Found in the September 1972 issue of Radio Electronics magazine, this signal injector is based on the HEP580. The circuit is powered by two batteries and its frequency is basically given by C1.
This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in...
This circuit was found in a 90s Electronic Engineering. The quadruple operational amplifier can be...
I found this circuit in an English publication from 1989. This configuration can be mounted with...