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.
This circuit was obtained in a documentation from the 80's. The components used are of the time,...
Obtained in a 90s Radio Electronics, this configuration appears with variations in other points of...
This circuit was obtained in a 90s EDN. The components used are from that time. The voltage...