Technical
This type of antenna is called a Hogg or horn-reflector antenna, invented by Alfred C. Beck and Harald T. Friis in 1941. It was built by D. C. Hogg. It consists of a flaring metal horn with a reflector mounted in its mouth, at a 45° angle. The reflector is a segment of a parabolic reflector, so the antenna is really a parabolic antenna fed off-axis. A Hogg horn combines several characteristics useful for radio astronomy: it is extremely broad-band, has calculable aperture efficiency, and the walls of the horn shield it from radiation coming from angles outside the main beam axis, so back and sidelobes are so minimal that scarcely any thermal energy is picked up from the ground. Consequently it is an ideal radio telescope for accurate measurements of low levels of weak background radiation. The antenna has a gain of about 43.3 dBi and a beamwidth of about 1.5° at 2.39 GHz. and an aperture efficiency of 76%.
Read more about this topic: Holmdel Horn Antenna
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