I monitor a P25 simulcast system. (as noted, P25 is irrelevant) and have used both a corner reflector (see Post #15) and a yagi. While both improved my signal, I finally went with the yagi. The relative locations of the site towers can govern how well a directional antenna will work. If your antenna is pointing at a site tower and all others are outside of the antennas "field of view" you'll likely get a good deal of improvement compared to an omnidirectional antenna. But, if two sites are in line with the directional antenna, you may still experience simulcast distortion, maybe even to a higher degree.