Antennas basically work like the sprinkler on the end of the hose. If you have a certain amount of signal (or water) coming from one antenna (or sprinkler) you will get a certain size area of coverage (10 feet from the indoor antenna/sprinkler for example). If you split that, and use two antennas it is just like splitting off of your spigot to two hoses and sprinklers. You are not providing more water (or more cell signal). You are taking the signal or water that you have, and putting half in each antenna or sprinkler location. You are not increasing the area that you are covering, you are simply taking the one 10 foot area, and creating two 5 foot areas. This may be appropriate for certain deployments, but it will not increase total coverage area.