摘要:

The anode-current/grid-voltage characteristics of valves are determined with the help of diagrams and design charts based on Langmuir's data on the current flow in plane diodes with consideration of initial electron velocities, and on Oertel's and Herne's equations for the amplification factor. The theory is extended to multi-grid valves and to valves possessing a more complicated shape. Special attention is given to the “variable-mu effect,” which represents one of the limiting factors in practical valve construction. A simple expression describing this effcct is derived, and a chart of the “variable-mu constant,” α, is presented, in which space charge is taken into account. Measurements on specially made experimental valves and on several types of modern mass-produced valves confirm the treatment of the variable-mu effect and show that the methods outlined in the paper, forming a complete design system, allow the prediction of the static valve characteristic with good accuracy even in closely spaced modern valves. Finally, the influences of a change in control-grid wire diameter, of a statistical variation of control-grid pitch, and of cathode misalignment, are discussed.

DOI:10.1049/ji-3-2.1946.0023

出版商:IEE    

年代:1946

数据来源: IET

DOI:10.1049/ji-3-2.1946.0024

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The initial development of a method of extending the range or improving the coverage of v.h.f. communication systems of the type used for police services is described. The method is based on the simultaneous amplitude modulation of a number of carriers closely spaced in frequency. The frequency spacing between the carriers is so chosen that they lie within the band-width of the v.h.f. receiver, without producing audible interaction components of importance.Two-carrier schemes employing separate transmitters at the same site have been found to give improved coverage, while two- and three-carrier schemes using separate sites have been found to give greatly increased range.An unsuccessful attempt to achieve the same object with frequency-modulated (f.m.) transmitters using the same nominal carrier frequency is described. The difficulties of employing frequency modulation with common modulation are discussed and considered to be fundamental.Single-station v.h.f. schemes upon which the development of the multi-carrier scheme is based are briefly described.

DOI:10.1049/ji-3-2.1946.0025

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper opens with a general theoretical analysis of a wave-guide junction ofnmembers in terms of an equivalent transmission line system. This is then applied to the particular case of a right-angled junction in a guide of rectangular section excited in the H01mode. The behaviour is expressed in terms of six parameters, the values of which have been calculated over a range of wavelengths around 10 cm and determined experimentally at four points within this range. A description of the experimental technique employed is given, and an assessment made of the order of accuracy attained in the measurements.

DOI:10.1049/ji-3-2.1946.0028

出版商:IEE    

年代:1946

数据来源: IET

DOI:10.1049/ji-3-2.1946.0029

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper describes the various types of transmission lines in use at transmitting stations of the British Broadcasting Corporation, their impedance, attenuation and power-carrying characteristics, together with results of various tests, general details of construction, and methods of matching the load to the transmission line. The major part of the work described was carried out before the end of 1943.The paper is written primarily from the point of view of the engineer engaged on design and practical work in the field. Data are included enabling the most suitable transmission line for any practical purpose to be designed. The range of frequencies considered is from 0.2 to 25 Mc/s; of this range those up to 2 Mc/s are considered as medium waves and those from 2 Mc/s to 25 Mc/s as short waves.

DOI:10.1049/ji-3-2.1946.0030

出版商:IEE    

年代:1946

数据来源: IET

摘要:

Espley has described a convenient method for the numerical calculation of the harmonic output of a circuit containing a non-linear element, such as a valve, the characteristic of which is given for equally-spaced values of the input voltage. A difference table was formed from these data; the terms of the central line of this table were then multiplied by the values of certain functions dependent on the type of the harmonic wanted and the amplitude of the input, and finally the products were added.The present paper shows that a similar procedure can be applied to the determination of intermodulation products of two input frequencies. The factors which now appear as multipliers of the difference terms can be obtained from a multiplication table of such Espley functions. The procedure is summarized in Section 5. The derivation of the result makes use of the operator properties of Sheppard's symbols δ and μ.

DOI:10.1049/ji-3-2.1946.0033

出版商:IEE    

年代:1946

数据来源: IET