Regenerative receiver is an older form of radio receiver that was in used in the 1920s and 1930s. It was invented by an American scientist named Edwin Armstrong. This radio uses only one valve or transistor for RF selection, amplification and detection of radio signals.
The transistor acts as an amplifier and the circuit has a feedback loop that feeds a part of the output signal back to the input in phase, which increases the amplification and signal gain, called as positive feedback or regeneration. The output of the transistor is fed back in phase to the input of the transistor through a tuned circuit. The tuned circuit allows only the positive feedback at its resonant frequency to pass through to the input of the amplifier. This positive feedback or regeneration produces very high loop gain by a factor of 1700 times or more and therefore increasing the sensitivity of the receiver.
The frequency selection or selectivity is made possible by the tuned circuit which is coupled to the antenna input. A specific frequency is tuned or selected by means of varying the capacitor or inductor in the tuned circuit or LC tank circuit. The signal amplification at the Q of the resonant tuned circuit also allows for selectivity of the receiver.
Detection is performed by the same active device and forms the regenerative detector. There is a regeneration control for controlling the amount of feedback so as to provide adequate regeneration. The regeneration control can increase the feedback from no oscillation to oscillations with smaller amplitude and to oscillations with larger amplitude. The regeneration control allows the reception of various modes of transmission such as AM, SSB, CW etc. For AM reception, a point is selected just before the onset of oscillations. The regeneration control is adjusted to get maximum gain, but not allowing the circuit to oscillate. For CW reception, the regeneration is adjusted so as to oscillate the circuit. The input signal mixes with the oscillation of the circuit by a few hertz difference. For SSB reception, the oscillation of the circuit acts as the carrier oscillator, and that oscillation mixes with the incoming signal. Thus SSB signals are resolved to get the speech signal. Precise tuning is necessary to adequately beat the oscillator signal with the incoming radio signal in order to receive a good CW or SSB signal.
Advantages:
Disadvantages:
Uses and Applications of Regenerative Receiver:
The transistor acts as an amplifier and the circuit has a feedback loop that feeds a part of the output signal back to the input in phase, which increases the amplification and signal gain, called as positive feedback or regeneration. The output of the transistor is fed back in phase to the input of the transistor through a tuned circuit. The tuned circuit allows only the positive feedback at its resonant frequency to pass through to the input of the amplifier. This positive feedback or regeneration produces very high loop gain by a factor of 1700 times or more and therefore increasing the sensitivity of the receiver.
The frequency selection or selectivity is made possible by the tuned circuit which is coupled to the antenna input. A specific frequency is tuned or selected by means of varying the capacitor or inductor in the tuned circuit or LC tank circuit. The signal amplification at the Q of the resonant tuned circuit also allows for selectivity of the receiver.
Detection is performed by the same active device and forms the regenerative detector. There is a regeneration control for controlling the amount of feedback so as to provide adequate regeneration. The regeneration control can increase the feedback from no oscillation to oscillations with smaller amplitude and to oscillations with larger amplitude. The regeneration control allows the reception of various modes of transmission such as AM, SSB, CW etc. For AM reception, a point is selected just before the onset of oscillations. The regeneration control is adjusted to get maximum gain, but not allowing the circuit to oscillate. For CW reception, the regeneration is adjusted so as to oscillate the circuit. The input signal mixes with the oscillation of the circuit by a few hertz difference. For SSB reception, the oscillation of the circuit acts as the carrier oscillator, and that oscillation mixes with the incoming signal. Thus SSB signals are resolved to get the speech signal. Precise tuning is necessary to adequately beat the oscillator signal with the incoming radio signal in order to receive a good CW or SSB signal.
Advantages:
- It has good performance and needs very few components for its construction.
- It has very high gain and sensitivity achieved as a result of positive feedback or regeneration.
- It has high Q or selectivity achieved due to the tuned circuits at the feedback circuit.
Disadvantages:
- It needs more skill to operate.
- This receiver can radiate signals into the air when the circuit oscillates.
- It can receive signal modes such as AM, CW or SSB, but not modes like FM.
Uses and Applications of Regenerative Receiver:
- It is used by radio enthusiasts for learning the regenerative techniques in radio receivers.
- It is used in limited radio control devices such as wireless networking and connectivity, opening doors, activating circuits etc.
- It is used in toys and walky-talkies.
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