The Iowa State Gun Shoot is a gun skeet shooting organization in Iowa that has a state shooting competition twice per year. They had an old wired PA system that needed replacement, but they didn't want to install a new wired system. The chose to go wireless instead.
They have 37 shooting stations lined up over a distance of 1000 yards and they needed a way to transmit messages so all stations could hear them. They found that one Wireless PA system installed every one hundred yards was sufficient enough to broadcast their messages over traffic and wind noise. Each wireless receiver has two horn speakers on it that are pointing in opposite directions.
This solution uses the long-distance, license-free MURS frequencies so no license was required. They use a wireless base station intercom to make the announcements.
Here is the solution that worked for them: Wireless PA System
Author: David Onslow