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

About: Journal of the Institution of Electrical Engineers - Part IIIA: Radiocommunication is an academic journal. The journal publishes majorly in the area(s): Transmitter & Crystal oven. It has an ISSN identifier of 2050-5493. Over the lifetime, 60 publications have been published receiving 488 citations.

Statistical theory of d.f. fixing

Abstract: The paper deals with the location of an object of u nknown position, on which bearings are taken from two or more stations whose positions are known, and provides solutions to the two problems:-(a) Given a set of bearings, what is the most probable position of the object?(b) How far from the true position is the position indicated by the “fix” likely to be?Diagrams are given to show the results of applying the theory to typical practical cases.It is shown that, subject to certain qualifications, reliability of a fix does not depend on the size of the particular “cocked hat” from which it is derived.It is proposed that the reciprocal of the root-mean-square error expected in the position of the fix should be adopted as the conventional standard quantity for measuring the reliability of a fix.

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

Abstract: 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.

The spectrum of modulated pulses

Abstract: Some methods proposed for evaluating the spectra of modulated pulse trains are discussed. The basic pulse-frequency, -phase, -length and -amplitude modulation systems are defined and the spectrum of a train of rectangular pulses sinusoidally modulated in any one of these ways is derived. Modulation by more than one tone is also considered. It is shown that in none of these methods is there any harmonic distortion or audio crosstalk. Anharmonic distortion arises from sidebands of harmonics of the pulse repetition frequency, and graphs are given to illustrate its magnitude. The formulae are extended to cover non-rectangular pulses, and it is shown that the distortions to be expected are practically the same as for rectangular pulses. The reproduction of transients is briefly examined. It seems that they suffer little distortion in form but that their timing is modified by the pulse modulation, the maximum time-shift being half the pulse repetition period.

Radio direction-finding by the cyclical differential measurement of phase

Abstract: This paper introduces a new general type of direction-finding and beacon system in which an appreciable reduction of the usual site errors is achieved by the use of aerial structures of wide aperture, the ambiguity normally associated with such systems being resolved by the manner in which the aerials are connected.Practical forms of the new system generally consist of a circularly disposed array of vertical aerials which are cyclically connected, singly or in groups, by a process of electronic commutation to a receiving device. The basic principle can best be appreciated by considering a single vertical aerial connected to a receiver and caused to move continuously along a circular path in the horizontal plane at a uniform rate. The motion of the aerial would impose a phase modulation on any received signal, and the horizontal direction of arrival of the signal could be determined if this modulation could be related to the law of motion of the aerial.Several types of direction-finder using the same basic principle are possible; these are outlined and classified. The practical and theoretical advantages of the system are discussed, and two directionfinders, one for use in the very-high-frequency band, the other in the high-frequency band, are described.The paper is confined to an account of the more important aspects of the subject, attention being paid to the fundamental requirements of the system and the means whereby they are met in practice. The mechanism whereby site errors are suppressed is outlined, and a comparison with the orthodox Adcock types of direction-finder is made, in which it is shown that, just as a phase-modulation communication system has certain inherent superiorities over an amplitudemodulation system, so the method of phase comparison has similaradvantages over other forms of direction-finder.

Dielectric-rod aerials

Abstract: This paper describes theoretical and experimental work carried out in the Admiralty Signal Establishment, and at the same time includes all the relevant material that the authors have been able to extract from German reports. It was decided to carry out this investigation when it became known that considerable importance had been attached to dielectric-rod aerials in Germany during recent years. The material of German origin is taken mainly from a translation by the authors of a paper by Mallach of the Vierjahresplan Institut fur Schwingungsforschung, Berlin.The fundamental principles governing the radiation characteristics of dielectric rods are considered, and brief reference is made to other dielectric aerials.