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.
This circuit was found in a 1969 CQ magazine. It is intended for coupling telephones to radio...
This circuit is from American documentation from the 1980s. The circuit can make use of any common...
We found this circuit in a 1977 documentation. The integrated circuit used is 4001. The signals...