Increasing the height of the antenna has the effect of making finer the lobing pattern. A fine-grained lobing structure is often filled in by irregularities in the ground plane. Specifically, if the ground plane deviates from a flat surface then the reinforcement and destruction pattern resulting from the ground reflections breaks down. Avoidance of lobe effects is one of the prime considerations when selecting radar location and the height of the antenna.
![](a_vertical_pattern.png)