摘要:

A first-order theory of velocity-modulation oscillators is developed, leading to an expression for their efficiency which takes into account the resonator losses and the corrections due to beam damping. The bunching properties of various field distributions are investigated and formulae are given which enable them to be calculated in all cases on the assumption that space-charge effects may be neglected.

DOI:10.1049/ji-3-2.1947.0055

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The paper is concerned with the electric strength of air when stressed by alternating fields of wavelengths 10.7 and 3.06 cm (2800 and 9800 Mc/s, respectively). The spark gaps used for the experiments consisted of either coaxial-line or waveguide transmission systems, and the electric stress was applied in the form of impulses lasting for one microsecond and repeated 400 times per second. Stress determinations were made by the relationship, afforded by Poynting's vector, between stress and power conveyed along the system. The method of measurement is described. The behaviour of the spark gap is shown to be dependent on the irradiation conditions of the gap, but a minimum value of breakdown stress exists which is independent of irradiation. In all cases this minimum stress was compared at atmospheric pressure with the continuous direct breakdown stress of the gap, and was found to be approximately 70% of the direct value, irrespective of the gap length and frequency. Differences with respect to gas pressure are shown to exist between the microwave behaviour of such gaps and the corresponding direct-voltage behaviour.

DOI:10.1049/ji-3-2.1947.0056

出版商:IEE    

年代:1947

数据来源: IET

摘要:

Curves and formulae are given for the calculation of field strength at any height and distance from the transmitter for the case of horizontally-polarized electromagnetic waves over a curved Earth or sea. Sufficiently within the optical range the field is calculated by ray theory, and appropriate quantities for calculating path difference and divergence of reflected ray are given. At exact optical cut-off the field is calculated by an approximate method believed to be accurate to 1 db, and is presented in the form of contour curves of equal field strength on a plot of receiver height against transmitter height. Sufficiently far beyond optical cut-off the field is given by the first term in the diffraction-formula series. To calculate the field near optical cut-off, a curve should be drawn of field against distance for the heights of transmitter and receiver in question which joins smoothly the ray-theory curve for inside optical range to the one-term curve for the region beyond and passes through the point determined for the actual cut-off distance. The case of vertically polarized waves is also briefly discussed, and curves and formulae are given for the reflection coefficient (including surface-wave term) where ray theory is applicable, and for one term of the diffraction formula in the region well beyond optical cut-off.

DOI:10.1049/ji-3-2.1947.0057

出版商:IEE    

年代:1947

数据来源: IET

摘要:

A survey of finishes and methods of protection for transformers and chokes used in communication equipment during the war shows that they do not withstand the climatic conditions experienced in different parts of the world. The design of hermetically sealed metal containers and the assembly and sealing of the whole transformer unit is described in considerable detail. This process is developed to cover the sealing of both existing and new transformers.The relative merits of a number of filling media are discussed and practical details of filling with bitumen under pressure are given. X-ray photographs show how difficult it is to obtain satisfactory results with this method of filling. Air-filling is described and it is seen to hold definite advantages, both in ease of production and in the performance of the component, over the original method of bitumen-filling under pressure. Results of tests on unsealed, sealed and bitumen-filled and sealed and air-filled transformers confirm the suitability of the hermetically sealed and air-filled transformer for use in almost every part of the world, both on land and in aircraft.

DOI:10.1049/ji-3-2.1947.0065

出版商:IEE    

年代:1947

数据来源: IET