DOI:10.1049/ji-3-1.1941.0002

出版商:IEE    

年代:1941

数据来源: IET

摘要:

It is shown in the paper that the chief factor limiting the application of the radiation method using horizontally polarized waves for the calibration of field-strength measuring sets to short radio waves is the difficulty encountered on longer wavelengths in preventing the radiation and reception of vertically polarized waves. This effect becomes more and more important with increase in wavelength and sets a practical upper wavelength limit to the radiation method of calibration at about 30 m. (frequency 10 Mc./s.).In order to assist in such calibrations, curves are given in the paper for the rapid computation at any wavelength up to 30 m. of the field-strength at a distance of 100 m. from any radiator of horizontally polarized waves.With the view of verifying these conclusions experimentally, a comparison was made of the radiation method and a laboratory method of calibrating a field-strength measuring set. The sensitivity of this measuring set, determined by the radiation method, was 4.8 μV per metre and 2.6 μV per metre at wavelengths of 8 m. and 20 m. (frequencies 37.5 and 15 Mc./s.) respectively. The corresponding sensitivities, found experimentally by the laboratory method, were 5.0 μV per metre and 2.5 μV per metre. The close agreement between the results obtained with the radiation and laboratory methods indicates that either may be used over the wave-band and investigated.

DOI:10.1049/ji-3-1.1941.0003

出版商:IEE    

年代:1941

数据来源: IET

摘要:

It is shown that a field-strength measuring set having a symmetrical closed-loop aerial coupled inductively through an electric screen to an unsymmetrical amplifier, can conveniently be calibrated in terms of a measured current passed through the coupling coil. The calibration so determined was found to be in satisfactory agreement with standard-field calibrations at wavelengths of 8 m. and 20 m.

DOI:10.1049/ji-3-1.1941.0004

出版商:IEE    

年代:1941

数据来源: IET

摘要:

The nature of internal discharges in actual insulation and also on model circuits exposed to alternating voltages is studied by means of a special oscillographic bridge equipment. A theory of the occurrence of these discharges is developed and is shown to agree with the oscillographic observations and to give correctly the effect of varying different conditions. Examples of the different kinds of phenomena which may occur are given, illustrating the qualitative and, in some instances, quantitative application of the theory. It is shown that, with alternating voltages, discharges, once initiated, can continue at a much lower voltage than that which corresponds to the critical or ignition stress in the dielectric.

DOI:10.1049/ji-3-1.1941.0005

出版商:IEE    

年代:1941

数据来源: IET

摘要:

This paper describes theoretical and experimental work on the dielectric loss of films of insulating liquids so thin that the motion of ions under an alternating field is limited by the boundaries of the film. Films of this thickness normally occur in porous, impregnated insulation, and lead to a dielectric loss angle which varies greatly with the applied stress.In Section (2) of the paper approximate equations are established for the dielectric loss of such a thin film, as a function of the applied stress. It is also shown that measurements on thin films afford a new method of deducing the ionic concentration, radius and mobility.In Section (3) experimental work is described upon films of an insulating liquid (trichlorbenzene)as thin as 0 03 mm. Such films show a large variation of loss angle with stress, agreeing closely with the predicted variation, except in one or two cases where the nature of the ionized impurities appeared to be abnormal. Values of ionic radius and mobility deduced from the equations of Section (2) check well with values known from electrolytic measurements. It is concluded that experiment confirms the theory put forward, except at very low stresses, where assumptions made in the theory are no longer valid.In Section (4) the equations of Section (2) are applied to an actual impregnated dielectric with non-uniform pore sizes, and it is shown that provided account is taken of the distribution of pore sizes, the theory will account satisfactorily for the variation with stress of the loss angle of condensers impregnated with liquids containing ionized impurities. Values of ionic radius and mobility deduced from these results are also of the right order of magnitude, but are less accurate than those obtained in Section (3), owing to lack of knowledge of the exact distribution of pore sizes.Detailed conclusions are given at the end of the paper.

DOI:10.1049/ji-3-1.1941.0006

出版商:IEE    

年代:1941

数据来源: IET

摘要:

The principles of interference measurement are examined in relation to the operation at ultra-high frequencies of frequency-changing circuits. A distinction is shown to exist between the application of the signal and the local oscillation to the same electrode and their application to separate electrodes of the frequency-changing valve. The design and performance of anapparatus is described which embodies the principles deduced.

DOI:10.1049/ji-3-1.1941.0007

出版商:IEE    

年代:1941

数据来源: IET

摘要:

The paper forms the sequel to an earlier one in which the radiation resistance of the cone and the cylinder were briefly considered. In the present investigation formulae are developed for calculating the power radiated by cylinders, cones and spheres having any assigned distribution of charge. No attempt is made upon the more complex problem of determining the charge distribution appropriate to these geometrical figures.As a preliminary, methods are given for calculating the component of field which is in phase with the current, for the systems of charge and current distribution considered later in the paper.The process of calculating successive terms in the series requires considerable patience and experience. It is hoped that the labour which has been expended here will be of service as a basis for more practical developments in the future. The formulae are presented in a way suitable for numerical computation. Little computation has in fact been performed, for lack of reliable information about the charge distribution appropriate to cones and thick cylinders. When such information is forthcoming then this paper should be very helpful for calculating the radiation characteristics. The various steps involved in the derivation of the formulae have been given in full because it was realized that they could, if required, be extended so as to apply to any surface of revolution.In short, the present work will be found to be directly applicable to many practical problems, when these problems have been defined more specifically: it is not worth while to use them now on fanciful specifications.The analysis contains only one assumption, namely that there is no phase difference between the elements of charge situated on different points of a radiating surface.In an Appendix the author gives an interpretation of the parametersLandCin the equation for the long line, and calculates the self-inductance of a hollow sphere.

DOI:10.1049/ji-3-1.1941.0008

出版商:IEE    

年代:1941

数据来源: IET