6 Transistor Super Regen Receiver by BC548

This little super-regenerative receiver is essentially an AM receiver, with “slope detection” used for FM. By tuning to one side of the carrier, the receiver’s tuned circuit converts FM to AM. The bandwidth is about 200KHz so wideband FM stations can be demodulated by tuning the receiver to the most linear point of the response curve, rather than the top of the curve as one would for AM. In practice, this simply means tuning for clearest sound.
The heart of the receiver is Q2 which is a Hartley oscillator, with its tuned circuit in the base circuit. It determines the frequency of oscillation and hence the receiving frequency.
RF amplifier Q1 is a self biased untuned common emitter amplifier, included to prevent aerial loading from affecting the detector’s oscillation frequency and amplitude. It also reduces any RF radiated from the aerial. RF is coupled into the oscillator coil by C2. The aerial can be a piece of wire cut to 75cm. A 75cm telescopic rod aerial is better but a proper outdoor FM aerial is preferred for non portable use.
Most simple super-regenerative detectors are self-quenched, however this makes it difficult to obtain the optimum quench waveform. Particularly for wideband FM, the quench waveform has considerable effect on sound quality.

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This entry was posted on Wednesday, December 19th, 2007 at 10:38 am and is filed under RF-Radio Frequency. You can follow any responses to this entry through the RSS 2.0 feed.