Found in a 73 magazine from the 1980s, this circuit generates signals from 3.2 to 22 MHz. FETs can be general-0purpose current types. No information about the coils is given.
We found this heart rate sensor circuit in a Popular Electronics from the 90s. The placement of...
This circuit, found in an old magazine of the year 1968, uses a Power germanium transistor. This...
This project came out in an article of mine (Newton C. Braga) in the Popular Electronics magazine of...