Desired to undesired signal ratio predictions for the VHF Omnirange (VOR) and Instrument Landing System (ILS) air navigation aids are presented. The parameters involved in these systems are given first. Propagation mechanisms applicable to VHF/UHF and the calculation of transmission loss and its variability are then discussed, and, third, the statistical nature of the desired-to-undesired signal ratio predictions is explained. The results of the study, presented in graphical form, supplement those given by the authors in an earlier ESSA Technical Report on the same subject. In addition to extending the range of variables previously considered, this report considers the glide slope portion of the ILS.