Frequency range is a term widely used.used in the course of physical and technical disciplines, in particular, in radio engineering. This concept implies both the operating range of a device and the frequency range allocated for broadcasting to a specific radio service. And also we can talk about the breakdown of the entire range of radio frequencies.
International rules strictly regulatethe use of broadcast radio systems (including satellite) of a strictly defined range. This is dictated by the need to ensure the compatibility of the work of different systems and eliminate mutual interference.
According to the Radio Regulations, the territory of the Earthdivided into three large areas. The first includes Europe, the CIS countries, Russia, Mongolia and Africa. The second is the territory of America (both North and South). The third is South and Southeast Asia, Australia, and the Pacific. Each region has its own distribution of radio frequency bands.
For satellite communications Regulationsprovides for frequency bands with the legend: L, S, C, X, Ku, Ka, K 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 being actively developed in Europe and America, but has not yet found wide application in our country.
The antenna efficiency depends on the number of wavelengthswhich are stacked across the antenna. With increasing frequency, the wavelength decreases (these values are inversely proportional) and large antennas are not required for receiving high-frequency signals. The frequency range C is received by an antenna measuring 2.5–4.5 meters, and for receiving K-band waves, the required antenna size is only 10–15 cm. With the same antenna sizes, operating in a high range, they 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 waves are:
- Dekametricheskie 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), the frequency range - up to 300 Hz.
- Hecto-kilometer (with a length of 100-1000 kilometers), related to ultra-low 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 - 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).
- Decimeter (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 mm), extremely high (up to 300 GHz).
The frequency range of 300-3000 GHz refers to the so-called. the range of hyperhigh frequencies.
In the early stages of radio developmentwaves were used mainly in the long and superlong range. But they, spreading over the earth's surface, were strongly absorbed, powerful transmitting devices were required. Sustained reception is conducted at medium waves, but it is difficult to ensure the transmission range at them, and this range is mainly used by local broadcasting with a radius of several hundred kilometers.
Short waves provide longer ranges, but are subject to interference and signal distortion. They are used, for the most part, in air and sea navigation and on main connected lines.
The main advantage of high-frequency ranges -the possibility of using antennas whose dimensions 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, made possible by the use of artificial satellites of the Earth.
