1st thanks for your reply , what I am trying to say that for class E i should choose the load network so as to let the voltage of the cap discharge completely before the switch turns on so I am going to use the port adapter (varying load) to determine this optimum load while in class F although I should choose load terminations at different harmonics but I will also use the port adapter in the same way ...... My problem may be that I don't know how to choose the load termination at different harmonics using port adapter