Bearing errors in the VHF omnirange due to scattering from wires

Scattering from obstacles in the vicinity of a VHF omnirange can cause bearing errors in aircraft receivers. A general formula is developed for the bearing error due to an arbitrary scatterer in terms of its scattering radiation pattern. The theory is then applied to get specific results for a long horizontal wire. The current distribution on the wire, the scattered field, and the bearing error are computed by a transform method, and all integrals are evaluated asymptotically by the saddle point method. The final result clearly shows the dependence of the bearing error on all system parameters. The theoretical conclusions are all found to be consistent with the results of numerous experiments carried out by the Federal Aviation Administration (FAA). Some results and speculations are presented for multiwire lines.