In 1887, Henry Hertz proved thatelectromagnetic energy can be sent into space in the form of radio waves that pass through the atmosphere at about the speed of light. This discovery helped to develop the principles of radio communication, which are used today. In addition, the scientist proved that radio waves are of an electromagnetic nature, and their main characteristic is the frequency at which energy oscillates between electric and magnetic fields. The frequency in Hz (Hz) is related to the wavelength λ, which is the distance that a radio wave passes during one oscillation. Thus, the following formula is obtained: λ = C / F (where C is equal to the speed of light).
The principles of radio communication are based on the transmission of information-bearing radio waves. They can transmit voice or digital data. To do this, the radio must have:
- A device for collecting information in an electrical signal (for example, a microphone). This signal is called the main frequency band in the usual audio range.
- A modulator of entering information into the frequency band of the signal at the selected radio frequency.
- Transmitter, a signal power amplifier that sends it to the antenna.
- Antenna from an electrically conductive rod of a certain length, which will emit an electromagnetic radio wave.
- A signal amplifier on the receiver side.
- Demodulator, which will be able to restore the original information from the received radio signal.
- Finally, a device for playing back the transmitted information (for example, a loudspeaker).
Principles of radio communication
The modern principle of radio communication was conceived inbeginning of the last century. At that time the radio was developed mainly for voice and music. But very soon it became possible to use the principles of radio communication for the transmission of more complex information. For example, such as text. This led to the invention of the Morse telegraph.
Common for voice, music or telegraph isthat the basic information is encrypted in audio signals that are characterized by amplitude and frequency (Hz). People can hear sounds in the range of 30 Hz and up to about 12,000 Hz. This range is called the sound spectrum.
The radio-frequency spectrum is divided into variousfrequency bands. Each of which has specific characteristics with respect to radiation and attenuation in the atmosphere. Highlight the communication applications described in the table below, which work in one or another range.
| LF-range | from 30 kHz | up to 300 kHz | It is mainly used for aircraft, lighthouses, navigation, as well as for information transfer. |
| FM Range | from 300 kHz | up to 3000 kHz | Used for digital broadcasting. |
| HF range | from 3000 kHz | up to 30000 kHz | This range is widely suitable for medium and long-range terrestrial radio communications. |
| VHF band | from 30000 kHz | up to 300,000 kHz | VHF is commonly used for terrestrial broadcasting and communications between ships and aircraft |
| UHF range | from 300,000 kHz | up to 3,000,000 kHz | With this spectrum, satellite positioning systems, as well as mobile phones, operate. |
Сегодня сложно представить, что делало бы humanity without radio communication, which has found its application in many modern devices. For example, the principles of radio communication and television are used in mobile phones, keyboards, GPRS, Wi-Fi, wireless computer networks and so on.
