Radio waves are commonly used to carry information through a process called modulation. Modulation involves encoding the information onto a carrier wave, which is a high-frequency sinusoidal waveform. The carrier wave serves as a "vehicle" to transmit the information over long distances.
There are several types of modulation techniques used in radio communication. The two most fundamental forms of modulation are amplitude modulation (AM) and frequency modulation (FM).
Amplitude Modulation (AM): In AM, the amplitude (strength) of the carrier wave is varied in proportion to the variations in the audio or data signal being transmitted. The audio or data signal, which contains the desired information, is typically at a lower frequency. By varying the amplitude of the carrier wave in accordance with the audio or data signal, the information is encoded into the radio wave. The receiver can then demodulate the received signal to extract the original information.
Frequency Modulation (FM): In FM, the frequency of the carrier wave is varied in response to the audio or data signal. The variations in the audio or data signal cause corresponding changes in the carrier wave's frequency. The receiver detects these frequency changes to decode the transmitted information.
In addition to AM and FM, there are other modulation techniques such as phase modulation (PM), quadrature amplitude modulation (QAM), and more, which provide increased data transmission rates and improved efficiency in specific applications.
It's important to note that before modulation, the original information needs to be converted into an appropriate format. For example, in audio communication, analog audio signals are often converted into digital format using analog-to-digital conversion techniques. The digital data can then be modulated onto the carrier wave using various modulation schemes.
At the receiving end, the demodulation process reverses the modulation process, extracting the original information from the received radio wave. The demodulated signal is then processed further to retrieve the desired audio, data, or other types of information.