Results of measurements on vertically polarized short-wave log-periodic antennas

Measurements were performed on a model antenna, and a helicopter was used to measure radiation patterns of antennas in the vertical and horizontal planes. Radiation pattern measurements and SWR measurements were also taken on the ground. Helicopter positions were checked from the ground with measurements based on photographs taken through a fish-eye camera lens. The frequency variation of half-power beamwidths in the horizontal and vertical planes, of the magnitude of the side lobes in the radiation patterns, and of the antenna gain was analyzed. Measurements based on the model are found in close agreement with the characteristics of a short-wave log-periodic antenna. The antenna SWR was improved by adding impedance-matching sections of transmission line.