Abstract: A high frequency heating generator which includes an electron tube amplifier, the output of which is connected to a resonant circuit that is electromagnetically coupled to a part to be heated, and a controlled frequency oscillator. The oscillator outputs a high frequency signal to the input of the amplifier. It also includes circuitry to measure the phase shift between the current output to the resonant circuit and the voltage at its terminals, and to modify the frequency of the oscillator as a function of this phase shift. The invention can be applied notably to devices for heating by electromagnetic induction, dielectric losses or plasma.