FM broadcasting is permitted in the FM broadcast bands between about 65 and 108 MHz in the very high frequency (VHF) range. In frequency modulation (FM) the frequency of the radio signal is varied slightly by the audio signal. AM broadcasting is also permitted in shortwave bands, between about 2.3 and 26 MHz, which are used for long distance international broadcasting. AM broadcasting is allowed in the AM broadcast bands which are between 148 and 283 kHz in the longwave range, and between 5 kHz in the medium frequency (MF) range of the radio spectrum. In amplitude modulation (AM) the strength of the radio signal is varied by the audio signal. Two types of modulation are used in analog radio broadcasting systems AM and FM. Modulation is the process of adding information to a radio carrier wave. All radios have a volume control to adjust the loudness of the audio, and some type of 'tuning' control to select the radio station to be received. The radio requires electric power, provided either by batteries inside the radio or a power cord which plugs into an electric outlet. The sound is reproduced either by a loudspeaker in the radio or an earphone which plugs into a jack on the radio. The most familiar form of radio receiver is a broadcast receiver, often just called a radio, which receives audio programs intended for public reception transmitted by local radio stations. 3.2 Tuned radio frequency (TRF) receiver.However radio receivers are very widely used in other areas of modern technology, in televisions, cell phones, wireless modems, radio clocks and other components of communications, remote control, and wireless networking systems. A broadcast receiver is commonly called a 'radio'. The most familiar type of radio receiver for most people is a broadcast radio receiver, which reproduces sound transmitted by radio broadcasting stations, historically the first mass-market radio application. A radio receiver may be a separate piece of electronic equipment, or an electronic circuit within another device. The information produced by the receiver may be in the form of sound, video ( television), or digital data. Radio receivers are essential components of all systems that use radio. The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation. The antenna intercepts radio waves ( electromagnetic waves of radio frequency) and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. During the golden age of radio, 1925–1955, families gathered to listen to the home radio receiver in the evening Girl listening to vacuum tube console radio in the 1940s.

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