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Block diagram of a crystal radio receiver Circuit diagram of a simple crystal radio. A crystal radio can be thought of as a radio receiver reduced to its essentials. [3] [39] It consists of at least these components: [22] [40] [41] An antenna in which electric currents are induced by radio waves.
A schematic of a simple superhet broadcast FM receiver. Note that there is no AGC loop, but simply uses a high-gain IF amplifier which is intentionally driven into saturation (or limiting). For single conversion superheterodyne AM receivers designed for medium wave (AM broadcast) the IF is commonly 455 kHz.
A simple crystal radio with no tuned circuit can be used to listen to strong AM broadcast signals. An early form of envelope detector was the crystal detector, which was used in the crystal set radio receiver. A later version using a crystal diode is still used in crystal radio sets today.
The Neutrodyne receiver, invented in 1922 by Louis Hazeltine, [133] [134] was a TRF receiver with a "neutralizing" circuit added to each radio amplification stage to cancel the feedback to prevent the oscillations which caused the annoying whistles in the TRF.
English: Circuit of the simplest possible crystal radio receiver. Circuits of this type were used in the first experimental crystal radio receivers in the pioneering days of radio, just after 1900. It consists of a crystal detector (semiconductor diode) DI connected between a long wire antenna and ground, with a sensitive earphone E1 attached ...
The reason for using the amplifier for "double duty" was to reduce the number of active devices, vacuum tubes or transistors, required in the circuit, to reduce the cost. The economical reflex circuit was used in inexpensive vacuum tube radios in the 1920s, and was revived again in simple portable tube radios in the 1930s. [7]
The radio circuit inside the ZN414 is based on a design known as Tuned Radio Frequency (TRF). The TRF design is much simpler than the popular, but more complex, superheterodyne radio circuit often used in modern AM receivers. It is principally the use of the TRF circuit that allows almost a whole radio to be fitted into one small, three pin ...
Envelope detectors are often a component of other circuits, such as a compressor or an auto-wah or envelope-followed filter. In these circuits, the envelope follower is part of what is known as the "side chain", a circuit which describes some characteristic of the input, in this case its volume.