This circuit for the 40 MHz band was published in Radio Electronics magazine in December 1957. Its purpose was to monitor the signals of the Russian satellite launched at the time.
To obtain variable frequency signals, the circuit in the figure is recommended. In this circuit, the...
This circuit was found in old English documentation. It can be improved by using resistors of...
This circuit was published in a 1979 magazine, but it can still be easily assembled as the...