Comparison of the Optimal Uniform and Nonuniform Lossy Helical Antennas

We present results for comparison of gain of the optimal uniform and nonuniform helical antennas taking into the account conductor losses. Critical conductivities are observed, for the given operating frequency and the helix axial length. Above the critical conductivity, the gain of the nonuniform helical antennas with linearly varying geometrical parameters is up to 2 dB higher than the gain of the optimal uniform antennas. However, below the critical conductivity, the difference between the gain of the nonuniform and uniform helical antennas is reduced, and the gain of those antennas becomes comparable. Data for the normalized critical conductivities are presented.