document updated 16 years ago, on Mar 8, 2009

In a dense urban area, reflection/multipath can be a BIG problem. If you have a highly-directional antenna, it may feel like chasing ghosts, because you may accidentally end up pointing the antenna in a totally different direction from where the AP really is. That is, it's easy to get stuck in local maxima.
There are various metrics you can use when aiming an antenna, and they can and do give conflicting information. It's important to understand the relative merits of each one.