Transmission frequency
The transmission frequency is a physical-technical characteristic for the wireless transmission of messages, as it is used for radio, voice radio, mobile phone, WLAN and also via satellite. It is essential that an oscillating circuit works in the transmitter, which generates an electrical oscillation which, emitted via an antenna, spreads as electromagnetic waves through the air or empty space in a spherical shape at the speed of light and, depending on the frequency , also penetrates walls and each other adapts to the curvature of the earth and thus has a large range .
Each receiver has a corresponding resonant circuit tuned to the desired frequency, which is excited to resonate by the transmitted wave ; the signal of this oscillation is then amplified and processed so that the original useful signal is restored and z. B. becomes audible as language or music.
Due to the different numbers of vibrations per second, separate signal flows can be realized that do not interfere with one another. However, since the entire space is filled by the oscillation due to the more or less spherical propagation (depending on frequency, antenna shape and transmission power), different signal flows cannot be set up on the same frequency without interfering with one another. Since every modulated transmission frequency is surrounded by signals adjacent to it, i.e. it occupies a bandwidth , frequencies cannot be placed as close together as desired if they are not to interfere with one another.
Therefore, the usable frequencies cannot be increased at will and are therefore in demand and controversial. The rule of thumb is that a useful frequency has a bandwidth of 20 kHz corresponding to the frequency range of our language. Accordingly, in the z. B. between 1 and 1.1 GHz can accommodate 1000 times as many useful signals as between 1 and 1.1 MHz.
administration
Broadcast frequencies are managed by government regulations and international agreements. In Germany, the Deutsche Bundespost administered the frequency assignments until around 1990 and laid down the criteria for testing and monitoring (e.g. for amateur radio ) of transmitting devices including transmitting antennas and of radio operators.
