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English: Block diagram of a regenerative radio receiver, a type of radio receiver widely used before World War 2. It consists of a tuned circuit that serves as a bandpass filter to select the desired radio signal out of all the signals picked up by the antenna, and a combined amplifier-detector to increase the power of the signal and extract the audio modulation (sound) signal from from the ...
English: Block diagram of a regenerative radio receiver, invented by Edwin Armstrong in 1912, is a type of radio receiver widely used up until the 1930s.. It consists of a tuned circuit that serves as a bandpass filter to select the desired radio signal out of all the signals picked up by the antenna, and a combined amplifier-detector to increase the power of the signal and extract the audio ...
Regenerative receivers require fewer components than other types of receiver circuit, such as the TRF and superheterodyne. The circuit's advantage was that it got much more amplification (gain) out of the expensive vacuum tubes , thus reducing the number of tubes required and therefore the cost of a receiver.
The regenerative receiver also had its heyday at the time where adding an active element (vacuum tube) was considered costly. In order to increase the gain of the receiver, positive feedback was used in its single RF amplifier stage; this also increased the selectivity of the receiver well beyond what would be expected from a single tuned circuit.
In order to achieve both good adjacent channel selectivity and image rejection, the double-conversion receiver uses two intermediate frequencies (IFs). The incoming radio frequency (RF) signal from the antenna is first mixed with a sinusoidal signal from the 1st local oscillator (LO) to give a high 1st IF frequency.
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.
In the regenerative receiver the gain (amplification) of a vacuum tube or transistor is increased by using regeneration (positive feedback); some of the energy from the tube's output circuit is fed back into the input circuit with a feedback loop. [29] [108] [120] [121] [122] The early vacuum tubes had very low gain (around 5).
Occasionally, a regenerative detector was used, to increase selectivity. Some TRF sets that were listened to with earphones didn't need an audio amplifier, but most sets had one to three transformer-coupled or RC-coupled audio amplifier stages to provide enough power to drive a loudspeaker. The schematic diagram shows a typical TRF receiver.