Our pilot boxes need to be replaced. We now have six, each 25 feet from its' neighbor. The prevailing wind is from the Easterly direction and 90 % of our takeoffs are toward the East end of the runway. The easternmost box gets buzzed occasionally when a plane rolls left on takeoff. The westernmost box gets buzzed sometimes on crosswind landings. There are times when pilots at one end do not hear the call outs from the other end because of the distance and background noise.
I would like to reduce the number of pilot boxes to four, which is our max for the number of flyers at one time and also reduce the spacing between the boxes. How close can the boxes be placed and still avoid radio interaction if we use only modern radios?