RF circuit design (4) - superregenerative SW receiver

EE October 1986 * The first three appeared in the February, March, and April issues of Elektor Electronics. Fig I. Block diagram of the short-wave re- ceiver. Table 1. Winding data for £2. A superregenerative receiver is provided with ample positive feed- back so as to be capable of oscil- lation at the desired radio frequency. It is also provided with a means by which oscillations can be stopped or started at will. During normal oper- ation, the relevant circuit is just oscillating. Block diagram From the block diagram in Fig. 1 it is seen that the RF signal intercepted by the aerial is fed to an RF stage, which not only serves to amplify the signal but also to decouple the aerial from the remainder of the receiver. The amplified signal is fed to a buffer and a detector stage. The output of the buffer may be used to drive a fre- quency counter to give a read-out of the received frequency. The de- modulated output from the detector is passed through a low-pass filter with a cut-o...