摘要:

The paper describes a computer program written to predict the effective service area of a transmitter in a v.h.f. mobile radio network. The computed results enable field-strength contours to be deduced, and hence provide more useful information than is possible by reference to standard statistical curves. The transmitter siting can be changed, and the field-strength contours recalculated, without the preparation of new geographical data. As a consequence, the efficiencies of a selection of possible transmitter sitings can be readily compared. The accuracy of the program is verified by comparing the computed results with field-strength measurements on a mobile radio installation operating at 86.2 MHz.

DOI:10.1049/piee.1969.0270

出版商:IEE    

年代:1969

数据来源: IET

摘要:

The first application of satellites for transmitting television to community antennas or for direct broadcasting to the public is likely to be to cover large areas with a single programme. At a later stage, however, it may be concluded that satellites could provide a service similar to that of the existing terrestrial systems, i.e. broadcasting to a large number of small contiguous areas with separate programmes. This presents problems associated with efficient use of the frequency bands which may be available and of the geostationary orbit. The effects of the parameters of the frequency-modulation method assumed, including the interference protection ratios, and of the antenna radiation patterns on these factors, are examined in some detail. From these considerations, an idealised model has been used to obtain generalised expressions, assuming a geometrical arrangement of the coverage areas. Where applicable, these have been used to determine the powers, bandwidths and orbital separations of the satellites serving a typical area such as Europe. It is shown that, for domestic reception via community antennas, four programmes could be provided to each of 30 countries, using eight satellites in 20° of orbital are. A bandwidth allocation of 400MHz at a frequency in the region of 12GHz has been assumed. Direct reception at domestic receivers would require greater satellite transmitter power than community reception, and the orbital are required would be approximately 35°.

DOI:10.1049/piee.1969.0271

出版商:IEE    

年代:1969

数据来源: IET

摘要:

This paper sets out a statistical analysis of the errors of position inherent in any position-finding system which utilises a number of ‘position-fixing planes’ and takes the point of maximum likelihood as the required position in 3-dimensional space. Formulas are given for the mean-square errors associated with the co-ordinates of position and also the covariances of these errors. A simple example is used to illustrate the use of the mean-square-error information, and expressions which give the co-ordinates of the maximum-likelihood point are derived for general application.

DOI:10.1049/piee.1969.0272

出版商:IEE    

年代:1969

数据来源: IET

摘要:

A consideration of the field distribution and the characteristics of an H guide, with the dielectric bar sub-divided into an arbitrary number of dielectric strips separated by air layers, is presented. Low-loss wave modes with the magnetic-field components parallel to the boundary surfaces are analysed. Approximate thin-layer equations which indicate methods leading to considerable improvements of the attenuation of the H guide are derived.

DOI:10.1049/piee.1969.0273

出版商:IEE    

年代:1969

数据来源: IET

摘要:

A state-space approach is used to derive an exact closed-form solution for both the transient and steady-state response of a general resonant transfer network. The usual assumption that the ratio of the switch closure time τ to the switching periodT, i.e. τ/T, approaches zero is removed in the analysis. The analysis also gives the time-varying network function of the resonant transfer network in closed form and in Fourier series which in turn yields frequency spectra of the output of the resonant transfer network. The approach is simple and suitable for computer simulation and experiment.

DOI:10.1049/piee.1969.0274

出版商:IEE    

年代:1969

数据来源: IET

摘要:

The paper describes the design and analysis of nonisotropic coupled-line couplers capable of measuring fast-risetime pulses travelling on matched transmission lines which are sited at high potentials. The general analysis which is given can be applied to other situations, and the derived theory is in accordance with the experimental results.

DOI:10.1049/piee.1969.0275

出版商:IEE    

年代:1969

数据来源: IET

摘要:

A general analysis is made of symmetrical multiended pilot-wire circuits terminated by impedances in parallel with the current sources. The fundamental-frequency-transmission characteristics of the pilot circuits are accounted for, and compensation for pilot phase shift is applied by a suitable choice of parallel impedance. A range of alternative amplitude-comparator relay characteristics is presented graphically on the basis of the complex ratio of the relaying current at any relay location to the phasor sum of relaying currents at the remaining terminations. A method is described by which the insertion of a simple network at the electrical centre of a system of symmetrical pilot circuits permits the application to multiterminal lines of schemes of protection requiring the correct termination of the pilot circuit in its characteristic impedance.

DOI:10.1049/piee.1969.0276

出版商:IEE    

年代:1969

数据来源: IET

摘要:

The paper forms a broad survey and appraisal of progress in the public distribution of electricity in Great Britain since the industry was nationalised in 1948. A statistical analysis of the principal growth features including sales, finance and persons employed is presented. Some assessment of the progress made and the present state of development is derived from international comparisons, by considering the relative growth of public supply and private generation, and by comparing the production and use of electrical energy with other fuels, i.e. coal, gas and oil. The comparative performance of individual UK area boards is assessed on selected criteria. The statistics are presented in diagrammatic form for each of the two decades since 1948 to give some indication of trends. The authors describe the UK electricity-supply organisation, with brief references to the negotiating and consultative machinery. Changes in the pattern of area-board administration are noted, with particular reference to the evolution of district management units. The paper also deals with technical changes and progress. Reference is made to the standardisation of systems and of the underlying principles and practice of system planning, and some of the more important changes in design of distribution switchgear, transformers, cables, overhead lines and metering equipment. Improvements in constructional techniques and in operation and maintenance of the systems are also noted. A Section on research and development traces the expansion of these activities, and lists a few of the more important projects undertaken.

DOI:10.1049/piee.1969.0277

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Calculations of the external thermal resistance of power cables installed in free air have so far been based on the heat-emission coefficienth, introduced by Whitehead and Hutchings in the form of empirical curves derived from experimental work. This paper gives new formulas forhfor the most important cases of cables installed in air.

DOI:10.1049/piee.1969.0280

出版商:IEE    

年代:1969

数据来源: IET

摘要:

In this paper, a theoretical formulation of a method of multiconductor transient analysis is developed. The method combines the use of the modified Fourier transform and the steady-state theory of natural modes. The virtues of this particular formulation are that the frequency dependence of parameters can be taken into account irrespective of the complexity of the expressions defining their steady-state values. The paper discusses the problem of the first pole to close when a power line is being energised from a source of infinite capacity. The argument is further extended to cover simultaneous pole closure of a circuit breaker. The mathematical representation of the source-side network is covered and two alternative methods of simulation of a multiconductor-source infeed are presented. Both methods are shown to retain the distributed-parameter nature of a source infeed, or a group of such infeeds, while achieving a reduction in the computation time that would otherwise be required to meet the needs of a fairly accurate form of representation. The numerical results of a series of digital-computer studies are presented. These illustrate various cases of practical important and highlight specific aspects of the behaviour of multiconductor systems.

DOI:10.1049/piee.1969.0281

出版商:IEE    

年代:1969

数据来源: IET