Although it uses a dual-channel FET, which is hard to find today, this circuit was released in a Radio Electronics issue in April 1986. It serves as a signal booster for a wide range of frequencies.
For those who like experimental circuits, here is a sequential flasher system with LEDs, which can be...
This circuit was found in an ancient American documentation. The integrated circuit is of the time...
This circuit was found in a 1977 Radio Shack documentation. The circuit is tuned to 1.4 kHz, but...