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, in addition to transforming a sinusoidal signal into a square, shifts its phase. The...
This transmitter, found in Raytheon documentation from 1957, has a range of a few meters. L1 can...
This circuit uses operational amplifiers that must be powered by a symmetrical source to implement a...