The purpose of this circuit is to measure the resistance of an antenna at the resonant frequency. The circuit is from an old American documentation for hams.
This circuit source a voltage proportional to the number of the input pulses. The circuit has a...
This circuit is from a 90's Radio Electronics. The circuit operates accurately up to about 15 kHz...
This is a circuit suggested by Linear Technology in a 1980s documentation. The integrated circuit is from...