摘要:

Following a brief history of the B.B.C.'s external services, the paper outlines the reasons for the present form of centralization at Bush House. The method of programme building is considered and the studio and recording facilities are detailed. The equipment in the control room and other technical areas is described. Installation problems are discussed and the paper concludes with some notes on practical experience with the installation in service.

DOI:10.1049/pi-b-2.1960.0155

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper describes the work done by the Cie Française de Télévision (C.F.T.) on the Henri de France system of colour television. First it defines the objectives of the team of research workers who have carried out this development. It then stresses the fundamental aspects and the special features of the system and describes the encoding and decoding units. Finally, it gives the practical results and theoretical aspects on the ease of transmission of the coded signals.

DOI:10.1049/pi-b-2.1960.0158

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Using a general method of mode-transducer design previously described, a simple H10-to-H20mode transducer was constructed. The reflection coefficient is calculated, and it is shown that for a transducer a few wavelengths in length the reflections are insignificant. The power transferred to the spurious modes was measured by the resonance method on two experimental models, 2 and 8 guide-wavelengths long. The longer transducer transforms 92% of the power into the required mode. The power in unwanted modes can be greatly reduced by the use of a simple absorptive mode filter.

DOI:10.1049/pi-b-2.1960.0162

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Much work has already been done towards establishing techniques for tapering the cross-section of waveguides without introducing significant reflections when waves are propagated along them. In the present paper the problem is approached from the aspect of maintaining a completely undisturbed field pattern outside the guide whatever its cross-section, so that the wave impedance remains constant. Examples are given illustrating how this result may, in principle, be achieved both for the hollow metal guides of rectangular and circular cross-section and for single-wire transmission lines. On the basis proposed it is shown that the surface impedance of the guide must always have a resistive component which has nothing to do with losses but is dependent solely upon the angle of the taper and represents energy crossing the interface from the field on one side to the field on the other.

DOI:10.1049/pi-b-2.1960.0163

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The difficulties of the usual cavity-resonator methods of measuring permittivity are discussed, and details are given of a new method which eliminates most of these at the expense of increasing the computation required to interpret the results. The theory of the new method is described in full, and typical examples of experimental results obtained by its use are given.

DOI:10.1049/pi-b-2.1960.0164

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper gives an account of scatter-propagation measurements made at S- and X-band during the period May, 1957 to May, 1959. The work at S-band continued throughout the whole of this time, while the X-band measurements were made during the period of year from June, 1958 to May, 1959.The S-band transmitter, using a 3.480 Gc/s c.w. magnetron with a power output of 500 watts, was established at Start Point in Devon. Receiving terminals were set up at Wembley, Middlesex, and Witnesham, Suffolk, at distances of 173 and 247 statute miles, respectively, from the transmitter, the former being maintained in operation throughout the whole of the experimental period and the latter for period of nine months from September, 1957 to June, 1958. Diurnal and seasonal variations in the median level of the received signal are discussed and a comparison is made of measurements taken simultaneously at Wembley and Witnesham. The distribution of the S-band fading rate as a function of level is studied and a limited amount of work concerned with the distribution of the duration of fades below a given level and the power spectrum of the detected signal is described.The transmission path for the X-band system, which used a pulsed magnetron at a frequency of 9.640 Gc/s, also lies between Start Point and Wembley; the pulse length was 2 microsec and the pulse-repetition frequency 500c/s, the peak power in the pulses being 180kW. The X- and S-band links were operated together whenever possible, and a comparison is made of the median level and fading rate of the signals received simultaneously at the two frequencies over the same propagation path. In addition, a series of measurements to investigate the aerial coupling loss of the X-band system are described.

DOI:10.1049/pi-b-2.1960.0165

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The reflectors are deep paraboloids having axially oriented dipoles at the foci. Odd-function aperture distributions and radiation patterns are derived by approximate methods and are compared with an experimental polar diagram. In spite of a null along the axis, strong coupling at short range is observed between two aligned aerials. This is associated with a coupling diagram of abnormal directivity, which may be explained by a principle of field-fitting between the incident field and the normal aperture distribution. A reduction of Maxwell's equations in paraboloidal co-ordinates to Bessel's equation is appended.

DOI:10.1049/pi-b-2.1960.0166

出版商:IEE    

年代:1960

数据来源: IET

DOI:10.1049/pi-b-2.1960.0167

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Electrical reflection on telephone circuits having appreciable times of propagation can cause delayed sidetone effects subjectively similar to echo. The variations in subjects' tolerance of this echo is examined experimentally as a function of echo attenuation and delay. The dispersion of tolerance between subjects is also considered, and this yields information in a form suitable for planning telephone networks so that echo will not cause excessive inconvenience.

DOI:10.1049/pi-b-2.1960.0168

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper reviews the industrial, biological and medical aspects of microwave radiation. The special methods of study of the properties of organic and biological materials are first discussed. The industrial applications of microwave heating processes are described and the effect of microwave radiation on biological tissues and living animals is examined. The operational hazards attaching to personnel in the neighbourhood of high-power equipment are pointed out and suggestions offered as to how these can be minimized. The paper concludes with a bibliography.

DOI:10.1049/pi-b-2.1960.0169

出版商:IEE    

年代:1960

数据来源: IET