DOI:10.1049/ji-3-1.1943.0002

出版商:IEE    

年代:1943

数据来源: IET

摘要:

The paper presents a survey and analysis of field intensity measurements obtained during the years 1937–1939, over the Post Office radio-telephone link between Guernsey and Chaldon, England, on wavelengths of 5 and 8 m. (frequencies 60 and 37.5 Mc./s.). The path between the stations was almost entirely over sea and about 85 miles in length, of which some 36 miles was outside the optical range. The data recorded have been analysed in such a way as to illustrate the general and detailed variations in received signal strength, and the manner in which these are dependent on various atmospheric conditions.The results of the analysis have shown that while the fading of the signals was similar in type on the two wavelengths, there was a difference in the secular variation of the amount of fading on 5 and 8 m. No diurnal or seasonal variation of signal intensity was noted, nor was there any definite diurnal variation in the amount of fading. The fading observed took various forms, ranging from a rapid type in which the changes occurred more or less periodically every three or four minutes, to a slow type of variation extending over one or more hours. The latter type was usually accompanied by a high level of signal intensity interrupted at long intervals by rapid and deep fading lasting from 10 to 30 minutes. The field strength records show a marked correlation between periods of negligible fading and the existence of low atmospheric pressure conditions generally, including lack of appreciable temperature inversion. The occurrence of fog and snow has a similar effect to that due to the prevalence of low pressure.A consideration of these results and of similar data obtained by other workers leads to the conclusion that abrupt changes in temperature and water vapour gradients in the atmosphere give rise to signal variations in good weather, while the absence of these discontinuities in bad weather allows of steadier signal conditions.

DOI:10.1049/ji-3-1.1943.0003

出版商:IEE    

年代:1943

数据来源: IET

摘要:

The paper describes the essential features of design and construction of field-strength measuring equipment for use at frequencies up to about 600 Mc/s, i.e. wavelengths down to about 50 cm. The equipment is of relatively narrow band-width (about 20 kc/s) and is primarily intended for the measurement of continuous-wave fields of the order of tens or hundreds of microvolts per metre. The paper is supplementary to a previous paper on the same subject and is intended to bring the information in the previous paper up to date in respect of recent practical and theoretical developments.An appendix to the paper briefly outlines the theory of the transference of received radio-frequency energy from an aerial to a diode detector or other load, by way of a closed tuned circuit.

DOI:10.1049/ji-3-1.1943.0008

出版商:IEE    

年代:1943

数据来源: IET

摘要:

The paper describes experiments made to determine the electrical properties of various ground surfaces from the reflection coefficient obtained for radiation incident normally on them. The subsoil on the sites investigated varied from wet clay to gravel; the corresponding values of dielectric constant ranged from about 5 to 60 and the conductivity values from less than 108up to not greater than 109e.s.u. The lowest values in each case refer to a site at which the soil had been dug out to a depth of 7 ft., and the new surface consisted of pure gravel. The results obtained for both electrical properties and reflection coefficient are in general agreement with previous experiments conducted at longer and shorter wavelengths by the same and other methods.

DOI:10.1049/ji-3-1.1943.0009

出版商:IEE    

年代:1943

数据来源: IET