Printed log-periodic antennas typically have 2, 4 or 8 arms. This 2-arm version included in Antenna Magus is the forerunner of the well-known LPDA antenna. It is linearly polarized, contrary to its circularly polarized 4-arm counterpart.
The graph below shows the typical reflection coefficient performance versus frequency for two designs: optimum vs compact with reference impedances of 188 Ohm and 150 Ohm respectively. This antenna typically operates over a wide bandwidth of 10:1 with approx. 5 dBi gain across the band.Typical S11 comparison for optimum vs compact designs.