Interesting, I think the device is an homemade one, I will try to swap the resistors. The electrolytic capacitor is "after" the diode so I guess it can be considered on the DC side?
Thanks
There's no need to swap the resistors.
Thinking about it some more, the 1M side is the input and the 50 ohm side is the output. The adapter is intended to bridge across the measurement point rather than terminate it. You'll have to use some form of splitter to make the connection. For lower frequencies, i.e. tens of MegaHertz, you can use a BNC 'T' connector. For higher frequencies, use a proper RF splitter followed by a 50 ohm feedthru terminator, followed by this unit.
Remember that the capacitor will charge to the peak voltage, so you have to scale that back to get RMS to calculate the power. Of course, if you're using this to tune for the peak value, that's unnecessary.
Ed