This circuit uses a lamp driven by the Hertz loop and measures its brightness with ordinary photovoltaic cells. The circuit is from a Radio Electronics from February 1964.
This S-meter circuit was found in a 1976 publication. The circuit is used to measure the signal...
Several versions of this circuit can be found on this website. This makes use of FETs that can...
With the circuit shown in the figure we have a frequency modulation which is produced by a...