A practical guide to anomalous propagation. I

In the case of large and expensive systems involving an operation at microwave frequencies, holes in coverage and other problems have developed months after operation began. It is pointed out that many of the anomalies causing these disturbances are well known and can be predicted well in advance of system operation. This two-part series is to provide some information regarding this subject. Refraction, which has been responsible for many an optical illusion, has also been responsible for abnormal propagation of waves in other regions of the electromagnetic spectrum. Thus, the increased use of microwave and millimeter-wave systems is leading to occurrences of peculiar behavior. Attention is given to aspects of anomalous behavior (AP), the three common duct types, ducts created by inversion, losses in ducts, and new possibilities for radar behavior about the evaporation duct.