An Investigation of Some Slow-Wave Conical Log-Spiral and Helical Antennas

The first part of the report is concerned with the characteristics of conical spiral antennas constructed with zig-zag, i.e., slow-wave geometry, arms. This construction permits a reduction in size of approximately 15 percent below that required for the conventional antenna. It also increases the pattern beamwidth and lowers the characteristic impedance. In part 2, a 2 14-turn monofilar conical helix, fed at the base of the cone against an inner metal core, was investigated. This small circumference approximately 14 wavelength antenna can be made to be an axial radiating structure, while the conventional helix of this size radiates a maximum of energy broadside to the antenna axis.