Electromagnetic Fields (EMF)
What is EMF?
Wireless communications systems use electromagnetic fields (EMF) to carry information from one point to another. In other words, without electromagnetic fields there will be neither wireless nor mobile telecommunication.
Electromagnetic fields are sometimes referred to as radiation. EMFs are the vehicle for
transporting information (or electronic data) from a mobile phone to a base station and viceversa.
Electromagnetic fields are made up of Electric and Magnetic Fields. Magnetic fields are created
when electric current flows: the greater the current, the stronger the magnetic field. An electric
field will exist even when there is no current flowing. They are created by differences in voltage.
That is, electric fields are present at every electrical power outlet in our homes.
When an electrical appliance such as a lamp, refrigerator or fan is turned on, electric current flows and magnetic fields are set up around the cable. These electric and magnetic fields moving together through space are what we refer to as electromagnetic fields.
So, as you can see, electromagnetic fields are present everywhere in our environment but are
invisible to the human eye, except visible light. The electromagnetic fields use for
telecommunications are invisible to the human eye.
In general, electromagnetic fields are produced by natural sources like the sun, the earth and the
ionosphere, and by artificial sources such as:
• Mobile Phones
• Radio Base Stations
• FM & TV Broadcast Antennas
• Radar Facilities
• Remote Controls
• Electric & Electronic Equipment
Most importantly, there are two types of Electromagnetic Fields, namely, non-ionising electromagnetic fields and ionising electromagnetic fields. Examples of non-ionising
electromagnetic fields are radio signals – the signals used for telecommunications. X-rays and
Gamma rays are typical examples of ionising electromagnetic fields.
Non-ionising electromagnetic fields do not possess enough energy to break or change chemical
bonds – that is, they cannot impart sufficient energy to completely remove an electron from an
atom or molecule. In contrast to this, ionising radiation, such as X-rays and Gamma rays, contain
significant energy to strip electrons from atoms and molecules, producing changes that can lead
to tissue damage.
It is refreshing to note that the Radio Frequency Signals (30 KHz – 300 GHz) which are used for
telecommunication are non-ionising electromagnetic fields.
One of the main characteristics which define an electromagnetic field (EMF) is its frequency or
wavelength. Frequency simply describes the number of oscillations or cycles per second of the
wave, while wavelength refers to the distance between one wave and the next. Wavelength and
frequency are inversely proportional: the higher the frequency, the shorter the wavelength.
Higher frequency electromagnetic fields possess more energy than lower frequency signals.
Electromagnetic fields of different frequencies interact with the human body in different ways.
When the wavelength is smaller than the human body (i.e., for higher frequency RF signals),
heating due to induced currents can occur. For wavelengths larger than the human body (i.e., for
Power frequencies and lower-frequency RF signals) heating via induced currents seldom occurs.
Finally, it’s good to know that radio energy dissipates over distance due to path loss along the
medium of propagation.