Characteristics of 1 to 8 wavelength uniform helical antennas

The measured voltage standing wave ratio (VSWR), gain, pattern, and axial ratio characteristics of a uniformly wound helical antenna are presented. Experimental parametric studies were made of 1) fixed length helices with variable diameter and pitch angle (8.6 to 10 turns), and 2) variable length helices with constant diameter and pitch angle (5 to 35 turns). Parametric curves are presented to show the gain and half-power beamwidth (HPBW) of a constant pitch helix as a function of axial lengthL/ circumferenceC/λ. Empirical expressions are derived for the antenna peak gain and bandwidth as a function of the helix parameters. In addition, the antenna gain-beamwidth products are examined.