Measuring RF Electromagnetic Fields at Mobile Communications Base Station and Broadcast Transmitter Sites.

Although it is possible to calculate the exposure level to high frequency electro magnetic fields caused by radio frequency applications, in practice this requires excessive effort, particularly within buildings. As a result, it is often more effective to measure the high frequency field in order to evaluate the exposure. Additionally, there will always be situations in the immediate vicinity of RF transmitting antennas where compliance with limit levels for personal safety cannot be determined with certainty by calculation, such as when the exact attenuation factor of a structural wall is unknown. In such cases, only on-site measurements can provide a final evaluation of safety in the area around the installation. This practical guide is intended to provide you with the necessary theoretical and practical background information that you need to correctly determine high frequency immission using specialist measuring devices, particularly in the vicinity of broadcast and mobile communications transmitters. The experience gained over the past fifteen years by the author from conducting more than 100 training seminars on the subject of determining exposure levels in the high frequency range has been included in this guide.The first chapter of this guide starts with important basic information. This includes discussion of the current international limit value specifications for high frequency electromagnetic fields for the frequency range above 10 MHz and the consequences of these specifications for the standard-compliant determination of immissions. The chapter also includes an introduction to the fundamental measurement principles as well as questions regarding performance of the measurements and quality assurance. To correctly capture the high frequency immission present at the measurement location, the measuring device used must be set up appropriately for each field source (e.g. FM radio transmitter or LTE mobile communications base station) that is to be investigated by measurement to determine its compliance within its locality with limit values. The device settings may vary considerably, depending on the field source and on the measuring device used, even though the theoretical basis for correctly capturing the immission is the same in every case. Because this book places particular emphasis on correct operation of the measuring equipment, the second chapter essentially begins with a thorough introduction to 5 the measuring device that is to be used as the reference device for the measurements described. This is the frequency-selective high frequency field strength measuring system SRM-3006 from Narda Safety Test Solutions, which is currently very widely used worldwide for frequency-selective measurement of high frequency fields. The author of this guide has also used this device for many years in his practical work, and can therefore draw on his long experience in handling the SRM-3006. The second chapter of this book first of all describes the important basic features of the measuring device. It then discusses in more detail how these features affect the correct determination of exposure, and gives an in-depth description of the various measurement modes and parameter settings of the SRM-3006. Chapter 3 gives an introduction to the major broadcasting and mobile communications systems in current use worldwide. The important system parameters that are relevant to correct determination of immission by measurement are then introduced. This is followed by a detailed description of how the SRM-3006 can be used to make a correct measurement of immissions for each of the RF systems mentioned. The chapter also shows how the measurement results are evaluated and how to make a correct comparison with the limit values and determine the standard-compliant sum of the individual signal contributions to the immission. The chapter not only looks at how to operate the measuring device, but also at how to evaluate the measured values properly. This post processing requirement is often underestimated, and is therefore often done incorrectly. Only the current internationally most widely distributed (and therefore most relevant) RF systems in the frequency range above 10 MHz are considered in this practical guide in order to keep this first edition within sensible limits. In the field of broadcasting, for example, classic AM broadcast radio in the range from around 0.1 to 30 MHz is not considered in detail, since this is fast disappearing from the global scene. Practically all the federal long and medium wave radio broadcasting transmitters in Germany had been decommissioned by the end of 2015, and a similar trend can be seen in many other countries. The only analog radio broadcast system considered in this guide is FM radio. In the digital broadcasting field, the guide looks at transmitters for DAB (Digital Audio Broadcasting) and DVB-T (Digital Video Broadcasting Terrestrial, i.e. terrestrial digital television) The immissions from GSM (2G), UMTS (3G) and LTE (4G) mobile communications base stations are considered in detail in this guide. The immissions from terminal equipment such as cellphones are not considered. This practical guide is aimed at both newcomers and experienced users of the SRM-3006. It does, however, assume that readers have a basic understanding of high frequency and radio technology as well as of the determination and evaluation of high frequency exposure. Those who use other frequency selective measuring devices to determine exposure levels will also find much universally applicable information in this book that they can apply in their everyday work. I am very grateful to Narda Safety Test Solutions in Pfullingen, Germany, for their support in the realization of this book. Thanks also to John Nutley, the translator of this book for his agreeable work and to Bernd Brozio for the layout of text, pictures and drawings. Further special thanks are due to Dr.-Ing. Christian Bornkessel of Ilmenau Technical University for his constructive advice and suggestions for improvement. Matthias Wuschek