The range of radio waves and their propagation

In textbooks on physics, abstruse formulas are given on the radio wave band, which are sometimes not fully understood even by people with special education and work experience. In this article, we will try to understand the essence without resorting to complexities. Nikola Tesla was the first to discover radio waves. In his time, where there was no high-tech equipment, Tesla did not fully understand what kind of phenomenon he later called ether. A conductor with alternating electric current is the beginning of a radio wave.

Sources of radio waves

The natural sources of radio waves are astronomical objects and lightning. An artificial radiator of radio waves is an electrical conductor with an alternating electric current moving inside it. The vibrational energy of the high-frequency generator propagates into the surrounding space by means of a radio antenna. The first working source of radio waves was radio transmitter-radio Popova. In this device, the high-frequency generator function was performed by a high-voltage storage device connected to an antenna - a Hertz vibrator. Artificial radio waves are used for stationary and mobile radar, radio broadcasting, radio communication, communication satellites, navigation and computer systems.

Range of radio waves

The waves used in radio communications are in the frequency range of 30 kHz to 3000 GHz. Based on the length and frequency of the wave, the propagation characteristics, the radio wave band is divided into 10 subbands:

1. SDV - very long.
2. DV - long.
3. SW - average.
4. HF - short.
5. VHF - ultrashort.
6. MV - meter.
7. DMV - decimeter.
8. SMV - centimeters.
9. MMV - millimeter.
10. SMMV - submillimeter

Frequency range of radio waves

The spectrum of radio waves is conditionally divided into sections. Depending on the frequency and length of the radio waves are divided into 12 subbands. The frequency range of radio waves is interrelated with the frequency of the alternating current of the signal. Frequency ranges of radio waves in the international radio regulations are represented by 12 names:

1. ELF - extremely low.
2. SNF - extremely low.
3. INCH - infra-low.
4. VLF - very low.
5. Low frequency - low frequencies.
6. MF - medium frequencies.
7. HF - high frequencies.
8. VHF - very high.
9. UHF - ultrahigh.
10. Microwave - super high.
11. EHF - extremely high.
12. GWH - hyperhigh.

As the frequency of the radio wave increases, its length decreases, as the frequency of the radio wave decreases, it increases. The propagation, depending on its length, is the most important property of a radio wave.

The propagation of radio waves 300 MHz - 300 GHz is called ultrahigh microwave because of their rather high frequency. Even the subranges are very extensive, so they are in turn divided into gaps, which include certain ranges of television and broadcasting, for maritime and space communications, terrestrial and aeronautical, for radar and radio navigation, for the transmission of medical data and so on. Despite the fact that the entire radio wave band is divided into regions, the indicated boundaries between them are conditional. The plots follow one after the other continuously, changing one into another, and sometimes overlapping.

Features of radio wave propagation

Propagation of radio waves is the transfer of energy by an alternating electromagnetic field from one part of space to another. In a vacuum, the radio wave propagates at the speed of light. When the environment is exposed to radio waves, propagation of radio waves can be difficult. This manifests itself in the distortion of signals, changes in the direction of propagation, slowing down the phase and group velocities.

Each of the types of waves is applied in different ways. Longer can better bypass the barriers. This means that the radio wave band can propagate along the ground and water planes. The use of long waves is widespread in submarine and sea vessels, which allows you to be in touch anywhere in the sea. At a wavelength of six hundred meters with a frequency of five hundred kilohertz tuned receivers of all lighthouses and rescue stations.

The propagation of radio waves in different bands depends on their frequency. The smaller the length and the higher the frequency, the more direct the path of the wave. Accordingly, the smaller its frequency and the longer the length, the more it is able to circumvent the barriers. Each range of radio wavelengths has its own propagation features, but there is no sharp change in the distinguishing features on the border of neighboring bands.

Characteristic of the spread

Extra long and long waves skirting the surface of the planet, spreading by the surface rays for thousands of kilometers.

The average waves are subject to stronger absorption, so they can overcome a distance of only 500-1500 kilometers. When the ionosphere is compacted in this range, it is possible to transmit the signal with a spatial beam, which provides communication for several thousand kilometers.

Short waves propagate only to close distances due to the absorption of their energy by the surface of the planet. Spatial ones are capable of repeatedly reflecting from the earth's surface and ionosphere, overcoming long distances, carrying out the transfer of information.

Ultra-short can transmit a large amount of information. Radio waves of this range penetrate through the ionosphere into space, therefore, for terrestrial communication purposes, they are practically unsuitable. The surface waves of these bands radiate outright, without bending the surface of the planet.

In the optical ranges, it is possible to transmit giant volumes of information. Most often, a third range of optical waves is used for communication. In the Earth's atmosphere, they are subject to attenuation, so in reality they transmit the signal for a distance of up to 5 km. But the use of such communication systems eliminates the need to obtain permits from telecommunications inspections.

The principle of modulation

In order to transmit information, the radio wave needs to be modulated by a signal. The transmitter emits modulated radio waves, that is, changed. Short, medium and long waves have amplitude modulation, therefore they are denoted as AM. Before modulation, the carrier wave moves with a constant amplitude. Amplitude modulation for transmission changes it in amplitude, according to the signal voltage. The amplitude of the radio wave varies in direct proportion to the voltage of the signal. Ultra-short waves have frequency modulation, therefore they are designated as FM. Frequency modulation imposes an additional frequency, which carries information. To transmit a signal over a distance, it needs to be modulated by a higher-frequency signal. To receive a signal, it is necessary to separate it from the subcarrier of the wave. With frequency modulation, interference is less, but the radio has to broadcast on VHF.

Factors affecting the quality and efficiency of radio waves

The quality and efficiency of receiving radio waves is affected by the method of directional radiation. An example is a satellite antenna that directs radiation to the location of the installed receiving sensor. This method has made it possible to make significant progress in the field of radio astronomy and to make many discoveries in science. He discovered the possibilities of creating satellite broadcasting, data transmission by wireless method and much more. It turned out that radio waves can radiate the Sun, many planets that are outside our solar system, as well as cosmic nebulae and some stars. It is assumed that outside of our galaxy there are objects that have powerful radio waves.

At the range of the radio wave, the propagation of radio waves is influenced not only by solar radiation, but also by meteorological conditions. So, meter waves, in fact, do not depend on weather conditions. And the range of distribution of centimeters strongly depends on weather conditions. Occurs because the water in the rain or at an increased level of humidity in the air short waves are scattered or absorbed.

Also, their quality is affected by obstacles on the way. At such times, the signal fades, while audibility deteriorates significantly or even disappears for a few moments or more. An example is the reaction of the TV to a flying plane, when the image flashes and white lines appear. This is due to the fact that the wave is reflected from the aircraft and passes by the TV antenna. Such phenomena with TVs and radio transmitters often occur in cities, as the radio wave band reflects on buildings, high-rise towers, increasing the wave path.