The Horn Antenna at Bell Telephone Laboratories in Holmdel, New
Jersey, was constructed in 1959 to support Project Echo--the
National Aeronautics and Space Administration's passive
communications satellite project.  The antenna is 50 feet in
length with a radiating aperture of 20 x 20 feet and is made of
aluminum. The antenna's elevation wheel is 30 feet in diameter
and supports the weight of the structure by means of rollers
mounted on a base frame. All axial or thrust loads are taken by
a large ball bearing at the apex end of the horn. The horn
continues through this bearing into the equipment cab. The
ability to locate receiver equipment at the apex of the horn,
thus eliminating the noise contribution of a connecting line, is
an important feature of the antenna. A radiometer for measuring
the intensity of radiant energy is found in the equipment cab.
The triangular base frame of the antenna is made from structural
steel. It rotates on wheels about a center pintle ball bearing
on a track 30 feet in diameter