Found in Philips' 90s documentation, this small source can use modern transistors like the BD135 for TR4 and the BC series for the rest.
This simple 1-transistor reflex receiver was published in Radio Electronics magazine in September 1959....
This circuit was found in the June 1982 issue of Radio Electronics magazine. It provides reference...
This circuit was found in an American documentation from the 90s. It consists of an optical memory...