An ambitious backyard project
In 1933, Bell Labs engineer Karl Jansky discovered that radio static was coming from the center of the Milky Way, but the astronomical community showed little interest. A young radio engineer and amateur radio operator from Wheaton, Illinois, Grote Reber, saw an opportunity. After being turned down for jobs to pursue this research, Reber decided to build his own instrument. In the summer of 1937, in his mother's backyard at 212 W. Seminary Avenue, he began construction on the world's first parabolic radio telescope.
Working alone and with his own funds, Reber designed and built a 9-meter (31.4-foot) diameter dish. The structure consisted of 72 wooden rafters covered with 26-gauge sheet iron, all weighing about two tons. This parabolic dish focused incoming radio waves to a receiver suspended 20 feet above its' surface. The entire assembly was completed in about four months and was designed to solve a problem with earlier optical telescopes: it could focus a wide range of wavelengths to the same point, avoiding chromatic aberration.
Charting the radio sky
Reber's first attempts at detecting cosmic signals failed. Receivers designed for 3300 MHz and 900 MHz detected nothing from space. In 1938, a third receiver operating at a lower frequency of 160 MHz finally succeeded, confirming Jansky's discovery of radio waves from the Milky Way. For nearly a decade, Reber was the only radio astronomer in the world. He conducted his observations at night to avoid radio interference from the spark plugs of passing cars, which created spikes on his chart recordings.
From 1938 to 1943, Reber systematically scanned the heavens, creating the first-ever radio contour maps of the sky. He published his findings in the Astrophysical Journal in 1944, showing a detailed map of radio emissions. The maps revealed that the strongest radio source was the center of our galaxy in the direction of Sagittarius. He also identified other bright radio "hotspots" in the constellations Cygnus and Cassiopeia. His work demonstrated that radio waves could penetrate interstellar dust that obscured visible light, showing the universe. Reber's surveys started the entire field of radio astronomy.