Previously wind turbines have moved into the neighborhood and now two solar plants are close to the range. This article in the New York Times discusses the impact wind turbines have on radar.
A proposed plant to be built by Sempra Energy is about eight miles away from Northrop's range. Another proposed solar plant is about the same distance south of Northrop's range in Los Angeles County .
Read here for more about the Tejon RCS Range. Tom Mahood built this great site about radar ranges in the Mojave a decade ago. Thankfully the Howland company maintains the pages from the original site these days.
Another way to look at the range is to watch the National Geographic Channel's special Hitler's Stealth Fighter. This video shows Northrop's range performing RCS testing on a full scale model of the Horton 229 flying wing.
According to an article (subscription required) Wednesday in the Valley Press written by Allison Gatlin, at the meeting of the Kern County Supervisors in Bakersfield, "Northrop Grumman contended that the solar plant could interfere with its Tejon Test Site facility by reflecting or emitting radio waves, increasing the background electromagnetic "clutter" and making its tests less accurate. The company also says the environmental impact report prepared for the project is incomplete in other areas."