How much base station antenna isolation is required?
We would like to see at least 30dB of isolation between base station antennas. Antenna isolation increases with distance. Antennas spaced at 3 feet horizontal spacing will provide about -39.4dB loss (isolation) between them. This increases to about -41.9dB at 4 feet and -43.84dB at 5 feet. As with anything RF, there ar many factors which can affect system performance. A big one when dealing with antenna isolation is that coupling to tower structures can reduce effective path loss between antennas. This could change the necessary spacing for any given installation. To calculate isolation for directional antennas like sector antennas, you have to add the front to back/ sidelobe spec to the gain (dBi). For instance; with a 16.5dB sector and a front to back spec of -14Bi, you have effective gain toward the side or back of the antenna of 2.5dBi or .35dBd. You can use the effective gain to calculate the best horizontal or vertical separate to give you the desired isolation. You’ll see that y
