How to Adjust a Hunter Rotor BackSearch all videosMore Hunter Videos ▼How to Adjust a Hunter RotorRight-click on the video format below and select Save As...MOV | WMVDownloadCategory: Field KnowledgeProduct Lines: RotorsProducts: PGJ, SRM, PGP-ADJ, PGP Ultra, I-20Length: Quick TipPublished: February 23, 2010 Adjusting the arc and radius of a rotor is an easy task. Most residential rotors are adjusted the same way. There are two adjustments that can be made on rotors, arc and radius. Arc: The degrees of coverage of a sprinkler from one side of pattern to the other. A 90-degree arc would be a quarter-circle sprinkler. In other words, the arc is how far to the left and to the right the sprinkler will be adjusted to rotate. Radius: The distance of throw from the sprinkler head to the furthest point of water application.