John Daniel Kraus was an American physicist and electrical engineer known for his contributions to electromagnetics, radio astronomy, and antenna theory. His inventions included the helical antenna, the corner reflector antenna, and several other types of antennas. He designed the Big Ear radio telescope at Ohio State University, which was constructed mostly by a team of OSU students and was used to carry out the Ohio Sky Survey. Kraus held a number of patents and published widely.
QSL card of John Kraus sent to shortwave listener, 1933
A helical antenna is an antenna consisting of one or more conducting wires wound in the form of a helix. A helical antenna made of one helical wire, the most common type, is called monofilar, while antennas with two or four wires in a helix are called bifilar, or quadrifilar, respectively.
Array of four axial-mode helical antennas used as a satellite tracking-acquisition antenna, Pleumeur-Bodou, France
A common form of normal-mode helical antenna is the "rubber ducky antenna" used in portable radios. A handheld two-way radio, with the rubber sleeve removed from the antenna.
Normal-mode helical UHF TV broadcasting antenna, 1954
End-fire helical satellite communications antenna, Scott Air Force base, Illinois, USA. Satellite communication systems often use circularly polarized radio waves, because the satellite antenna may be oriented at any angle in space without affecting the transmission, and axial-mode (end-fire) helical antennas are often used as the ground antenna.
