DOI:10.1049/pi-b-1.1957.0105

出版商:IEE    

年代:1957

数据来源: IET

DOI:10.1049/pi-b-1.1957.0107

出版商:IEE    

年代:1957

数据来源: IET

DOI:10.1049/pi-b-1.1957.0108

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The paper relates in brief the development of the control apparatus by the author for the Denny-Brown type of ship stabilizer from the initial ON-OFF control, to the present proportional control using roll and roll-velocity functions. The use of roll acceleration and a feedback control are also discussed.Predictions of the performance of a stabilizer by step-by-step and analogue methods are given, the functioning of the analogue computer is described and examples of results are included.Some practical results from sea experience and a brief account of the stabilizing demonstration given during the lecture also appear.The paper is complementary to one being presented before The Institution of Naval Architects, which deals more with the ship aspect of the subject.

DOI:10.1049/pi-b-1.1957.0109

出版商:IEE    

年代:1957

数据来源: IET

摘要:

An end-fire aerial, such as a Yagi or a dielectric-rod aerial, can be regarded as a structure which supports the dipole type of surface wave. Radiation occurs at the end of the aerial, the radiation pattern being determined by the transverse field distribution of the surface wave. It is shown that this leads to a simple relation between the beam width of the pattern and the ratio of the wavelength of the surface wave to that in free space. Further, this approach shows that the beam width tends to a non-zero value as the aerial length increases, in contrast with previous theories which predict that it decreases to zero with increasing length. In applying the theory to practical aerials, allowance must be made for the radiation which also occurs from the end of the aerial at which the surface wave is excited. Theoretical and experimental patterns for several end-fire aerials are compared, and it is shown that good agreement can be obtained.

DOI:10.1049/pi-b-1.1957.0110

出版商:IEE    

年代:1957

数据来源: IET

摘要:

From simple waveguide theory it is shown that the characteristic wave impedance of air-filled (or evacuated) and dielectric-filled waveguides of equal cross-section propagating E-modes can be matched for any free-space wavelength and relative permittivity of the dielectric. For low-permittivity dielectrics, reflectionless transmission may be obtained for a bandwidth of 20%. It is possible to design a waveguide window on these lines, the thickness of which—unlike that of the resonant-iris window—is not critical. The simplicity of the structure appears suitable for high-power microwave valves. A universal design-chart is derived from which the window diameter for the matched condition may be read off directly for any free-space wavelength and relative permittivity of the dielectric. A window design with broadband mode-transformers is described.

DOI:10.1049/pi-b-1.1957.0111

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The rapid component of the variation of signal strength from distant radio transmitters operating in the 6–18 Mc/s frequency band has been examined experimentally, and the results of the measurements are compared with various statistical laws which have been suggested from theoretical considerations. The rapid component of fading is found to agree closely with a Rayleigh distribution. A characteristic time-constant for the rapid fading is suggested and its value determined for a number of distant stations.Measurements have also been made of the correlation between signal strength variations in two spaced aerials and in two aerials at the same place but set at right angles. From these results a comparison of space and polarization, diversity is made. It is concluded that both systems could, on average, give equal performance. The two diversity systems were also compared in operation on a telegraph circuit between Barbados and England, the number of telegraphic distortions being counted in each aerial in turn. There was no significant difference between the two systems.By combining the fading-law results and the diversity-correlation results, the improvement due to diversity may be expressed in terms of an equivalent power gain; the gain is higher on communication circuits which are initially good than on those which are poor.

DOI:10.1049/pi-b-1.1957.0112

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The problem of distortion of frequency-modulated waves by 4-terminal linear passive networks has become of increasing importance with the development of multi-channel f.m. communication systems. The paper surveys the somewhat confusing historical background of this subject and after discussion of some essential basic concepts presents a detailed analysis of the problem of small-order distortion. An attempt has been made, using the work of Medhurst,1to present the results in a form suitable for computer programming.Special attention is given to networks which satisfy the minimum-phase condition, because thereby distortion becomes expressible in terms of the amplitude response alone. The results show in a visual yet quantitative manner the error involved in the use of the quasistationary solution.

DOI:10.1049/pi-b-1.1957.0113

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The cathode material transfer under the action of the ‘normal arc’ has been measured for a number of elements and alloys. In all cases auxiliary circuits were used to record the accumulative arc duration and the voltage/current characteristics of the arc, from which the total arc energy as well as the total charge passed in the arc could be accurately calculated. Within the experimental errors the material transfer from the cathode was found to be directly proportional to the total charge passed in the arc—a relationship first proposed by R. Holm. It is shown that, for most practical purposes, the cathode ‘normal arc’ transfer can be calculated with a reasonable accuracy according to the formula given by Llewellyn Jones.

DOI:10.1049/pi-b-1.1957.0114

出版商:IEE    

年代:1957

数据来源: IET

DOI:10.1049/pi-b-1.1957.0115

出版商:IEE    

年代:1957

数据来源: IET