The frequency range is a term that is widely used in the course of physical and technical disciplines, in particular, in radio engineering. By this concept is meant both the operating range of any device, and the frequency range allocated for broadcasting to a specific radio service . And also we can talk about the breakdown of the whole range of radio frequencies.
International rules strictly regulate the use of different radio systems for broadcasting (including satellite ones) of a strictly defined range. This is dictated by the need to ensure the compatibility of the work of different systems and to eliminate mutual interference.
According to the Radio Regulations, the territory of the Earth is divided into three large regions. The first includes Europe, the CIS countries, Russia, Mongolia and Africa. The second is the territory of America (both North and South). The third - South and South-East Asia, Australia, the Pacific. Each district has its own distribution of radio frequency bands.
For the operation of satellite communication, the Regulation provides frequency bands with the symbols L, S, C, X, Ku, Ka, K ranging from 1452 MHz to 86.0 GHz. The vast majority of satellite systems operate in the C and Ku bands. Ka range is actively developed in Europe and America, but in our country has not found wide application yet.
The efficiency of the antenna depends on the number of wavelengths that fit within the antenna. With increasing frequency, the wavelength decreases (these quantities are inversely proportional) and high-frequency signals do not require large antennas. The frequency range C is adopted by the antenna size of 2.5-4.5 meters, and for receiving waves of the K-band, the required antenna size is only 10-15 cm. At the same dimensions, antennas operating in a high range have a larger gain.
In broadcasting, each transmitting station also has its own frequency range. There is a classification of radio waves over the range and wavelength. According to her, the waves are:
- Decametric with a wavelength of the order of 10 000-100 000 km, the frequencies of which are classified as extremely low (3 - 30 Hz).
- Megametric (the wavelength is 1000-10 000 km), the frequency range is up to 300 Hz.
- Hectokilometrovye (with a length of 100-1000 kilometers), relating to ultralow frequencies (up to 3000 Hz).
- Super long (length - 10-100 kilometers) - very low (up to 30 kHz).
- Long (length is 1-10 kilometers) - low (up to 300 kHz).
- Medium (length 100-1000 meters) - medium frequencies, up to 3000 kHz.
- Short, having a length of 10-100 meters - is so-called. High frequencies (up to 30 MHz).
- Ultra-short or meter (length 1-10 meters), very high (up to 300 MHz).
- Decimetric (length 10-100 centimeters), ultra-high, up to 3000 MHz.
- Centimeter (length 1-10 centimeters), ultra-high (up to 30 GHz).
- Millimeter (length 1-10 millimeters), extremely high (up to 300 GHz).
The frequency range 300-3000 GHz refers to the so-called. Range of hyperhigh frequencies.
At the initial stages of the development of radio communications, waves of a basically long and very long range were used. But they, spreading over the earth's surface, were strongly absorbed, powerful transmitting devices were required. Steady reception is conducted on medium waves, but it is difficult to provide the transmission distance, and this range, mainly local radio broadcasting with a radius of several hundred kilometers, is used.
Short waves provide a longer range, but are subject to interference and signal distortion. They are used, for the most part, in air and sea navigation and on the main lines of communication.
The main advantage of high-frequency ranges is the possibility of using antennas whose dimensions are comparable with the wavelength, radiation is effective only if this condition is met. The construction of long-range communication systems based on the propagation of waves within the limits of visibility became possible with the use of artificial Earth satellites.