This circuit was found in an American documentation of the 90s. Optical resources with the LDR as a lens can help in obtaining directivity and sensitivity.
This circuit was found in a 1965 General Electric documentation. SCRs and unijunction may be...
The BA1404 integrated circuit (not very easy to obtain) consists of a complete stereo FM...
This circuit is from a Radio Electronics documentation from July 1959. In this documentation the...