This variable frequency oscillator for radio transmission covers the range from 1.6 MHz to 20 MHz, depending only on the coil used. The circuit is very stable and can be used in amateur equipment.
This LED special effects circuit was found in the February 1992 Radio Electronics magazine. The...
Found in an American publication from the 1980s, this circuit can be found in commercial sound...
Found in Philips' 90s documentation, this small source can use modern transistors like the BD135...