The International Amateur Radio Union (IARU) is a federation of national associations of certified radio amateurs, representing over 150 countries and separate territories around the world.

The three IARU Regions are organised to broadly mirror the structure of the International Telecommunications Union (ITU) and its related regional telecommunications organisations. The Regions comprise:
- IARU Region 1: Europe, Africa, the Middle East and Northern Asia
- IARU Region 2: The Americas
- IARU Region 3: Asia-Pacific

The IARU represents the interests of the Amateur Radio Service worldwide to relevant international organisations, promoting the interests of amateur radio and seeking to protect and enhance its spectrum privileges.

IARU makes input on Euroloop proposals

Background

In 1996 the International Railway Organisation, UIC, made proposals to CEPT for spectrum approval for the development a high-speed data-communication system for railway rolling stock. The proposals were a technical solution to improve management of trains by giving the train drivers early notice of the forward signal status. This apparently would avoid less braking & acceleration with the result that trains could to run faster and closer together.

The 1996 proposals included one by Siemens for an HF transmission system between track-to-train called Euroloop. The spectrum requirements seem somewhat uncertain but the proposal mentioned plans to use spread spectrum on a centre frequency of 6.78MHz. At that time Euroloop was not considered to be either a long-term solution or one that would be widely adopted, as a GSM-R based communication system, called Euroradio, was expected to replace it. GEC/Alstrom propose a microwave solution as a competitor to Euroloop. CEPT’s Spectrum Engineering Working Group, SE24, in advising CEPT’s Frequency Management Working Group, WGFM, found both solutions suitable from the spectrum management perspective, albeit with some caveats. Following the WGFM decision the Euroloop system was taken forward for development. However, some years later it was found that Euroloop needed to work at a higher frequency in order to avoid interoperability problems with another railway system called Eurobalise, a 6.5MHz wide spread-spectrum system centred on 4.24MHz. Thus, CEPT’s WGFM was approached again, to see if it would support a frequency change for Euroloop. The new proposals are for a spread-spectrum system between 9 and 18MHz, centred on 13.5MHz. The matter was referred back to SE24 in mid-2005.

The current proposal is for a HF spread-spectrum signal that would be received by the Euroloop equipment in the rolling stock. The mechanism would be through magnetic field coupling to emanations from lengths of terminated leaky coax laid along the side of the rail. Although, somewhat wrongly termed loops, these linear lengths of leaky coax vary in length from 300m to 1000m.

IARU’s role in SE24

IARU has been represented by John Gould, G3WKL, RSGB HF Manager, on this issue since mid-November 2005. His approach to the problem was twofold. Firstly, to see if there was a potential problem from ionospheric propagation and secondly, to gain some idea of the impact for those living close to a railway line.

SE24’s focus as a spectrum engineering group is on short-range radio devices, so its members are well versed in undertaking short-range field-strength modelling. Experts from NATO, the Broadcasting industry and the German regulator, BnetzA led the short-range modelling work for Euroloop. The group seemed less experienced, and somewhat sceptical about possible ionospheric propagation of Euroloop signals. Thus, this was an area of modelling that fell to IARU to undertake.

The ionospheric propagation concern was akin to our concerns over PLT, which is the aggregation at the receiver of signals from multiple Euroloop installations. The details of the modelling can be downloaded by clicking here. The model is fairly simplistic and thus avoids complex statistical methods, which probably couldn’t have been carried out in the time, and may well have been over complicated given the data available on the Euroloop proposals. The overall outcome, detailed in the paper, is that so long at Euroloop is specified around 10dB below the level proposed to CEPT there should not be significant effects on the noise floor across Region 1 (and presumably further afield, though this has not been specifically modelled). The paper details some field tests that allowed limited validation of the modelling. It would have been scientifically nice to do more, but SE24 were not keen to extend the field-testing further. The tests that were undertaken did at least confirm that the calculations were relatively close to some of the measured values of field strength over a path from Switzerland to the UK.

Turning to the effects on the noise floor for those Amateurs or SWLs living, or rather having their HF station near to a railway line, the problem is of more concern. Some very approximate statistics, based upon field strength modelling carried out by NATO, would suggest that around 1.2% of Amateurs would be effected. This percentage is for those who live in the quietist radiolocations adjacent to railway lines that have a Euroloop installation. For those living in the centre of towns and cities and near to Euroloop installations this percentage could reduce by an order of magnitude. This variation is all to do with the normal environmental fluctuations in noise floor and the distance over which the spread-spectrum signal from the Euroloop might exceed this level. John Gould's paper detailing this part of the work can be downloaded here. The NATO calculations are quite complex and based on a well-established method used by CEPT, so are not linked to this summary. The proposers of Euroloop are not being specific as to which countries may adopt Euroloop, but they have said that it is likely to be no more than 10 (of the CEPT countries). The understanding is that the Benelux group of countries are likely to be amongst those countries who may install Euroloop if it’s spectrum requirements are agreed. Other countries may choose to adopt different solutions, for example it is understood that the UK may install GSM-R, or Euroradio.

Further work

SE24 is now in its process of drafting a report on the spectrum issues and compatibility considerations for presentation to WGFM. It is the responsibility of that working group to agree whether or not to accept the request for a frequency change and what conditions or specification to apply.

All the papers on this topic can be found on the CEPT website (www.ero.dk)

Acknowledgements

A number of Amateurs have assisted in this work. In particular thanks are due to Robin Page-Jones, G3JWI, for his help and support in the modelling, and Peter Martinez, G3PLX, and Andy Talbot, G4JNT, for undertaking the field trials.