a I want to make a sensor that can read the voltage/current at the node vin, no matter how the mismatch between the source and the load. I could always find the Zeq by using this Vin reading / Iin reading to find out the Zeq right? If i multiply Vin and Iin, I should get the power delivered to the Zeq which equals to Power generated by the source - power being reflected. Please correct me if I'm wrong about this

 

You will need a RF impedance/phase/magnitude monitor. A current and voltage sensor that might be subject to high potentials that those power levels.
https://www.electronicdesign.com/te...ign-automatic-impedance-matching-in-rf-design

https://forum.allaboutcircuits.com/threads/board-burns.153544/post-1480640
https://forum.allaboutcircuits.com/threads/board-burns.153544/post-1480932

 

View attachment 268762a I want to make a sensor that can read the voltage/current at the node vin, no matter how the mismatch between the source and the load. I could always find the Zeq by using this Vin reading / Iin reading to find out the Zeq right? If i multiply Vin and Iin, I should get the power delivered to the Zeq which equals to Power generated by the source - power being reflected. Please correct me if I'm wrong about this

Not sure if you were thinking about this or not, but, you most likely have to take into consideration the phase angle between voltage and current. The phase angle changes the real power levels. In fact, most AC circuits have to take into account the phase angle because many loads are reactive.
If you have some details on the load we can look at the theoretical aspects a lot better.

 

I have a two questions...
1) why not measure the impedance at a lower power with a cheap VNA? The impedance/mismatch isn't going to change with power (assuming the components can handle that power), so why measure it under power??? If something changes the match at 5kw, I guarantee you will know about it without needing "sensors"!
2) If I may ask, what is this for? The reason I ask, and don't take this the wrong way, is that those types of power amplifiers are so expensive and take so much power that it is typical for the person implementing it to be well versed in the area of RF and 3-phase industrial power. So, when you say "no matter the mismatch", I can only assume you do not appreciate the tens of thousands of volts that can be produced in the matching network or on the antenna, nor the fact that a mismatch greater than 3:1 with that power level will likely fry the unit in spectacular fashion. This makes me think you purchased this thing second-hand and plan to go pirate radio on us (forgive me if I am wrong, and if I am, surely you would understand my concern).

Please, give us more info!!!

 

Are you trying to read an RFID tag from across the state? How about a simple SWR bridge?