With this circuit from the September 1989 issue of Radio Electronics magazine, it is possible to receive VLF band signals on a common radio, just like the signals emitted by the previous receiver.
The audio signal generated by the oscillator stage is amplified by an LM380 and reproduced with...
This old integrated amplifier is from a Japanese publication from 1972. The integrated circuit is...
This second-order low-pass Salen-Key filter was obtained from an American 1980s documentation. Formulas...