Self-excited HF generator - has triode tube with switched grid resistors forming fast power regulation circuit with series of s-c switches

The self-excited HF generator has a triode tube whose grid impedance is formed by a basic resistor (Rg) and a series chain resistors (R1-R3) each of which is bridged by a transistor switch (T1 etc.) (or other form of s-c switch). The bases of the transistors are connected to the secondary windings (W1 etc.) belonging to a transformer whose single primary receives the control pulses. The resistors are thereby switched in and out according to the HF power. The advantage lies in the extremely high response time of the regulating circuitry.