VSWR and power control

Analog Devices has an extensive portfolio of Logarithmic detectors. The link below shows a list of them that would work down to 10MHz input frequency.

Selection Table for Logarithmic Detectors | Parametric Search | Analog Devices

However, almost all our detectors' absolute maximum input RF power rating is no more than 20dBm, and the upper 3dB error power level is less than 10dBm. Therefore, both the incident and reflected signals must be properly attenuated to prevent the log detector from damage and to maintain accuracy. 120 watts is 50.8dBm You need to select a directional coupler with high coupling and use attenuator pads to lower the signal level to the log detector input to within its dynamic range.