This receiver was found in a 1924 book by Gernsback. The circuit uses three tubes and is powered by 3 batteries of different voltages, common at the time.
This antenna for the frequencies 146 or 440 MHz was found in a magazine 73 for Amateur Radio of...
This circuit, when connected to the 110 V power grid makes it possible to test capacitors with...
This two-input limit detector was found in an American 1980s documentation. The circuit can be...