This circuit for RF measurements at 200 MHz was found in no documentation two years 80. At a sensitivity of 1V peak and the components used are still common in these days.
This circuit was found in an Electronic Design from 1967. The circuit uses two triacs being T2...
Found in old American documentation, this circuit can use crystals between 27.5 and 33 MHz...
This shield from the 60's uses a germanium transistor of the time and a common type of relay of...