How the radio works

Simplifying, we can say that, basically, a radio receiver in an electrical circuit is designed in such a way that allows you to filter or separate a tiny stream, which is generated by the antenna, the effect of electromagnetic waves (the phenomenon is called induction electromagnetic) which usually arrive by air (although travel by any means, including the vacuum) and then selectively amplified thousands of times to send it to an element with an electromagnet, which is the speaker (or speaker), which transforms electrical information into sound. In this circuit there is a variable capacitor, which in the old radios were attached to a button or control knob, so it is the turn varies the condenser capacity. The effect of the variation in the capacity of the capacitor in the circuit is filtered flows of different frequency, and therefore, to hear what passed by different radio stations. The simplest radio receiver that we build is known as the origins of the radio receiver galena. It was called so because the material that was used as a semiconductor diode detector was a small stone of this material making contact on a thin wire which is called bearded cat. This component is the immediate predecessor of silicon or germanium diodes currently used. This receiver allows only rudimentary hearing power stations and not very distant, since no amplification of any kind. Evolution of receptors Lafayette HA-700 receiver, 1962, tube The initial diode galena was subsequently replaced by the vacuum valve, component-based e-Edison Effect, ie the property that have the hot metal to release electrons. This valve allowed to get better sensitivity. Old radio The invention of the transistor to the late 40s, led to the miniaturization of receivers, and its easy portability, not dependent on electrical power. Also reception techniques have evolved significantly since the early days of radio, beginning with the use of other types of modulation other than amplitude, the modulation frequency, single sideband, digital modulation, the different configurations of receptors, the evolution of the components from the valve termique the transistor and then to the integrated circuit. Portable radio that runs on batteries With respect to the configuration, the receiver more elaborate and more efficient, in terms of sensitivity and selectivity combined is called super-heterodyne, although there have been more simple but less efficient, as the radio tuner, the regenerative and the super -regenerative.