摘要:

The B.B.C. Television Centre is the first television headquarters and programme production centre built by the B.B.C. and one of the few buildings in the world constructed expressly for television programme origination. The Centre is at present equipped for producing about twenty hours of programme per week from four production studios and their ancillary areas, and for maintaining continuity of the network programme as a whole. The Centre is principally intended for the production of live programmes but has considerable facilities for the production and reproduction of programmes in recorded form. When completed the Centre will have some ten or eleven studios and will be capable of originating and handling programmes for two programme chains. The Centre includes facilities for all phases of work concerned with programme origination, including recording and standards conversion. It is initially equipped for black-and-white operation on 405-line standards, but has been designed so as to be ready for conversion to the requirements of other television standards and for colour.Arising from the large power requirement of television production, the Television Centre also contains a large amount of heavy power equipment.

DOI:10.1049/pi-b-2.1962.0188

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The engineer's interest in thermo-electric phenomena has in the past been mainly confined to devices, based on the Seebeck effect, for the measurement of temperature and r.f. power and radiation by means of thermocouples or thermopiles constructed from metals. Even with the best combination of metals available the use of the Seebeck effect for generation is barely feasible, and the use of the Peltier effect for refrigeration is quite impracticable.The success of germanium and silicon in the production of transistors and junction rectifiers has encouraged the study of the mechanism of electrical and thermal transport in semiconductors. Thus, it has been possible to select potentially efficient thermo-electric alloys and compounds from the vast range of semiconductors available.In the case of bismuth telluride a high figure-of-merit material has been obtained which makes refrigeration of small volumes a practical proposition. A generator efficiency approaching 5% is possible with bismuth telluride in the case where the ideal efficiency would not exceed 25% with temperature limits of 300–400° K.Many people1elsewhere have recorded the search for thermo-electric materials and the optimization of their thermo-electric properties. The object here is to explain simply the basic principles of generators and cooling units in a quantitative manner. The salient features which emerge indicate the potentialities of bismuth telluride for the generation of power and heat pumping, in particular refrigeration of small volumes and local cooling.The paper is based on work carried out by the author on the engineering applications of bismuth telluride.

DOI:10.1049/pi-b-2.1962.0191

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The mechanical problems involved in ensuring that a disc-reproducing stylus follows with sufficient accuracy the path cut during the recording process are discussed. The modulated groove acts upon the spherical stylus as a moving plane inclined tox-,y- andz-axes, and forces are therefore generated in unwanted directions which can result in a form of distortion (translation distortion). The magnitudes of these forces and their influence on the effective path of the stylus are approximately analysed in terms of groove and pick-up parameters.Attention is drawn to the fundamental difference between the actions of the stylus in tracing lateral and vertical modulation, and to the conditions necessary for the maintenance of continuous two-point contact between stylus and groove. An approximate analysis is given from which a pick-up's ‘modulation capability’ may be assessed. The playing weight is of major importance in this connection, and the factors influencing the choice of an appropriate value are discussed, with reference to both single-channel lateral and 45/45 stereophonic records.Finally a pick-up designed in accordance with these principles is briefly described.

DOI:10.1049/pi-b-2.1962.0192

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-b-2.1962.0194

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Silicon controlled rectifiers may be used for the generation of high-power audio frequencies up to at least 10kc/s. The use of these components in the place of transistors can result in considerable savings in equipment size and weight. Also, by reducing the number of components used, an improvement in reliability should be realized.The generator described here employs a series self-quenching circuit instead of the better-known parallel inverter. A general analysis of the circuit is given, and expressions required for the design of a generator are derived. This theory is applied to a circuit required to deliver approximately 2kW into a near-resistive load at a frequency of 10kc/s. Results obtained from such a generator are given, and some practical difficulties encountered in the construction of the circuit are outlined.

DOI:10.1049/pi-b-2.1962.0195

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Receiving-type valves have been developed suitable for operation at supply voltages in the region of 20–50V and having workable mutual conductances of up to about 20 mA/V. The requisite electrode geometry is attained by the use of a new valve component known as a double grid.

DOI:10.1049/pi-b-2.1962.0196

出版商:IEE    

年代:1962

数据来源: IET

摘要:

It is shown that a Fourier expansion of the inverse of the barrier capacitance describes the potential noise performance of a semiconductor parametric diode better than the commonly used expansion of the capacitance itself. The Fourier coefficients are evaluated for point-contact and graded-junction diodes.Experiments carried out on diodes in two different amplifiers have given results in good agreement with the theoretical analysis over a wide range of pump power. Germanium, silicon and gallium-arsenide diodes all showed clearly defined pumping conditions for optimum noiseperformance.The theoretical analysis suggests a definition of a simple static figure of merit (an extension of Uhlir's cut-off frequency) which is sasily measurable at microwave frequencies. The noise performance expected from this figure of merit agrees well with the minimum noise temperatures measured for germanium and gallium-arsenide diodes in a degenerate amplifier at 2.4Gc/s. For silicon diodes the measured noise was higher than predicted by the simple theory, owing to the eerious influence of an anomalous reverse current.

DOI:10.1049/pi-b-2.1962.0197

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Microwave power division employing the field-controllable microwave permeability of ferrites has been used as the basis of current-controlled variable attenuators and switches. Three such devices are described:(a) A 4-port device in waveguide, with ferrite phase shift controlling power division between two ports of exit. Its operating range is 2.7-3.3 Gc/s.(b) A 3-port device, in waveguide or stripline, with a similar basis of control. However, its most suitable application is with a fixed field, as a circulator.(c) A cross-polarization waveguide device using a ferrite to control the rotation of polarization, thereby forming a reflective switch. It is simple and has a good bandwidth, but frequency control is difficult.The construction, mode of operation, and performance are given in each case.

DOI:10.1049/pi-b-2.1962.0198

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-b-2.1962.0199

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-b-2.1962.0200

出版商:IEE    

年代:1962

数据来源: IET