We find this circuit in American documentation from the 1980s. It consists of a frequency folder using a varicap. The capacitors and coils depend on the frequency of operation.
Despite being from a 1970 General Electric documentation this circuit can be used as a shield if...
This is another quick adder that we found in an Electronic Design from the 80s. It also applies to...
This circuit was found in a 1969 Mullard documentation. Used transistors can be replaced with...