A modified Wheeler cap method for measuring antenna efficiency

An antenna efficiency measurement technique is presented which is based on the classic Wheeler Cap method. Wheeler´s original method is regarded as one of the simplest and most accurate for measuring electrically small antennas, but the assumed RLC equivalent circuit model may not be appropriate for all antennas. In the present method we transform measured reflection coefficient data such that either a series or parallel RLC approximation is always valid in the vicinity of resonance. This procedure provides the capability to achieve significant improvements in accuracy over measuring the efficiency of VHF and UHF antennas in anechoic chambers.