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Radio and Electronic Engineer

Issue 5 • Date May 1975

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Displaying Results 1 - 11 of 11
  • Leaky feeders

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    Freely Available from IEEE
  • A general study of the leaky-feeder principle

    Page(s): 205 - 214
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1224 KB)  

    The principle of using the leakage fields of a transmission line to provide mobile radio communication in tunnels has been studied theoretically and experimentally. A mode-conversion theory is developed to account for the fields observed round imperfect bifilar and coaxial lines, and predictions from it are confirmed by observation: the internal velocity ratio of the cable used is an important factor in the coupling achieved, and standing-wave effects are normally to be expected at both ends of such a line regardless of impedance matching. For any given line and operating conditions an optimum frequency can be shown to exist. Systems aspects are considered briefly and a proved technique for providing duplex two-way communication using one-way line repeaters is described. View full abstract»

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  • Practical performance of radiating cables

    Page(s): 215 - 223
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    Experimental techniques are described, which are used to establish the coupling loss between a radiating cable and an antenna, the attenuation per unit length of the cable and its sensitivity to mounting position. Eight different cables were evaluated over a frequency range of 42¿460 MHz. Field strength plotting and digital computer analysis techniques were used to reduce the data recovered from the experiment. View full abstract»

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  • Leaky coaxial cable for communication in high speed railway transportation

    Page(s): 224 - 228
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    The practical performance of leaky coaxial cables is affected by the surrounding materials. Coupling loss and transmission loss vary according to the distance between a concrete wall and the cable. Some experiments were conducted using concrete walls on an experimental railway, and several kinds of installation methods were tested. It was confirmed that the effect of snow was small. It is also shown that the newly developed antenna, the main beam of which had the same directivity pattern as that of the leaky coaxial cable, was very effective in reducing coupling loss and fluctuation of received power. View full abstract»

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  • Electromagnetic theory of the leaky coaxial cable

    Page(s): 233 - 240
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    The transfer of electromagnetic fields through a grid made of conducting strips similar to the braid of a coaxial cable is expressed by means of a transfer surface impedance relating the tangential electric field to the discontinuity of the tangential magnetic field. This impedance is calculated as a function of the grid parameters. It is then used to establish the electromagnetic theory of a braided coaxial cable located along the axis of a perfectly conducting cylinder. This leads to the existence of two uncoupled modes having the main part of their energy confined on one side of the sheath, with leakage on the other side. This result is compared with the classical coupled line theory. View full abstract»

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  • Control of mode conversions on bifilar line in tunnels

    Page(s): 241 - 247
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    The influence of frequency and of the position of the line on mode conversions is studied and previous observations of other researchers are explained. The means whereby exchanges between the two propagation modes may be provoked at the level desired, to meet the needs of propagation and coupling between the transmitter and the balanced mode are investigated. These investigations lead to the definition and realization of an ideal mode converter. Such a mode converter reduces the coupling loss, whatever the frequency, and allows a good control of the field level in the tunnel. It consists in introducing a four-port network or a transformer on the line, where a mode conversion is needed. Theoretical curves, checked experimentally, are given, which make it possible to determine the nature of the four-port network as a function of the conversion coefficient desired. View full abstract»

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  • Field leakage and crosstalk, with special reference to radiating cables with perforated tape screens

    Page(s): 248 - 252
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    Field leakage is considered as a special case of cable crosstalk, and comparison is made with the theory published by D. J. R. Martin. Important parameters are the cable dielectric permittivity and the surface transfer impedance of the screen. Perforated type screens are treated by Kaden's theory, and the results give reasonable agreement with experimental measurements of surface transfer impedance. View full abstract»

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  • CEI proposals for reorganization of the engineering profession

    Page(s): 257 - 261
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    The Council of Engineering Institutions (CEI) issued on 17th April the full text of a report by the Council's Executive Committee to the Board of CEI concerning the future organization of the engineering profession. The paper is not yet CEI policy since this can only be determined by the CEI Board itself. It is however being presented here in full to receive as wide and early publicity as possible among IERE members. The CEI Board is to consider the paper at a special meeting on 29th May, and if the report is approved at that meeting, the Special Resolutions required to implement the proposals will be prepared and sent out in time for them to be put before the Board at its meeting on 24th July. Comment by members will be welcomed and may be addressed to the Institution. View full abstract»

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  • Obituary

    Page(s): 263 - 264
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    Freely Available from IEEE
  • New books received

    Page(s): 266 - 267
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