Generalitat de Catalunya

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What're they?

An antenna is a device capable of transmitting and receiving signals in the form of electromagnetic waves. Mobile phone antennas receive and send calls to and from telephones located within a limited coverage radius. They do so by transmitting and receiving electromagnetic waves within a specific range of frequencies. Such antennas measure approximately 1-3 metres (6½-10 feet), depending on the system being used. A large number are mounted on a tower or mast normally measuring 15-50 metres (50-150 feet) in height.

What are they composed of?

Mobile phone antennas are made of metal, sometimes with a fibreglass casing, and are generally fixed to an iron mast. The source of the signal transmitted to a mobile phone may be a receiving dish or a telephone line, for which the antenna serves the same function as a loudspeaker. There is also a case containing equipment such as amplifiers for providing the transmitting antenna with the necessary coverage area and a receiving antenna connected to other amplifiers for enhancing weak signals sent by mobile phones (occasionally, the transmitting and receiving antennas are one and the same).

Maximum levels: the safety guideline

As the safety guideline for electromagnetic radiation exposure, the International Commission on Non Ionising Radiation Protection (ICNIRP) has set a maximum powerdensity limit of 61 V/m (10 W/m²) for frequencies in the range of 10-300 GHz. NOTE: For the GSM 900 mobile phone network, the limit is 41 V/m (4.5 W/m²). In Catalonia, the safety guideline sets a limit of 27 V/m (4 W/m²). This is provided for by Decree 148/2001.. Regulations for the maximum level of exposure to mobile telephonic radiation. Comparison between Spanish and European regulations (which are the same) and those of Catalonia:

 

Frequency range	Spain and Europe	Catalonia
900 MHz	41,19	27,46
1800 MHz	58,25	38,83
2-300 GHz	61,40	41,19

 

Safety zone: protection parallelepiped

Safety zone: protection parallelepiped. This is the minimum distance that should be maintained from the mobile phone antenna. This space is known as the protection parallelepiped (a parallelepiped is a six-sided figure made up of six parallelograms) and people are advised not to enter this zone for safety reasons. These dimensions must be increased fivefold for areas lacking in the adequate safety protection measures for schoolchildren.

An example of the safety distance

Example: A 750 watt running microwave oven with the door open. Distance: So as not to suffer the effects of the energy released, it is necessary to maintain a distance of 4 metres from the microwave oven.

Example: A rooftop mobile phone antenna. Distance: The safety distance is 4½ metres (approx.). Even so, for additional safety, Catalan regulations recommended a distance of 10 metres. This space is referred to as the protection parallelepiped. It is forbidden to enter this space.

The RFMS (Radio Frequency Monitoring System) is the system used by the Generalitat for monitoring the electromagnetic emissions of mobile phone antennas.

Interview to Jordi Boldú, of the Center of Telecommunications and Information Technologies. Generalitat of Catalonia.

Why was the SMRF (Radio Frequency Monitoring System) created?

Human beings are unable to detect most electromagnetic fields, such as the signals emitted by mobile phone antennas. This means that some people feel a certain distrust towards this kind of antenna. So, by compensating the invisibility of electromagnetic fields by establishing proper regulations, the system provides some assurance that signal levels stay below legally permitted limits. Our responsibility then, to some extent, is to transmit that confidence to people in general, keep a definite environmental quality control and ensure that regulations are met. This system also allows for the implementation of the UMTS (Universal Mobile Telecommunications System), the third generation (3G) mobile telephony system which is central to developing technologies in Catalonia.

What does the SMRF consist of and how does it work?

The system consists of a probe that picks up signals from any direction and measures electrical field levels every half second, 24 hours a day, the whole year round, under regulations set by the Generalitat of Catalonia. The system has database back up and affords a second by second display of its readings. The signal data, which is stored in the actual probe, is transmitted to the lab located in the Generalitat's Centre of Telecommunications and Information Technologies (CTTI).

What happens if signal levels top the limits permitted in Catalonia?

Should signal levels exceed the established limit of 27 V/m (volts per metre), a team from the CTTI takes field readings and then notifies them to the relevant local authorities and the Ministry of the Environment and Housing. Directly afterwards, it gets in touch with the mobile phone operators that have antennas serving the particular area, so as to pinpoint the cause of the excessive signal levels and to re-establish the legally permitted limits.

Where is the RFMS located in Catalonia?

The Telecommunications and Information Technologies Centre (CTTI) hosts a website for consulting electromagnetic-energy emissions produced by mobile phone base stations. The website permits various search-types, by town and comarca, using a database and interactive map.Search

Why is there an increasing number of inner city antennas?

There are more antennas in built up areas than in the countryside, due to the fact that there are many shaded areas in inner cities. A shaded area occurs where handsets are short of coverage because a physical obstacle, typically, a building, blocks antenna coverage. This greatly weakens the signal. Also, since there are more people making calls in a built up area, the handling capacity of each mobile phone base station, which is limited to a certain number of calls per hour, gets saturated. Additional stations therefore need to be installed to handle the greater call load.

• Electromagnetic wave:An antenna releases energy in the form of electromagnetic waves made up by different kinds of electric and magnetic elements. For this reason, electromagnetic radiation can be charted on a spectrum ranging from very high to very low frequencies. Light, for example, is just one of these waves and, like those of mobile telephony, consists of radiation in the form of non-ionizing waves
• Ionizing and non ionizing waves NThe world is teeming with electromagnetic waves like those we can pick up using appliances such as radios, mobile phones, radars and televisions. Waves that can pass through molecules (x-rays and gamma rays) are known as ionizing waves, whereas non-ionizing waves (radio waves, microwaves and mobile phone waves) are not capable of doing this and so cause the body they collide with to overheat, as the power density exceeds the limits set.
• Radiation: Radiation refers to energy emissions in the form of waves, produced by antennas, or in the form of highly energised particles, e.g. neutrons, ions.
• Emission:Emission refers to the reception of energy waves, in this case from electromagnetic mobile phone antennas, in a specific area.
• Frequency: Frequency is a measure of the rate of an occurrence over unit of time. Under the International System of Units, the resulting value is given in Hertz, named after the German physicist Heinrich Rudolf Hertz. Hence, a frequency of 1 Hz means the rate of the occurrence is once every second. And for the case at hand, it represents the number of waves passing through a point each second.
• Protection parallelepiped:This is the safety zone surrounding the antenna which, as a precaution, the general public should not enter. This distance increases fivefold in areas where there are schoolchildren regularly present.
• Coverage:A mobile phone is provided with coverage when located within the range of a mobile phone antenna and can therefore be used to make calls.
• Shaded zone:A shaded zone is an area where a mobile phone apparatus is not capable of placing or receiving calls because there is no network coverage. This happens when the electromagnetic wave transmitted or intercepted by one of these antennas meets a physical obstacle, normally a building or a mountain, causing an interruption to the signal.
• Power density S (W/m²): Power density measures the power in watts per unit area: in this case, 1 sq. metre. It represents the number of watts localised in 1 sq. metre and is the standard measure under the International System. This is the power falling perpendicularly on a surface, divided by the surface area, expressed in W/m².
• Power density and distance: Power density is inversely proportional to the distance squared. So, as the distance increases, the power density decreases by the sum of the root.

• Catalonia: Decree 148/2001 on the environmental distribution of mobile phone installations.
• Spain: Royal Decree 1006/2001 on radio emissions.
• Europe:European Council Recommendation 1999/519/CE on the limitation of exposure of the public to electromagnetic fields.

• Secretary's Office of Telecommunications and Society of the Information. Department of Government and Public Administrations.
• General Direction of Environmental Quality.
• Department of Environment and Housing.
• Center of Telecommunications Information Technologies.

With the participation of the Localred local group, respective councils and Wavecontrol S.L., the Catalan engineering firm which initiated development of the hardware and programming for the RFMS network in a combined effort with the Grup de Compatibilitat Electromagnètica (Electromagnetic Compatibility Group) at the UPC (Polytechnic University of Catalonia).

We thank their availability to the owners of the placements, where the RFMS have been installed.