In 1887, Heinrich Hertz proved that electromagnetic energy could be sent into space in the form of radio waves that travel through the atmosphere at about the speed of light. This discovery helped develop the principles of radio communication that are still in use today. In addition, the scientist proved that radio waves are electromagnetic in nature, and their main characteristic is the frequency at which energy fluctuates between electric and magnetic fields. The frequency in hertz (Hz) is related to the wavelength λ, which is the distance a radio wave travels in 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-carrying radio waves. They can transmit voice or digital data. To do this, the radio must have:
- A device for collecting information into an electrical signal (for example, a microphone). This signal is called baseband in the normal audio range.
- Modulator for entering information into the signal frequency band at the selected radio frequency.
- A transmitter, a signal power amplifier that sends it to an antenna.
- An antenna made of a conductive rod of a certain length,which will emit an electromagnetic radio wave.
- Signal booster on receiver side.
- A demodulator that will be able to recover the original information from the received radio signal.
- Finally, a device for reproducing the transmitted information (for example, a loudspeaker).
Radio Communication Principles
The modern principle of radio communication was conceived at the beginning of the last century. At that time, radio was developed mainly for the transmission of voice and music. But very soon it became possible to use the principles of radio communication to transmit more complex information. For example, such as text. This led to the invention of the Morse telegraph.
The common thing for voice, music or telegraph is that the basic information is encrypted in audio signals, which are characterized by amplitude and frequency (Hz). Humans can hear sounds ranging from 30 Hz to about 12,000 Hz. This range is called the audio spectrum.
The radio frequency spectrum is divided into different frequency ranges. Each of which has specific characteristics regarding radiation and attenuation in the atmosphere. There are communication applications described in the table below that operate in one or another band.
| LF-range | from 30 kHz | up to 300 kHz | Mainly used for aircraft, beacons, navigation, and information transmission. |
| FM Band | from 300 kHz | up to 3000 kHz | Usedfor digital broadcasting. |
| HF band | from 3000 kHz | up to 30000 kHz | This band is widely suitable for medium and long distance terrestrial communications. |
| VHF band | from 30000 kHz | up to 300000 kHz | VHF is commonly used for terrestrial broadcasting and ship and aircraft communications |
| UHF band | from 300000 kHz | up to 3000000 kHz | This spectrum is used by satellite positioning systems, as well as mobile phones. |
Today it is hard to imagine what humanity would do without radio communication, which has found its application in many modern devices. For example, the principles of radio and television are used in mobile phones, keyboards, GPRS, Wi-Fi, wireless computer networks, and so on.
