scholarly journals Note on horizontal receivers and transmitters in wireless telegraphy

1908 ◽  
Vol 81 (549) ◽  
pp. 394-397
Keyword(s):  
Wave Length ◽  
Current Strength ◽  
Transmitted Wave ◽  
Maximum Efficiency ◽  
Electric Force ◽  
Wave Detector ◽  
The Earth ◽  
Spark Gap ◽  
Wireless Telegraph ◽  
Formed Part

In a communication published in the ‘Proceedings,’ Mr. Marconi has given the results observed when a straight horizontal conductor is substituted for the usual vertical conductor employed as a transmitter or receiver at a wireless telegraph station. The object of the following note is to consider the theory of such an arrangement, or at any rate one aspect of it. The receiver, as being the more important, will be considered first. Let AB (fig. 1) represent the horizontal receiver, consisting of a straight conductor having the end A connected to a spark-gap CC 1 or other wave-detector. The electric oscillations in AB can be represented by a distribution of Hertzian oscillators along AB, and, if L denotes the current strength at any point of AB, it must satisfy the conditions L= 0 at B, the free end, and d L/ ds = 0 at A, since the electric force perpendicular to AB at A must vanish. If the distance of AB from the earth is not too small, the effect of the oscillations belonging to the image in the earth of AB on those in AB may be neglected, the radiation from the free end B will be approximately symmetrical with respect to AB, and the oscillations in AB are then approximately the same as if BA formed part .of a semi-infinite straight conductor in which a system of oscillations is being maintained, B being the free end and A. the first node from the free end; the wave-length of these oscillations is very approximately five times the length of AB, and therefore the receiver is of maximum efficiency when its length is one-fifth of the length of the transmitted wave, a result observed by Marconi. When the distance of AB from the earth is so small that the effect of the oscillations in the image of AB in the earth on the oscillations in AB is not negligible, the radiation from the free end B will not be symmetrical with respect to AB, but may be taken as being approximately symmetrical with respect to some line through B making an angle with BA; the wave-length of the oscillations in AB is therefore equal to the wave-length of the oscillations in a bent conductor joining AB; that is greater than five times the length of AB, and, therefore, in this case the receiving conductor has its maximum efficiency when its Length is somewhat less than one-fifth of the length of the transmitted wave, result also observed by Marconi. To examine the effect of the orientation of the receiver, consider a straight conductor BAB' twice the length of AB (fig. 2) and its image B 1 A 1 B 1 ' in the horizontal plane, A and A 1 being their middle points respectively.

scholarly journals The transmission of electric waves around the Earth's surface

1916 ◽  
Vol 92 (643) ◽  
pp. 493-500 ◽  
Keyword(s):  
General Formula ◽  
Magnetic Force ◽  
Wave Length ◽  
Angular Distance ◽  
Electric Force ◽  
Present Communication ◽  
The Earth ◽  
Perfect Conduction ◽  
Electric Waves

The value of the magnetic force at a point on the earth's surface, due to a simple oscillator placed on the surface with its axis normal to the surface, has been recently calculated by Love for a wave-length of 5 kilom. at certain distances from the oscillator. His results for the case of perfect conduction are the same as the corresponding series when the surface of the earth is supposed to be imperfectly conducting, The object of the present communication is to obtain the general formula for the case of imperfect conduction. Let r, θ, ϕ be the polar co-ordinates of a point, where r is its distance from the centre of the earth, θ its angular distance from the oscillator, E r , E θ , E ϕ the components of the electric force, and α, β, γ , the corresponding components of the magnetic force. Then, Since there is symmetry round the axis of the oscillator, α =0, β =0, γ =0; and throughout space outside the surface

scholarly journals VII. Note on 'spectroscopic papers'

1879 ◽  
Vol 29 (196-199) ◽  
pp. 166-168
Keyword(s):  
Royal Society ◽  
Wave Length ◽  
The Sun ◽  
Decimal Point ◽  
The Earth

In a recent communication to the Royal Society, Mr. Lockyer has criticised our statement of Young’s wave-length identifications of certain chromospheric lines. As to the wave-length, we have throughout our table omitted all figures after the decimal point merely for the sake of not cumbering the table. The numbers, Young tells us, are not his own, but taken from Ǻngström’s catalogue. Moreover, as to Young’s identifications with metallic lines, he states expressly that they were taken from the maps of Kirchhoff, Ǻngström, and Thalén, and Watts’s “Index of Spectra.” But our object was not to criticise Young’s work, but only to use it for the purpose of comparing the behaviour of certain metals on the earth and in the sun, and the conditions under which certain lines appear, or do not appear, or are reversed.

THE EQUATION OF MOTION OF A GEOPHONE ON THE SURFACE OF AN ELASTIC EARTH

Geophysics ◽  
1944 ◽  
Vol 9 (1) ◽  
pp. 29-35 ◽  
Author(s):  
Alfred Wolf
Keyword(s):  
Wave Length ◽  
Elastic Solid ◽  
Damping Force ◽  
High Frequencies ◽  
Elastic Earth ◽  
Linear Dimensions ◽  
The Earth ◽  
Restoring Forces ◽  
System Equations

The motion of a geophone case placed on the surface of an elastic earth does not follow faithfully the motion of the earth at high frequencies. In effect, a weight placed on the surface of an elastic solid constitutes a damped oscillating system. The elastic restoring forces are determined by the area of contact between the weight and the surface of the solid and by the elastic moduli of the solid. The damping force is due to emission of elastic waves by the oscillating weight. The motion of the solid also contributes to the inertia of the system. Equations are developed for these forces on the assumption that the wave length is long compared to the linear dimensions of the area of contact between the weight and the elastic solid. This leads to a determination of the frequency of oscillation and of the decrement of such a system.

Experiments on the control of the Lucerne flea (Sminthurus viridis (L) and the Red-Legged earth mite (Halotydeus destructor (Tuck.)) in pastures in Western Australia.

1954 ◽  
Vol 5 (2) ◽  
pp. 317 ◽  
Author(s):  
MMH Wallace
Keyword(s):  
Western Australia ◽  
Residual Effects ◽  
Maximum Efficiency ◽  
Halotydeus Destructor ◽  
The Earth ◽  
Highly Effective ◽  
Low Volume

Experiments with BHC, chlordane, and parathion against the lucerne flea (Sminhurus viridis (L.)) and the red-legged earth mite (Halotydeus destructor (Tuck.)) in pastures are described. All insecticides were applied by means of a low-volume boom spray delivering 5 gal per acre. BHC applied at the rate of 2 lb 50 per cent. dispersible powder per acre had no effect on the lucerne flea population but killed approximately 90 per cent. of the earth mites present. Chlordane applied a t the rate of ½ lb per acre achieved no control of either pest. Parathion applied at the rate of ¼ pt of 20 per cent. emulsion per acre gave practically 100 per cent. control of lucerne fleas. Its residual effects were negligible and fleas hatching from eggs laid prior to spraying were not harmed. Equally good immediate control was achieved by applications of parathion at one-half the above concentration. The addition of DDT to the spray ensured the destruction of all earth mites as well as the lucerne flea. DDT gave no evidence of control of the lucerne flea in previous experiments. The experiments show that parathion is a highly effective insecticide against the lucerne flea but for maximum efficiency it should be applied early in the season before any eggs have been laid. The toxicity of the parathion sprays to grazing stock is discussed.

scholarly journals Further measurements on wireless waves received from the upper atmosphere

1927 ◽  
Vol 116 (775) ◽  
pp. 682-693 ◽  
Keyword(s):  
Closed Loop ◽  
Wave Length ◽  
Direct Proof ◽  
Relative Magnitude ◽  
Upper Atmosphere ◽  
Circle Plane ◽  
The Earth ◽  
Direction Finder ◽  
Short Period ◽  
Attention To Detail

In previous papers the authors have described the development of experimental methods of measuring the directions and relative intensities of both the electric and magnetic forces in wireless waves received at the earth’s surface from a distant transmitting station. In this work it was seen that the detection of the arrival of waves deflected from the upper atmosphere, and polarised with their electric force in a horizontal plane, was rendered difficult owing to the relatively great reflecting powTer of the earth resulting from its high conductivity. By a suitable choice of wave-length and careful attention to detail in the design and construction of the apparatus, however, the methods employed enabled measurements to be made on both vertically and horizontally polarised waves. The results of such measurements enabled a direct proof to be given of the fact that the fading of wireless signals on a vertical aerial and the variations of bearings experienced on the closed-loop type of wireless direction-finder are due to the reception respectively of vertically and horizontally polarised waves deflected from the upper atmosphere in their passage from the transmitter to the receiver. On arrival at the receiver, these indirect or atmospheric waves interfere with the direct or ground waves, in a manner determined by their relative magnitude and phase, and produce the intensity and apparent direc­tional variations mentioned above. The results of such interference phenomena have been investigated experimentally by Appleton and Barnett and by Holling-worth. In a more recent publication the present authors have provided experimental evidence showing that the path of the indirect waves is confined to the great circle plane between the transmitter and receiver. The measurements of the quantities in the received waves as previously described by the authors were confined to observations on the transmissions from the Bournemouth broadcasting station over a short period. The object of the present paper is to describe the continuation of these measurements and their extension to the transmissions from other stations.

THE IMPEDANCE OF AN ANTENNA ABOVE A CIRCULAR GROUND PLATE LAID UPON A PLANE EARTH

1954 ◽  
Vol 32 (3) ◽  
pp. 205-222 ◽  
Author(s):  
G. Bekefi
Keyword(s):  
Wave Length ◽  
Variational Formula ◽  
Radial Electric Field ◽  
Theoretical Work ◽  
Approximate Theory ◽  
Conducting Plane ◽  
True Value ◽  
The Earth ◽  
Recent Theoretical Work ◽  
Ground Plate

Recent theoretical work by Storer, concerning the impedance of a vertical antenna in contact with a circular metal disk, is extended to include the case when the system is laid upon an imperfectly conducting plane earth. The expression for the impedance of the antenna is cast into a form which is stationary with respect to small variations (about the true value) of the unknown radial electric field over the surface of the earth. Numerical results are given for the case when the ground plate is sufficiently large as compared to the wave length of the radiation; the effect of variations in dielectric constant of the earth upon the impedance is shown. These calculations are compared to those obtained from the approximate theory of Monteath.A second variational formula for the antenna impedance is developed in terms of surface currents flowing in the metal ground plate. The application of this method becomes useful when the ground plate is not too large in comparison with the wave length.

scholarly journals THE MAGNETIC PROPERTIES MEASUREMENT OF COIL FOR GRAVITATIONAL ACCELERATION DETERMINATION

2020 ◽  
Vol 5 (2) ◽  
pp. 119-128
Author(s):  
Cherly Salawane ◽  
Supriyadi Supriyadi ◽  
Ronaldo Talapessy ◽  
Mirtha Yunitha Sari Risakotta
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Field Strength ◽  
Electric Current ◽  
Graphical Method ◽  
Current Strength ◽  
Gravitational Acceleration ◽  
The Earth ◽  
The Magnetic Field ◽  
A Current

The value of the gravitational acceleration of the earth above the earth’s surface depends on the position of the latitude and longitude of the earth’s surface, in other words, because the shape of the earth’s surface is not round like a ball. The magnitude of gravity is not the same everywhere on the surface of the earth. The purpose of this study is to analyze the value of the earth’s gravitational acceleration in a laboratory using a current balance with a graphical method. Fluctuations in the value of the magnetic field strength (B) and the value of the electric current strength (i) on the current balance cause the value of laboratory gravitational acceleration (glab) to vary in the transfer of electric charge (q) according to coil type. The magnitude of the earth’s gravitational acceleration value obtained in a laboratory with a current balance for each type of coil is as follows: SF-37 glab-nr=9.89 m/s2, SF-38 glab-nr=9.90 m/s2, SF-39 glab-nr=9.76 m/s2, SF-40 glab-nr=9.95 m/s2, SF-41 glab-nr=9.75 m/s2 dan SF-42 glab-nr=9.93 m/s2. The results obtained indicate that the value of the earth’s gravitational acceleration in a laboratory close to the literature value is the value of the glab-nr in the SF-37 coil type of 9.89 m/s2.

scholarly journals On the connection between the ray theory of electric waves and dynamics

1931 ◽  
Vol 132 (819) ◽  
pp. 83-98 ◽  
Keyword(s):  
Phase Velocity ◽  
Critical Frequency ◽  
Wave Length ◽  
Ray Theory ◽  
Electronic Density ◽  
Short Waves ◽  
The Earth ◽  
Variable Distribution ◽  
The Waves ◽  
Electric Waves

1. In the study of the transmission of electric waves round the earth (especially in the case of what are now known as short waves of frequencies between 3·3 X 10 7 and 3·3 X 10 6 , 10, to 100 M in wave-length) we have to consider the behaviour of such waves in the ionised region of the upper atmo­sphere. For the purposes of the analysis of the wave motions, this region may be considered as one in which there is a variable distribution of electronic density represented by N ϵ , say, which is taken as a function of the co-ordinates x, y, z . The electronic density is of major importance, the ions, in general, being so heavy that their reaction on the waves is small compared with that of the electrons. The phase velocity V in the medium is then, as is well known, c /√1 — v 0 2 / v 2 where v 0 is the critical frequency of the medium at any point x, y, z given by v 0 2 = N e 2 c 2 /π m , and in respect of this (the quantity N) is a function of the co-ordinates x, y, z . The group velocity U is c √1 — v 0 2 / v 2 , so that UV = c 2 .

scholarly journals Experimental researches in electricity. Twenty-fourth series. On the possible relation of gravity to electricity

1851 ◽  
Vol 5 ◽  
pp. 994-995 ◽  
Keyword(s):  
Electric Current ◽  
The Other ◽  
Electric Force ◽  
The Earth ◽  
Gravity And Magnetic ◽  
Experimental Relation ◽  
Other Substances ◽  
Fourth Series ◽  
Experimental Researches ◽  
Electric Action

Under the full persuasion that all the forces of nature are mutually dependent, and often, if not always, convertible more or less into each other, the author endeavoured to connect gravity and magnetic or electric action together by experimental results, and though the conclusions were, when cleared from all error, of a negative nature, he still thinks that the principle followed and the experiments themselves deserve to be recorded. Considering that some condition of the results produced by gravity ought to present itself, having a relation to the dual or antithetical character of the magnetic or electric forces, it seemed to the author that the approximation of two gravitating bodies towards each other, and their separation, were the only points which offered this kind of coincidence; and therefore, using the earth as one gravitating body, he employed a cylinder of metal, glass, resins, or other substances, as the other, and endeavoured to ascertain when the latter was allowed to fall, being surrounded by a helix of wire, whether any electric current was generated. Sometimes the cylinder was allowed to fall through the helix; at other times with the helix; and occasionally the helix was made the falling body. But when the various sources of error which sprung up were gradually removed, no traces of electric action remained which could be referred to the power of gravity. In order to obtain a greater effect, an aparatus was employed (being nearly that, used in the 23rd Series of these Researches) by which the effect of raising a body from the earth could be combined with that of a falling body by the fit use of commutators (if any action at all were produced). The apparatus was very good, and gave exceedingly delicate results, as was shown by other consequences of its action; but in respect of gravity it produced no effect whatever. Notwithstanding his failure in obtaining any experimental relation between gravity and magnetic or electric force, the author still expresses his conviction that there is a relation, and his hopes that it may be hereafter practically demonstrated.

scholarly journals The transmission of electric waves over the surface of the Earth

1915 ◽  
Vol 91 (627) ◽  
pp. 219-219
Keyword(s):  
Sea Water ◽  
Wave Length ◽  
Diffraction Theory ◽  
Small Extent ◽  
The Earth ◽  
Similar Series ◽  
Moderate Resistance ◽  
Perfect Conduction ◽  
Electric Waves ◽  
Good Agreement

An analytical solution of the general equation of electrodynamics is obtained for the case of waves generated by a vibrating doublet in presence of a conducting sphere, and is adapted to obtain the known solution for perfect conduction, and the correction for moderate resistance, such as that of sea-water. The known solution is expressed by the sum of a series involving zonal harmonics, and the correction by a similar series. Different results have been obtained by different writers who have investigated the numerical value of the former sum. In the paper a new method of summing the series is explained, and worked out in detail for the wave-length 5 km. In the case of perfect conduction the result confirms that found by H. M. Macdonald. The effect of resistance is found to be a slight increase of the strength of the signals at considerable distances, counteracting to some small extent the enfeebling effect of the curvature of the surface. A comparison is instituted between the results of the theory and those of recorded experiments. From these it had previously been inferred that the diffraction theory fails to account for the facts; but, after a discussion of the experimental evidence, it appears that the observations may admit of a different interpretation, according to which the results of the diffraction theory would be in good agreement with those of daylight observations at great distances.

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