3 MHz and 30 MHz radiations 1 Bandwidth antennas Central frequency 1 Electric field signatures 1 Electric fields 1 Geographical regions 1 Ground flash 1 Lightning 1 Negative ground flashes 1 Return stroke 1 Sweden 1 Temperate regions 1 Thunderstorms 1 Time duration 1 Wide-band 1 atmospheric electricity 1 comparative study 1 electric field 1 lightning 1 temperate environment 1 thunderstorm 1