Topic

Determination of exposure to the population living near digital radio and television transmitters

Start

01.10.2004

End

31.03.2006

Project Management

IMST GmbH, Kamp-Lintfort

Objective

All over Germany, transmitters for digital radio (DAB) and in particular for digital television (DVB-T) are currently being set up and taken into operation. Digital broadcasting is intended to replace the existing analogue terrestrial radio and television transmitters in the medium term. The research project investigated the changes in the high-frequency exposure to the general public caused by the dissemination of this technology.

The objective of the project was to quantify the exposure to the population due to electromagnetic fields created by DAB and DVB-T transmitters with the help of computer simulations and measuring campaigns and to assess the exposure under consideration of the relevant standards. The results had to be compared to the exposures caused by the existing analogue television and radio networks. Different scenarios (indoor/outdoor, high-density or low-density areas, varying distances to the transmitter etc.) had to be defined and investigated.

The first step was to determine the particular characteristics associated with receiving signals from DVB-T and DAB transmitters. To this end, it was necessary to define and validate the appropriate measuring and calculation methods. The procedures had to be assessed with respect to their limitations and to be described including their uncertainties and the total range of errors to be expected.

Results

In the considered areas around Munich and Nuremberg the exposure averaged over 198 measuring points (analogue and digital television as well as radio [only VHF and DAB]) increased significantly during the introduction of DVB-T. An increase in the exposure could also be observed at most of the individual measuring points after the introduction of DVB-T. The measuring positions were chosen randomly although weighted by the population density, so that more measurements were carried out in densely populated areas than in low-density areas. In particular the urban areas classified as “portable indoor” (with respect to the supply) show a significant increase in exposure. Outside urban areas (areas classified as having “fixed antenna” supply) the analogue television signals issued by surrounding transmitters still dominate the immissions caused by DVB-T transmitters.

In radio broadcasting the exposures caused by the analogue VHF technology currently still prevail over the electromagnetic fields created by the digital DAB signals. Digital DAB and analogue VHF will coexist at least for the foreseeable future.

Another interesting result of the research project is that the exposure levels observed vary considerably. The highest and lowest values recorded at the 300 measuring points (certain measuring points were chosen under systematic aspects in addition to the randomly chosen measuring points so that other factors such as the interrelation between the altitude of the immissions and their distance to the transmitter could be investigated) varied by more than 50dB (equivalent to a factor 100,000). However, even the highest value measured was 400 times below the limit values, even after the introduction of DVB-T.

The final report, which includes all interim reports, is available for download in the form of three PDF files in German:

Final Report, Part 1 (2.516 KB)

Final Report, Part 2 (4.416 KB)

Final Report, Part 3 (5.615 KB)

References

• M. Schubert, C. Bornkessel, M. Wuschek and P. Schmidt: Exposure of the general public to digital broadcast transmitters compared to analogue ones, Radiation Protection Dosimetry, Vol. 124, No. 1, 2007, pp. 53-57, doi:10.1093/rpd/ncm337

Conclusion

The research results have shown that the introduction of DVB-T cannot be expected to reduce the general exposure to the population due to electromagnetic fields. A reduction as predicted by manufacturers and operators could not be confirmed in the study areas of northern and southern Bavaria. On the contrary, densely populated urban areas and/or areas intending to provide “portable indoor” supply will probably result in an increase in exposure. The encoding gain offered by DVB-T is obviously more than compenstated by the increase in programmes and the ambition to ensure in-house supply.