This circuit was found in an ancient American documentation. With it is possible to double the frequency of a transmitter For the range of 6 meters obtaining 8 W. The circuit makes use of varicap.
Any small sound amplifier from 200mW to 1W can be used in this simple circuit. Or circuit of two...
This setting applies to virtually any photo transistor and any operational amplifier. The power...
We found this circuit in an American 1980s documentation. The circuit uses a piezoelectric transducer...