the majority of braodcast tramsitters emit radiation outside residential areas

Broadcasting, point-to-point microwave links, amateur radio

Transmitters for radio and TV programmes are usually placed at elevated locations outside residential areas. Although amateur radio transmitters are located in residential areas,

they are only used for limited periods. Point-to point microwave links only transmit in very narrow cones.

The majority of broadcast transmitters emit radiation outside residential areas

Contents

Broadcasting > P 7 Broadcasting

Transmitting power > P 7 Broadcasting transmission installations  

serve the purpose of transmitting radio  Radio > P 7 and TV programmes through the air. They  

are usually placed at elevated locations,  Precautionary regulations of the ONIR > P e.g. on hilltops or in the mountains. Some  

large-scale facilities are named after the  Television > P mountain peak they are situated on, e.g. La  

Dôle, Chasseral, Rigi, Säntis, Monte San Sal- Point-to-point microwave links > P 0 vatore, and in addition there are numer-

ous smaller installations. In Switzerland,  Point-to-point microwave  approximately 400 radio and 600 TV sta- links in Switzerland > P 0 tions broadcast programmes. Their loca-

tions and details concerning their trans - Strongly focused radiation > P 0 mitting power and programmes broadcast  

can be found at www.funksender.ch.

Limit values for point-to-point  

microwave transmitters > P 0 Transmitting power

Amateur radio > P Broadcasting installations that cover a  

large area use high transmitting power.  Limit values for amateur  Due to Switzerland's topography, most of  

radio installations > P these high-output systems are installed  Broadcasting stations on the Rigi, canton

at elevated locations, and this means that  of Schwyz (left) and Bantiger, canton of Bern there are usually no residential buildings  (above). The directional dishes in the lower in their immediate vicinity. The radia- section of the towers link the station

tion from these transmitters is narrow - with other transmitters. The antennae for ly focused vertically and directed slightly  broadcasting TV and radio programmes are downwards while it is omnidirectional hor- at the top.

Radio

Radio programmes are broadcast at a vari- 0s. Its sound quality is better than that ety of frequencies. Each frequency range is  of medium wave, and it is possible to broad- named after the corresponding wavelength. cast in stereo.

Medium wave (MW): Medium wave is the  T-DAB digital radio: This is intended as a name given to the range from 00 kHz to  medium-term extension of VHF. T-DAB stands MHz. It was this frequency range that was  for terrestrial digital audio broadcasting. used to broadcast the first radio programmes  It was introduced in Switzerland in . In

in Switzerland in the 0s, and was later  addition, digital radio programmes are also also used by national stations such as  broadcast via cable and satellite.

Beromünster, Sottens and Monte Ceneri.  With DAB, the sound signal is digitised

After the introduction of VHF (very high  before it is broadcast, i.e. it is converted to frequency), medium wave began to lose  a numerical sequence based on and 0

ground due to its inferior sound quality.  similar to the method of storing data on a Since the mid-0s, only two stations have  music CD. The receiver then converts the continued to use medium wave ("Option  digital data back into words and music. musique" and "Musigwälle "). Thanks to this technology it is now possible

to listen to the radio while driving, without Very high frequency (VHF): Nowadays, most  the problem of interference. DAB is prima- radio programmes are broadcast on VHF. This rily used in the VHF range between and frequency range is between 0 and 00 MHz,  0 MHz.

and within this range the band from 7. to

0 Hz is reserved for radio programmes. VHF

has been in use in Switzerland since the

Broadcasting, point-to-point microwave links, amateur radio

izontally. There are also fill-in transmitters  than analogue technology, this advantage  higher transmitting power. Whether dig- that supply valleys via antennae with low  would be lost again if more programmes  ital TV (DVB-T) will lead to lower transmis- transmitting power. were to be transmitted using wireless  sion power, and thus to lower radiation ex- Outside of cities and urban centres, broad- technology in the future. posure, therefore depends on the number casting transmitters usually account for  Digital transmission requires lower trans- of programmes to be transmitted in the the largest proportion of high-frequency  mission power than analogue technology  future, and on requirements relating to background radiation. But in densely pop- for the same reception quality, but this ad- reception quality.

ulated areas, it is often signals from base  vantage, too, would be lost again if TV sig-

station antennae that predominate. nals were also to be designed for recep-

At present it is difficult to assess the im- tion by mobile (portable indoor) TV sets

pact of the changeover from analogue to  equipped with a smaller antenna, instead

digital transmission technology on radia- of for fixed outdoor reception (i.e. via an

tion exposure. Although digital technology  aerial on the roof). In this case, the at-

requires fewer frequencies for transmit - tenuation of the building shell would have

ting a certain number of TV programmes  to be offset by using a correspondingly

20 Reproduced with the kind permission of swisstopo (BA056863)

10 Lyss

Burgdorf

0 Bantiger broadcasting tower

Bern

Depiction of electric field strength in the surroundings of the Bantiger broadcasting

tower (canton of Bern). The calculations are based on simplified assumptions that do not

10 take diffraction and reflection into account.

Münsingen Due to the topography of the region, there Schwarzenburg is no visual contact with the transmitter in

the areas shown in white. Although the elec-

tric field strength here is very low (less than 0.1 V/m), it is usually still possible to receive

20 radio and TV signals.

km 20 10 0 10 20

0.1 0.3 1 3 10

Installation limit value

Scale of electric field strength in volts per metre (V/m).

Designation  Wavelength  Frequency  Frequencies used in  Precautionary regulations of the ONIR

Switzerland

At places of sensitive use, broadcasting

Long wave (LW)  1 – 10 km  30 – 300 kHz  Not used transmission installations are required Medium wave (MW)  100 – 1000 m  300 kHz – 3 MHz  531 kHz – 1.5 MHz  to comply with the installation limit val-

(MW radio) ue specified by the ONIR. An installation Short wave (SW)  10 – 100 m  3 – 30 MHz  Discontinued as of  comprises all broadcasting antennae on

the end of 2004 the same mast or otherwise located close- Very high frequency  1 – 10 m  30 – 300 MHz  47 – 68 MHz  ly together.

(VHF)  (analogue TV) The installation limit value must be com-

87.5 - 108 MHz  plied with at maximum transmitting pow- (VHF radio) er, and is as follows:

174 - 230 MHz – 8.5 volts per metre (V/m) for medium To date: analogue TV  wave transmitters

and digital radio – 3.0 V/m for all other transmitting instal-

In future:  lations

digital radio and TV

Microwaves  1 mm – 1 m  300 MHz – 300 GHz  470 – 862 MHz Since most broadcasting installations are To date: analogue TV,  located outside of residential areas, they

in future digital TV can usually comply with the installation 1452 - 1492 MHz limit value without difficulty. The only ex- In future: to be  ception here concerns some mountain res- considered for  taurants or cable car/railway stations lo - transmission of local  cated close to a transmitter. Here it is digital radio  possible that the limit value may be ex- programmes ceeded. Unlike mobile phone base stations

for which compliance with the installation limit value is compulsory, in certain ex- ceptional cases the authorities may allow broadcasting installations to exceed their installation limit value.

Television

Nowadays we receive most TV programmes

viacable or satellite. However, the program- mes of Swiss TV are also broadcast via terrestrial transmitters using frequencies in the VHF range (7 to MHz and 7 to 0 MHz) as well as higher frequencies (70 to MHz).

DVB-T: At the end of 00, TV also began converting from conventional analogue technology to DVB-T (which stands for digital video broadcasting terrestrial). This new technology offers higher sound and picture quality as well as the advantage of broadcasting additional data. It also uses frequencies more efficiently. For example, with DVB-T it is possible to simultaneously transmit two to six digital programmes (depending on the desired quality) on one conventional analogue channel.

The city of Zurich is served by the broadcasting tower at nearby Üetliberg. Since the majority of broadcasting transmitters are located in mountains or on hilltops, residential areas are seldom exposed to intensive radiation.

Broadcasting, point-to-point microwave links, amateur radio

Point-to-point microwave links

50

m 0 100 200 300 400 500

Depiction of the radiation of a point-to-point microwave link. The significance of the colours is  indicated in the colour scale below.

< 0.1 0.3 1 3 10

Scale of electric field strength in volts per metre (V/m).  These directional antennae on the Jakobshorn

(canton of Grisons) link mobile phone base stations and switching centres over relatively short distances.

Point-to-point microwave links in Switzerland

In Switzerland there is a nation-wide point- tances this falls to 10 to 100 mW. As a  limit values, and are usually able to do to-point microwave network with typical  rule, point-to-point microwave installa- so without difficulty. The only exception distances of 50 to 70 kilometres between  tions do not transmit pulsed signals, but  that might arise here is if someone stands the transmission and reception antennae.  rather continually and with constant out- close to the antenna directly in the main These distances are bridged with frequen- put power.  beam. In such cases the human body would cies of 4 to 13 gigahertz (GHz). The requi- Despite the initial narrow focusing of the  considerably attenuate or even interrupt red parabolic antennae have a diameter  signal, it nonetheless widens somewhat  the signal, and for this reason, such situ-

of up to several metres and are usually  on its way to the reception antenna. This  ations are of course undesirable for op- installed on high towers in exposed loca- means that it covers a considerably wider  erational reasons. Point-to-point micro- tions (e.g. on hilltops). area than that of the targeted parabolic  wave link antennae are therefore installed In addition to the national network, point- antenna. The further the two stations are  at elevated locations and if necessary are to-point microwave links over shorter dis- apart, the wider the covered area.  fenced in so that no one is likely to block tances are being used to an increasing ex- Apart from the main beam, parabolic an- the signal. This also ensures that the ex- tent. These can be used to connect mobile  tennae also produce a variety of signifi- posure limit values are complied with. The phone base stations with their switching  cantly weaker secondary beams, referred  Ordinance does not specify any installa- centre. To cover shorter distances of a few  to as side lobes. Since these leave the  tion limit values for point-to-point trans- hundred metres up to a few kilometres,  transmitter at a different angle than the  mitting facilities.

frequencies in the range from 18 to 38 GHz  main beam, they can also reach the ground

are used. The respective parabolic anten- beside and beneath the antenna. Meas-

nae have a correspondingly smaller diam- urements carried out near a powerful

eter of several dozen centimetres. transmitter within the national network

have yielded scattered radiation readings

Strongly focused radiation of between 0.03 and 0.15 volts per me- Point-to-point microwave links

tre (V/m). If any exposure is measured in

Parabolic antennae focus the radiation to  the vicinity of point-to-point transmit - Point-to-point microwave links are used for such an extent that it is confined within  ting antennae, this can be attributed to  wireless transmission of phone calls, data and a narrow beam propagating linearly be- side lobes. radio and TV programmes between two points tween the transmitting and receiving sta - with direct visual contact. They support and tions. Thanks to this property, point-to- Limit values for point-to-point  complement data transmission via the cable point transmitters can work with very low  microwave transmitters network. In difficult terrain they are easier to transmitting power compared with broad- install and more economical to operate than casting transmitters. For longer distanc - Stationary point-to-point transmitting  cable systems. Point-to-point microwave sys- es, all they require is a few hundred milli- installations are covered by the ONIR.  tems comprise a parabolic antenna at both watts per frequency, and for shorter dis- They have to comply with the exposure  locations (transmission and reception).

Amateur radio

In Switzerland there are approximately  5,000 amateur radio users, and through - out the world there are more than a mil- lion. In most cases, the required equip- ment is installed in private homes, though  it is also possible to operate amateur radio  from a car, ship or aircraft. For amateur  radio, numerous frequencies are available,  ranging from long wave to microwave. The  necessary  antennae  are  often  in- stalled on the roof or in the immediate  vicinity. Since do-it-yourself and experi- mentation are an important aspect of this  hobby, there are numerous different con- structions. For low frequencies, fixed wire  antennae are usually used, and for short- wave frequencies, many people use verti- cal aerials and directional antennae, while  in the VHF and microwave ranges, direc- tional antennae, vertical aerials and par- Amateur radio aerials can take very different forms. The one shown here is a Yagi roof aerial. abolic antennae are common.

By contrast with mobile communication or

broadcasting, amateur radio systems are  Limit values for amateur  

not permanently in use and therefore do  radio installations

not generate permanent radiation, since  

they only do so when they are actually  Amateur radio installations have to com-

transmitting. An amateur radio licence  ply with the exposure limit values spec-

permits a maximum transmitting power of  ified by the ONIR. These are between 28

1,000 watts, but in practice, many systems  and 87 volts per metre, depending on the

only have an output of up to 100 watts. frequency used. Otherwise no installation

Since the antennae are often located in  limit value has to be complied with as long

residential areas, their distance from oth- as the system is not in operation for more

er residential buildings is relatively short.  than 800 hours a year. This is almost al-

For this reason, amateur radio equipment  ways the case with hobby users. However, Amateur radio equipment

can account for the main proportion of  if a system exceeds the above threshold, it

exposure to high-frequency radiation in  has to comply with the applicable installa-

their immediate vicinity when they are in  tion limit value at places of sensitive use.

use. All stationary installations are sub- This limit value is 8.5 V/m for long wave and

ject to the ONIR and must comply with the  medium wave transmitters and 3.0 V/m

defined limit values.  for all other frequency bands. The can-

tons or municipalities are responsible for

the enforcement of the ONIR in the area

of amateur radio.

Amateur radio frequencies

Frequency range  Frequencies used in Switzerland

for amateur radio

Long wave  135.7 - 137.8 kHz

Medium wave  1.81 - 2 MHz

Short wave  Several bands between

3.5 and 29.7 MHz

VHF  50 - 52 MHz

144 - 146 MHz

Microwave  Several bands between

430 MHz and 250 GHz

Wireless devices in buildings Contents

Wireless devices in buildings > P More and more wireless applications

Cordless phones > P

are now also being used indoors, e.g.

Technical data of cordless phones > P cordless phones, wireless headphones,

baby monitors and WLAN stations for  Cbaalsceu slat taet dio en xs p >o Ps ure from DECT wireless connection to the Internet.  Wireless networks – WLAN > P

Although their transmission power  Transmitting power > P

is often relatively low, these devices  WLAN: technical data > P

can dominate the indoor exposure  WLAN: measured exposure > P

to high-frequency radiation. To keep  Bluetooth > P

exposure as low as possible, these  Bluetooth: technical data > P devices should be used at a due  Bluetooth: calculated exposure > P distance from places where people  Baby monitors > P

spend lengthy periods of time,  Technical data of wireless including bedrooms, living rooms,  baby monitors > P

home offices and children's rooms.

More miniature transmitters also in private households

Wireless devices  The signal pulses at 100 Hz. The transmit- der unfavourable circumstances, interfer- in buildings ting power during a single pulse is 250 mil- ence-free operation will no longer be pos-

liwatts (mW), and the time averaged level  sible. CT1+ phones, which in turn interfere

is 10 mW. This means it is lower than that with mobile phone communications, have Mobile phone base stations, broadcasting  of a GSM mobile phone operating under to be put out of operation.

transmitters and other wireless systems  poor reception conditions, which in this

operated outdoors are not the only sour- case transmits with a pulse power of 1,000

ces of high-frequency radiation. An in- or 2,000 mW, corresponding to a time av-

creasing variety of wireless devices are now  eraged output of 125 or 250 mW. But un-

being used indoors, too, e.g. wireless net- like a cordless phone, a mobile phone ad-

works (WLAN), cordless phones and baby justs its transmitting power to the recep -

monitors. Some of these technologies use  tion conditions, and in ideal circumstances

similar frequencies to those used by mo- can reduce it thousandfold.

bile communication systems, others make  The transmitting power from DECT base

use of higher frequencies. They operate  stations is also 250 mW in the pulse and

with relatively low transmitting power, but  the average level is 10 mW for each hand- Calculated exposure from DECT base stations because they are used indoors, they are of- set served by the base station. DECT base

ten located very close to spots frequently  stations are available on the market with  Distance from  Calculated electric field occupied by the inhabitants. up to six handsets. DECT base station  strength (time averaged) Most of these technologies work with  While  the  latter  only  transmit  during  (source: Federal Office of pulsed transmission, though the pulse pat- a call, the DECT base station transmits  Communications)

terns vary considerably.  permanently, i.e. even when no call is in  0.5 m  0.7 – 4.9 V/m

progress (in which case the average trans- 1.5 m  0.2 – 1.6 V/m

mitting power is 2.5 mW). To minimise ex- 3 m  0.1 – 0.8 V/m Cordless phones posure, the base station should be kept  7 m  0.05 – 0.4 V/m

as far away as possible from places where

people spend lengthy periods of time, e.g.

Cordless phones comprise a base station  beds, armchairs, workdesks.

connected to the fixed phone network, plus  As an alternative to DECT phones, there

one or more handsets for cordless phon- are some cordless phones on the market

ing. Most devices in use today are based  that are based on the CT1+ standard. Here

on the DECT standard and operate in a  the base station only transmits during a

frequency range from 1,880 to 1,900 MHz.  call, and the signal is not pulsed. However,

DECT stands for digital enhanced cordless the frequency bands used by such models

telecommunications. will be attributed to mobile telephony as

of the end of 2005. This means that, un-

Technical data of cordless phones

DECT  DECT  CT1+  CT1+

Base station  Handset  Base station  Handset Frequency  1880 – 1900 MHz  1880 – 1900 MHz  930 – 932 MHz  885 – 887 MHz Pulse  100 Hz  100 Hz  none  none Maximum trans-  250 mW  250 mW  10 mW  10 mW

mitting power  

Mean trans-  10 mW  10 mW  10 mW  10 mW

mitting power  (per handset)  

during call  

Mean trans-  2.5 mW  0 mW  0 mW  0 mW

mitting power  (per handset)

without call  

Transmission  Transmits  Only transmits  Only transmits  Only transmits  status  permanently  during a call  during a call  during a call  Range  Approx. 50 m indoors, approx. 300 m outdoors

Unlike conventional telephones with cords, DECT cordless phones and their base stations emit pulsed radiation.

Wireless devices in buildings

Wireless networks – WLAN

Transmitting power

WLAN stands for Wireless Local Area Net- WLAN at home and in the office: Wireless  In Switzerland, WLAN applications oper- work. This technology is used for con- Internet access can also be set up at home.  ate in the frequency bands of 2.4 or 5.2 necting several computers to one anoth- Here the WLAN base station is connected to 5.7 gigahertz, depending on the rele-

er without the need for cables. It can also  via the phone line or TV cable. Within com- vant standard.

be used for transferring data to periph- panies, computers and peripheral devices  Access points transmit not only during eral devices such as printers, scanners and  can be connected both to the Internet and  data transfer, but also in standby mode. beamers. It enables connections both in- to an intranet via access points. The corresponding control signal is pulsed side buildings and in the public zone, and  WLAN applications operated via an ac- with a frequency of 10 to 100 hertz (Hz). also permits wireless access to the Inter- cess point are referred to as infrastruc- During data transfer, both the access point

net or a company intranet. ture networks. If no access point is avail- and the communication card of the com- Hot spots: One example of use of WLAN able, end devices can communicate direct- puter transmit signals that have a higher

in the public zone is wireless broadband  ly with one another, thus forming an ad  pulse frequency – up to 250 Hz, depending Internet access from highly frequented  hoc network. on the quality of the wireless connection locations such as railway stations, air- and the number of involved stations.

ports, restaurants, universities, etc. At a  With 100 mW, 200 mW or 1 W, the maxi- hot spot, the laptop establishes contact  mum WLAN transmitting power is often by means of its wireless card with a fixed  higher than that of DECT base stations transmission and reception station that  and phones. Compared with the WLAN base is connected to the Internet via a serv- station (access point), the radiation ex -

er. These WLAN base stations are called  posure caused by the WLAN wireless card access points. A fee may or may not be  of the computer is usually higher, since charged for Internet access, depending  the latter is normally located closer to on the hot spot. the user.

WLAN: technical data

Standard  IEEE 802.11b  IEEE 802.11h Frequency  2.4 - 2.4835 GHz  5.15 - 5.35 GHz,

5.47 - 5.725 GHz

Maximum  100 mW  200 mW - 1 W transmitting power  (power control

as required) Pulse in standby mode  10 - 100 Hz  10 - 100 Hz Pulse during data

transfer  10 - 250 Hz  10 - 250 Hz Range  ~30 m indoors  ~30 m indoors

~300 m outdoors  ~300 m outdoors

WLAN: measured exposure

Access points in public areas (100 mW/200 mW) Distance to access point  Measured maximum

electric field strength

1 m  0.7 – 3 V/m

2 m  0.4 – 1.5 V/m

5 m  0.1 – 0.7 V/m

10 m  0.05 – 0.4 V/m

Access points at home (100 mW/200 mW) Distance to access point  Measured maximum electric field strength

1 m  0.7 – 1.3 V/m

5 m  0.1 – 0.3 V/m

WLAN wireless cards for computers (100 mW/200 mW) Distance to WLAN card  Measured maximum

electric field strength

50 cm  1.1 – 4.9 V/m

1 m  0.7 – 2.8 V/m

Stationary WLAN installations in areas accessible to the public have to comply with the exposure limit values specified by the ONIR. Due to the low transmitting power, this is generally the case already. By contrast with mobile phone base stations, the Ordinance does not specify any precautionary limit values for WLAN.

Bluetooth Baby monitors

Bluetooth devices operate at relatively low levels of transmitting power, and this means that

radiation exposure is also low. Baby monitors are devices for acoustic

monitoring of babies and small children. Bluetooth is a standard for wireless data  Three performance categories exist for  The transmitter picks up sounds via a mi- transfer over short distances, e.g. be- Bluetooth devices, with maximum trans- crophone and transmits them to a receiv- tween a computer and a printer, or be- mitting power of 1 mW, 2.5 mW or 100 er that plays back the sounds via a loud- tween headphones and a mobile phone.  mW (i.e. lower than those for DECT and speaker. The two devices can be connected It differs from WLAN technology in that WLAN). via a dedicated cable, the electricity sup- the range is shorter and it uses a differ - ply in the house or via a wireless system. ent transmission protocol. For data trans- Wireless baby monitors are operated at fer, Bluetooth uses 79 different frequency  27.8 or 40.7 MHz. Some models transmit channels around 2.4 GHz. The frequencies  permanently and therefore also gener - are changed 1,600 times a second (and the  ate radiation continuously, while others signal therefore is pulsed at a frequency  only transmit when a sound is emitted. of 1,600 hertz). Electrosmog exposure can be reduced by

choosing the right device:

– Baby monitors that transfer sounds via the power supply do not generate any significant electrosmog exposure.

Bluetooth: technical data – The wireless monitors that generate the

lowest radiation exposure are those that Frequency  Transmitting power  Pulse frequency  Range  only transmit when a sound is made.

2.4 - 2.4835 GHz  1 mW  1,600 Hz  approx. 10 m – Regardless of the type of device, wire-

2.4 - 2.4835 GHz  2.5 mW  1,600 Hz  approx. 15 m less monitors should be kept at a min-

4. - 2.4835 GHz  100 mW  1,600 Hz  approx. 100 m imum distance of 1.5 to 2 metres from the baby.

Bluetooth: calculated exposure

Transmitting power  Maximum electric field   Maximum electric field

(power control as  strength at a distance  strength at a distance  Technical data of wireless baby monitors required)  of 50 cm  of 1 m

1 mW  approx. 0.4 V/m  approx. 0.2 V/m Frequency  Transmitting power  Range

5. mW  approx. 0.6 V/m  approx. 0.3 V/m 27.8 MHz  100 mW  approx. 400 metres 100 mW  approx. 3.5 V/m  approx. 2 V/m 40.7 MHz  10 mW  approx. 400 metres

Index Glossary

Amateur radio  51 Frequency: Frequency refers to the number  Published by:

Baby monitors  55 of oscillations per second, and it is measured  Swiss Agency for the Environment, Base station antenna  42 in hertz (Hz) ( Hz = oscillation per second).  Forests and Landscape SAEFL Bluetooth  55 In the field of wireless communication, kilo- The SAEFL belongs to the Federal

Cable lines  26 hertz (,000 Hz), megahertz (,000,000 Hz)  Department of the Environment,

Clock radios  32 and gigahertz (,000,000,000 Hz) are widely  Transport, Energy and Communications Computer monitors  32 used units. (DETEC).

Cordless phones  53

Current  22 High-frequency radiation: Non-ionising  Concept and text:

Direct current (DC) transport systems  37 radiation with a frequency of 0 kilohertz  Alexander Reichenbach,

Domestic installations  30 to 00 gigahertz is referred to as high- Non-Ionising Radiation Section, SAEFL Electric field strength  41 frequency radiation. Here, the electric and  Assistance: