Found in American documentation from the 90s, this circuit can measure frequencies on a linear scale from 0 to 1 kHz. The components can be changed to measure other ranges.
For reference only, this is the first IF amplifier stage of a common transistor radio from the...
This circuit from July 1975 Radio Electronics uses any operating system with a symmetrical source....
This setting is valid for other transconductance operational amplifiers. The circuit is from...