The system comprises either a nanosecond solid-state operating switch (SOS)-generator (see, e.g., Rukin, 1995) or a RADAN pulsed power source (see, e.g., Mesyats , 1993) that charges resonantly a short pulse-forming line (PFL) through a decoupling inductor, an active converter, a matched load, and several built-in voltage and current probes. The active converter comprises an additional 1-ns PFL charged through a peaking spark gap (SG) and a secondary decoupling inductor by the first PFL, and two SGs (chopping and peaking gap). The peaking SG and active converter are set in one body and operate in$ N _2$at pressure up to 6 MPa. Driven by RADAN, the converter generates bipolar subnanosecond pulses having peak-to-peak amplitude up to 270 kV across 46.6-$Omega $load. The pulsewidth of each half wave of bipolar pulses on full-width at half-maximum is 280 ps, with the risetime of the first half wave of about 160 ps. The SGs' gaps can be regulated without system depressurizing (a technique adopted from Shpak , 1996). Circuit analysis accounting for the distributed character of the components and numerous parasitic parameters is presented. Mapping of main SG parameters (gap distance and pressure) was performed. Waveforms probed at different locations of the pulser systems, from the SOS-generator and from the RADAN to the load, are shown. The bipolar subnanosecond pulses had very stable rise, while the fall jitter was around 50 ps. The experimental results are in fair agreement with the simulation. Pulsers were tested with a transverse electromagnetic horn antenna. An effective potential of 910 kV was obtained.