How are signals transmitted and received in radio communication

For radio communication, radio waves must first be emitted. In the radio wave transmitter, there is an important component called the oscillator, which can generate high-frequency alternating current. When the high-frequency alternating current flows through the antenna, a high-frequency electromagnetic field is generated in space. Because this electromagnetic field is undergoing periodic changes, new electromagnetic fields are generated around, so radio waves are emitted.

Radio broadcasting transmits sound, and television broadcasting transmits not only sound but also images. The high-frequency alternating current generated by the oscillator is used to carry information such as sound and images, and is also called a carrier wave. The information to be transmitted is added to the carrier wave and transmitted, and the information can be transmitted to a distant place. Adding information to the carrier is to make the carrier change with the signal. This technique is called modulation.

There are many radio and television stations in the world, and they emit electromagnetic waves all the time. Therefore, there are many electromagnetic waves around us. When receiving radio broadcasts, you must first select the one you need from the many electromagnetic waves. When we turn the knob of the radio to select a station, we are actually selecting the electromagnetic waves we need. This is technically called tuning.

How are signals transmitted and received in radio communication

After tuning, the receiver gets a specific high-frequency signal current with information. This high-frequency signal current is not the required information itself. To obtain the required sound and image information, they must be "taken out" from the high-frequency signal current. This process is called demodulation. The signal obtained by demodulation is usually amplified. If the transmission is sound information, you can make the speaker emit sound; if the transmission is image information, you can make the monitor display images.

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