This filter for receiving audio in telegraphy was found in a magazine 73 for radio amateurs, in an edition of the 80s. The circuit is tuned to 700 Hz and has a 200 Hz bandpass.
We found this circuit in a documentation from the 50s. It is based on CK722 germanium transistors. The...
Found in an English publication from the 1960s, this circuit uses period components, including the...
This oscillator can generate 2 to 10 MHz signals and was found in an American 1980s documentation. The...