Radio technology or radio is a term for the method of wirelessly transmitting signals of all kinds with the help of modulated electromagnetic waves in the radio frequency range ( radio waves ). One form of wire-based transmission of these signals is what is known as carrier frequency technology .
Applications in industry and medicine that only use high frequency as a tool (such as hardening and melting furnaces or therapy devices), on the other hand, usually use unmodulated radio waves without imprinted information and are therefore not assigned to radio technology.
History and origin of the term
The existence of radio waves was predicted in 1864 by James Clerk Maxwell on the basis of theoretical considerations and confirmed experimentally on November 11, 1886 by Heinrich Hertz for the first time. The name "funk" goes back to the term spark . The first transmission systems worked with spark gaps - the strong, harmonic-rich current and voltage impulses created the desired radio waves. Guglielmo Marconi achieved the first radio link in 1895 with a pop-spark transmitter and a replica of a receiver by Alexander Stepanowitsch Popow over a distance of about five kilometers. These pioneers of radio technology are now considered to be the first radio amateurs .
The physicist Ferdinand Braun received the Nobel Prize in Physics in 1909 for his contribution to the development of telegraphy by radio. He shared the prize with Marconi, who successfully implemented it in practice and carried out the first transatlantic radio transmission. On September 20, 1898, Braun had set up the first wireless communication system at the Physics Institute in Strasbourg , which shortly afterwards extended 30 km to the Vosges town of Mutzig . Marconi set up the first wireless connection over the Bristol Channel in 1897 , and in the same year Braun set up a radio link from Cuxhaven that reached 3 km to the Kugelbake . On September 24, 1900, such a connection was created over the 62 km long route Cuxhaven - Helgoland . The first transatlantic radio transmission between Poldhu ( The Lizard Peninsula , Cornwall ) and St. John's (Newfoundland) was achieved on December 12, 1901 .
This primitive and now undesirable generation of radio waves only allowed messages to be transmitted using Morse code , for example from the major radio station in Nauen to the ships of the Imperial Navy or to the radio stations in German South West Africa . Only after the discovery of the oscillator circuit with an electron tube by Alexander Meißner and the developments based on it after 1913 could further types of modulation be developed. The prerequisite for this is an initially constant output power, which can be changed in a targeted manner when transmitting sound, images and later also data.
The first voice message was sent in 1900 by Reginald Fessenden . The first radio broadcast took place for Christmas in 1906. Fessenden read the Christmas story from the Bible. The transmission could be received within 500 meters.
Radio technology is based on the fact that a carrier signal ( electromagnetic wave ) - an initially sinusoidal alternating voltage of constant amplitude - can be changed in a targeted manner by means of a type of modulation through a communication signal. For example, the frequency or the amplitude of the alternating voltage is changed in the rhythm of the signal. The modulated wave is emitted via an antenna and received by another antenna on the receiver side. The original message is recovered by demodulation and can then be made audible or visible ( television ) or processed in some other way.
The advantage over competing transmission types is that
- there are very many different carrier frequencies that do not influence each other
- no electrical cables have to be laid between the transmitter and receiver
- the number of radio receivers is practically not subject to any technical restrictions
- Sender and receiver are very well camouflaged and can possibly hardly be discovered
The disadvantage is that
- you can listen to the broadcasts without being discovered. However, the use of the transmitted data can be made more difficult by encryption
- communication can be made difficult or impossible by jammers
- the technical effort is considerable, but this is becoming less and less important due to advances in microelectronics
- In the entire range of the transmitter, each frequency band can only be used by a single transmitter, unless technologies such as directional radio , single-frequency networks or time division multiplexing are used
In the case of radio and television , one participant transmits the radio or television station, and all other participants on this channel only receive without transmitting themselves. The transmission is unidirectional - it only goes in one direction.
With radiotelephony or Morse code , several people send alternately on the same channel (usually one frequency or a pair of frequencies) so that communication in both directions is possible. In contrast to unidirectional transmission (e.g. broadcasting), this enables information to flow in both directions.
In addition to Morse code and speech, still and moving images, for example weather satellite images or television, and data of all kinds are transmitted.
In the recent history of radio technology, communication protocols such as GSM , UMTS (both for cell phones ), IEEE 802.11 (wireless computer network) or Bluetooth (wireless communication with digital peripheral devices) are often used directly by the devices .
Although the technology nowadays differs greatly from that of 1920, the eponymous word component radio has been used in terms such as radio , mobile radio , radio , etc. and in the company name Telefunken to this day.
A new development in radio technology was made possible by extremely energy-saving miniaturization: batteryless radio technology for use in switches and sensors. Batteryless radio technology is also already being used to network different types of devices. The energy required for the transmission process is obtained from the environment through energy harvesting (e.g. from pressing a button, temperature difference, light or vibrations).
Problems and glitches
As seen physically above about 60 MHz electromagnetic waves propagate quasi optically be relay stations needed when the globe ( globe is to be sparked). Nowadays this task is carried out by z. B. satellites.
Gases ( earth's atmosphere ) can impair the signal path. This leads to a multitude of effects that depend on the frequency used , the density of the gas, the ionization and the stratification in the signal path. A transmission through liquid and solid media leads to a strong attenuation of the signal.
At frequencies greater than about 100 MHz, there is increasing interference from reflections on masonry, metal structures, wires or towers. The reflections lead to staggered double reception with signal corruption and group delay distortion. There is partial or complete cancellation of signal components in opposite phase. The movements of the transmitting or receiving antenna or other objects in the signal path can impair the transmission (use with passive radar and in radar motion detectors!). There are ghosting images in TV reception and problems with using GPS .
- Aurora (scattering and reflection on northern lights ionization layers, see aurora borealis # Influence on technical facilities )
- Echo reception ("ghost images" through different reception paths caused by reflection)
Effects of wireless propagation in the earth's atmosphere
- Fading (fading, strongly changing field strength )
- Flutter fading (fading with rapidly changing field strength)
- Maximum Usable Frequency (highest usable shortwave frequency that is still reflected by the ionosphere)
- Meteor scatter (scattering and reflection from ionized meteorite traces)
- Mögel-Dellinger effect , English Sudden ionospheric disturbance (SID)
- Near fading and daily attenuation in the medium wave range
- Reflection on the ionosphere
- Reflection on the sporadic E-layer
- selective carrier shrinkage
- Tropo propagation ( overreach due to reflection and tunneling in inversion layers )
There are numerous applications of radio technology, officially they are divided into radio services . Examples are:
- Amateur radio
- Commercial radio
- BOS radio (e.g. police radio )
- Radio data transmission (also for mobile telephony )
- Aeronautical radio
- Radio navigation
- Radio remote control (building services, research, industry and model making)
- Everyone's radio ( CB radio , SRD , PMR446 , DMR446 )
- Mobile marine radio service
- RFID ( radio frequency identification device , radio chips)
- Radio ( radio and television )
- Train radio
Depending on their needs, a variety of technical and organizational forms are used, such as
- Analog or digital signal transmission
- Unidirectional or bidirectional operation
- Radio networks
- Communication satellites
- Directional radio
- Terrestrial transmission
- Wolfgang Schreier : The emergence of radio technology . Deutsches Museum, Munich 1996, ISBN 3-924183-35-X .
- Artur Fürst: Under the spell of Nauen . Deutsche Verlags-Anstalt, Stuttgart, Berlin 1923.