What you need to know about the antennas of mobile telephone ground stations

/ Updated on 06.02.2007

What is the function of antennas?

Antennas are used in all radiocommunications services (radio and television stations, police force and fire brigade communication systems, mobile telecommunications, etc.) in order to establish communications.

The choice of antenna depends on the type of service to be provided. Antennas for mobile telephones are installed on masts or buildings, in sufficient height and number to guarantee coverage of a specific geographical area. They emit radiation at such locations, thus ensuring sufficient "signal strength".

What kind of radiation is emitted?

There are two main types of electromagnetic radiation: ionising radiation (e.g. X-rays) and non-ionising radiation (e.g. radiocommunications services).

The operation of mobile phones requires a sufficient level of electromagnetic signal - non-ionising radiation - at the user's location, as is likewise the case for the reception of radio or television signals.

Why are there so many antennas?

Given the fact that mobile communications are bi-directional, and due to mobile phones' reduced emission power, the volume of routed traffic and the terrain's specific morphology, a large number of ground stations are need in urban areas. This is why there are considerably more antennas for mobile telephone service than, for example, for television broadcast/re-broadcast stations, which normally ensure coverage using more powerful transmitters.

There is an antenna located near to me. What do I need to know?

Mobile phone ground station antennas emit radiation in a directional manner, operating a bit like a shower-head. This means that radiation is targeted at specific locations, rather than being scattered with equal intensity over the entire area surrounding the antenna. Radiation emission normally occurs horizontally, with a maximum 120o aperture and a slight inclination towards the ground (normally 8o). This means that even in the immediate environs of a ground station antenna the radiation levels may be very low, particularly below, above and behind the antenna.

The radiation level also diminishes to 1/4 (one quarter) of same each time we double our distance from the station. For example, the radiation level at three metres from the antenna will drop to 25% of that level at a distance of six metres, 6.25% at 12 metres and 1.56% at 24 metres. 

Theory and practice have shown that when an antenna is located on top of a building, proper installation and the attenuation resulting from construction material and roofing mean that the radiation in residential dwellings located immediately below an antenna is very low.

Should special precautionary measures be taken?

Although mobile phone ground stations emit a very low level of radiation, people should still approach antenna structures with care, respecting the access limits and minimising the time spent close to indicated areas.

Who authorises installation of antennas?

There are various kinds of authorisation. Mobile operators require a licence to use a specific frequency bloc. This licence - a network usage  licence, including ground stations - is granted by ANACOM, which has exclusive powers to issue radio licences (and only for such purpose). Its responsibilities also include the inspection of ground station operations and monitoring the radiation levels resulting from transmissions.

The fact that ANACOM has granted a network usage  licence does not mean that other entities, with jurisdiction over territorial planning, preservation of the environment and cultural heritage, do not also intervene. In ensure compliance with the respective territorial plans and other applicable norms, such entities, particularly local authorities, intervene following a request to install a ground station and corresponding antennas on land or buildings, specifically with regard to the exact location of the antennas  and the inspection of same.

Do rules for governing emission levels exist?

Yes. As a precautionary measure, ANACOM has adopted a recommendation by the European Union Council of Ministers on this matter, which defines reference levels for non-ionising radiation. In addition to the rules for proper installation, fixed radiocommunications stations must ensure that their emissions do not exceed the specified reference levels.

The Portuguese Parliament likewise approved on 11 June 2002 a resolution recommending that the government should draw up a Code of Conduct and Good Practices within the period of one year, in order to set guidelines for the installation and location of all equipment generating electromagnetic fields, including mobile phone and radio antennas. 

What should I do if I have any doubts?

ANACOM is endowed with inspection powers in the context of spectrum management, in order to ensure proper use of the spectrum. If you have any questions or complaints, please visit  our internet site (www.anacom.pthttps://www.anacom.pt/render.jsp?categoryId=2958), which has a section on electromagnetic fields. Our contacts are also listed in this leaflet.
If you are worried about the possible effects of radiation exposure, you are advised to contact the health authorities.

What is ANACOM?

The ICP - Autoridade Nacional de Comunicações (ANACOM) is the regulatory authority for the postal and telecommunications markets in Portugal. ANACOM's powers include management of the radio spectrum; it is also responsible for protecting the interests of communications service users, specifically by increasing their understanding of the issues involved.