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Improved methods for the measurement of radiofrequency emissions from railways

A report for OFCOM by York EMC Services Ltd, University of York

Authors: A J Rowell, D Bozec & D W Welsh


Summary

This study has built upon previous work for the Radiocommunications Agency [1] to produce a measurement system that is able to characterise the radiated emissions from moving trains in more detail than the methods currently employed and defined in the EN50121 standard [2]. The system has been employed in making measurements of the emissions from trains on mainline routes, local routes and on a light rail (tram) system. Both AC and DC overhead supply systems and DC conductor rail supply systems have been measured as well as vehicles that derive their power from on-board diesel engines.

The measurement system has given results of both continuous monitoring of a frequency range and an envelope type detector function realised using spectrum analysers to give an indication of the broadband and transient emissions emanating from the train. The results obtained using this system are most usefully examined using an animated display. Some examples have been included for download with the report, however it is impractical to include many animations and so a selection of graphs has been included to illustrate the results of the measurements performed.

Some additional measurements have been made using a fast sampling oscilloscope to capture transient waveforms and to compare this approach to the use of the spectrum analyser envelope detector.

Measurements have indicated that:

The use of the techniques investigated are not necessarily confined to the measurement of railway systems but may also be applied to other equipment. The use of the spectrum analyser to indicate transient emissions may be of particular use in determining the interference potential of common household goods employing switching of loads (for example a thermostatically controlled steam iron). This may present a suitable higher frequency method for the measurement of discontinuous interference.

References

  1. “Potential electromagnetic interference to radio services from railways”, T Konefal, DAJ Pearce, CA Marshman, LM McCormack; York EMC Services Ltd for Radiocommunications Agency [back]
    [go to reference 1 report]
  2. CENELEC: EN50121 (parts 1-5: 2000) – “Railway Applications: Electromagnetic Compatibility” [back]

Downloads:

Format Document
PDF Main report (3,476 kB)
AVI Example 1 - Measurement of Class 91 stock, 9kHz - 59 kHz (14,105 kB)
AVI Example 2 - Measurement of Class 91 stock, 30MHz - 530MHz (3,245 kB)
AVI Example 3 - Measurement of ‘Voyager’ stock, 100kHz - 150 kHz (2,910 kB)

Last updated: 2004-Aug-17

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