interfere with the notions of magnetic poles and point charges of electricity. A logical method of developing the theory from conventional experiments on the forces between magnets, between magnets and current-carrying loops, and between electric charges, is to proceed from magnetic poles to magnetic shells and from these to loops of current, and then bring in the definition of the ampere to evaluate the magnetic constant; consideration of the forces between electric charges follows and, together with identification of rate of change of charge and electric current, leads to the law of induction, to Maxwell's equations, and to wave propagation, which, in conjunction with the known velocity of light, gives the value of the electric constant. The theory is then extended to material media.A treatment suitable for beginners is outlined in Section 9.

DOI:10.1049/pi-b-2.1960.0124

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper is an introduction to the theory of solid-state masers with particular reference to the travelling-wave maser. The relevant properties of paramagnetic ions are described and the quantum theory of maser action is outlined qualitatively. A semi-classical treatment is developed which is based on the classical equation of motion of a magnetic dipole. It is used to evaluate the engineering characteristics of a travelling-wave maser which employs the comb type of slow-wave guide.

DOI:10.1049/pi-b-2.1960.0127

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Although the difficulties involved in the measurement of dielectric properties increase with frequency, a conventional cavity method with minor modifications has proved satisfactory at millimetre wavelengths.A cavity, ½in in diameter, was excited in an H01mode by means of coupling holes. It was found to have sufficiently low wall loss to enable the loss tangents of disc specimens of magnesium-titanate and titanium-dioxide ceramics to be measured. Both loss tangents were of the order of 0.0003, and the relative permittivities were 14 and 80, respectively.Although a high degree of accuracy is not claimed, useful results can be obtained with relatively simple equipment. A convenient method of marking small frequency intervals is described.

DOI:10.1049/pi-b-2.1960.0128

出版商:IEE    

年代:1960

数据来源: IET

摘要:

During investigations of mica capacitor failures of various equipments during the last ten years and studies to improve their reliability, many mechanisms of failure have been examined. The principal features of the mechanisms are described and illustrated, and are summarized in tabular form for quick reference. Some methods of examination and dissection of these capacitors with the minimum loss of evidence are given in detail.This work does not imply that the proportion of mica capacitors which fail in service is excessive. Some of the causes of failure would occur in other types of capacitor, perhaps to a similar extent.

DOI:10.1049/pi-b-2.1960.0129

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Some aspects of an f.m. c.w. radar with a sawtooth frequency sweep are considered. The exact beat note for a discrete target is calculated and its Fourier transform is obtained. A scheme previously given by Gnanalingam for producing a coherent system is shown to be only approximately valid, and an alternative method is proposed. The effect of Doppler shift on the return is discussed. Range discrimination is examined critically.

DOI:10.1049/pi-b-2.1960.0130

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Published information on the intensity of noise from the galaxy, the sun and from other extra-terrestrial sources is presented in a form which shows their importance relative to the internal noise of typical receiving installations. Particular attention is paid to a half-wave horizontal dipole aerial and to an aerial with a 20° pencil beam directed horizontally.

DOI:10.1049/pi-b-2.1960.0131

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The causes of long-term failure under practical conditions of use or storage of different types of fixed resistors commonly used in electronic equipment have been investigated. Some reported life tests have proceeded without interruption for almost four years. Carbon-composition (grade 2) resistors under load fail by slow thermal degradation of the resistive material. Drift of value may also occur if unloaded resistors of this type are stored in a damp atmosphere. Vitreous-enamelled wire-wound resistors made with fine wire may fail during tropical exposure both unloaded and especially when lightly loaded with direct current. This is owing to electro-chemical corrosion taking place at faults in the vitreous coating. High-stability cracked-carbon (grade 1) resistors may fail rapidly under light d.c. load by electro-chemical action if moisture condensation occurs and the protective paint or varnish coating is inadequate.Tests for long-term resistor stability are critically discussed.

DOI:10.1049/pi-b-2.1960.0132

出版商:IEE    

年代:1960

数据来源: IET