A study of the sheath helix with a conducting core and its application to the helical antenna

A theoretical study of the sheath helix antenna with a conducting core is made via the complex solutions of an associated determinantal equation. The variation of the characteristics of operation with respect to core size and pitch angle is established. A comparison of the complex solutions for the sheath helix and tape helix indicates that a good understanding of the helical antenna can be gained from the sheath model. In particular, explaining broadside radiation in terms of complex solutions is shown to give results in agreement with previously reported empirical data. However, this comparison also points out the limitations of the sheath model in predicting the operational parameters accurately.