摘要:

The paper is concerned with the use of lamps in a non-linear bridge, operating as the “indicator” of a voltage stabilizer. The characteristics of various types of lamp are considered with regard to their suitability for this purpose, e.g. the effect of ambient temperature and vibration. Experimental and mathematical results are given for the response time of various lamps when used in this circuit. Methods of overcoming this delay by means of suitably designed capacitance-resistance networks are given, together with experimental results. The paper is restricted to the use of a d.c. supply for the bridge.

DOI:10.1049/ji-3-2.1946.0052

出版商:IEE    

年代:1946

数据来源: IET

摘要:

It is shown that the probability distribution of pulse distortion magnitudes in a multi-channel pulse-transmission system forms an important consideration in the design of such systems, and if properly taken into account may form the basis of considerable economies in design. An analysis of inter-channel interference distortion is given, and it is shown how the probability distribution may be determined for the type of system likely to be encountered in practice, i.e. with interference of equal amplitudes from two adjacent channels on each of two or more links in tandem. It is shown that on a typical multi-channel v.f. telegraph system with two links in tandem, only about one pulse in a thousand is distorted more than half the maximum amount, and only one in six hundred thousand more than three-quarters the maximum amount. In the case of a single-link multi-channel v.f. telephone dialling system, only about one in eighty thousand pulses is distorted more than half the maximum amount and only one in forty million more than three-quarters the maximum; on two links in tandem, only about one pulse in ten thousand is distorted more than one-quarter of the maximum amount, and only one in a million more than one-third of the maximum. It is quite evident, therefore, that the maximum distortion need not be the basis of design, but instead some smaller figure, say one-quarter to three-quarters of the maximum.

DOI:10.1049/ji-3-2.1946.0053

出版商:IEE    

年代:1946

数据来源: IET

摘要:

A method for the calculation of the field components of free electromagnetic oscillations in metal cavities of any shape is described with reference to Klystron resonators. Whereas in a previous paper a method for computing solutions of Laplace's equations was given, the present paper is concerned with the wave equation δφ + (ε2/c2)φ=0. Again, the differential equation is replaced by a system of difference equations, which in the case of free vibrations are homogeneous and soluble only for certain values of the parameterε2/c2, the proper values. A method for finding the lowest value ofε2/c2without solving a determinantal equation is described. The boundary of Klystron resonators contains sharp corners, often feather edges, which present a special problem. In order to obtain the necessary accuracy for the circuit parameters, with a reasonable amount of computation work, it is essential to take account of the analytic behaviour of the fields near sharp corners. This is done in a manner which is particularly well suited to the relaxation method of solution of the equations, and a great deal of computation work is thereby saved. Once the field components and the resonant frequency are found, the beam impedance and the damping constant are easily determined.

DOI:10.1049/ji-3-2.1946.0054

出版商:IEE    

年代:1946

数据来源: IET

摘要:

In this paper is calculated the radiation resistance of a circular loop of any radius and also its polar diagram of electric field at a large distance. It is shown that, according to the radius, the field can be zero in the equatorial plane or at any angle of elevation. It is shown that the “high-angle” radiation can be sensibly removed by using two concentric and coplanar loops having suitably chosen radii: but with this disposition the current must be supplied to both loops and it is impracticable to induce one current from the other. The “high-angle” radiation can also be much reduced by the use of two similar coaxial large loops in parallel planes, and this offers a disposition which may be useful in practice. The power gain of a stack ofNsimilar small loops is shown to be equal numerically to the gain of anN-member in-line array of electric doublets; and it can be shown that this is true whatever the radius of the loop, but one or more side lobes can be sensibly obliterated by suitable choice of this radius. Having regard to the difficulties of “feeding,” inherent in the construction of all aerial systems, it would seem that a pair of parallel large loops is one of the simplest systems for obtaining a horizontal electric field concentrated mainly in a zone of about ± 30° from the equator. The choice between two such loops and a stack of small loops depends very much on the wavelength to be used.

DOI:10.1049/ji-3-2.1946.0057

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper examines the effects of carrier frequency, size of reflecting obstacle, distance of reflecting obstacle from transmitter and from receiver, and degree of definition of the television picture, on the incidence of reflection troubles in television reception. The diffraction problem is treated by a simple mathematical approximation which has been previously used in optics.

DOI:10.1049/ji-3-2.1946.0059

出版商:IEE    

年代:1946

数据来源: IET

摘要:

A study is made of the mutual interference problems which arise when a number of stations transmitting c.w. signals and having the same frequency tolerance share a given frequency band. On the assumption that the transmitters are grouped into a number of channels spread over the frequency band, it is shown that, for a given receiver selectivity specified by its gate width, no practical advantage is gained by spacing the channel frequencies closer together than by a value which is about 75% of the nominal transmitter tolerance band-width, although (except over a limited region when the receiver gate is wider than the transmitter tolerance) a spacing equal to the nominal tolerance band-width should not be exceeded. For a given separation between channels it is demonstrated that, in general, the interference falls with reduction of the receiver gate-width.

DOI:10.1049/ji-3-2.1946.0060

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The term “communication receiver” is sufficiently vague to demand some measure of definition. The first Section of the paper therefore discusses briefly the historical background and the features and applications of the type of receiver which, to the best of the authors' knowledge, are generally accepted as being implied by this term.The second Section covers the mechanical considerations which apply to (and to some extent limit and define) the complete receiver.The third Section, in which it is hoped that the main interest of the paper will be found, discusses the electrical features of this type of receiver. From a brief review of overall circuit considerations, it passes to a discussion of specific characteristics, dealing in some detail with the extent to which theoretical limits of signal/noise ratio are achieved in representative designs. In addition to treating the factors limiting such fundamental characteristics as signal/noise ratio, selectivity, etc., this Section gives some attention to such ancillary features as electrical band-spread methods, listening-through facilities, etc.In the discussion of both the electrical and the mechanical features of these receivers, the object has been to give a critical survey of the nature of the design problems and the solutions adopted in typical receivers, rather than to cover detailed design information in connection with any particular feature.The paper concludes with Sections devoted respectively to current practice in supply-circuit arrangements and possible future tendencies.

DOI:10.1049/ji-3-2.1946.0064

出版商:IEE    

年代:1946

数据来源: IET