Series and Parallel-fed Linearly Polarized Helical Aerials

A comparison is made between series-fed and parallel-fed linearly polarized helical aerials. The series-fed aerial has been found to have a polarization which rotates significantly with frequency, and the magnitude of this rotation has been found to be in good agreement with the theoretical predictions of the sheath helix analysis. The parallel-fed aerial is useful over the same bandwidth as the single helix for spacings greater than half a wavelength.