摘要:

A hot electron, thin-film, cold-cathode device is described which has an emission efficiency much higher than previously reported for similar cathodes. Measurements of the emission current and distributionat various voltages indicate the importance of a coherent scattering process, which if not considered in the design of the cathode will severely limit the emission efficiency. The important conditions for a more efficient cold cathode are specified and discussed with respect to previous cold cathodes designed to surmount other loss processes which are shown to be of secondary importance to coherent scattering

DOI:10.1049/ree.1967.0050

出版商:IERE    

年代:1967

数据来源: IET

摘要:

The trend towards automation in hydrographic survey and oceanography calls for automatic read-out of depth from an echo sounder. A system of signal selection is described which includes an automatic time gate synchronized with the sea-bed echo. Automatic gain control is also used to maintain optimum amplitude discrimination throughout varying conditions. A recording echo sounder forms an integral part of the apparatus and is used to check the signal selection by identification of the selected echo

DOI:10.1049/ree.1967.0051

出版商:IERE    

年代:1967

数据来源: IET

摘要:

In geological survey, the simultaneous operation of these three equipments on one vessel can have considerable merit.The sideways-looking sonar (known as the ‘Transit Sonar’) has a range of 600 yd and gives an approximately true plan of the sea bed on dry paper 6 in. wide when the ship moves at 5.7 (or 2.85) knots over the ground. The record produced by the ‘Transit Sonar’ may be readily correlated with the corresponding Admiralty chart.The Strata Recorder operates at 9.6 kHz, at which frequency the acoustic waves penetrate the sea bed. Good resolution is obtained on dry paper due to the use of short pulses and relatively narrow acoustic beams. A special circuit gives time-varied gain, triggered by the sea-bed echo, to employ the dynamic range of the paper in the optimum way.The precision echo sounder records on dry paper 10 in. wide. The capacitor- discharge transmissions at 32 kHz are switched by a silicon controlled rectifier.The position of the survey vessel at any instant may be obtained from a radio position-fixing system or by visual fixes.Some examples of interesting sea-bed features are portrayed in the figures, each a combination of the simultaneous records correlated in time on the same scale, together with their geological and topographical interpretations. Sand waves of wavelength 13 ft (4 m) and as little as 9 in. (23 cm) high have been resolved quite readily

DOI:10.1049/ree.1967.0052

出版商:IERE    

年代:1967

数据来源: IET

摘要:

The paper outlines the growth of television wired broadcasting in the United Kingdom. After considering the fundamental problems involved in the use of video h.f. and v.h.f. frequencies, it describes the way these problems have been solved for h.f. and v.h.f. systems. Brief descriptions of practical h.f. and v.h.f. systems are given and this is followed by a comparison of the relative costs of these two systems. It is concluded that, if a large section of a town is to be wired, the h.f. system is the most economical overall. Blocks of flats in a town that has no h.f. distribution system can most economically be dealt with by a v.h.f.system. Various borderline cases in between the two extremes are dealt with. The precautions necessary for distributing colour television are mentioned, and suggestions made for appropriate tolerances to which wired broadcasting operators should work. Finally, the author gives someindication of the way in which wired broadcasting may develop in the future

DOI:10.1049/ree.1967.0053

出版商:IERE    

年代:1967

数据来源: IET

摘要:

A simple system designed to demonstrate the possibility of transmission of information over an optical path, using a microwave sub-carrier, is described. It is shown that a satisfactory signal/noise ratio can easily be obtained under laboratory conditions, and the practical limitations of such a system are briefly outlined.

DOI:10.1049/ree.1967.0054

出版商:IERE    

年代:1967

数据来源: IET

摘要:

The design of a new instrument for measuring the velocity of sound in sea water with improved accuracy is described. A particular feature of the instrument is that it may be towed through the water without causing appreciable errors

DOI:10.1049/ree.1967.0055

出版商:IERE    

年代:1967

数据来源: IET

摘要:

An N.T.S.C.-type colour-television signal can be converted into a driving signal for a one-gun display tube without full demodulation of the sub-carrier signal. With the adoption of the PAL system for colourtelevisionbroadcasts in many countries of Europe the question arises whether similar methods can be devised for transcoding a PAL signal into a driving signal for dot-sequential display systems. The analysis of this problem leads to the conclusion that a slight modification of the PALswitching axis or a slight modification of the composition of the luminance signal is desirable. Practical conversion methods are discussed and some experiments are described. Employment of the standard PAL signal instead of the modified signal introduces small errors which are hardly observable. It is concluded that conversion of the PAL chrominance signal into a driving signal for one-gun display systems is well within the possibilities and does not require complex circuitry

DOI:10.1049/ree.1967.0056

出版商:IERE    

年代:1967

数据来源: IET