Rec. Itu-r bs. 1698




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Rec. ITU-R BS.1698

RECOMMENDATION ITU-R BS.1698

Evaluating fields from terrestrial broadcasting transmitting systems
operating in any frequency band for assessing exposure to
non ionizing radiation

(Question ITU-R 50/6)


(2005)

Scope


This Recommendation is intended to provide a basis for the derivation and estimation of the values of electromagnetic radiation from a broadcasting station that occurs at particular distances from the transmitter site. Using such information, responsible organizations can then develop appropriate standards that may be used to protect humans from undesirable exposure to harmful radiation. The actual values to be applied in any regulation will naturally depend on decisions reached by responsible health agencies, domestic and worldwide.
The ITU Radiocommunication Assembly,

considering

a) that radio-frequency energy may have unsafe effects on the human body;

b) that radio-frequency energy may induce harmful electric potentials in conducting material;

c) that radio-frequency energy may have harmful effects on apparatus (such as radiocommunication apparatus, navigation instruments, cardiac pacemakers, scientific or medical equipment, etc.);

d) that radio-frequency energy may lead to unintentional ignition of inflammable or explosive material;

e) that determination of hazardous radiation levels and electric potentials, in terms of spectrum content, intensity, cumulative effects, etc., are being made by competent authorities;

f) that determination of areas where radio-frequency fields and electric potentials exceed safe levels are being made by competent authorities;

g) that persons not associated with such systems may be exposed inadvertently to such radiation (including travellers by air) or to such electric potentials;

h) that persons operating and maintaining radio transmitting systems may be required to work in close proximity to the source of such radio-frequency exposures,

recommends

1 that Annex 1 to this Recommendation should be used to evaluate the electromagnetic fields generated by terrestrial broadcasting transmitting systems operating in any frequency band, for assessing exposure to non-ionizing radiation.

Annex 1

Evaluating fields from terrestrial broadcasting transmitting systems


operating in any frequency band for assessing exposure to
non ionizing radiation

CONTENTS

Page

1 Introduction 3

2 Characteristics of electromagnetic fields 4

2.1 General field characteristics 4

2.1.1 Field components 4

2.1.2 Far field 4

2.1.3 Near field 7

2.1.4 Polarization 7

2.1.5 Modulation 7

2.1.6 Interference patterns 13

2.2 Field-strength levels near broadcasting antennas 13

2.2.1 LF/MF bands (150-1 605 kHz) 13

2.2.2 HF bands (3-30 MHz) 13

2.2.3 VHF/UHF bands (30 MHz-3 GHz) 14

2.2.4 SHF (3-30 GHz) 14

2.3 Mixed frequency field 16

2.4 EMF inside buildings 16

3 Calculation 17

3.1 Procedures 17

3.1.1 Closed solutions 17

3.1.2 Numerical procedures 18

4 Measurements 20

4.1 Procedures 20

4.1.1 LF/MF bands 20

4.1.2 HF bands 21

Page

4.1.3 VHF/UHF bands 21

4.1.4 SHF bands 21

4.2 Instruments 21

4.2.1 Introduction 21

4.2.2 Characteristics of the measurement instruments for electric and magnetic field 22

4.2.3 Narrow band instrument types and specifications 23

4.3 Comparison between predictions and measurements 24

5 Precautions at transmitting stations and in their vicinity 24

5.1 Precautions to control the direct health effects of RF radiation 24

5.1.1 Employee (occupational) precautionary measures 25

5.1.2 Precautionary measures in relation to the general public 26

5.2 Precautions to control the indirect RF radiation hazards 26

Appendix 1 to Annex 1 – Examples of calculated field strengths near broadcasting antennas 27

Appendix 2 to Annex 1 – Comparison between predictions and measurements 41

Appendix 3 to Annex 1 – Limits and levels 62

Appendix 4 to Annex 1 – Additional evaluation methods 71

Appendix 5 to Annex 1 – Electromedical devices 75

Appendix 6 to Annex 1 – References 76


1 Introduction


For many years the subject of the effects of electromagnetic radiation has been considered and attempts have been made to quantify particular limits that could be used to protect humans from undesirable effects. Studies in many countries by various organizations have resulted in various administrative regulations. It is noteworthy and understandable that no single standard has emerged from all the efforts in this regard.

This Recommendation is intended to provide a basis for the derivation and estimation of the values of electromagnetic radiation from a broadcast station that occur at particular distances from the transmitter site. Using such information, responsible organizations can then develop appropriate

standards that may be used to protect humans from undesirable exposure to harmful radiation. The actual values to be applied in any regulation will naturally depend on decisions reached by responsible health agencies, domestic and worldwide.

It is noted that this ITU-R Recommendation and ITU-T Recommendations cover similar material, but with an emphasis on different aspects of the same general subject. For example, ITU T Recom­mendations K.52 (Guidance on complying with limits for human exposure to electromagnetic fields) and K.61 (Guidance to measurement and numerical prediction of electromagnetic fields for compliance with human limits for telecommunication installations) provide guidance on compliance with exposure limits for telecommunication systems. Appropriate reference information is included in Appendix 6.


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