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.
If mounted with SMD components, this transmitter will be so small that it can be installed inside a...
Unlike the previous one, this circuit uses only one resistor in the base polarization. The...
This circuit was obtained in a 1974 Motorola timers publication. Transistors allow equivalents, the 2N2646...