Part 1
What are electromagnetic fields?
Electromagnetic fields can be generated artificially,
but naturally also occur in the environment. They belong to the
"non-ionizing radiation ".
In static and low-frequency fields, the electrical and
magnetic components are considered separately. In the case of high-frequency
fields, the two components are closely coupled to one another, so that one
speaks here of electromagnetic fields.
Low frequency electrical and magnetic fields can
create electrical fields and currents in the body. Biological tissue can be
heated by high-frequency electromagnetic fields.
The task of radiation protection is to ensure that the
strength of the fields is so low that there is no damage to health.
How are the electromagnetic fields divided?
Like the entire electromagnetic spectrum, the
electromagnetic fields are divided into different areas based on their physical
properties. This happens either
based on frequency or
based on the wavelength .
The frequency has the unit of measurement Hertz ( Hz ;
1 Hz = 1 oscillation per second). The wavelength is given in meters ( m ).
Frequency and wavelength are firmly connected with each other via the speed of
propagation. At high frequencies, the wavelengths are small, while low
frequencies are associated with long wavelengths.
When do we speak of fields, when do we speak of waves or
radiation ?
Instead of the term "electromagnetic
fields", the terms "electromagnetic waves" or
"electromagnetic radiation " are also used. The different terms
describe different physical properties:
" Field " describes the spatial distribution
of a force effect that can be exerted on electrical charges and currents
"Wave" describes the spread of a
time-varying field in space.
" Radiation " describes the transport of
energy.
Where can you find static, low-frequency and
high-frequency fields?
• A
static magnetic field of natural origin is the earth's magnetic field.
• There
is a permanent electric field in the atmosphere between the earth and the
ionosphere : the fair weather field.
• Artificial
low-frequency electrical fields exist on all electrical lines and electrical
devices to which a voltage is applied.
• Low-frequency
magnetic fields occur on all electrical devices and lines in which alternating
current flows.
• High-frequency
electromagnetic fields are used, for example, in mobile radio, for WLAN or in
cordless phones.
How do electromagnetic fields work?
Due to their different physical properties, the
different areas of the electromagnetic spectrum have different effects on
biological organisms. The energy of the individual photons is particularly
important . It increases continuously with increasing frequency .
Electromagnetic fields belong to "non-ionizing
radiation ". The photons of non-ionizing radiation have, in contrast to
ionizing radiation not have enough energy to ionize atoms and molecules, i.e.,
from the shell electron "knocked out" and thus positively charged
particles (ions) to produce. Among other things, this means that, in contrast
to X-rays, for example, their energy is too low to directly damage the genetic
material and thus to be directly involved in the development of cancer.
• Low
frequency electrical and magnetic fields can create electrical fields and
currents in the body .
• Biological
tissue can be heated by high-frequency electromagnetic fields .
High frequency fields
High frequency fields
They are generally radiated by an antenna and can
transmit energy and information over long distances. Due to the wide range of
possible uses of high-frequency electromagnetic fields, especially for modern
communication ( e.g. radio, television, mobile communications, cordless
telephones, WLAN and Bluetooth), people are nowadays surrounded by a large
number of different transmission devices that work with different transmission
powers and frequencies.
Bluetooth, Wireless Local Area Networks ( WLAN )
Bluetooth
The short-range radio Bluetooth primarily aims at the
coupling of peripheral devices in the office area (e.g. PC, notebook , laptop
and palmtop , organizer , printer, scanner ). Many smartphones also contain a
Bluetooth transmitter.
The frequency range used is between 2400 and 2483 MHz
.
Bluetooth has three transmission power classes:
• Class
1: maximum transmitting power of 100 mW
for applications with ranges up to approximately 100
meters,
• Class
2: maximum transmitting power of 2.5 mW
for ranges in the area of the office workspace up to a
few 10 meters,
for applications in the immediate vicinity up to
approx. 10 meters.
WIRELESS INTERNET ACCESS
WLAN is used to set up local computer networks. The
devices can be wirelessly networked with each other via factory-installed radio
interfaces in laptop and tablet computers or with appropriate plug-in cards.
Central access points ( access points, hot spots ) enable connection to
higher-level network structures, in the professional field, for example, to a
company-owned data network. Many smartphones also have a WLAN interface. In
public places such as hotels or airports, but also in the private sector,
wireless Internet connections are possible without using a mobile network.
Like Bluetooth, WLAN also uses the 2.4 GHz frequency
band. In addition, frequencies between 5 and 6 GHz can be used.
The maximum permissible radiation power of the devices
depends on the frequency range used:
• Frequency
range around 2400 MHz : 100 mW EIRP
• Frequency
range from 5150 to 5350 MHz : 200 mW EIRP when used exclusively in closed rooms
and
• Frequency
range from 5470 to 5725 MHz : 1 W EIRP .
Recommended limits are observed
Investigations within the framework of the German Mobile
Communication Research Program have shown that immissions from WLAN and
Bluetooth devices in typical home or office environments are significantly
below the recommended limit values (see project Determination of exposure when
using wireless transmission methods in the home and office ).
Tips for users of smartphones and tablets
Just like classic mobile phones, smartphones use high-frequency
electromagnetic fields for the transmission of voice and data. In addition
to cell phone connections, smartphones can generally also use wireless LAN ( WLAN ) .
The same applies to tablets: They use high-frequency fields for WLAN connections
and often have built-in cell phones.
Smartphones, cell phones and tablets
with LTE or UMTS are
less radiation
Modern mobile terminals have an advantage over older models:
they often transmit in the UMTS or LTE standard. Both
standards are less radiation than the GSM standard when
establishing a connection .
In the GSM standard,
the call is set up with maximum performance. The device then regulates down to
the required transmission power . With the UMTS or LTE standard,
the mobile device does exactly the opposite. The connection establishment
begins with the lowest transmission power and then increases
to the required power.
According to the current state of science and technology, mobile
communications pose no health risk. However, the technology is still too
young for a final assessment of long-term effects. Even with effects on
children, not all questions have been answered conclusively. The Federal Office
for Radiation Protection therefore supports further research in these areas and
advises users not to neglect preventive care.
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