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 circuit, from a 1988 documentation, consists of an automatic temperature control using an NTC...
This power supply, found in an Argentine publication from the 1970s, uses a wire potentiometer of 25 W or more...
With this type of circuit, it is possible to obtain high input impedances and, at the same time,...