Frequency range is a term that is widely used in the course of physical and technical disciplines, in particular, in radio engineering. This concept means both the operating range of a device and the frequency range allocated for broadcasting to a particular radio service . And also we can talk about a breakdown of the entire range of radio frequencies.
International rules strictly regulate the use by various radio communication systems of broadcasting (including satellite) 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 Earth’s territory 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 Southeast Asia, Australia, the Pacific region. Each region has its own distribution of radio frequency bands.
For the operation of satellite communications, the Regulation provides frequency ranges with the symbols: L, S, C, X, Ku, Ka, K in the range from 1452 MHz to 86.0 GHz. The vast majority of satellite systems operate in the C and Ku bands. The Ka range is actively mastered in the countries of Europe and America, but has not yet found wide application in our country.
The effectiveness of the antenna depends on the number of wavelengths that fit in the diameter of the antenna. With increasing frequency, the wavelength decreases (these values are inversely proportional) and large antennas are not required to receive high-frequency signals. The frequency range C is received by an antenna measuring 2.5-4.5 meters, and to receive the waves of the K range, the required antenna size is only 10-15 cm. With the same dimensions, antennas operating in a high range have a higher gain.
In broadcasting, each transmitting station also has its own frequency range. There is a classification of radio waves by range and wavelength. According to her, there are waves:
- Decametric with a wavelength of about 10,000-100,000 kilometers, the frequencies of which are classified as extremely low (3 - 30 Hz).
- Megametric (wavelength - 1000-10 000 kilometers), frequency range - up to 300 Hz.
- Hectokilometer (with a length of 100-1000 kilometers) related to ultra-low frequencies (up to 3000 Hz).
- Extra-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 - this is the so-called. high frequencies (frequencies up to 30 MHz).
- Ultrashort 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), ultrahigh (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. hyper-frequency range.
At the initial stages of the development of radio communications, waves of mainly a long and super-long range were used. But they, spreading over the earth's surface, were strongly absorbed, powerful transmitting devices were required. Stable reception is carried out on medium waves, but it is difficult to provide transmission range on them, and this range is mainly used by local broadcasting with a radius of several hundred kilometers.
Shortwaves provide greater range, but are subject to noise and signal distortion. They are used, for the most part, in air and sea navigation and on trunk communication lines.
The main advantage of the high-frequency ranges is the possibility of using antennas, the dimensions of which are comparable to the wavelength, radiation is effective only if this condition is met. The construction of long-distance communication systems based on the propagation of waves within sight became possible with the use of artificial Earth satellites.