This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
Details of the coil of this two-transistor generative receiver were not given. We found it in a...
This very high input impedance circuit is suggested by Texas Instruments. The circuit can be...
This circuit from an 80's publication also features low input capacitance. FET can be a modern...