Knife-Edge Bending

Laboratory experiments demonstrated long ago that light rays are refracted (bent) when passing over a knife-edge obstacle aligned at right angles to their path. Under the right conditions that phenomena can cause a mountain to exhibit radio signal 'obstacle gain.' In other words, it can cause radio signals received on the other side of a mountain to be stronger than if the mountain didn't exist. That phenomenon is known as Knife-Edge Bending. Radio signal obstacle gain is rarely noticeably below VHF, because ground wave, ionospheric sky wave, and noise signals at lower frequencies usually are stronger than signals due to Knife-Edge Bending. ©2004 Tigertek, Inc. All rights reserved.

• October Fact-of-the-Day Index