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Electromagnetic Fields > ... > Applications of High Frequency Fields
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Applications of High Frequency Fields
Numerous technologies use high frequency (HF) electromagnetic fields: Every day life cannot be imagined without broadcasting and television, cordless phones increase comfort when phoning indoors and in the garden, babies are monitored in their rooms using baby monitors, computers are linked to each other and to peripheral devices by using Wireless LAN (WLAN) and Bluetooth and recently ultrawideband (UWB) technologies, police and fire brigades use their own radio network for communication. Moreover high frequency fields are applied for radar units, in microwave ovens and for electronic article surveillance systems. At present new applications for high frequency fields in the terahertz range are developed and tested (e.g., security scans at airports). The strongest increase in use, however, has been stated in mobile telecommunication for some years. UMTS and WiMAX technology for fast data transmission will further increase the frequency of utilisation.
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Mobile communication – GSM and UMTS
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For mobile communication the GSM (Global System for Mobile Communications) and the UMTS (Universal Mobile Telecommunication System) Standard are used at pre-sent. The frequency range for the German D-network lies around 900 MHz, for the E-network around 1800 MHz and for UMTS between 1900 an 2170 MHz.
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Other Radio Services
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Government agencies and emergency services, such as police forces, fire brigades, ambulance and Frontier Police operate their own radio network strictly separated from other radio networks (abbreviated as BOS in Germany). Personal radio services permit citizens a short-distance communication. They are free of charge and do not require a licence. Amateur radio is an experimental radio service with devices and antennas being frequently modified. It requires a licence.
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Cordless phones
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Cordless phones for houses and gardens use radio waves for communication between handsets and a base station connected to a fixed line telephone network.
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WiMAX
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WiMAX (Worldwide Interoperability for Microwave Access) is a new standard for regional radio networks, promising much better coverage and data rates (theoretically several kilometres and Mbit/s). Therefore WiMAX is frequently denoted as “big brother” of WLAN technology. Especially in rural areas, where cable-bound DSL connections to the Internet are missing due to economic reasons, WiMAX is seen as an interesting alternative for network providers to handle the so-called “last mile” to the customer. The frequency range usable for WiMAX technology in principle goes from 2 – 66 GHz.
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Baby Monitors
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Baby monitors may use two different technologies to transfer noise from the nursery to parents and thus give them the opportunity to control their babies or toddlers from the distance: the electrical grid of the house or flat or a radio system. Today most of the baby monitors apply wireless communication.
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Broadcasting and Television
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Radio stations work at frequency ranges between 1.4 and 108 MHz, television stations between 174 and 890 MHz. The number of stations is low compared to mobile telecommunication. Transmitter power, however, can be very high, up to several million watt (MW) depending on the size of the area to be powered and on the frequency range. Safety distances in the main radiating direction of the antenna can therefore amount to several hundred meters. High radio towers usually do not require safety distances at ground level.
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Further applications
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Radar units are applied for many purposes. Best known are radar systems for civil and military aviation supervision, weather radar or traffic supervision radar. High frequency radiation at a frequency of 2.45 GHz is used in microwave ovens for the rapid heating of food. Some types of electronic article surveillance systems also work with high frequency radiation at frequencies between 1.8 and 10 MHz or between 2400 and 2500 MHz. At present new applications for the millimetre/terahertz range of the electromagnetic spectrum are developed. For airport security screening security scans are tested worldwide using terahertz radiation. Workstations are surrounded by electromagnetic fields with a wide frequency range due to their mode of operation
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