A radio receiver is an electronic device that takes a transmitted signal, extracts the original signal from it and amplifies that signal. The process of extracting the signal is called demodulation. A radio station, for example, will broadcast a signal which is then detected by a receiver. The receiver, in turn, will separate that signal from many others and then play it through its speakers. There are several different types of signals that the receiver can be designed to demodulate and decode including sounds, pictures and digital data, to name a few.
Alexander Stepanovich Popov designed and implemented the first radio receiver in 1896. It was based on electromagnetic waves, which were proven to exist by James Clerk Maxwell only a few years earlier in 1887. It took only a few more years until the first radio system was able to transmit communications across the Atlantic in 1901. In the time between then and the present day, the receiver has seen a great many technological advances. One of the most significant advances was the invention of the superheterodyne, or superhet, receiver.
These advances have allowed the radio receiver to become more compact while also being able to receive better signals amid crowded radio traffic. This traffic includes a wide range of radio frequencies that are uses for many purposes. Examples of these frequencies are FM, AM, VHF and UHF, but there are many more ranging from extremely low to extremely high frequencies. The receiver is still undergoing many technological advances, especially with the recent increase in the use of digital signals. These digital signals have paved the way for new technologies such as satellite radio and digital TV (DTV).
A radio receiver can come in a great deal of varieties. High fidelity audio receivers are used in home stereo systems not only to listen to radio broadcasts, but also to decode hi-fi signals from other input sources such as DVD players, Blu-Ray Disc players, old-fashioned VCRs and more. A crystal radio receiver runs on the power that is received from radio waves. Measurement and telemetry receivers measure and report a wide array of data based on the signals received and are used for scientific purposes. Other varieties include communications receivers, satellite television receivers, portable transistor radios and radio scanners.