The circuit is from the 1990 Motorola Linear Databook. The circuit can be implemented with other operational amplifiers. The power supply must be symmetrical.
This goniometer for the medium wave range was found in a 1967 documentation. It can be adapted to work...
This circuit was originally designed for testing crystals used in color televisions, but it works...
This circuit was found in an American 80's documentation. The operational may be a modern type...