Crystal oscillator (CB9504E)

This circuit was found in a 90s Popular Electronics. It can generate signals from 3 to 10 MHz.

Photometer (CB7360E)
This 1964 Electronic Design circuit uses a photo-FET as a sensor. The component is rare today. |...
Simple Metal Detector (CB5335E)
This metal detector circuit uses an AM radio as an indicator. The radio is placed off-station and tuned...
FET Super Regenerative Receiver (CB13314E)
This circuit is from a 1976 technical documentation. The FET can be MPF102 or BF245 and the coil...