Aerial;
Antenna

A device from which radio waves are transmitted and received. There are different designs in operation.

A metallic rod or wire for sending and receiving radio waves or microwaves.

AGNIR

The Advisory Group on Non-Ionising Radiation (AGNIR) is an independent advisory group of experts. Until April 2005 it reported to the Board of the NRPB; it now reports to a sub committee of the HPA that is concerned with radiation, chemical and environmental hazards.

Amplitude Modulation

The encoding of a carrier wave by varying its amplitude or height, in accordance with an input signal, so that it carries the desired information.

Cell

A geographic area of coverage that a Radio Base Station covers.

Electric Field

A field of force surrounding a charged body or associated with a fluctuating magnetic field, with which charged particles interact.

Electromagnetic Waves

Electromagnetic waves are emitted by many natural and man-made sources and play a very important part in our lives.

Electromagnetic waves are used to transmit and receive signals from mobiles phones and their base stations. The type of electromagnetic waves mobile phones use are called radio frequency (RF) waves.

EMC

Electromagnetic compatibility

EMF

Electromagnetic fields

ETSI

European Telecommunications Standards Institute

Field Strength

The amplitude of the electric or magnetic fields. Related to the Power Density through the impedance of free space.

Fields

See Electric Field.

Frequency

Frequency is the number of times per second at which an electromagnetic wave oscillates. It determines the wave's properties and usage. Frequencies are measured in hertz (Hz). 1 Hz is one oscillation per second, 1 kHz a thousand, 1 MHz is a million and 1 GHz is a thousand million. Frequencies between 30 kHz and 300 GHz are widely used for telecommunications, including broadcast radio and television, and comprise the radio frequency band.

Health Impact

A health impact can be positive or negative. A positive impact contributes to good or improving health whereas a negative one causes or contributes to ill-health.

HPA

The Health Protection Agency (HPA) is an independent body that protects the health and well-being of the (UK) population. The Agency plays a critical role in protecting people from infectious diseases and in preventing harm when hazards involving chemicals, poisons or radiation occur. It also prepares for new and emerging threats, such as a bio-terrorist attack or virulent new strain of disease.

ICNIRP

The International Commission on Non-Ionising Radiation Protection (ICNIRP) is an independent scientific body which has produced an international set of guidelines for public exposure to radio frequency waves. These guidelines were recommended in the Stewart Report and adopted by the Government, replacing the National Radiological Protection Board (NRPB) guidelines.

Ionising

A process in which an atom or molecule loses or gains electrons, acquiring an electric charge or changing an existing charge.

Macrocell

A macrocell provides the largest area of coverage within a mobile network. The antennae for macrocells can be mounted on ground-based masts, rooftops or other existing structures. They must be positioned at a height that is not obstructed by terrain or buildings. Macrocells provide radio coverage over varying distances depending on the frequency used, the number of calls made and the physical terrain. Macrocell base stations have a typical power output in tens of watts.

Mast

A ground-based structure that supports antennae at a height where they can satisfactorily send and receive radio waves. A typical mast is 15m high, and of steel lattice or tubular steel construction. New slimmer versions of masts (monopoles) can be painted to blend in with their surroundings, disguised as trees or used in conjunction with street lighting and CCTV cameras. Masts themselves play no part in the transmission of the radio waves.

Maximum Ground Level Emission

Maximum Ground Level Emission or the beam of highest intensity usually occurs between 50m and 200m from an antenna. The ground level emission within this area is the highest circling a base station. It is nevertheless usually many thousands of times lower than international public exposure guidelines. Emission levels reduce rapidly as the distance increases from the antenna. The highest emissions levels are directly in front of the antenna.

Microcell

Microcells provide additional coverage and capacity where there are high numbers of users within urban and suburban macrocells.

Near Field

The near field is the region within one wavelength of an antenna, where the electric and magnetic fields are not related to each other solely by the characteristic impedance of free space.

Non-ionising radiation

Radiation that does not break chemical bonds in matter. When non-ionising radiation passes through body tissues, it does not have sufficient energy to damage DNA directly.

NRPB

On 1 April 2005 the National Radiological Protection Board (NRPB) joined the Health protection Agency (HPA). The NRPB had two main functions: to advance knowledge about the protection of mankind from radiation hazards and to provide information and advice to persons in the UK with responsibilities relating to protection from radiation hazards. The NRPB produced a set of national guidelines for public exposure to Radio Frequency waves. These have the same scientific foundation as the ICNIRP guidelines.

Picocell

A picocell provides more localised coverage than a microcell. These are normally found inside buildings where coverage is poor or where there are a high number of users such as airport terminals, train stations or shopping centres.

Power Density

The energy flowing from an antenna through a unit area normal to the direction of propagation in a unit time. This is measured in watts per square metre.

Radio Base Station

A radio base station is a macrocell, microcell or picocell site and consists of transmitters and receivers in a cabin or cabinet connected to antennae by feeder cable.

RF

Radio Frequency

SAR

SAR (Specific Absorption Rate) is a measure of the amount of RF power absorbed in any part of the human body due to the use of equipment such as mobile phones or by human exposure close to other transmitting sources.

TETRA

TErrestrial Trunked RAdio, typically used by utilities and emergency services.

Thermal effect

A heating effect.

Transmitter

Electronic equipment that generates radio frequency electromagnetic energy and is connected to an antenna via a feeder cable.  

Wavelength

Wavelength is the distance in metres between any two 'similar' points on a radio wave. This portion of the wave is referred to as one complete cycle. The lower the frequency of a wave the longer the wavelength.

The distance between corresponding points on two consecutive waves. For example, the wavelength of ocean waves is the distance between one crest and the next, or one trough and the next.

WHO

World Health Organisation