Found in Ferranti's 1969 documentation this circuit has a maximum operating frequency of 7.5 MHz. The circuit can be designed with modern transistors.
This circuit was obtained in a 1976 amateur radio manual. The circuit can be made with a 2N2222...
This simple receiver, which requires a good antenna and grounding, was found in an Argentine...
This comparator with two Texas Instruments operators was obtained in a company application manual....