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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.
@Logicfest -- Not so fast, bucko! The problem with satellite radio is that it costs money. AM and FM radio are available for free and you can't beat that price.
Also, you are forgetting about people who are fanatical about things like shortwave. I can't imagine a day when you won't have a bunch of high quality short wave receivers around and international broadcasts covering everything imaginable are the norm.
I think the popularity of satellite radio will grow, but it will augment conventional radio instead of totally replacing it.
Bonus points for pointing out digital, satellite radio because that is the wave of the future. We may well be approaching the day when a Sirius radio receiver will take the place of conventional AM/FM radios.
There is a problem with those digital signals, though. Conventional radio receivers will still play if a signal gets a little weak. With a digital signal, it is either on or off. There is no dealing with a weak signal in those things -- the signal just vanishes completely.
In other words, there is still a lot of room for improvement in the satellite radio world. But that stuff will dominate one day. Count on it.
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