Sistemas de comunicación tren-tierra

• Autores: Manuel Alonso Wehrli
• Localización: Revista A.I.T., ISSN 0378-3294, Nº. 28, 1979, págs. 23-29
• Idioma: español
• Títulos paralelos:
  • Train-earth communication systems
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• Resumen

  • On the field of railways, train-earth communication systems in long distances have been started to use, directed to improve traffic and safety in the long lines. Some of these systems, operating already, have been lay on France, South Africa, Ivory Coast, Gabon, etc.

    The objective required for the installation of a railway communication system is to establish a reliable connection for voice and data transmission between running trains and the control centre.

    One of the main aspects to be considered in order to this purpose, is to define the location and number of fixed stations that are necessary to cover certain line.

    In a previous study of a railway radiocommunication network, the reaches of different communications are estimated approximately, using besides topographic data, the results of propagation measurements carried out in other regions with a similar relief.

    Carrying out propagation measurements in real conditions are always necessary to realice the final design. On railway lines with intense traffic, the propagation measurements must be done when the regular trains are passing and even it is convenient to use these same trains to affect the measures. For these reasons, a measure equipment controlled by computer have been developed. It allows to obtain in a little time measures on a section covered at high speed. The propagation measure equipment includes:

    - Four fixed stations fitted in vans. Each one of these stations includes a self-powered transmitter, an antenna post of 22 m, several aerials and coaxial cables, as well as a transceiver for service communications with the measurement vehicle.

    A mobile measurement equipment controlled by computer that can be placed on an appropriate wagon and allows for field intensity measurements up to an speed of 120 km/h. Three UHF receivers, connected to separate antennas, are mounted on the roof of the wagon. They are tunable for several frequencies, with a measure range from 1uV to 1mV RMS (dynamic, 60 dB). The usage of three different frequencies of reception allows for measuring, simultaneously and in dependently, the field intensity of three fixed stations.