We demonstrate a high power repetitive rf source using gyromagnetic nonlinear transmission line to produce rf oscillations. Saturated NiZn ferrites act as active nonlinear medium first sharpening the pumping high voltage nanosecond pulse and then radiating at central frequency of about 1 GHz: shock rise time excites gyromagnetic precession in ferrites forming damping rf oscillations. The optimal length of nonlinear transmission line was found to be of about 1 m. SINUS-200 high voltage driver with Tesla transformer incorporated into pulse forming line has been designed and fabricated to produce bursts of 1000 pulses with 200 Hz repetition rate. A band-pass filter and mode-converter have been designed to extract rf pulse from low-frequency component and to form TE(11) mode of circular waveguide with linear polarization. A wide-band horn antenna has been fabricated to form Gaussian distribution of radiation pattern. The peak value of electric field strength of a radiated pulse at the distance of 3.5 m away from antenna is measured to be 160 kV/m. The corresponding rf peak power of 260 MW was achieved.