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Electrical Engineers - Part IIIA: Radiocommunication, Journal of the Institution of

Issue 16 • Date March-April 1947

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Displaying Results 1 - 25 of 29
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  • Radio-wave propagation research in the Department of Scientific and Industrial Research during the years 1937¿1946

    Page(s): 879 - 892
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2391 KB)  

    The fundamental study of the propagation of radio waves has formed an important part of the programme of the Radio Research Board, which was established under the Department of Scientific and Industrial Research in 1920. The object of the present paper is to survey the progress made in this field during the decade ending in 1946, and to indicate the manner in which the investigations concerned have been developed to meet the requirements of those responsible for applying radio waves to various practical uses. The researches described cover the radio-frequency spectrum from about 10 kc/s up to 50000 Mc/s or more. They deal with the transmission of radio waves along the surface of the earth, and illustrate the manner in which this transmission is influenced by the electrical properties of the ground and the curvature of the earth and by the corresponding properties and slopes of natural and man-made protuberances on the ground. The characteristics of the ionosphere have been studied intensively for over twenty years, and during the past decade considerable advance has been made in our knowledge of this region of the atmosphere and of the manner in which radio waves are propagated through it. With the advance of radio technique and developments to shorter and shorter wavelengths, it has become clear that wave propagation in the lower atmosphere is greatly affected by the vertical gradient of the temperature and humidity of the air; the associated phenomena have been studied directly, and, in addition, the electrical properties of the constituents of the atmosphere, solid, liquid and gaseous, have been determined at the very high radio frequencies relevant to this portion of the investigation. Finally, the important part played by radio noise of either atmospheric or extraterrestrial origin has been studied with a view to understanding more clearly the manner and circumstances in which such noise can either influence the successful transmission of intelligence by radio - waves, or provide a means of increasing our knowledge of such phenomena as those associated with thunderstorms and activity on the surface of the sun. This survey attempts to show what an important part the study of wave propagation plays in numerous applications of radio technique, and demonstrates that there is still much further work to be done before the full requirements of those using the technique can be met in a satisfactory manner. View full abstract»

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  • The accuracy of sky-wave delay measurements

    Page(s): 893 - 898
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (884 KB)  

    The paper describes an experimental investigation of the limitations imposed by the ionosphere upon the accuracy of sky-wave path-time measurements. The measurements were made at intervals between August, 1942, and the middle of 1944, covering the frequency range 2¿16 Mc/s, and consisted of observations at vertical incidence and at oblique incidence over ranges up to 6000 km. The limiting accuracy of path-time measurement at vertical incidence was found to be of the order of ± 5 ¿sec, while at oblique incidence it was in the region of ± 10 to ± 20 ¿sec under normally favourable conditions. The instrumental techniques involved in the various phases of the work are briefly described, and the probable mechanism of the shortperiod variations about the mean path-time is discussed. View full abstract»

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  • The development of quartz crystal production

    Page(s): 899 - 911
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    In the inter-war period, 1918¿1939, the quartz crystal evolved from being a material of academic interest to being the source of a vital component for both wartime and peacetime radiocommunication. This paper outlines some of the problems experienced in turning the United Kingdom quartz industry over from an annual production capacity of a few thousand quartz crystal vibrators in 1938, to nearly two million in 1945. By development of machine processes, production changed from skilled hand-working to semi-skilled bulk production and was accompanied by increasingly stringent testing so as to provide a much improved final product. Some details are given of the automatic and other machine processes, of the way in which the serious activity-ageing problem of the piezo-electric element was solved, of the peculiarities of the production problem in respect of raw-material faults, and of the performance specified for the finished component. Quantities of redundant crystal units accumulated from early production and units on redundant frequencies were recovered and re-processed with a consequent saving in raw material. New types of crystal units and future developments are touched on and it is concluded that fewer crystal units, of improved types, will be required in future, to maintain a radio network of better performance and of capacity similar to that used in the late war. View full abstract»

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  • Fixed high-stability carbon resistors

    Page(s): 912 - 914
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    High-stability fixed resistors of a wide range of values were developed during the war for special applications. Smooth ceramic rods were coated with carbon films, by pyrolitic decomposition of methane in a continuous furnace. The resistance value so obtained was increased by cutting a spiral track on the coated surface of the rod. A layer of graphite was applied to the ends of the rods, which were then fitted with metal caps and lead wires as contacts. Protection from atmospheric influences and mechanical damage was provided by specially developed lacquers, or alternatively, by hermetically sealing the resistors in glass envelopes. A description of the furnace used and its control characteristics are given. Typical stability characteristics of the resistors are quoted. View full abstract»

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  • Crystal filters for radio receivers

    Page(s): 915 - 926
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1593 KB)  

    Crystal filters can be effectively employed to give highly selective i.f. channels in communication receivers. The first example is the pair of 465-kc/s single-section bridged-T crystal filters designed for the Army receivers R206 and R201 during the early part of the war. The second is the set of channel and carrier filters for the Post-Office two-channel single-sideband receiver. These are of recent design. Foster's Theorem for two-terminal reactance networks is described and applied briefly to the solution of the properties and elements of a lattice network¿the starting point of filter design. Properties of the particular forms of lattice network necessary in crystal filters for radio receivers are discussed. Resistance compensation is explained. The application of the equivalent circuit of a crystal resonator to filter networks is discussed and the properties of some applicable quartz cuts are outlined. The method of calculation of L-and C-element values is given. Finally, the design of a new type of two-section half-lattice channel filter is brieflv described. View full abstract»

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  • The control and elimination of electrical (Dauphiné) twinning in quartz

    Page(s): 927 - 938
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    Quartz for telecommunication purposes has to be of the highest crystalline quality. A considerable proportion of raw material is rejected on account of electrical twinning. The war-time need for economy of quartz led to an investigation of means of removing this defect. The paper surveys the experimental methods used in exploring the possibilities of untwinning quartz. The basis of these methods is a heat treatment of the quartz plate while subjected to a system of stresses applied to the plate by temperature gradients, pure bending, longitudinal compression or torque. The effect of crystallographic orientation is discussed, and the new physical phenomenon of ¿piezocrescence¿ is defined. The paper also describes the practical application of the untwinning techniques to quartz-crystal plates, with particular reference to the requirements of telecommunication. It is shown that the method employing heat treatment with an applied torque may be successfully applied to many important types of quartz crystals including the BT and AT cuts. The proportion of success and the occurrence of quartz showing anomalous behaviour are discussed. View full abstract»

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  • C.W. radio aids to approach and landing

    Page(s): 943 - 952
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    The problems involved in the design of landing approach systems are complicated by psychological and aerodynamic considerations. The display of intelligence from the system is of great importance, and the form that it should take has influenced system design. The first attempt to provide guidance in azimuth made use of the magnetic field surrounding a cable on the ground, but this was superseded by radio systems. Keyed signals produced by overlapping field patterns were favoured in this country until fairly recently, but these have been replaced by modulation separation systems as being more suitable for operation of the preferred indicator. Guidance in elevation is provided by a ¿glide-path¿ system, which is preferably of the overlapping pattern type and provides a straight line of descent. Distortion of the course characteristics by re-radiation from objects near the transmitter is a problem which can only be solved by restricting the energy radiated towards the interfering object. This is achieved in present systems by the use of arrays, but the employment of equipment operating on centimetre wavelengths offers convenience in obtaining greater directivity. It is considered desirable to control the automatic pilot from the landing approach system, and experiments to this end are in progress, the results of which will probably affect the design of landing systems. View full abstract»

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  • C.W. radio aids to homing and blind approach of naval aircraft

    Page(s): 953 - 960
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    A brief historical account is given of the development of c.w. homing beacons for use by the Fleet Air Arm. The equipment at present in use on aircraft carriers and at naval air stations is described. The method used to compensate for changes in direction of the ship's head so that the beacon always transmits the correct homing information is detailed. The factors affecting the choice of a particular type of homing aid are discussed. An account is given of experiments with a Lorenz type of beacon for blind approach to aircraft carriers. The present equipment is described. The paper concludes by emphasizing that the requirements for fully automatic homing, approach and landing set a problem for the future that may require separate solutions for shipborne and land-based aircraft. View full abstract»

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  • The development of monitoring and remote-control equipment for radio aids to naval flying

    Page(s): 961 - 967
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    The various homing and blind-approach systems which have been installed or proposed for use in aircraft carriers and naval air stations require some system that will give a constant check on their performance, so that the transmission of correct information may be maintained. This paper describes a comprehensive system of monitoring and remote control which has been developed for this purpose, and concludes with a consideration of the requirements of such a system. View full abstract»

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  • The Consol navigation system

    Page(s): 968 - 976
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    The Consol navigation system embodies a chain of independently operated medium-frequency radio stations with respect to each of which bearings may be taken with the aid of a standard communication receiver. The principles of operation of the constituent stations are given and the equipment required is briefly described. Factors influencing the accuracy of the system and ranges to be expected in various parts of the world are discussed. View full abstract»

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  • A time-multiplex radio-frequency phase-comparison method for navigational systems

    Page(s): 977 - 983
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (937 KB)  

    A method of using time multiplex to provide a continuous wave navigational aid is discussed theoretically. The practicability of the system has been demonstrated by the construction and experimental use of low-power equipment. The use of the scheme for various navigational problems is discussed and the present programme of development is outlined. View full abstract»

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  • Note on a short-range radio position-finding system using modulated continuous waves

    Page(s): 984 - 989
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    The paper describes a position-finding system by which the polar co-ordinates of any suitably equipped aircraft can be determined at a single base station using phase-comparison range-finding apparatus and a v.h.f. automatic direction-finder in conjunction with conventional communication equipment.¿ An experimental model is described in which azimuth and range are displayed on a single cathode-ray oscillograph, which may be installed in an airport control tower. Range is indicated without ambiguity up to 100 nautical miles, and there is no azimuthal ambiguity. So far, the model has been used primarily to demonstrate the principles of the system, in conjunction with an aircraft fitted with an experimentally modified Service type of v.h.f. communication equipment. The results of a limited number of tests suggest that, with airborne equipment specifically designed for use with the system, the probable error in range measurement should be less than 1 mile. Azimuthal accuracy is not here discussed, but in a companion paper it is shown that the probable instrumental error of the direction-finder is less than 1.5 deg, implying a probable lateral error less than 2.5 miles at the maximum non-ambiguous range of 100 nautical miles. View full abstract»

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  • The omni-directional radial-track guide

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    The paper describes only the technical aspects and operation of the omnidirectional radial-track guide. The former, which refer entirely to experimental work at the Royal Aircraft Establishment, Farnborough, are divided into the general requirements for both ground and airborne equipment, and give essential details of the various possible presentations on the ground and in the air. Practical results are given, and the paper concludes with a reference to future development. View full abstract»

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  • Low-reading absolute altimeters

    Page(s): 1001 - 1011
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    Efforts have been made over the past twenty years to design a lowreading absolute altimeter for use in aircraft. At the present time the most successful instrument of this type is the frequency-modulation radio altimeter. The paper deals in detail with the problems involved in the design, installation and use of this type of equipment. The discussion is illustrated by reference to various instruments that have been designed. View full abstract»

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  • A survey of the problems involved in the provision of radio aids to marine navigation

    Page(s): 1012 - 1015
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    This paper endeavours to show how the mariner's requirements for a navigational aid affect the design of such apparatus by the radio engineer. The classification and requirements laid down at the International Meeting on Radio Aids to Marine Navigation (London, March, 1946) are stated, and in the following Sections the performance required from the various classes is related to the radio frequency chosen, and to the design of the system. The method of presenting the information is next reviewed, and the special problems encountered in marine navigation outlined. The paper then suggests other possible requirements that might modify those laid down at I.M.R.A.M.N. and concludes with a brief review of the main problems facing the designer of a radio navigational aid. View full abstract»

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  • Very-long-wave phase differences between spaced aerial systems

    Page(s): 1016 - 1022
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    The paper describes some investigations into the propagation of very-low-frequency radio waves, in which the variations of phase difference between signals received at two points about ten wavelengths apart were measured. Observations were made using two telegraph transmitters on frequencies of 17.2 kc/s and 18.4 kc/s at distances of 1030 km and 5650 km respectively; propagation with ground wave predominant, sky wave only, and both sky and ground wave, was observed. Two sets of measurements were made at each distance, to give an indication of seasonal variations. The results indicated that a navigational aid using these frequencies and a base line of about ten wavelengths would give a probable error of equivalent bearing of less than 0.2 deg near the median line of the system at these distances, and probably at most intermediate distances. Larger variations which were observed at certain times of the night appeared to be due to the sunrise or sunset line crossing the propagation path obliquely. An analysis of the periodicity of variations showed that observations would have to be averaged for a period of the order of half an hour to gain any appreciable increase in accuracy. View full abstract»

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Aims & Scope

The Journal of the Institution of Electrical Engineers - Part IIIA: Radiocommunication was published by the IET in 1947.

Full Aims & Scope