DP-AMP Sixty One Directional Coupler

The subject of measuring power is always underestimated. I have tried several directional couplers, but I was never satisfied. In my opinion, I needed a little more precision and, above all, a linear frequency response from 1.8 MHz to 70 MHz. I developed a directional coupler based on a Sontheimer-Frederick directional coupler with two logarithmic amplifiers of the type AD8307 from Analog Devices. This gave me the necessary linearity and the output voltages for the outgoing and reflected power can be processed directly with an AD converter.