This circuit was obtained from an American 1980s documentation. The frequency depends on the crystal and the circuit may be a PNP that reaches the generated frequency.
This filter was found in an 80's English publication. However, it can be implemented with modern...
This circuit, which can be used as a shield, was found in old documentation. The circuit must be...
Found in Philips documentation from 1968 this circuit operates at frequencies up to 10 MHz with 76...