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1887

Radio and Electronic Engineer

Volume 36, Issue 4, October 1968

Volumes & issues:

Volume 36, Issue 4

October 1968

The world's mine oyster
Institution Notices
Transistors in the regulating unit of electronic voltage stabilizers
  • Author(s): G.N. Patchett
  • Source: Radio and Electronic Engineer, Volume 36, Issue 4, p. 195 –206
  • DOI:  10.1049/ree.1968.0089
  • Type: Article
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  • p. 195 –206 (12)
    Transistors may be used in both d.c. and a.c. voltage stabilizers and their use is considered in both applications although emphasis is placed on their use in a.c. voltage stabilizers. The operating conditions of transistors in a.c. stabilizers are different from their normal operating conditions in amplifiers and care is necessary to prevent damage to them. The operation of a transistor essentially as a variable resistor is considered. Transistors fed from auxiliary sources of power (either d.c. or a.c.) may absorb power or give out power and a number of circuits are considered including those using a complementary pair.
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Letter to the Editor: Superdirective arrays
The design of active filters using the in-line pole approximation
  • Author(s): L.N. Hulley  and  G. Musgrave
  • Source: Radio and Electronic Engineer, Volume 36, Issue 4, p. 209 –217
  • DOI:  10.1049/ree.1968.0091
  • Type: Article
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  • p. 209 –217 (9)
    A synthesis is presented which has enabled a practical switchable filter to be realized which will give an optimum linear phase response together with satisfactory amplitude and transient response using a computed in-line pole distribution. Theoretical and practical characteristics are compared for a fourth- and sixth-order filter and the appropriate circuit diagrams are given. The application of this type of filter is discussed with particular reference to the field of medical electronics.
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Television and Education
A positioning system using three-valued codes
  • Author(s): A. Pugh
  • Source: Radio and Electronic Engineer, Volume 36, Issue 4, p. 219 –224
  • DOI:  10.1049/ree.1968.0093
  • Type: Article
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  • p. 219 –224 (6)
    A significant simplification of the computation circuits for positioning systems is achieved by the use of three-valued codes. The use of the odd radix makes it possible to provide a control system symmetrical to positive and negative quantities which relieves the necessity to complement digital information. The paper discusses the construction of suitable cyclic codes and gives the logical design for the necessary conversion logic. Design proposals for the remainder of the control system are also corporated.
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Colour television studio equipment and problems
  • Author(s): F.G. Parker
  • Source: Radio and Electronic Engineer, Volume 36, Issue 4, p. 225 –239
  • DOI:  10.1049/ree.1968.0094
  • Type: Article
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  • p. 225 –239 (15)
    The paper outlines the nature of a studio complex and the problems which arise from the introduction of colour television beginning with those associated with the colour separation signals. Special reference is made to the problems arising from the use of four-tube colour cameras particularly from the point of view of monitoring their outputs as well as the methods of coding to ensure accurate colour reproduction on commercial receivers. In a studio using the PAL system of colour television certain extra pulses are required for use with the coders and the generation and distribution of these pulses is discussed.The problems arising in the coding process are dealt with and in particular special consideration is given to the problems due to the colour axis switching feature of the PAL system. The effect of the axis switching on the increased precision needed in the quadrature between the two axes is also considered as well as its effect on the crosstalk problems. The design of a practical operational coder is outlined with particular reference to the problems of carrier balance and the effect of the axis switching on this parameter.The effect of colour on the mixing equipment is considered and particular reference is made to the problem of burst-stabilization during the operation of the fader controls. The subject of special effects is also discussed including the production of synthetic colour captions from black and white originals. The synchronization of the various sources at the mixer is considered in outline in so far as it affects the mixer.The design of a suitable decoder for use with colour picture monitors in a colour studio is outlined and also the general arrangements for colour picture monitoring. The requirements of a signal distribution system within a studio complex are discussed with reference to such parameters as differential gain and chrominance luminance delay.Finally, the paper considers the method of line-up necessary to ensure that coding, decoding and monitoring equipment is working correctly. In particular, a method is outlined whereby coding equipment can be completely set up using an oscilloscope to monitor the output of a coder.
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Of Current Interest . . .
An approximate calculation of the phase constant for a rectangular waveguide containing a dielectric
Processing ceramics to give suitable substrate characteristics
  • Author(s): B.C. Waterfield
  • Source: Radio and Electronic Engineer, Volume 36, Issue 4, p. 244 –246
  • DOI:  10.1049/ree.1968.0097
  • Type: Article
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  • p. 244 –246 (3)
    The selection of the substrate material is dependent on the application for which the deposited circuit is intended. The normal production specifications for substrates are discussed and a brief description given of the production methods available. The reasons for the impurity ratio in the ceramic must be considered relevant to the type of deposition that will be applied and the degree of adherence that is required; there is also a connection between impurity level and surface finish which will affect the choice of metallizing media. In terms of both cost and surface texture, ‘as fired’ ceramics are favoured. Any subsequent machining operations will tend to expose voids which can be clearly seen on roughness traces, though a general ‘flattening’ of crystal peaks will take place. If a higher degree of surface finish is obligatory, then great care is needed in the selection of ceramic with particular reference to the size of grain and alumina content. Finally, the factors affecting the costs of production substrates are considered in light of the aspects discussed.
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High-speed computer logic with gunn-effect devices
  • Author(s): H.L. Hartnagel  and  S.H. Izadpanah
  • Source: Radio and Electronic Engineer, Volume 36, Issue 4, p. 247 –255
  • DOI:  10.1049/ree.1968.0098
  • Type: Article
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  • p. 247 –255 (9)
    The application of the Gunn effect for fast logic circuits is discussed. In particular, several new devices, such as comparators, which rely on the possibility of domain-nucleating control are described. The ultimate time-constants of these new devices can be at least one order of magnitude better than the most advanced monolithic structures with conventional transistor and diode circuitry. Finally, two circuits, namely, an adder and a shift register, incorporating these new Gunn-effect devices are proposed.
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