Radio waves are electromagnetic oscillations that propagate in space at the speed of light. Electromagnetic radiation is characterized by frequency, wavelength and power of the energy carried. The frequency of electromagnetic waves shows how many times per second the direction of the electric current changes in the emitter and therefore how many times per second the value of the electric and magnetic fields change in each point of space.
Frequency is measured in hertz (Hz). 1 Hz is one oscillation per second, 1 megahertz (MHz) is a million oscillations per second. Knowing that the speed of electromagnetic waves is equal to the speed of light, we can determine the distance between points in space where the electric (or magnetic) field is in the same phase. This distance is called the wavelength. The radio waves (radio frequencies) used in radio engineering occupy a region, or more scientifically, a spectrum from 10,000 m (30 kHz) to 0.1 mm (3,000 GHz). International agreements divide the entire spectrum of radio waves used in radio communications into bands:
| Frequency range | Abbreviated name of the range | Name of the waveband | Wavelength |
| 3-30 kHz | VLF (Very low frequencies) | Myriameter | 10-100 km |
| 30-300 kHz | LF (Low frequencies) | Kilometer | 1-10 km |
| 300-3000 kHz | MF (Mid frequencies) | Hectometric | 0.1-1 km |
| 3-30 MHz | HF (High frequencies) | Decameter | 10-100 m |
| 30-300 MHz | VHF (Very High Frequency) | Meter | 1-10 m |
| 300-3000 MHz | UHF (Ultra High Frequency) | decimeter | 0.1-1 m |
| 30-3000 MHz | VHF (Ultra Short Wave) | Meter | 0.1-10 m |
| 3-30 GHz | Microwave (Super High Frequency) | centimeter | 1-10 cm |
| 30-300 GHz | EHF (Extremely high frequencies) | Millimeter | 1-10 mm |
| 300-3000 GHz | HHF (Hyper High Frequency) | decimillimeter | 0.1-1mm |
In addition to separating the frequency range on the basis of wavelength, the following designations are used in mobile official and civil communications:
| Frequency range, MHz | Designation in Russian | Designation in English | Notes |
| 2-30 | HF (Short waves) | SW (Short Wave) | It is used for long-distance communications both for official and amateur radio purposes. |
| 25-30 | cb | CB (Citizen Band) | Civil and amateur radio band. 40 channels of the section 26.965-27.405 MHz are intended for unlicensed communication. |
| 33-50 | Low Band | LB (Low Band) | Range of mobile terrestrial communications and occasional broadcasting. |
| 108-136 | Aviation | Air Band | Range for aviation radio communication. |
| 136-174 | VHF (Very High Frequency) | VHF (Very High Frequency) | Mobile radio range. It is divided into amateur radio, maritime, television and radio broadcasting, service and other sections. |
| 300-337 | river range | River Band | Range of river navigation |
| 400-512 | UHF (Decimeter waves); UHF (Ultra High Frequency) | UHF (Ultra Hugh Frequency) | Mobile radio range. Sometimes it is also called VHF, meaning the entire 136-512 MHz section, which is also true. Includes both unlicensed areas and areas for official use. |
