摘要:

The paper commences by very briefly reviewing the causes and characteristics of travelling waves on transmission lines. It is pointed out that these transients can be represented mathematically by a combination of two or more exponential functions, and four typical wave-shapes are selected and employed throughout the paper for illustrative purposes.A general operational impedance equation, involving the Heaviside operatorpis then given. The particular operar tional equations of the circuits dealt with in the paper can be immediately deduced from this general one; and these in turn can be solved directly by means of further general solutions.Various circuits connected to transmission lines are then discussed, their practical applications are pointed out, and (by means of the general solutions) equations are given which show their response to any incident travelling wave. These equations are then plotted and examined for specific values of the circuit constants, and for the cases in which the travelling waves are given by the four typical shapes chosen earlier in the paper.Finally, a series of high-speed cathode-ray oscillograms is reproduced which bear interesting comparison with the mathematical results obtained and check many of the theoretical premises.

DOI:10.1049/jiee-1.1934.0070

出版商:IEE    

年代:1934

数据来源: IET

摘要:

Following an Introduction reviewing the essential requirements of a high-speed cathode-ray oscillograph for the recording of short-time transients, consideration is devoted to the design and construction of an instrument of this description adapted to both internal electron-blackening and to external light-blackening photography. The problems discussed include the construction of a cold-cathode discharge tube, the disposition of deflection plates, the operation of the time-sweep and beam-trap circuits, and the methods of synchronizing these with the transient under examination; this last leading to questions of voltage-division and delay necessary for synchronization.

DOI:10.1049/jiee-1.1934.0071

出版商:IEE    

年代:1934

数据来源: IET

摘要:

The engineer, faced with the problem of designing beam arrays for transmission and reception purposes, should satisfy himself that his proposals are technically and economically sound. He thus requires to know the anticipated performance and cost of each section of complete array systems, to enable him to arrange an equable balance between gain in distant field strength and capital outlay needed to obtain this gain. The factors concerned in the solution of the problem are:-(1) the angle of elevation of the axis of the main lobe of radiation of the beam to give the highest gain in field;(2) the economical design, fabrication, and erection, of structures to support the array;(3) the most economical type of feeders and transmission lines to use, having regard to the energy losses and pick-up of the lines.These three factors are investigated in the paper, and, from the results of the investigation, deductions are drawn regarding the gain of a horizontal type of array composed of numbers of half-wave radiators grouped in various ways. It is shown that the cost of array systems increases rapidly not only with wavelength but also with the angle to the vertical at which the radio energy is required to be projected or received.

DOI:10.1049/jiee-1.1934.0082

出版商:IEE    

年代:1934

数据来源: IET

摘要:

The paper describes a method of measuring the angle of incidence of downcoming short waves in which the phase difference between the e.m.f.'s in two similar horizontal aerials at the same height above the ground is determined from the trace on the fluorescent screen of a cathode-ray oscillograph, to the deflecting plates of which are applied the two aerial e.m.f.'s after similar amplification by receivers of the type developed at the Radio Research Station for cathode-ray direction-finding.As the main object in view is the measurement of the downcoming angles of 20-metre waves from Lawrenceville, New York, working on the radio-telephone circuit to London, the aerial system used is designed for most efficient operation on this wavelength: but it is found quite practicable to use it on wavelengths up to 64 metres and also for signals from directions not widely divergent from that of the straight line at right angles to the aerials.The results obtained show that, over the period January–April, 1933, one main ray accompanied by other and smaller-amplitude rays is, in general, received at Slough from the 20-metre Lawrenceville stations during their normal working period. The average angle of incidence of this main ray is 72° (measured to the normal to the ground).Throughout the first four months of the year, the angle of incidence remained fairly constant over the working period, but, from about the beginning of April, 1933, the angle of incidence of the one main ray which was still present began to grow throughout the day. At the commencement of transmission, at noon G.M.T., the angle of incidence is of the same order as that obtaining throughout the day in the “winter” months. The angle increases gradually until values of 80° to 85° are obtained towards sunset. A drop in average field strength of the transmissions has also been noted since April.The deduction that one main ray accompanied by smaller-amplitude rays is generally present in the downcoming radiation from Lawrenceville has been confirmed by the preliminary results of some short-duration 20-metre pulse transmissions from that station.

DOI:10.1049/jiee-1.1934.0084

出版商:IEE    

年代:1934

数据来源: IET

摘要:

Two methods of measurement of the grid-anode capacitance of screen-grid valves are described.In the first the working value of this capacitance is deduced from measurements of the change in the input capacitance of the valve upon reducing the anode load from a known value to zero. It is necessary to know the amplification factor of the stage. A description of the bridge employed for its measurement is given in Appendix 1.The second method measures the grid-anode admittance with the filament cold. The result is obtained in terms of the ratio of the readings of two voltmeters and the settings of a variable air condenser covering a range of capacitance over which it can be calibrated directly.

DOI:10.1049/jiee-1.1934.0085

出版商:IEE    

年代:1934

数据来源: IET

摘要:

The paper describes the quartz-crystal control arrangements for a radio transmitter designed to radiate a standard frequency of 1785 kilocycles per sec.The special feature of the quartz oscillator is its mode of support. It rests on four pins screwed into holes drilled into the edges of the oscillator in its nodal plane. By the use of this method of mounting the damping of the oscillator is decreased, and frequency-changes due to movement between the electrodes are nearly eliminated. The quartz plate was tested as a resonator, and its edge was ground until one strong resonance was obtained well removed from neighbouring resonances. It was then found to give a good performance as an oscillator. Tilting the mounting produced a maximum frequency-change of 2 parts in 106, and the frequency varied linearly with temperature and smoothly with air-gap. The frequency was adjusted to 1785 kilocycles per sec.The feeble oscillations of the crystal were amplified in two transformer-coupled stages and were then fed to the power valves of a transmitter. Changes of 5 per cent in the tuning of the amplification and power stages produced frequency-changes of only a few parts in 107.The frequency of the transmitter showed a stability of 1 part in 107over short periods and 1 part in 106from day to day.A small condenser connected between the grid and the plate of the valve driving the crystal enabled the frequency of oscillation to be adjusted so that it could be maintained at a value within 1 part in 107of that of the standard tuning-fork.

DOI:10.1049/jiee-1.1934.0086

出版商:IEE    

年代:1934

数据来源: IET

DOI:10.1049/jiee-1.1934.0087

出版商:IEE    

年代:1934

数据来源: IET